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Release Specific Information for HDF5 1.8

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# Software Changes from Release to Release for HDF5-1.8

This document is designed to help developers maintain HDF5-based applications as they are used with successive releases of HDF5. To that end, this document lists the changes at each release that a maintenance developer needs to be aware of:

- New or changed features or tools
- Syntax and behavioral changes in the existing application programming interface (the API)
- Certain types of changes in configuration or build processes
- Bugfixes and performance enhancements in the C library are automatically picked up by the C++ and Fortran libraries. The Java library will pick up the same bugfixes and enhancements at its next subsequent release as it is always built with the latest released version of the C library.

The release notes also list changes made to the library, but these notes tend to be more at a more detail oriented level. The release notes may include new features, bugs fixed, supported configuration features, platforms on which the library has been tested, and known problems. The release note files are listed below and can be found at the top level of the HDF5 source code tree in the release_docs directory of the distributed HDF5 source code.

- RELEASE.txt - Technical notes regarding the current release of the HDF5 library
- HISTORY-1_8.txt - Technical notes for previous 1.8 releases of the HDF5 library by release
- HISTORY-1_0-1_8_0_rc3.txt - Technical notes for releases prior to the 1.8.0 release of the HDF5 library by release

#### Are you porting an existing application from HDF5 Release 1.6.x to HDF5 Release 1.8.x?

If you are porting an existing application from any HDF5 version in the Release 1.6.x series to any version in the Release 1.8.x series, refer to "What's New in HDF5 1.8.0". This document, with the documents linked in its introduction, provides a guide to the changes introduced in the transition from the 1.6.x series to HDF5 Release 1.8.0 and discussions of various compatibility issues.

## Release 1.8.23 of February 2023 versus Release 1.8.22

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.22 to Release 1.8.23.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

- None.

#### In the C High Level Interface

- None.

#### In the C++ Wrapper

- None.

### Compatibility Notes and Report and Comments

The interface compatibility report provides a full list of the changed symbols.

## Release 1.8.22 of February 2021 versus Release 1.8.21

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.21 to Release 1.8.22.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

The following are new C functions in this release:

Function | Description
--- | ---
H5Pget_fapl_hdfs | Gets the information of the given Read-Only HDFS virtual file driver
H5Pget_fapl_ros3 | Gets the information of the given Read-Only S3 virtual file driver
H5Pset_fapl_hdfs | Sets up Read-Only HDFS virtual file driver
H5Pset_fapl_ros3 | Sets up Read-Only S3 virtual file driver

#### In the C High Level Interface

- None.

#### In the C++ Wrapper

- None.

### Compatibility Notes and Report and Comments

The interface compatibility report provides a full list of the changed symbols.

## Release 1.8.21 of May 2018 versus Release 1.8.20

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.20 to Release 1.8.21.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

- None.

#### In the C High Level Interface

- None.

#### In the C++ Wrapper

- Many changes were made to improve the C++ API model. Please review the RELEASE.txt file or the compatibility report below for complete information on the C++ changes in this release.

### Compatibility Notes and Report and Comments

The interface compatibility report provides a full list of the changed symbols.

## Release 1.8.20 of November 2017 versus Release 1.8.19

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.19 to Release 1.8.20.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

- None.

#### In the C High Level Interface

- None.

#### In the C++ Wrapper

- Many changes were made to improve the C++ API model. Please review the RELEASE.txt file or the compatibility report below for complete information on the C++ changes in this release.

### Compatibility Notes and Report and Comments

#### Compatibility report for Release 1.8.20 versus Release 1.8.19

The following interface compatibility report provides a full list of the changed symbols: API compatibility report for the HDF5 Library between 1.8.19 and 1.8.20 versions on x86_64

## Release 1.8.19 of June 2017 versus Release 1.8.18

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.18 to Release 1.8.19.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

The following new C functions were added:

- H5Dget_chunk_storage_size
- H5PLappend
- H5PLget
- H5PLinsert
- H5PLprepend
- H5PLremove
- H5PLreplace
- H5PLsize

#### In the C High Level Interface

The following new C function was added:

- H5DOread_chunk

#### In the C++ Wrapper

Many changes were made to improve the C++ API model. Please review the RELEASE.txt file or Compatibility report below for complete information on the C++ changes in this release.

### Compatibility Notes and Report and Comments

#### Compatibility report for Release 1.8.19 versus Release 1.8.18

The following interface compatibility report provides a full list of the changed symbols: API compatibility report for the HDF5 Library between 1.8.18 and 1.8.19 versions on x86_64

## Release 1.8.18 of November 2016 versus Release 1.8.17

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.17 to Release 1.8.18.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

- None.

#### In the C++ Interface (main library wrappers)

- The macro H5_NO_NAMESPACE was deprecated.
- A number of new member functions were added or removed. See RELEASE.txt for detail.

### Compatibility Notes and Report and Comments

#### Compatibility report for Release 1.8.18 versus Release 1.8.17

The following interface compatibility report provides a full list of the changed symbols: API compatibility report for the HDF5 Library between 1.8.17 and 1.8.18 versions on x86_64

## Release 1.8.17 of May 2016 versus Release 1.8.16

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.16 to Release 1.8.17.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

The following new C functions and environment variable enable setting a relative path for raw data files associated with datasets using external storage:

Functions:

- H5Pset_efile_prefix
- H5Pget_efile_prefix

Environment variable:

- HDF5_EXTFILE_PREFIX

#### In the C High-Level Interface

The following new functions have been added in the Packet Table (H5PT) high-level interface:

- H5PTcreate
- H5PTget_dataset
- H5PTget_type

H5PTcreate replaces H5PTcreate_fl, which is deprecated and may be removed in a future release.

The following functions were previously removed from the library distribution but are once again publicly available. Reinstated in its original form:

- H5PTis_varlen

An updated form of H5PTfree_vlen_readbuff reinstated as:

- H5PTfree_vlen_buff

#### In the C++ Interface (main library wrappers)

New member function added in DSetCreatPropList:

- H5::DSetCreatPropList::setNbit() was added to set up N-bit compression for a dataset.

New overloaded const member functions added in ArrayType:

The following functions were added to provide const versions; the non-const versions have been marked deprecated.

- ArrayType::getArrayNDims() const
- ArrayType::getArrayDims() const

The datamembers ArrayType::rank and ArrayType::dimensions have been removed. This is an implementation detail and should not affect applications.

#### In the C++ High-Level Interface

New constructor added in FL_PacketTable:

An overloaded constructor has been added to FL_PacketTable. The function now takes a property list identifier to provide flexibility on creation properties such as compression.

- `FL_PacketTable(hid_t fileID, const char* name, hid_t dtypeID, hsize_t chunkSize = 0, hid_t plistID = H5P_DEFAULT)`

New member functions added in PacketTable Two accessor wrappers were added to class PacketTable.

- `PacketTable::GetDataset()` returns the identifier of the dataset associated with the packet table.
- `PacketTable::GetDatatype()` returns the identifier of the datatype that the packet table uses.

New member functions added with a char* argument: Overloaded functions have been added to provide a `const char*` argument. The existing versions of these functions will be deprecated in future releases.

This also removes the following warning: `deprecated conversion from string constant to "char*" [-Wwrite-strings]`

ifdef blocks removed: The `#ifdef VLPT_REMOVED` blocks have been removed from the packet table library source code except for the following functions:

- `VL_PacketTable::IsVariableLength()` was moved to `PacketTable`.
- `VL_PacketTable::FreeReadBuff()` is now `PacketTable::FreeBuff()`.

### Compatibility Notes and Report

Changed shared library interface version numbers (soname)

For HDF5 Release 1.8.17, the shared object version numbers have changed as follows.

Library | Release 1.8.16 | Release 1.8.17 | Reason for Change
--- | --- | --- | ---
HDF5 C Library | 10.1.0 | 10.2.0 | Added APIs
HDF5 High-level C Library | 10.0.2 | 10.1.0 | Added APIs
C++ Library | 11.0.0 | 12.0.0 | Changes in existing APIs
High-level C++ Library | 11.0.0 | 11.1.0 | Added APIs
All others | 10.0.2 | 10.0.3 | Code changes that did not result in interface changes

#### Compatibility report for Release 1.8.17 versus Release 1.8.16

The following interface compatibility report provides a full list of the changed symbols: API compatibility report for the HDF5 Library between 1.8.16 and 1.8.17 versions on x86

## Release 1.8.16 of November 2015 versus Release 1.8.15

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.15 to Release 1.8.16.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

New HDF5 Plugin Interface (H5PL) A new HDF5 Plugin Interface (H5PL), enabling programmatic control of dynamically loaded plugins, was introduced at HDF5 Release 1.8.15. This interface was only partially documented at that time, but more complete documentation is now available:

- Dynamic Plugins in HDF5 in Advanced Topics in HDF5
- H5PL: Plugin Interface in the HDF5 Reference Manual
  - H5PLset_loading_state
  - H5PLget_loading_state

The following new C function has been added: This function reports whether the linked version of the HDF5 Library was built with the thread-safety feature enabled.

- H5is_library_threadsafe

The following flag has been removed:

- H5F_ACC_DEBUG flag for H5Fopen/create
  The flag H5F_ACC_DEBUG was used to provide extra debugging information for HDF Library developers. This flag and the underlying functionality have been removed from the library due to disuse. The symbol remains defined since it was visible in H5Fpublic.h, but it has been set to zero (0) and has no effect anywhere in the library.
- H5Fopen

#### In the C++ Interface

The following features have been added:

- New class H5::ObjCreatPropList for the object creation property list class
  The new class H5::ObjCreatPropList is derived from H5::PropList and is a baseclass of H5::DSetCreatPropList. Additional property list classes will be added to the library in future releases and some of those will be derived from H5::ObjCreatPropList.
- New wrappers for the C functions H5Pset_attr_phase_change/H5Pget_attr_phase_change and H5Pset_attr_creation_order/H5Pget_attr_creation_order

The following wrappers were added to the class H5::ObjCreatPropList for the respective C functions:

C Function | C++ Wrapper
--- | ---
H5Pset_attr_phase_change | H5::ObjCreatPropList::setAttrPhaseChange
H5Pget_attr_phase_change | H5::ObjCreatPropList::getAttrPhaseChange
H5Pset_attr_creation_order | H5::ObjCreatPropList::setAttrCrtOrder
H5Pget_attr_creation_order | H5::ObjCreatPropList::getAttrCrtOrder

#### Library Configuration

- Use of thread-safety with the HDF5 High-level Library has been declared unsupported in the build tools: Autotools and CMake.
- The global lock used by the thread-safety mechanism is not raised to the high-level library level, making it possible that the library state could change if a context switch were to occur in a high-level library call. Because of this, the combination of thread-safety and the high-level library is officially unsupported by The HDF Group.
  Though this combination has never been supported in HDF5, this was not enforced by the build systems. With this release, the combination has been explicitly flagged as unsupported in Autotools and CMake, the build systems used with HDF5.

The new unsupported declaration will cause an Autotools configure step to fail if `--enable-threadsafe` and `--enable-hl` are combined unless additional options are specified (see below). Since the high-level library is built by default, this means that these extra configuration options will need to be used any time `--enable-threadsafe` is selected.

To use Autotools to build an application with `--enable-threadsafe`, use one of the following approaches:

- Use `--disable-hl` to disable the high-level library. (Recommended)
- Use `--enable-unsupported` to build the high-level library with the thread-safety feature.

To use CMake to build an application with HDF5_ENABLE_THREADSAFE=ON, use one of the following approaches:

- Use `HDF5_BUILD_HL_LIB=OFF` to disable the high-level library. (Recommended)
- Use `HDF5_ALLOW_UNSUPPORTED=ON` to build the high-level library with the thread-safety feature.

Since this combination is unsupported, applications using it must be carefully tested for potential thread-safety failures.

### Compatibility Notes and Report

#### Decoupled shared object version numbers (soname)

Shared object version numbers, soname, for HDF5 wrapper libraries, such as the C++ and Fortran libraries, have been decoupled from the shared object version number for the HDF5 library. In this and future releases, each library's soname will be maintained on an individual basis according to the interface changes specific to each wrapper library.

#### Changed shared library interface version numbers (soname)

For HDF5 Release 1.8.16, the shared object version numbers have changed as follows.

Library | Release 1.8.15 | Release 1.8.16 | Reason for Change
--- | --- | --- | ---
HDF5 Library | 10.0.1 | 10.1.0 | Added APIs
C++ Library | 10.0.1 | 11.0.0 | Changes in existing APIs
High-level C++ Library | 10.0.1 | 11.0.0 | Changes in existing APIs
All others | 10.0.1 | 10.0.2 | Code changes that did not result in interface changes

#### Compatibility report for Release 1.8.16 versus Release 1.8.15

The following interface compatibility report provides a full list of the changed symbols: API compatibility report for the HDF5 Library between 1.8.15 and 1.8.16 versions on x86

## Release 1.8.15 of May 2015 versus Release 1.8.14

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.14 to Release 1.8.15.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

The following new C functions have been added: Memory allocation functions that use the library's allocator.

- H5allocate_memory
- H5resize_memory

The following functions enable programmatic control of the loading of dynamic plugin filters in user applications:

- H5PLset_loading_state
- H5PLget_loading_state

For preliminary documentation, see New HDF5 APIs Provide Programmatic Control of Dynamic Plugins. Final documentation is anticipated in July 2015.

#### In the C++ Interface

The following features have been added: New wrappers for the C functions H5Pset_libver_bounds and H5Pget_libver_bounds The following wrappers have been added to class `H5::FileAccPropList`. The first sets the bounds on versions of the HDF5 Library format to be used when creating or writing objects; the second retrieves the current settings:

- `void setLibverBounds(H5F_libver_t libver_low, H5F_libver_t libver_high) const;`
- `void getLibverBounds(H5F_libver_t& libver_low, H5F_libver_t& libver_high) const;`

New wrappers to retrieve the version of an object header The following wrappers have been added to class `H5::CommonFG` to retrieve the object header version of an object in a file or group, given the object's name.

- `unsigned childObjVersion(const char* objname) const;`
- `unsigned childObjVersion(const H5std_string& objname) const;`

A new DataType constructor A new DataType constructor takes a PredType object and invokes H5Tcopy to generate another datatype identifier from a predefined datatype.

The following features have been changed: Combined `H5File::getObjCount` overloaded methods The following methods:

- `ssize_t getObjCount(unsigned types) const;`
- `ssize_t getObjCount() const;`

have been combined into the following:

- `ssize_t getObjCount(unsigned types = H5F_OBJ_ALL) const;`

Deprecated constructors The following two constructors of the classes AbstractDs, IdComponent, H5Location, and H5Object are no longer appropriate after the data member id was moved from IdComponent to the sub-classes in previous releases:

- `<Classname>(const hid_t h5_id);`
- `<Classname>(const <Classname>& original);`

The copy constructors have been no-ops and are removed in this HDF5 Release 1.8.15. The other constructors will be removed in HDF5 Release 1.10 and are expected to be removed from HDF5 Release 1.8.17 if their removal causes no problems.

#### In the Fortran Interface

The following Fortran 2003 API has been added:

- h5tenum_insert_f

Operation of the new Fortran 2003 version of this API is more consistent with the operation of the C API than was the Fortran 90 version.

Users are strongly encouraged to use the Fortran 2003 API.

Several global variables have been added in the Fortran API. These global variables are equivalent in definition to the comparable C definitions:

- H5G_UDLINK_F
- H5G_SAME_LOC_F
- H5O_TYPE_UNKNOWN_F
- H5O_TYPE_GROUP_F
- H5O_TYPE_DATASET_F
- H5O_NAMED_DATATYPE_F
- H5O_TYPE_NTYPES_F

For parallel applications A fix for issues encountered upon calling MPI_Finalize without having closed everything in an HDF5 file

An attribute destroy callback has been attached to MPI_COMM_SELF that shuts down the HDF5 Library when MPI_COMM_SELF is destroyed, that is, on MPI_Finalize. This should fix several issues that users see when they forget to close HDF5 objects before calling MPI_Finalize().

### Compatibility Report and Comments

#### Compatibility report for Release 1.8.15 versus Release 1.8.14

API compatibility report for the HDF5 Library between 1.8.14 and 1.8.15 versions on x86

Changed shared library interface version number (soname)

In the C++ interface, two overloaded methods have been combined into a single method and one constructor has been deprecated.

Due to these changes, the shared library interface version number (soname) has been increased. For a full list of the changed symbols, see the interface compatibility report linked immediately above.

## Release 1.8.14 of November 2014 versus Release 1.8.13

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.13 to Release 1.8.14.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the main library C Interface

- No new C functions have been added.

The behavior of the following C function has been changed:

- H5Pset_core_write_tracking, The function H5Pset_core_write_tracking has been modified to enforce the limitation that the value of the page_size parameter cannot equal 0 (zero):

The following performance optimization has been implemented in the Parallel HDF5 library: The algorithm for writing chunk fill values for new datasets has been optimized to write out all chunk fill values collectively in a single MPI-IO call. This was previously done independently by rank 0 (zero) one block at a time. This optimization should produce a significant performance improvement when creating chunked datasets in parallel, most notably when chunk dimensions are relatively small. This optimization will be evident in use of the following function:

- H5Dcreate

#### In the high-level library C Interface

- High-level HDF5 interfaces now ensure that strings are null-terminated and will not overflow a buffer.
- In several high-level functions, the type from the file was previously reused as the memory type and no check is made to ensure that a string was actually null-terminated.
- All high-level functions now check for NULL pointers; verify that a received a string is null-terminated; and verify that the string will not overflow the buffer. The minimum length of the buffers is now used in strncmp to avoid overflow.

#### In the main library C++ Interface

No new C++ methods have been added.

The following changes have been made in the C++ interface:
Changed defaults

- Default value of class member id:
  The data member id in several classes that represent HDF5 objects are now initialized to H5I_INVALID_ID.
- Default value of a PropList member id:
  The data member id in class PropList is now initialized to H5P_DEFAULT.

In HDF5 Release 1.8.13 and earlier, the above were initialized to 0 (zero).

Changed file access flags

- The flag H5F_ACC_CREAT has been removed from the C++ interface.\

#### In the main library Fortran Interface

- No new Fortran subroutines have been added.

Changed Fortran INTEGER parameter types:
Types of the following Fortran parameter constants have been changed from INTEGER to INTEGER(HID_T):

- H5FD_CORE
- H5FD_MULTI
- H5FD_FAMILY
- H5FD_SEC2
- H5FD_LOG
- H5FD_STDIO
- H5FD_MPIO

Other internal int types have been changed to hid_t, but this change is expected to be transparent to the user.

### Compatibility Report and Comments

#### Compatibility report for Release 1.8.14 versus Release 1.8.13

API compatibility report for the HDF5 Library between 1.8.13 and 1.8.14 versions on x86

Changed shared library interface version number (soname)

- To increase the maintainability of HDF5, an architectural change has been made that required renaming several public symbols in H5Ppublic.h.
- Due to these changes, the shared library interface version number (soname) has been increased. For a full list of the changed symbols, see the interface compatibility report linked immediately above.

## Release 1.8.13 of May 2014 versus Release 1.8.12

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.12 to Release 1.8.13.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

The following new C functions have been added:
To free memory allocated by HDF5 function calls:

- H5free_memory - This function should be used to free memory that has been allocated by HDF5 API calls such as H5Tget_member_name and H5Pget_class_name. The primary value for this call is on Windows systems, where it is common for application code and the HDF5 Library to be using different C run-time libraries (CRT). Using this new call ensures that the same CRT handles both the allocation and free.
  This function can also be useful in any case where the library uses a different memory manager than the application, such as when a debug memory manager is in use or when the HDF5 Library is wrapped for use in a managed language like Python or Java.

New configuration property for the CORE driver:

- H5Pset_core_write_tracking - This function sets a property in the file access property list to track the dirty regions in the file and write out only the changed regions on flush or close operations. This function is used with the CORE driver, H5Pset_fapl_core.
  Additionally, a page aggregation size can be set that will aggregate small writes into larger writes. For example, setting a 1 mebibyte (1 MiB) page aggregation size will logically partition the the in-memory file into 1 MiB pages that will be written out in their entirety if even a single byte is dirtied.
- H5Pget_core_write_tracking - This function retrieves the property set by H5Pset_core_write_tracking.

The following C functions have been modified:

- H5Rget_name - The function signature has been changed to return the size of the buffer required to read the name (not including the NULL terminator) if the name parameter is passed as NULL. The size parameter is ignored in this case.
- H5Zfilter_avail - This function has been updated to correctly identify dynamically loaded filters. If a filter is not found among registered filters, the function now checks for dynamically loaded filters.

#### In the C++ Interface

The following new features have been added:
Wrappers to the class H5Object to get an object's name:

- `ssize_t getObjName(char *obj_name, size_t buf_size = 0)`
- `ssize_t getObjName(H5std_string& obj_name, size_t len = 0)`
- `H5std_string getObjName()`

Wrappers to the class H5CommonFG to get a child object's type from a group or file:

- `H5O_type_t childObjType(const H5std_string& objname)`
- `H5O_type_t childObjType(const char* objname)`
- `H5O_type_t childObjType(hsize_t index, H5_index_t index_type = H5_INDEX_NAME, H5_iter_order_t order = H5_ITER_INC, const char* objname = ".")`

Wrappers to the class DSetMemXferPropList for setting or getting a transform property list:

- `void DSetMemXferPropList(const char* expression)`
- `void setDataTransform(const char* expression)`
- `ssize_t getDataTransform(char* exp, size_t buf_size = 0)`
- `H5std_string getDataTransform()`

Wrapper to CompType for setting the size of a compound datatype:

- `void setSize(size_t size)`

Overloaded functions to provide prototypes that declare constant arguments const:

- `DataSet::fillMemBuf`
- `DataSet::getVlenBufSize`
- `DataSpace::extentCopy`
- `DataType::commit`
- `FileAccPropList::setSplit`
- `H5File::getVFDHandle`

Additional overload to the class H5Location to get a comment as a char*:

- `ssize_t getComment(const char* name, size_t buf_size, char* comment)`

Additional overloads to the class Attribute to get an attribute's name for convenience:

- `ssize_t getName(char* attr_name, size_t buf_size=0)`
- `ssize_t getName(H5std_string& attr_name, size_t buf_size=0)`

#### In the Fortran Interface

The following new Fortran subroutines have been added:

Fortran2003 subroutines:

- h5pset_file_image_f
- h5pget_file_image_f
- h5fget_file_image_f (Added in Release 1.8.11, but not documented at that time.)

The following Fortran subroutine has been changed:

- h5pset_chunk_cache_f - The values of the constants H5D_CHUNK_CACHE_NSLOTS_DFLT_F and H5D_CHUNK_CACHE_NBYTES_DFLT_F have been changed to INTEGER(KIND=size_t).

#### Other New Features

Parallel I/O support:

- Parallel I/O support has been enhanced to allow collective I/O on point selections.

#### Thread safety (Windows only)

- The thread-safe HDF5 library no longer leaks thread-local storage resources on Windows with Win32 threads. This cleanup can only be performed when the library is built as a shared library, so a thread-safe HDF5 static library with Win32 threads is no longer supported.
  This change affects only Windows environments.

Also see Build and Configuration below.

#### Command-line Tools with Changed Behavior

h5repack

h5repack has been updated to correctly handle dynamically loaded filters.

### Build and Configuration

#### Thread safety

When configuring a thread-safe HDF5 Library with `--enable-threadsafe`, it is no longer necessary to specify `--with-pthreads` if the Pthreads library is in a standard location.

#### Removed Functions and Wrappers

The MPI-POSIX driver has been removed. The following C functions and the corresponding Fortran subroutines and C++ wrappers therefore are no longer included in the HDF5 distribution:

- H5Pset_fapl_mpiposix
- H5Pget_fapl_mpiposix

Applications performing parallel I/O should use the MPI-IO driver, H5Pset_fapl_mpio.

## Release 1.8.12 of November 2013 versus Release 1.8.11

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.11 to Release 1.8.12.

### New and Changed Functions, Classes, Subroutines, Wrappers, and Macros

#### In the C Interface (main library)

The following C functions have been modified:

- H5Zunregister now checks for open objects using a filter before allowing the filter to be unregistered.
- H5Dscatter and H5Dgather signatures have changed slightly. The src_buff parameter type is now `const void *` (previously: `void *`).

#### In the C++ Interface

The following new C++ class has been added:

- `H5::H5Location` The class H5::H5Location has been added as a base class of H5File and H5Object. It represents the location concept in the C library, where an identifier of an HDF5 object or an HDF5 file being passed in as a loc_id parameter.

The following member functions and their overloaded versions have been moved from various subclasses into the base class H5Location:

- createAttribute()
- openAttribute()
- attrExists()
- renameAttr()
- removeAttr()
- flush()
- getFileName()
- getNumAttrs()
- getObjType()
- iterateAttrs()
- setComment()
- getComment()
- removeComment()
- reference()
- dereference()
- getRegion()

The following wrappers for C functions have been added:

- `H5Location::getRefObjType` - Retrieves the type of the object that an object reference points to.
  Corresponding C function: H5Rget_obj_type2
- `H5Location::attrExists` - Determines whether an attribute with a given name exists.
  Corresponding C function: H5Aexists
- `H5Location::setComment` - Attaches a comment to an object.
  Corresponding C function: H5Oset_comment
  Two overloaded versions of H5Location::setComment have been added to take "." in place of the name of the object.

In the classes DataSet, DataType, and Group, the following constructors have changed as follows:
These constructors

- `DataSet(H5Object& obj, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`
- `DataSet(H5File& h5file, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`
- `DataSet(Attribute& attr, const void* ref, H5R_type_t ref_type = H5R_OBJECT);` have changed to
- `DataSet(const H5Location& loc, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`
- `DataSet(const Attribute& attr, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`

These constructors

- `DataType(H5Object& obj, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`
- `DataType(H5File& h5file, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`
- `DataType(Attribute& attr, const void* ref, H5R_type_t ref_type = H5R_OBJECT);` have changed to
- `DataType(const H5Location& loc, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`
- `DataType(const Attribute& attr, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`

These constructors

- `Group(H5Object& obj, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`
- `Group(H5File& h5file, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`
- `Group(Attribute& attr, const void* ref, H5R_type_t ref_type = H5R_OBJECT);` have changed to
- `Group(const H5Location& loc, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`
- `Group(const Attribute& attr, const void* ref, H5R_type_t ref_type = H5R_OBJECT);`

#### New Command-line Tool Options and Option Parameters

h5dump

h5dump has a new option for identifying objects by a full or partial path:

- `-NP`
- `--any-path=P`

The h5dump attributes-only option, `-A or --only-attr`, now accepts an optional parameter value of 0 (zero):

- `-A 0`
- `--only-attr=0` Specifying this value has the effect of reversing the role of the option to display everything except attributes.

h5repack

The h5repack option `-f, --filter` has a new parameter, UD, to enable the use of user-defined filters:

- `-f UD=<filter_parameters>`
- `--filter=UD=<filter_parameters>`

h5stat

h5stat has three new options for setting print thresholds: For attributes:

- `-aN`
- `--attribute=N`

For links in a group:

- `-lN`
- `--links=N`

For dimension sizes:

- `-mN`
- `--dims=N`

### Build and Configuration

#### CMake and Autotools configuration

A new configuration option can be used to change the default plugin path:

- Autotools configure option `--with-default-plugindir=location`
- CMake option -DH5_DEFAULT_PLUGINDIR:PATH=location

CMake configuration

- CMake builds of HDF5 now create *.so.{lt_version} files with the same version as configure.

Autotools configure flag

- The configure flag FFLAGS has been renamed to FCFLAGS.

Compile Scripts with Changed Behavior

- h5cc and h5pcc
- h5c++
- h5fc and h5pfc

These compile scripts have been modified to change the default behavior to link to shared libraries in environments where HDF5 has been configured with `--disable-static`.

Command-line Tools with Changed Behavior h5dump

h5dump output now displays USER_DEFINED_FILTER where it previously displayed UNKNOWN_FILTER.

h5dump now correctly exports subsetted data to a file using the `-o, --output` option.

## Release 1.8.11 of May 2013 versus Release 1.8.10

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.10 to Release 1.8.11.

### New and Changed Functions and Subroutines

#### The following new high-level C function has been added

- H5DOwrite_chunk - This function writes a data chunk directly into a file, bypassing hyperslab selection, data conversion, and the filter pipeline. The user must be careful with the function and clearly understand the I/O process of the library. See Direct Chunk Write Function for additional information. H5DOwrite_chunk is the first function in HDF5 High Level Optimizations library.

#### The following new C functions have been added

- H5Dscatter and H5Dgather - These functions scatter data to and gather data from a selection within a memory buffer.

#### The following new Fortran subroutines have been added

Fortran90 subroutines:

- h5odecr_refcount_f
- h5oexists_by_name_f
- h5oget_comment_f
- h5oget_comment_by_name_f
- h5oincr_refcount_f
- h5oopen_by_idx_f
- h5oset_comment_f
- h5oset_comment_by_name_f

h5oclose_f was introduced in HDF5 Release 1.8.8 but remained undocumented until this release.

Fortran2003 subroutines:

- h5oget_info_f
- h5oget_info_by_idx_f
- h5ovisit_by_name_f

#### New Feature: Dynamically Loaded Filters

HDF5 now detects and dynamically loads external filters, reducing the need for an application to register custom filters or for a developer building on HDF5 to compile a custom filter into a customized HDF5 distribution.

See HDF5 Data Pipeline Dynamically Loaded Filters for further information.

#### New Command-line Tool Option

h5dump and h5import

h5dump has a new option to output the DDL structure of a file or object:

- `-O<filename>`
- `--ddl=<file_name>` [-O above is dash-uppercase-o.]

h5import can now take the output of `h5dump -O<ddl_filename> -o<data_filename>` directly as input files. See Export from h5dump and Import into HDF5.

#### New Configuration and Build Tool

- cmakehdf5 - This new build command script is similar to buildhdf5 and is available in\ the bin/ directory of the distributed source code.
- For HDF5, the CMake minimum is now 2.8.10.

#### Function, Subroutines, and Feature with Changed Syntax or Behavior

The return value of the following high-level C function has changed:

- H5DSget_scale_name - This function has been changed to not include the NULL terminator in the returned size of of the dimension scale name (bug fix).

#### In the Fortran subroutines

- h5pset_external_f and h5pget_external_f - the type of the offset parameter has changed to INTEGER(KIND=OFF_T) to support 8-byte integers, matching the C type definition of off_t.
- The HDF5 Library now supports data conversion from enumeration to integer and floating-point numeric datatypes.

#### Command-line Tools with Changed Behavior

h5diff - When comparing two files or objects, h5diff now recognizes a unique extra attribute attached to an object as a difference and returns with an exit code of 1. Previously, h5diff did not recognize the extra attribute as a difference.

h5ls - The content of the `h5ls --help` output has been revised.

h5dump - has been updated to display the compression ratio for user-defined filters. In h5dump output, UNKNOWN_FILTER has been changed to USER_DEFINED_FILTER.

#### Removed Functions and Wrappers

The following C functions and the corresponding C++ wrappers have been removed:

- `H5Pset_dxpl_multi`
- `H5Pget_dxpl_multi`
- `H5::DSetMemXferPropList:setMulti`
- `H5::DSetMemXferPropList:getMulti`

## Release 1.8.10 of November 2012 versus Release 1.8.9

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.9 to Release 1.8.10.

### New and Changed Functions and Subroutines

#### The following new C function has been added

- H5Pget_mpio_no_collective_cause

The following new Fortran subroutine has been added:

- h5pget_mpio_actual_io_mode_f

The syntax of the following high-level C function has changed:

- H5TBAget_fill - This function's return type has been changed to h5tri_t. A return value of 1 indicates that a fill value is present, 0 indicates that no fill value is present, and a negative value indicates an error. (The former return type was herr_t.) Note that H5TBAget_fill and a companion function H5TBAget_title, both in the HDF5 Table (H5TB) high-level API, are undocumented. These functions will be added to the HDF5 Reference Manual shortly after HDF5 Release 1.8.10.

Changed Command-line Tool h5import has been updated to accept an input file created by h5dump.

## Release 1.8.9 of May 2012 versus Release 1.8.8

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.8 to Release 1.8.9.

### New and Changed Functions

A new high level C function and Fortran subroutine were added to HDF5 Lite (H5LT) to determine whether an HDF5 path is correct and resolves to a valid HDF5 object:

- h5LTpath_valid
- h5ltpath_valid_f

The new file image operations feature consists of the following functions and their associated callbacks, struct, and ENUM. This feature enables an application to load a file into memory (as a file image) and to operate on that file image without the overhead of disk I/O. This feature provides the following functions:

- H5LTopen_file_image
- H5Fget_file_image
- H5Pset_file_image
- H5Pget_file_image
- H5Pset_file_image_callbacks
- H5Pget_file_image_callbacks

For the callbacks, struct, and ENUM, see H5Pset_file_image_callbacks. Use of this feature is described in HDF5 File Image.

The following functions were modified or added to the HDF5 Library to allow an application to control the operation of copying committed datatypes with H5Ocopy:

#### Function with changed interface

- H5Pset_copy_object - New flag for use with H5Pset_copy_object:
  H5O_COPY_MERGE_COMMITTED_DTYPE_FLAG

Function with changed behavior:

- H5Ocopy - This function's behavior is changed, but only with the use of the new flag, H5O_COPY_MERGE_COMMITTED_DTYPE_FLAG.

New functions and callback function:

- H5Pset_mcdt_search_cb
- H5Pget_mcdt_search_cb
- H5O_mcdt_search_cb_t
- H5Padd_merge_committed_dtype_path
- H5Pfree_merge_committed_dtype_paths Use of this capability is described in Copying Committed Datatypes with H5Ocopy.

The following C functions and Fortran subroutines were added to provide a mechanism to ensure sequential consistency in parallel environments using MPI I/O:

- H5Fset_mpi_atomicity
- H5Fget_mpi_atomicity
- h5fset_mpi_atomicity_f
- h5fget_mpi_atomicity_f

The following function was added at Release 1.8.5 but was not documented at that time. It is mentioned here for those who may have missed its introduction:

- H5Oexists_by_name

#### New Fortran Subroutines

The following Fortran subroutines have been added in this release:

- h5ltpath_valid_f
- h5ocopy_f
- h5fset_mpi_atomicity_f
- h5fget_mpi_atomicity_f

Where a subroutine is part of a new HDF5 feature, that feature is described above.

#### Fortran Subroutine with Changed Behavior

The content of the buffer returned by the following Fortran subroutine has changed as noted:

- h5ltget_attribute_string_f - If the returned buffer requires padding, h5ltget_attribute_string_f now employs space padding; this buffer was previously returned with a C NULL terminator.

#### Command-line Utilities with New Options and/or Changed Behavior

h5repack has one new option and improved performance under certain circumstances:

- `-Mn, --metadata_block_size=n` Sets the metadata block size in the output file. Performance is improved when repacking large chunked datasets (for example, when dataset size exceeds 128 MB).

h5stat has one new option:

- `-S, --summary` Displays a summary of file space usage for a file.

h5dump has one new option, a new capability, and updated output:

- `--no-compact-subset` Disables compact subsetting to allow the left-hand square bracket character ( `[` ) in a dataset name.
- The files parameter now accommodates wildcards. With this change, h5dump command-line options can be applied across multiple files without listing the files individually.

h5dump output has been updated for this release to improve compliance with the HDF5 DDL specification and to improve readablilty. This output is now fully compliant with the HDF5 DDL specification, but these changes may affect some user scripts:

- Whitespace has been modified.
- Display errors, such as misplaced brackets, have been fixed.
- When printing superblock content, user block content is now properly displayed within the superblock.

## Release 1.8.8 of November 2011 versus Release 1.8.7

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.7 to Release 1.8.8.

### New C Functions

Two new parallel I/O functions enable an application to query whether or how a collective I/O operation actually completed:

- H5Pget_mpio_actual_chunk_opt_mode
- H5Pget_mpio_actual_io_mode

#### Updated Fortran Interface, including Fortran 2003 Features

The HDF5 Fortran interface has been extended and upgraded to Fortran 2003 for this release.

See Configure and Build Changes below for the configure options to use when building HDF5 with Fortran 2003 enabled.

Features enabled in this upgrade are described in New Features in the HDF5 Fortran Library:

- Adding Support for the Fortran 2003 Standard (PDF only). In general, the links below are to technical descriptions (reference manual entries, for example) of specific interfaces.

Terminology:

- If the Fortran compiler in use is Fortran 2003 compliant and the installed HDF5 Library was configured using both the `--enable-fortran` and `--enable-fortran2003` flags, the resulting HDF5 Fortran Library is referred to below as a Fortran 2003 environment. Without either of the Fortran 2003 compliant compiler or the `--enable-fortran2003` flag, the resulting HDF5 Fortran Library is referred to below as a Fortran 90 environment.

#### New Fortran 2003-only subroutines

New subroutines available only in Fortran 2003 environments:

- h5dvlen_reclaim_f
- h5eset_auto_f
- h5literate_by_name_f
- h5literate_f
- h5ovisit_f
- h5oget_info_by_name_f
- h5tconvert_f

#### Subroutines with Fortran 90 versions and extended features in Fortran 2003 environments

Subroutines in this section have extended support in Fortran 2003 environments, but are new or unchanged in Fortran 90 environments.

All existing Fortran 90 subroutines, including those not mentioned below, are available in both Fortran 90 and Fortran 2003 environments.

Subroutines with support for the derived type C_PTR in Fortran 2003 environments:

- h5pget_f
- h5pget_fill_value_f
- h5pinsert_f
- h5pregister_f
- h5pset_f
- h5pset_fill_value_f
- h5rcreate_f
- h5rdereference_f
- h5rget_name_f
- h5rget_object_type_f

Subroutines with support for the derived type C_PTR and a changed signature in Fortran 2003 environments:

- h5aread_f
- h5awrite_f
- h5dread_f
- h5dwrite_f

Subroutine with additional optional parameters in Fortran 2003 environments:

- h5pcreate_class_f

#### New and updated Fortran 90 subroutines

New Fortran 90 subroutines:

- h5pset_nbit_f
- h5pset_scaleoffset_f

Updated Fortran 90 subroutines:

- h5open_f
- h5close_f - has been modified in this release to close only the HDF5 Fortran Library interface; it no longer closes the underlying HDF5 Library.
- h5check_version_f
- h5get_libversion_f
- h5garbage_collect_f
- h5dont_atexit_f

#### New Fortran utility functions and derived types

New Fortran utility functions:

- `h5offsetof` Available only in Fortran 2003 environments.
- h5kind_to_type Available in either Fortran environment.

New Fortran derived types in Fortran 2003 environments:

- hvl_t Described in New Features.
- h5o_info_t See h5ovisit_f.

#### New high level Fortran interface

New Fortran subroutines in the HDF5 Dimension Scale high-level interface, H5DS:

- h5dsset_scale_f
- h5dsattach_scale_f
- h5dsdetach_scale_f
- h5dsis_attached_f
- h5dsis_scale_f
- h5dsset_label_f
- h5dsget_label_f
- h5dsget_scale_name_f
- h5dsget_num_scales_f

These subtroutines are available in both Fortran 90 and Fortran 2003 environments.

#### C Functions with Changed Capability

- H5Tcreate now supports fixed-length and variable-length string types.

#### Driver Changes on Windows Systems

Changed behavior:

- HDF5's Windows driver has been modified in this release to be a wrapper of the POSIX-compliant SEC2 driver. This change should be transparent to all user applications.

New default driver:

- As of this release, the default driver on Windows systems is changed to SEC2; it had previously been the Windows driver. If you wish to use the Windows driver in an application, it remains fully available. In such cases, the driver must be set explicitly with a H5Pset_fapl_windows call.

#### Command-line Utilities with Changed Behavior

- h5jam now checks the file that is to be inserted into the user block and does not allow the insertion if it is an HDF5 file. This is necessary because an HDF5 file in the user block will make the original HDF5 portion of the file inaccessible.
- h5diff with the `--delta` option reports two NaN values as equal regardless of the type of NaN (as described in the reference manual entry).
- h5diff, when comparing a file to itself, now reports no differences.

### Configure and Build Changes

configure now uses the same flags and symbols in its tests as are used to build the library.

To build HDF5 with the Fortran 2003 interfaces requires the use of two configure options:

- `--enable-fortran`
- `--enable-fortran2003`

Note that building the Fortran 2003 interfaces requires a Fortran 2003-capable compiler and that `--enable-fortran2003` cannot be used alone.

The `--enable-h5dump-packed-bits` configure option has been removed. The code that this option enabled is now always compiled into h5dump.

When building on Linux systems, the HDF5 Library now links with the bsd_compat library.

#### Parallel Library and Configuration Changes

The parallel HDF5 library now always compiles code to take advantage of MPI functionalities that allow for the use of complex derived datatypes during IO and that allow for collective IO when one or more processes do not contribute to the operation.

This was previously conditionally compiled into the library and controlled by configure via the `hdf5_cv_mpi_special_collective_io_works` and `hdf5_cv_mpi_complex_derived_datatype_works` cache values. These values were preset in the `config/*` files based on the compiler and/or system or could be set on the configure line. Support for these cache values has been removed and they no longer have an effect on the compilation of the use of these MPI functionalities.

## Release 1.8.7 of May 2011 versus Release 1.8.6

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.6 to Release 1.8.7.

### New C Functions and Macros

Three new functions enable the caching of files opened through external links. This cache can improve the performance of external links in heavy use cases:

- H5Pset_elink_file_cache_size
- H5Pget_elink_file_cache_size
- H5Fclear_elink_file_cache

Two new macros enable compile-time inclusion or exclusion of code depending on the version of the HDF5 Library against which an application is to be linked:

- H5_VERSION_GE
- H5_VERSION_LE

#### C Functions with Changed Capability

- H5Tcommit1
- H5Tcommit2
- H5Tcommit_anon - HDF5 has long blocked creating a dataset or attribute with such a datatype.

HDF5 now allows the size of any dataspace dimension to be 0 (zero). This was previously allowed only if the maximum size of the dimension was unlimited. Though their signatures have not changed, the range of valid parameter values is affected for the following functions:

- H5Screate_simple
- H5Sset_extent_simple
- H5Pset_external

Note that no data can be written to a dataset in which the size of any dimension is set to zero.

In the logging file driver, implementation of the following flags has been completed:

- H5FD_LOG_TIME_OPEN
- H5FD_LOG_TIME_READ
- H5FD_LOG_TIME_WRITE
- H5FD_LOG_TIME_SEEK

Two new flags have been added:

- H5FD_LOG_NUM_TRUNCATE
- H5FD_LOG_TIME_STAT

- H5Pset_fapl_log - HDF5 now blocks committing a datatype that cannot hold any data. This currently includes compound datatypes with no fields and enumerated datatypes with no members.

#### Fortran Subroutines with Changed Capability

Several `h5ltmake_dataset*_f` and `h5ltread_dataset*_f` subroutines have been modified to allow them to create or read arrays of up to seven dimensions. They had previously been limited to three dimensions.

- h5ltmake_dataset_f
- .h5ltmake_dataset_int_f
- .h5ltmake_dataset_float_f
- h5ltmake_dataset_double_f
- h5ltread_dataset_f
- h5ltread_dataset_int_f
- h5ltread_dataset_float_f
- h5ltread_dataset_double_f
- h5tbget_field_info_f has a new maxlen_out parameter. This parameter is optional.

#### Command-line Utilities with New Options

h5diff has a new verbose with levels option to display additional attribute information:

- `-vn, --verbose=n`

h5dump has one new option to enable reporting of the HDF5 Library's error stack:

- `--enable-error-stack`

#### Command-line Utility with Changed Option Name

h5ls has one changed option name:

- `--enable-error-stack` replaces `--error`. The `--error` option is deprecated but remains available.

#### Command-line Utilities with Changed Behavior

Attribute comparison with h5diff has been corrected to compare all attributes with common names when comparing objects. Previously, h5diff compared attributes correctly only when two objects had the same number of attributes and all attribute names were identical; if there was either a value or name difference between two attributes, subsequent attributes were not compared.

h5diff `--use-system-epsilon` now employs the formula `'|a - b|'` instead of `'|a - b| / b'`.

h5copy now accepts the same file as the source and target file; this enables object copying within a file.

h5dump now displays reference types as described in DDL in BNF for HDF5:

- `H5T_REFERENCE {H5T_STD_REF_OBJ}` - Object reference
- `H5T_REFERENCE {H5T_STD_REF_DSETREG}` - Dataset region reference

#### Configure and Build Changes

Configure now generates Makefiles that build in silent make mode by default. In this mode, compile and link lines are significantly simplified for clarity. You can opt out of this default with either of the following approaches:

- Use the `--disable-silent-rules` flag at configure time to override the default and view actual compile and link lines during the build.
- Use the make command with the `V=1` option to run a verbose make.

The new configure option `--enable-unsupported` can be used to stop configure from preventing the use of unsupported configure option combinations. For example, use of this option enables building HDF5 with the unsupported and untested configurations of C++ in a parallel environment or Fortran with a threadsafe library. `WARNING: Use --enable-unsupported at your own risk! This option may result in a library that does not compile or does not run as expected.`

#### Parallel HDF5

mpicc and mpif90 are now the default C and Fortran compilers on Linux systems when `--enable-parallel` is specified but no $CC or $FC is defined.

## Release 1.8.6 versus Release 1.8.5, February 2011

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.5 to Release 1.8.6.

#### C Functions with Additional Capability

H5Tset_order and H5Tget_order can now be used with all datatypes. See the related note regarding H5T_ORDER_MIXED immediately below.

ENUM with New Member H5T_order_t, an ENUM used to set or indicate datatype endianness, includes a new member:

- H5T_ORDER_MIXED

The function H5Tget_order returns this value when called on a compound datatype whose members are not all of the same endianness.

#### Command-line Utilities with New Options

h5diff has one new option:

- `--exclude-path`

h5ls and h5diff have two new options:

- `--follow-symlinks`
- `--no-dangling-links`

#### Command-line Utilities with Changed Behavior

- h5diff now compares member objects and groups recursively when two files or groups are specified to be compared.
- h5ls now displays object and attribute names exactly as stored in the file rather than interpreting them for output. For example, if an attribute is named `\ttemp` in the file, h5ls will output that name as `\ttemp` rather than converting the leading `\t` to a tab.
- h5repack can now convert a dataset to compact layout.

#### Compiler Script Arguments and Environment Variables

h5cc, h5fc, h5c++, h5pcc, and h5pfc arguments have been expanded to enable the user to add compiler and linker flags that will take precedence over the flags from the HDF5 build.

The arguments CPPFLAGS, CFLAGS, LDFLAGS, and LIBS have been duplicated with the prefix H5BLD_ to put the flags and paths from the HDF5 build in the correct places and to allow the script user to add entries in CPPFLAGS, CFLAGS, LDFLAGS, and LIBS that will take precedence over those from the HDF5 build. Changes to these entries can be made persistent by editing CFLAGSBASE, CPPFLAGSBASE, LDFLAGSBASE, and LIBSBASE near the top of the script. If the change is to be temporary, the user can set HDF5_CFLAGS, HDF5_CPPFLAGS, HDF5_LDFLAGS, or HDF5_LIBS in the environment.

The new order of arguments for these scripts is as follows:

- `$CLINKER`
- `$H5BLD_CPPFLAGS`
- `$CPPFLAGS`
- `$H5BLD_CFLAGS`
- `$CFLAGS`
- `$LDFLAGS`
- `$clibpath`
- `$link_objs`
- `$LIBS`
- `$link_args`
- `$shared_link`

#### Thread Safety on Windows

This release adds support for thread safety on Windows using the Windows threads library. See the file RELEASE.txt in the distributed HDF5 source code (hdf5/release_docs/RELEASE.txt) for details.

#### Parallel HDF5

The Parallel HDF5 build process has changed to use mpiexec instead of mpirun.

## Release 1.8.5 versus Release 1.8.4, June 2010

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.4 to Release 1.8.5.

### New C Function

The following function was added to the HDF5 Library at this release, but was not documented at that time:

- H5Oexists_by_name (This note added in November 2011, shortly following Release 1.8.8.)

#### C Functions with Additional Capability

The following functions have been modified to accommodate filters set on a group creation property list:

- H5Pall_filters_avail
- H5Pget_filter1
- H5Pget_filter2
- H5Pget_filter_by_id1
- H5Pget_filter_by_id2
- H5Pget_nfilters
- H5Pmodify_filter
- H5Premove_filter
- H5Pset_deflate
- H5Pset_filter
- H5Pset_fletcher32

Related to H5Zregister, the calling protocol for the `can_apply` and `set_local callback` functions has been extended to accommodate the use of filters on group creation property lists.

#### New C++ Member Function and Overloaded Member Functions

The following C++ member function is new in this release:

- `size_t DataSet::getInMemDataSize` - To simplify getting a dataset's data size in memory.

The overloaded forms of the following C++ member functions are new in this release:

- `CommonFG::getObjnameByIdx` - Overloaded to take `char*` for name.
- `CommonFG::getObjTypeByIdx` - Overloaded to return type name as `char*`.

#### Command-line Utility with New Options

h5diff has two new options:

- `--follow-links`
- `--no-dangling-links`

#### Fortran Subroutines with Changed Interface

The link type parameter values associated with the following Fortran subroutines have changed in this release:

- h5lget_info_f
- h5lget_info_by_idx_f

Valid values for the parameter link_type have changed to the following:

- H5L_TYPE_HARD_F
- H5L_TYPE_SOFT_F
- H5L_TYPE_EXTERNAL_F
- H5L_TYPE_ERROR_F

These values previously began with the string `H5L_LINK_`.

#### CMake

This release includes an adaptation enabling HDF5 builds with CMake. This early-stage adaptation is distributed to provide an opportunity for early access and experimentation; the CMake-related files should not be viewed as final and may change before the next release.

While the initial development effort has been focused on Microsoft Windows platforms, the HDF5 Library has been successfully built with CMake on Linux and Mac OS X.

See the file CMake.txt in the distributed HDF5 source code (hdf5/release_docs/CMake.txt) for details.

## Release 1.8.4 versus Release 1.8.3, November 2009

This section lists interface-level changes and other user-visible changes in behavior in the transition from HDF5 Release 1.8.3 to Release 1.8.4.

#### Embedded HDF5 Library Settings Information

Library settings are now embedded in an HDF5 executable so that an "orphaned" executable can be queried (via the Unix strings command, for example) to display the library settings used to build it. The embedded settings information is the same as that normally found in the libhdf5.settings file.

This capability may be disabled with the use of the `--disable-embedded-libinfo` flag during configure.

### New and Changed Functions

#### New Fortran Subroutine and Constant

The following Fortran subroutine is new in this release:

- h5oopen_by_addr_f - The following Fortran constant, corresponding to the C constant H5T_ORDER_NONE, has been added in this release: H5T_ORDER_NONE_F

#### New C++ Member Functions

New C++ member functions are provided to determine a dataset's or attribute's data size in memory:

- `size_t DataSet::getInMemDataSize() const`
- `size_t Attribute::getInMemDataSize() const`

The size in each case is in bytes.

#### Function with Changed Interface or Behavior

- H5check_version now displays embedded library information (see above) if a version mismatch is detected.

The function has also been changed to suppress the warning message entirely if `$HDF5_DISABLE_VERSION_CHECK` is set to 2 or higher.

#### Fortran Subroutines with Changed Syntax

The following Fortran subroutines have changed syntax in this release:

- h5lget_info_f - The type of the parameter address has changed from INTEGER to INTEGER(HADDR_T). (This note added on 13 January 2010.)
- h5lget_info_by_idx_f - `h5lget_info_by_idx_f (loc_id, group_name, index_field, order, n, &link_type, f_corder_valid, corder, cset, address, val_size, &hdferr, lapl_id)` - The parameters link_type, address, and val_size have been added; the parameter data_size has been removed.

#### Tools with Changed Interface or Behavior

h5diff has one new option:

- `--use-system-epsilon` - With this option, h5diff returns a difference if and only if the difference between two data values exceeds the system value for epsilon (that is, if `|a-b| > epsilon`).
  The tool's default behavior has also changed; without this option, the tool now checks for strict equality. Prior default behavior was to use an epsilon internally defined in HDF5.
  This option has no short form.

h5dump has one new option and the behavior of another set of options has changed:

- `-R or --region` - With this option, h5dump prints the data pointed to by a region reference. Without this option, h5dump prints only the reference.

Usage of the subsetting parameters has changed. All of `START`, `STRIDE`, `COUNT`, and `BLOCK` now have default values. If those defaults are satisfactory, h5dump no longer requires that all four be specified when subsetting a dataset.

#### Changed Library Configuration

The following configuration flag is new with this release:

- `--disable-embedded-libinfo` - This flag disables the embedding of HDF5 Library settings in an HDF5 executable.

## Release 1.8.3 versus Release 1.8.2, May 2009

This section lists API-level changes and changes in behavior in the transition from HDF5 Release 1.8.2 to Release 1.8.3.

### New Functions

#### C functions

The following C functions are new for this release and are documented in the HDF5 Reference Manual.

- H5Pset_elink_cb - Sets the user-defined function for traversing external links.
- H5Pget_elink_cb - Retrieves the user-defined function for traversing external links.
- H5Pset_elink_acc_flags - Sets the flags for accessing external links.
- H5Pget_elink_acc_flags - Retrieves the flags for accessing external links.
- H5Pset_chunk_cache - Sets the chunk cache parameters.
- H5Pget_chunk_cache - Retrieves the chunk cache parameters.
- H5Dget_access_plist - Returns a copy of the dataset access property list.
- H5Iis_valid - Determines whether an identifier is valid.

#### Fortran Subroutines

The following subroutines are new in this release:

- h5dget_access_plist_f
- h5iis_valid_f
- h5pset_chunk_cache_f
- h5pget_chunk_cache_f

#### Function with Changed Behavior

- H5set_free_list_limits

The HDF5 Library now dynamically creates separate factory free lists to manage blocks of a fixed size; these blocks were previously managed within the blockfree lists. Factory free lists use the same settings as specified in H5set_free_list_limits for block free lists.

While the API has not changed, users may see both a performance boost and increased memory usage.

#### Tools with Changed Interface or Behavior

h5diff default behavior is now to detect and compare NaNs. Use the `-N` or `--nan` option (below) to turn this behavior off and avoid the performance penalty that NaN detection and comparison entalis. (NaN detection and comparison became the default in in HDF5 Release 1.6.8.)

This tool has two new options:

- `-c, --compare` Lists objects that are not comparable.
- `-N, --nan` Avoids NaNs detection.

h5dump now correctly specifies an XML DTD or a schema URL.

h5dump binary output now defaults to NATIVE.

- The new `-b, --binary` option can be used to specify alternate binary formats.

h5repack - When a user does not specify a chunk size, h5repack now defines the default chunk size to be the same same as the size of the hyperslab used to read the chunks.

## Release 1.8.2 versus Release 1.8.1, November 2008

This section lists API-level changes and changes in behavior in the transition from HDF5 Release 1.8.1 to Release 1.8.2.

### New Functions

#### C functions

The following C functions are new for this release and are documented in the HDF5 Reference Manual.

- H5Pset_elink_fapl - Sets the file access property list for external link traversal.
- H5Pget_elink_fapl - Retrieves the file access property list identifier for the external link access property list.

#### Fortran Subroutine

The following subroutine is new in this release:

- h5tget_native_type_f

#### New C++ Wrappers

A number of C++ wrappers were added/removed. See RELEASE.txt for details.

#### Functions with Changed Syntax

The following function syntaxes have changed; the affected return values and parameter are noted as underscored red text.

#### C functions

- H5Fget_obj_count - Returns ssize_t
- H5Fget_obj_ids - Returns ssize_t

#### Changed Fortran Subroutines

The optional parameter mounted has been added to the following subroutines:

- h5gget_info_f
- h5gget_info_by_idx_f
- h5gget_info_by_name_f

Changed Data Structure

- H5G_info_t - A mounted filed has been added to the H5G_info_t struct.

#### Tools with Changed Interface or Behavior

- h5diff now returns 1 if the files differ in structure, i.e., if the file graphs differ by any object.
  The tool's error return code has been changed to 2.

- h5repack and h5diff
  The standard command-line syntax of both tools has been changed to parallel that of h5dump. The new syntax of each is as follows:
  `h5repack [OPTIONS] file1 file2`
  `h5diff [OPTIONS] file1 file2 [object1 [object2]]`

In each case, the old syntax remains available (though undocumented) to avoid breaking existing scripts.

h5repack - The following new options control the addition of user block data to an existing HDF5 file:

- `-u U, --ublock=U` - Specifies the name of the file containing the user block data to be added.
- `-b B, --block=B` - Specifies the size of the block to be added.

The following new options set parameters governing the tool's use of H5Pset_alignment:

- `-t T, --threshold=T` - Specifies the threshold value for H5Pset_alignment.
- `-a A, --alignment=A` - Specifies the alignment value for H5Pset_alignment.

h5repack

- now supports multiple instances of the `'-f'` or `'--filter'` option, allowing the use of multiple I/O filters with an object.
- With no change in the command-line syntax, h5repack now retains an existing userblock when repacking an HDF5 file.

h5import

- The floating point format flag TEXTFPE, for scientific notation, has been deprecated. The flag TEXTFP, which accepts scientific notation, should be used instead.

h5import

- now imports string data with the STR keyword in the INPUT-CLASS configuration field.

h5dump and h5ls

- These tools now traverse external links when performing recursive traversals.

h5dump

- Binary output now defaults to NATIVE with the `'-b'` option, optionally accepting NATIVE, FILE, BE, and LE.
- The new `'-m T'` or `'--format T'` option enables a user-defined formatting string for printing floating-point numbers.

With no change in the command-line syntax, h5dump now prints a compression ratio when compression filters are in use.

#### Deprecated Functions

The following functions are deprecated as of this release:

- H5Pset_preserve and H5Pget_preserve - The original role of these functions is now part of the core HDF5 Library functionality.

#### Changed File Installation

The file libhdf5_fortran.settings is no longer installed with the HDF5 Library; the original content of that file is now included in libhdf5.settings.

#### Changed Library Configuration

It is no longer necessary to manually set an SZIP library path in LD_LIBRARY_PATH when building HDF5 with shared SZIP libraries; configure will determine the correct path from the `--with-szlib` flag, prepending it to and exporting LD_LIBRARY_PATH.

Note that if an SZIP library path is set in a user-supplied LD_LIBRARY_PATH, in an existing script, for example, that does not necessarily need to be changed; configure will prepend the SZIP library path extracted from `--with-szlib` to the user-supplied LD_LIBRARY_PATH.

## Release 1.8.1 versus Release 1.8.0

HDF5 Release 1.8.1 is a minor release with several bugfixes and optimizations and limited new features.

The most significant new feature is an expanded set of Fortran90 APIs, enabling essentially all new C library features of Release 1.8.0.

### New Functions and Tools

#### C functions

There are no new C functions for Release 1.8.1.

#### Fortran subroutines

The following Fortran subroutines are new for Release 1.8.1 and are documented in the HDF5 Reference Manual. H5A

- h5acreate_f
- h5acreate_by_name_f
- h5adelete_by_idx_f
- h5adelete_by_name_f
- h5aexists_f
- h5aexists_by_name_f
- h5aget_create_plist_f
- h5aget_info_f
- h5aget_info_by_idx_f
- h5aget_info_by_name_f
- h5aget_name_by_idx_f
- h5aget_storage_size_f
- h5aopen_f
- h5aopen_by_idx_f
- h5aopen_by_name_f
- h5arename_f
- h5arename_by_name_f

H5D

- h5dcreate_anon_f
- h5dcreate_f
- h5dopen_f
- h5dset_extent_f

H5G

- h5gcreate_anon_f
- h5gcreate_f
- h5gget_create_plist_f
- h5gget_info_f
- h5gget_info_by_idx_f
- h5gget_info_by_name_f
- h5gopen_f

H5L

- h5lcopy_f
- h5lcreate_external_f
- h5lcreate_hard_f
- h5lcreate_soft_f
- h5ldelete_f
- h5ldelete_by_idx_f
- h5lexists_f
- h5lget_info_f
- h5lget_info_by_idx_f
- h5lget_name_by_idx_f
- h5lmove_f

H5O

- h5olink_f
- h5oopen_f

H5P

- h5pget_attr_creation_order_f
- h5pget_attr_phase_change_f
- h5pget_char_encoding_f
- h5pget_copy_object_f
- h5pget_create_inter_group_f
- h5pget_data_transform_f
- h5pget_elink_prefix_f
- h5pget_est_link_info_f
- h5pget_fapl_direct_f
- h5pget_link_creation_order_f
- h5pget_link_phase_change_f
- h5pget_local_heap_size_hint_f
- h5pget_nlinks_f
- h5pget_obj_track_times_f
- h5pget_shared_mesg_index_f
- h5pget_shared_mesg_nindexes_f
- h5pset_attr_creation_order_f
- h5pset_attr_phase_change_f
- h5pset_char_encoding_f
- h5pset_copy_object_f
- h5pset_create_inter_group_f
- h5pset_data_transform_f
- h5pset_elink_prefix_f
- h5pset_est_link_info_f
- h5pset_fapl_direct_f
- h5pset_libver_bounds_f
- h5pset_link_creation_order_f
- h5pset_link_phase_change_f
- h5pset_local_heap_size_hint_f
- h5pset_obj_track_times_f
- h5pset_nbit_f
- h5pset_nlinks_f
- h5pset_scaleoffset_f

H5R

- h5rget_name_f

H5S

- h5sdecode_f
- h5sencode_f
- h5sextent_equal_f

H5T

- h5tcommit_anon_f
- h5tcommit_f
- h5tcommitted_f
- h5tcompiler_conv_f
- h5tdecode_f
- h5tencode_f
- h5tget_create_plist_f
- h5topen_f

#### C++ wrappers

There are no new C++ wrappers for Release 1.8.1.

#### Functions and Tools with Changed Syntax

C functions with changed syntax:

There are no C functions with changed syntax in Release 1.8.1.

Fortran subroutines with changed syntax:

In the following Fortran subroutines, spos is a new parameter indicating the position of the sign bit:

- `h5tset_fields_f(type_id, spos, epos, esize, mpos, msize, hdferr)`
- `h5tget_fields_f(type_id, spos, epos, esize, mpos, msize, hdferr)`

Changed C++ wrappers:

- The class AbstractDS was moved out of H5Object.
- The class Attribute now multiply inherits from IdComponent and AbstractDs.
- The class DataSet now multiply inherits from H5Object and AbstractDs.

In addition, data member `IdComponent::id` was moved into subclasses:

- Attribute
- DataSet
- DataSpace
- DataType
- H5File
- Group
- PropList

`IdComponent::dereference` was incorrect;
it was changed from:

- `void IdComponent::dereference(IdComponent& obj, void* ref)`

to:

- `void H5Object::dereference(H5File& h5file, void* ref)`
- `void H5Object::dereference(H5Object& obj, void* ref)`

Tools with changed syntax:

- The command-line syntax of h5repack was changed in Release 1.8.0 to the following:
  `h5repack [OPTIONS] in_file out_file`
- Since this would be incompatible with existing user scripts, the original syntax has be re-enabled in this release:
  `h5repack -i in_file -o out_file [OPTIONS]`
- h5repack now understands either syntax.

An h5repack option to set the minimum number of links in indexed format was introduced in Release 1.8.0 as:

- `-d min_indexed_links`
- `--indexed=min_indexed_links`.

In Release 1.8.1, the `-i` form has been changed to `-d` as follows:

- `-d min_indexed_links`
- `--indexed=min_indexed_links`

The command-line syntax of h5diff was changed in Release 1.8.0 to the following:

- `h5diff [OPTIONS] file1 file2 [object1 [object2 ] ]`

Tools with new options h5dump

- `-m T` or `--format T` - Sets format of floating point output

#### Changed Behavior or Output

Changed library behavior:

- A 4GB limit on the size of dataset chunks is now properly enforced when a dataset is created.
- The HDF5 Library now works more effectively with external links. Some valid external links that previously failed will now be properly recognized. See H5Lcreate_external.

C functions with changed behavior:

- The behavior of H5Lcreate_external has changed as described immediately above.

### Tools with changed output:

Tools with changed behavior and changed output:

- The `h5dump -p` option now prints the compression ratio if a compression filter is associated with a dataset.
- h5dump now supports external links, displaying the target objects (datasets, groups, and named datatypes).

### Changed Library Configuration

The following configuration flag is new with this release:

- `--disable-sharedlib-rpath`

### Removed Patch Requirement

The patch that was required for Cygwin with HDF5 Release 1.8.0 has been rolled into this release and no longer needs to be applied by the user.

## Release 1.8.0 versus Release 1.6.x

HDF5 Release 1.8.0 is a major release with several new features and a variety of bugfixes, optimizations, and portability enhancements.

See the document "What's New in HDF5 1.8.0" for a high-level overview of the new functionality in this release. The following pages assume a familiarity with that overview.

This section provides details of the API-level changes that have been made in the transition to HDF5 Release 1.8.0 from the Release 1.6.x series.

### API Compatibility Macros with Associated Renamed and New Functions

Release 1.8.0 introduces API compatibility macros designed to facilitate application migration. These macros are intended to facilitate developer management of a clean, step-by-step migration from an older HDF5 Library to the new release; they can also be used to enable older applications to use the new library without requiring that the application be rewritten. See API Compatibility Macros for a full description.

Macros are identified in reference manual function indexes by an italic typeface.

The new macros and the old and new functions to which they may be mapped are as follows:

Macro | Old Function | New Function
--- | --- | ---
H5Acreate | H5Acreate1 | H5Acreate2
H5Aiterate | H5Aiterate1 | H5Aiterate2
H5Dcreate | H5Dcreate1 | H5Dcreate2
H5Dopen | H5Dopen1 | H5Dopen2
H5Eclear | H5Eclear1 | H5Eclear2
H5Eget_auto | H5Eget_auto1 | H5Eget_auto2
H5Eprint | H5Eprint1 | H5Eprint2
H5Epush | H5Epush1 | H5Epush2
H5Eset_auto | H5Eset_auto1 | H5Eset_auto2
H5Ewalk | H5Ewalk1 | H5Ewalk2
H5Gcreate | H5Gcreate1 | H5Gcreate2
H5Gopen | H5Gopen1 | H5Gopen2
H5Pget_filter | H5Pget_filter1 | H5Pget_filter2
H5Pget_filter_by_id | H5Pget_filter_by_id1 | H5Pget_filter_by_id2
H5Pinsert | H5Pinsert1 | H5Pinsert2
H5Pregister | H5Pregister1 | H5Pregister2
H5Rget_obj_type | H5Rget_obj_type1 | H5Rget_obj_type2
H5Tarray_create | H5Tarray_create1 | H5Tarray_create2
H5Tcommit | H5Tcommit1 | H5Tcommit2
H5Tget_array_dims | H5Tget_array_dims1 | H5Tget_array_dims2
H5Topen | H5Topen1 | H5Topen2

(H5Dcreate and H5Dopen added to the above list in November 2010, prior to Release 1.8.6.)

### New Functions and Tools

C functions The following C functions are new for Release 1.8.0 and, unless otherwise noted, are documented in the HDF5 Reference Manual.

Recursive iteration

- H5Lvisit `herr_t H5Lvisit(hid_t group_id, H5_index_t index_type, H5_iter_order_t order, H5L_iterate_t op, void *op_data)`
- H5Lvisit_by_name `herr_t H5Lvisit_by_name(hid_t loc_id, const char *group_name, H5_index_t index_type, H5_iter_order_t order, H5L_iterate_t op, void *op_data, hid_t lapl_id)`
- H5Ovisit `herr_t H5Ovisit(hid_t group_id, H5_index_t index_type, H5_iter_order_t order, H5O_iterate_t op, void *op_data)`
- H5Ovisit_by_name `herr_t H5Ovisit_by_name(hid_t loc_id, const char *object_name, H5_index_t index_type, H5_iter_order_t order, H5O_iterate_t op, void *op_data, hid_t lapl_id)`

"Format bounds" property Release-to-release format compatibility

- H5Pset_libver_bounds `herr_t H5Pset_libver_bounds(hid_t fapl_id, H5F_libver_t low, H5F_libver_t high)`
- H5Pget_libver_bounds `herr_t H5Pget_libver_bounds(hid_t fapl_id, H5F_libver_t *low, H5F_libver_t *high)`

Configurable compact-or-indexed groups (compact and large groups)

- H5Pset_link_phase_change `herr_t H5Pset_link_phase_change(hid_t gcpl_id, unsigned max_compact, unsigned min_dense)`
- H5Pget_link_phase_change `herr_t H5Pget_link_phase_change(hid_t gcpl_id, unsigned *max_compact, unsigned *min_dense)`
- H5Pset_est_link_info `herr_t H5Pset_est_link_info(hid_t gcpl_id, unsigned est_num_entries, unsigned est_name_len)`
- H5Pget_est_link_info `herr_t H5Pget_est_link_info(hid_t gcpl_id, unsigned *est_num_entries, unsigned *est_name_len)`
- H5Pset_nlinks `herr_t H5Pset_nlinks(hid_t lapl_id, size_t nlinks)`
- H5Pget_nlinks `herr_t H5Pget_nlinks(hid_t lapl_id, size_t *nlinks)`

User-defined links

- H5Lcreate_ud `herr_t H5Lcreate_ud(hid_t link_loc_id, const char *link_name, H5L_type_t link_type, const char *udata, size_t udata_size, hid_t lcpl_id, hid_t lapl_id)`
- H5Lregister `herr_t H5Lregister(const H5L_class_t *link_class)`
- H5Lunregister `herr_t H5Lunregister(H5L_type_t link_cls_id)`
- H5Oincr_refcount `herr_t H5Oincr_refcount(hid_t object_id)`
- H5Odecr_refcount `herr_t H5Odecr_refcount(hid_t object_id)`

External links

- H5Lcreate_external `herr_t H5Lcreate_external(const char *file_name, const char *object_name, hid_t link_loc_id, const char *link_name, hid_t lcpl_id, hid_t lapl_id)`
- H5Lunpack_elink_val `herr_t H5Lunpack_elink_val(char *ext_linkval, size_t link_size, const char **filename, const char **obj_path)`
- H5Pset_elink_prefix `herr_t H5Pset_elink_prefix(hid_t lapl_id, const char *prefix)`
- H5Pget_elink_prefix `herr_t H5Pget_elink_prefix(hid_t lapl_id, const char **prefix)`

Link creation order tracking and indexing

- H5Pset_link_creation_order `herr_t H5Pset_link_creation_order(hid_t ocpl_id, unsigned crt_order_flags)`
- H5Pget_link_creation_order `herr_t H5Pget_link_creation_order(hid_t ocpl_id, unsigned *crt_order_flags)`
- H5Gget_create_plist `hid_t H5Gget_create_plist(hid_t group_id)`
- H5Gget_info_by_idx `herr_t H5Gget_info_by_idx(hid_t loc_id, const char *group_name, H5_index_t index_type, H5_iter_order_t order, hsize_t n, H5G_info_t *group_info, hid_t lapl_id)`
- H5Tget_create_plist `hid_t H5Tget_create_plist(hid_t dtype_id)`

Link API (H5L), an all-new interface (includes user-defined and external links)

- H5Lcopy `herr_t H5Lcopy(hid_t src_loc_id, const char *src_name, hid_t dest_loc_id, const char *dest_name, hid_t lcpl_id, hid_t lapl_id)`
- H5Lcreate_external `herr_t H5Lcreate_external(const char *file_name, const char *object_name, hid_t link_loc_id, const char *link_name, hid_t lcpl_id, hid_t lapl_id)`
- H5Lcreate_hard `herr_t H5Lcreate_hard(hid_t obj_loc_id, const char *obj_name, hid_t link_loc_id, const char *link_name, hid_t lcpl_id, hid_t lapl_id)`
- H5Lcreate_soft `herr_t H5Lcreate_soft(const char *target_path, hid_t link_loc_id, const char *link_name, hid_t lcpl_id, hid_t lapl_id)`
- H5Lcreate_ud `herr_t H5Lcreate_ud(hid_t link_loc_id, const char *link_name, H5L_type_t link_type, const char *udata, size_t udata_size, hid_t lcpl_id, hid_t lapl_id)`
- H5Ldelete `herr_t H5Ldelete(hid_t loc_id, const char *name, hid_t lapl_id)`
- H5Ldelete_by_idx `herr_t H5Ldelete_by_idx(hid_t loc_id, const char *group_name, H5_index_t index_field, H5_iter_order_t order, hsize_t n, hid_t lapl_id)`
- H5Lexists `htri_t H5Lexists(hid_t loc_id, const char *name, hid_t lapl_id)`
- H5Lget_info `herr_t H5Lget_info(hid_t link_loc_id, const char *link_name, H5L_info_t *link_buff, hid_t lapl_id)`
- H5Lget_info_by_idx `herr_t H5Lget_info_by_idx(hid_t loc_id, const char *group_name, H5_index_t index_field, H5_iter_order_t order, hsize_t n, H5L_info_t *link_val, hid_t lapl_id)`
- H5Lget_name_by_idx `ssize_t H5Lget_name_by_idx(hid_t loc_id, const char *group_name, H5_index_t index_field, H5_iter_order_t order, hsize_t n, char *name, size_t size, hid_t lapl_id)`
- H5Lget_val `herr_t H5Lget_val(hid_t link_loc_id, const char *link_name, void *linkval_buff, size_t size, hid_t lapl_id)`
- H5Lget_val_by_idx `ssize_t H5Lget_val_by_idx(hid_t loc_id, const char *group_name, H5_index_t index_field, H5_iter_order_t order, hsize_t n, char *value_buf, size_t size, hid_t lapl_id)`
- H5Lis_registered `htri_t H5Lis_registered(H5L_type_t link_cls_id)`
- H5Literate `herr_t H5Literate(hid_t loc_id, H5_index_t index_type, H5_iter_order_t order, hsize_t *idx, H5L_iterate_t op, void *op_data)`
- H5Literate_by_name `herr_t H5Literate_by_name(hid_t loc_id, const char *group_name, H5_index_t index_type, H5_iter_order_t order, hsize_t *idx, H5L_iterate_t op, void *op_data, hid_t *lapl_id)`
- H5Lmove `herr_t H5Lmove(hid_t src_loc_id, const char *src_name, hid_t dest_loc_id, const char *dest_name, hid_t lcpl, hid_t lapl)`
- H5Lregister `herr_t H5Lregister(const H5L_class_t *link_class)`
- H5Lunpack_elink_val `herr_t H5Lunpack_elink_val(char *ext_linkval, size_t link_size, const char **filename, const char **obj_path)`
- H5Lunregister `herr_t H5Lunregister(H5L_type_t link_cls_id)`
- H5Lvisit `herr_t H5Lvisit(hid_t group_id, H5_index_t index_type, H5_iter_order_t order, H5L_iterate_t op, void *op_data)`
- H5Lvisit_by_name `herr_t H5Lvisit_by_name(hid_t loc_id, const char *group_name, H5_index_t index_type, H5_iter_order_t order, H5L_iterate_t op, void *op_data, hid_t lapl_id)`

Enhanced attribute handling

- H5Acreate2 `hid_t H5Acreate2(hid_t loc_id, const char *attr_name, hid_t type_id, hid_t space_id, hid_t acpl_id, hid_t aapl_id, hid_t lapl_id)`
- H5Adelete_by_idx `herr_t H5Adelete_by_idx(hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n, hid_t lapl_id)`
- H5Adelete_by_name `herr_t H5Adelete_by_name(hid_t loc_id, const char *obj_name, const char *attr_name, hid_t lapl_id)`
- H5Aget_info `herr_t H5Aget_info(hid_t attr_id, H5A_info_t *ainfo)`
- H5Aget_info_by_idx `herr_t H5Aget_info_by_idx(hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n, H5A_info_t *ainfo, hid_t lapl_id)`
- H5Aget_info_by_name `herr_t H5Aget_info_by_name(hid_t loc_id, const char *obj_name, const char *attr_name, H5A_info_t *ainfo, hid_t lapl_id)`
- H5Aget_name_by_idx `ssize_t H5Aget_name_by_idx(hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n, char *name, size_t size, hid_t lapl_id)`
- H5Aget_storage_size `hsize_t H5Aget_storage_size(hid_t attr_id)`
- H5Aiterate2 `herr_t H5Aiterate2(hid_t obj_id, H5_index_t idx_type, H5_iter_order_t order, hsize_t *n, H5A_operator2_t op, void *op_data)`
- H5Aiterate_by_name `herr_t H5Aiterate_by_name(hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t *n, H5A_operator2_t op, void *op_data, hid_t lapd_id)`
- H5Aopen `hid_t H5Aopen(hid_t loc_id, const char *obj_name, const char *attr_name, hid_t aapl_id, hid_t lapl_id)`
- H5Aopen_by_idx `hid_t H5Aopen_by_idx(hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n, hid_t aapl_id, hid_t lapl_id)`
- H5Arename_by_name `herr_t H5Arename_by_name(hid_t loc_id, const char *obj_name, const char *old_attr_name, const char *new_attr_name, hid_t lapl_id)`

Managing large numbers of attributes

- H5Pset_attr_phase_change `herr_t H5Pset_attr_phase_change(hid_t ocpl_id, unsigned max_compact, unsigned min_dense)`
- H5Pget_attr_phase_change `herr_t H5Pget_attr_phase_change(hid_t ocpl_id, unsigned *max_compact, unsigned *min_dense)`

Attribute creation order tracking and indexing

- H5Pset_attr_creation_order `herr_t H5Pset_attr_creation_order(hid_t ocpl_id, unsigned crt_order_flags)`
- H5Pget_attr_creation_order `herr_t H5Pget_attr_creation_order(hid_t ocpl_id, unsigned *crt_order_flags)`
- H5Aget_create_plist `hid_t H5Aget_create_plist(hid_t attr_id)`

Shared object header messages (SOHM)

- H5Pset_shared_mesg_index `herr_t H5Pset_shared_mesg_index(hid_t fcpl_id, unsigned index_num, unsigned mesg_type_flags, unsigned min_mesg_size)`
- H5Pset_shared_mesg_nindexes `herr_t H5Pset_shared_mesg_nindexes(hid_t plist_id, unsigned nindexes)`
- H5Pset_shared_mesg_phase_change `herr_t H5Pset_shared_mesg_phase_change(hid_t fcpl_id, unsigned max_list, unsigned min_btree)`
- H5Pget_shared_mesg_index `herr_t H5Pget_shared_mesg_index(hid_t fcpl_id, unsigned index_num, unsigned *mesg_type_flags, unsigned *min_mesg_size)`
- H5Pget_shared_mesg_nindexes `herr_t H5Pget_shared_mesg_nindexes(hid_t fcpl_id, unsigned *nindexes)`
- H5Pget_shared_mesg_phase_change `herr_t H5Pget_shared_mesg_phase_change(hid_t fcpl_id, unsigned *max_list, unsigned *min_btree)`

Enhanced local heap size management (group meta data)

- H5Pset_local_heap_size_hint `herr_t H5Pset_local_heap_size_hint(hid_t gcpl_id, size_t size_hint)`
- H5Pget_local_heap_size_hint `herr_t H5Pget_local_heap_size_hint(hid_t gcpl_id, size_t size_hint)`

UNICODE support

- H5Pset_char_encoding `herr_t H5Pset_char_encoding(hid_t plist_id, H5T_cset_t encoding)`
- H5Pget_char_encoding `herr_t H5Pget_char_encoding(hid_t plist_id, H5T_cset_t encoding)`

Object API (H5O), all new

- H5Oclose `herr_t H5Oclose(hid_t object_id)`
- H5Ocopy `herr_t H5Ocopy(hid_t src_loc_id, const char *src_name, hid_t dst_loc_id, const char *dst_name, hid_t ocp_plist_id, hid_t lcpl_id)`
- H5Odecr_refcount `herr_t H5Odecr_refcount(hid_t object_id)`
- H5Oget_comment `ssize_t H5Oget_comment(hid_t object_id, char *comment, size_t bufsize)`
- H5Oget_comment_by_name `ssize_t H5Oget_comment_by_name(hid_t loc_id, const char *name, char *comment, size_t bufsize, hid_t lapl_id)`
- H5Oget_info `herr_t H5Oget_info(hid_t object_id, H5O_info_t *obj_info)`
- H5Oget_info_by_idx `herr_t H5Oget_info_by_idx(hid_t loc_id, const char *group_name, H5_index_t index_field, H5_iter_order_t order, hsize_t n, H5O_info_t *obj_info, hid_t lapl_id)`
- H5Oget_info_by_name `herr_t H5Oget_info_by_name(hid_t loc_id, const char *object_name, H5O_info_t *object_info, hid_t lapl_id)`
- H5Oincr_refcount `herr_t H5Oincr_refcount(hid_t object_id)`
- H5Olink `herr_t H5Olink(hid_t obj_id, hid_t new_loc_id, const char *new_link_name, hid_t lcpl, hid_t lapl)`
- H5Oopen `hid_t H5Oopen(hid_t loc_id, const char *name, hid_t lapl_id)`
- H5Oopen_by_addr `hid_t H5Oopen_by_addr(hid_t loc_id, haddr_t addr)`
- H5Oopen_by_idx `hid_t H5Oopen_by_idx(hid_t loc_id, const char *group_name, H5_index_t index_field, H5_iter_order_t order, hsize_t n, hid_t lapl_id)`
- H5Oset_comment `herr_t H5Oset_comment(hid_t object_id, const char *comment)`
- H5Oset_comment_by_name `herr_t H5Oset_comment_by_name(hid_t loc_id, const char *name, const char *comment, hid_t lapl_id)`
- H5Ovisit `herr_t H5Ovisit(hid_t group_id, H5_index_t index_type, H5_iter_order_t order, H5O_iterate_t op, void *op_data)`
- H5Ovisit_by_name `herr_t H5Ovisit_by_name(hid_t loc_id, const char *object_name, H5_index_t index_type, H5_iter_order_t order, H5O_iterate_t op, void *op_data, hid_t lapl_id)`

Object creation or copying with "create intermediate groups" property

- H5Pset_create_intermediate_group `herr_t H5Pset_create_intermediate_group(hid_t gcpl_id, unsigned crt_intermed_group)`
- H5Pget_create_intermediate_group `herr_t H5Pget_create_intermediate_group(hid_t gcpl_id, unsigned *crt_intermed_group)`

Object copy properties

- H5Ocopy `herr_t H5Ocopy(hid_t src_loc_id, const char *src_name, hid_t dst_loc_id, const char *dst_name, hid_t ocp_plist_id, hid_t lcpl_id)`
- H5Pset_copy_object `herr_t H5Pset_copy_object(hid_t cplist_id, unsigned copy_options)`
- H5Pget_copy_object `herr_t H5Pget_copy_object(hid_t cplist_id, unsigned *copy_options)`

Improved object and file information retrieval

- H5Aget_info `herr_t H5Aget_info(hid_t attr_id, H5A_info_t *ainfo)`
- H5Aget_info_by_name `herr_t H5Aget_info_by_name(hid_t loc_id, const char *obj_name, const char *attr_name, H5A_info_t *ainfo, hid_t lapl_id)`
- H5Aget_info_by_idx `herr_t H5Aget_info_by_idx(hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n, H5A_info_t *ainfo, hid_t lapl_id)`
- H5Fget_info `herr_t H5Fget_info(hid_t obj_id, H5F_info_t *bh_info)`
- H5Gget_info `herr_t H5Gget_info(hid_t group_id, H5G_info_t group_info)`
- H5Gget_info_by_name `herr_t H5Gget_info_by_name(hid_t loc_id, const char *group_name, H5G_info_t group_info, hid_t lapl_id)`
- H5Gget_info_by_idx `herr_t H5Gget_info_by_idx(hid_t loc_id, const char *group_name, H5_index_t index_type, H5_iter_order_t order, hsize_t n, H5G_info_t group_info, hid_t lapl_id)`
- H5Lget_info `herr_t H5Lget_info(hid_t link_loc_id, const char *link_name, H5L_info_t *link_buff, hid_t lapl_id)`
- H5Lget_info_by_idx `herr_t H5Lget_info_by_idx(hid_t loc_id, const char *group_name, H5_index_t index_field, H5_iter_order_t order, hsize_t n, H5L_info_t *link_val, hid_t lapl_id)`
- H5Oget_info `herr_t H5Oget_info(hid_t object_id, H5O_info_t *obj_info)`
- H5Oget_info_by_name `herr_t H5Oget_info_by_name(hid_t loc_id, const char *object_name, H5O_info_t *object_info, hid_t lapl_id)`
- H5Oget_info_by_idx `herr_t H5Oget_info_by_idx(hid_t loc_id, const char *group_name, H5_index_t index_field, H5_iter_order_t order, hsize_t n, H5O_info_t *obj_info, hid_t lapl_id)`

Name of referenced object

- H5Rget_name `ssize_t H5Rget_name(hid_t loc_id, H5R_type_t ref_type, void *ref, char *name, size_t size)`

Anonymous object creation

- H5Dcreate_anon `hid_t H5Dcreate_anon(hid_t loc_id, hid_t type_id, hid_t space_id, hid_t dcpl_id, hid_t dapl_id)`
- H5Gcreate_anon `hid_t H5Gcreate_anon(hid_t loc_id, const char *name, hid_t gcpl_id, hid_t gapl_id)`
- H5Tcommit_anon `herr_t H5Tcommit_anon(hid_t loc_id, hid_t type_id, hid_t tcpl_id, hid_t tapl_id)`
- H5Lcreate_hard `herr_t H5Lcreate_hard(hid_t obj_loc_id, const char *obj_name, hid_t link_loc_id, const char *link_name, hid_t lcpl, hid_t lapl)`

New-style object creation and open functions (includes anonymous object creation)

- H5Dcreate_anon `hid_t H5Dcreate_anon(hid_t loc_id, hid_t type_id, hid_t space_id, hid_t dcpl_id, hid_t dapl_id)`
- H5Dcreate2 `hid_t H5Dcreate2(hid_t loc_id, const char *name, hid_t type_id, hid_t space_id, hid_t lcpl_id, hid_t dcpl_id, hid_t dapl_id)`
- H5Dopen2 `hid_t H5Dopen2(hid_t loc_id, const char *name, hid_t dapl_id)`
- H5Gcreate_anon `hid_t H5Gcreate_anon(hid_t loc_id, const char *name, hid_t gcpl_id, hid_t gapl_id)`
- H5Gcreate2 `hid_t H5Gcreate2(hid_t loc_id, const char *name, hid_t lcpl_id, hid_t gcpl_id, hid_t gapl_id)`
- H5Gopen2 `hid_t H5Gopen2(hid_t loc_id, const char *name, hid_t gapl_id)`
- H5Tcommit_anon `herr_t H5Tcommit_anon(hid_t loc_id, hid_t type_id, hid_t tcpl_id, hid_t tapl_id)`
- H5Tcommit2 `herr_t H5Tcommit2(hid_t loc_id, const char *name, hid_t type_id, hid_t lcpl_id, hid_t tcpl_id, hid_t tapl_id)`
- H5Topen2 `hid_t H5Topen2(hid_t loc_id, const char *name, hid_t tapl_id)`

User-defined identifiers

- H5Iregister `hid_t H5Iregister(H5I_type_t type, void *object)`
- H5Iregister_type `H5I_type_t H5Iregister_type(size_t hash_size, unsigned reserved, H5I_free_t free_func)`
- H5Idestroy_type `herr_t H5Idestroy_type(H5I_type_t type)`
- H5Iinc_type_ref `int H5Iinc_type_ref(H5I_type_t type)`
- H5Idec_type_ref `int H5Idec_type_ref(H5I_type_t type)`
- H5Iget_type_ref `int H5Iget_type_ref(H5I_type_t type)`

Other identifier API (H5I) enhancements

- H5Iclear_type `herr_t H5Iclear_type(H5I_type_t type, hbool_t force)`
- H5Inmembers `int H5Inmembers(H5I_type_t type, hsize_t *num_members)`
- H5Iobject_verify `void * H5Iobject_verify(hid_t id, H5I_type_t id_type)`
- H5Iremove_verify `void * H5Iremove_verify(hid_t id, H5I_type_t id_type)`
- H5Isearch `void * H5Isearch(H5I_type_t type, H5I_search_func_t func, void *key)`
- H5Itype_exists `htri_t H5Itype_exists(H5I_type_t type)`

Compression filters: N-bit and scale-offset

- H5Pset_nbit `herr_t H5Pset_nbit(hid_t plist_id)`
- H5Pset_scaleoffset `herr_t H5Pset_scaleoffset(hid_t plist_id, H5Z_SO_scale_type_t scale_type, int scale_factor)`

User-defined datatype conversion callback functions

- H5Pget_type_conv_cb `herr_t H5Pget_type_conv_cb(hid_t plist, H5T_conv_except_func_t *func, void **op_data)`
- H5Pset_type_conv_cb `herr_t H5Pset_type_conv_cb(hid_t plist, H5T_conv_except_func_t func, void *op_data)`

Datatype compiler conversion check

- H5Tcompiler_conv `htri_t H5Tcompiler_conv(hid_t src_id, hid_t dst_id)`

Dataset array size reduction

- H5Dset_extent `herr_t H5Dset_extent(hid_t dset_id, const hsize_t *size)`

Dataspace equivalence

- H5Sextent_equal `htri_t H5Sextent_equal(hid_t sid1, hid_t sid2)`

Direct I/O, bypassing system cache

- H5Pset_fapl_direct `herr_t H5Pset_fapl_direct(hid_t fapl_id, size_t alignment, size_t block_size, size_t cbuf_size)`
- H5Pget_fapl_direct `herr_t H5Pget_fapl_direct(hid_t fapl_id, size_t *alignment, size_t *block_size, size_t *cbuf_size)`

Parallel I/O optimization (collective chunk I/O)

- H5Pset_dxpl_mpio_chunk_opt `herr_t H5Pset_dxpl_mpio_chunk_opt(hid_t dxpl_id, H5FD_mpio_chunk_opt_t opt_mode)`
- H5Pset_dxpl_mpio_chunk_opt_num `herr_t H5Pset_dxpl_mpio_chunk_opt_num(hid_t dxpl_id, unsigned num_chunk_per_proc)`
- H5Pset_dxpl_mpio_chunk_opt_ratio `herr_t H5Pset_dxpl_mpio_chunk_opt_ratio(hid_t dxpl_id, unsigned percent_num_proc_per_chunk)`
- H5Pset_dxpl_mpio_collective_opt

Enhanced error handling (H5E)

- H5Eauto_is_v2 `herr_t H5Eauto_is_v2( hid_t estack_id, unsigned *is_stack )`
- H5Eclear2 `herr_t H5Eclear2( hid_t estack_id )`
- H5Eclose_msg `herr_t H5Eclose_msg( hid_t mesg_id )`
- H5Eclose_stack `herr_t H5Eclose_stack( hid_t estack_id )`
- H5Ecreate_msg `hid_t H5Ecreate_msg( hid_t class, H5E_type_t msg_type, const char* mesg )`
- H5Eget_auto2 `herr_t H5Eget_auto2( hid_t estack_id, H5E_auto2_t *func, void **client_data )`
- H5Eget_class_name `ssize_t H5Eget_class_name( hid_t class_id, char* name, size_t size )`
- H5Eget_current_stack `hid_t H5Eget_current_stack( void )`
- H5Eget_msg `ssize_t H5Eget_msg( hid_t mesg_id, H5E_type_t mesg_type, char mesg, size_t size )`
- H5Eget_num `ssize_t H5Eget_num( hid_t estack_id )`
- H5Epop `herr_t H5Epop( hid_t estack_id, size_t count )`
- H5Eprint2 `herr_t H5Eprint2( hid_t estack_id, FILE * stream )`
- H5Epush2 `herr_t H5Epush2( hid_t estack_id, const char *file, const char *func, unsigned line, hid_t class_id, hid_t major_id, hid_t minor_id, const char *msg, ...)`
- H5Eregister_class `hid_t H5Eregister_class( const char* cls_name, const char* lib_name, const char* version )`
- H5Eset_auto2 `herr_t H5Eset_auto2( hid_t estack_id, H5E_auto2_t func, void *client_data )`
- H5Eset_current_stack `herr_t H5Eset_current_stack( hid_t estack_id )`
- H5Eunregister_class `herr_t H5Eunregister_class( hid_t class_id )`
- H5Ewalk2 `herr_t H5Ewalk2( hid_t estack_id, H5E_direction_t direction, H5E_walk2_t func, void * client_data )`

Meta data cache management

- H5Fget_mdc_config `herr_t H5Fget_mdc_config(hid_t file_id, H5AC_cache_config_t *config_ptr)`
- H5Fget_mdc_hit_rate `herr_t H5Fget_mdc_hit_rate(hid_t file_id, double *hit_rate_ptr)`
- H5Fget_mdc_size `herr_t H5Fget_mdc_size(hid_t file_id, size_t *max_size_ptr, size_t *min_clean_size_ptr, size_t *cur_size_ptr, int *cur_num_entries_ptr)`
- H5Freset_mdc_hit_rate_stats `herr_t H5Freset_mdc_hit_rate_stats(hid_t file_id)`
- H5Fset_mdc_config `herr_t H5Fset_mdc_config(hid_t file_id, H5AC_cache_config_t *config_ptr)`
- H5Pget_mdc_config `herr_t H5Pget_mdc_config(hid_t plist_id, H5AC_cache_config_t *config_ptr)`
- H5Pset_mdc_config `herr_t H5Pset_mdc_config(hid_t plist_id, H5AC_cache_config_t *config_ptr)`

File read/write status

- H5Fget_intent `herr_t H5Fget_intent(hid_t file_id, unsigned *intent)`

Arithmetic data transform on I/O

- H5Pget_data_transform `herr_t H5Pget_data_transform( hid_t plist_id, char* expression, size_t size)`
- H5Pset_data_transform `herr_t H5Pset_data_transform( hid_t plist, const char* expression )`

Dataspace and datatype serial conversion

- H5Sdecode `hid_t H5Sdecode( const void *buf )`
- H5Sencode `herr_t H5Sencode( hid_t obj_id, void *buf, size_t *nalloc )`
- H5Tdecode `hid_t H5Tdecode( const void *buf )`
- H5Tencode `herr_t H5Tencode( hid_t obj_id, void *buf, size_t *nalloc )`

Enhanced filter management

- H5Pget_filter2 `herr_t H5Pget_filter2( hid_t plist_id, unsigned idx, unsigned int *flags, size_t *cd_nelmts, unsigned cd_values[], size_t namelen, char name[], unsigned *filter_config)`
- H5Pget_filter_by_id2 `hid_t H5Pget_filter_by_id2( hid_t plist_id, H5Z_filter_t filter_id, unsigned int *flags, size_t *cd_nelmts, unsigned int cd_values[], size_t namelen, char name[], unsigned int *filter_config)`

Comparison of properties

- H5Pinsert2 `herr_t H5Pinsert2( hid_t plid, const char *name, size_t size, void *value, H5P_prp_set_func_t set, H5P_prp_get_func_t get, H5P_prp_delete_func_t delete, H5P_prp_copy_func_t copy, H5P_prp_compare_func_t compare, H5P_prp_close_func_t close)`
- H5Pregister2 `herr_t H5Pregister2( hid_t class, const char * name, size_t size, void * default, H5P_prp_create_func_t create, H5P_prp_set_func_t set, H5P_prp_get_func_t get, H5P_prp_delete_func_t delete, H5P_prp_copy_func_t copy, H5P_prp_compare_func_t compare, H5P_prp_close_func_t close)`

Two-way conversion between datatype and text description of datatype

- H5LTtext_to_dtype `hid_t H5LTtext_to_datatype( const char *text, H5LT_lang_t lang_type)`
- H5LTdtype_to_text `herr_t H5LTdtype_to_text( hid_t datatype, char *str, H5LT_lang_t lang_type, size_t *len)`

Fortran subroutines: New Fortran subroutines in the main library are not yet included for Release 1.8.0-beta. See below for Fortran routines for High-Level HDF5 APIs.

C++ wrappers: There no new C++ wrappers for Release 1.8.0-beta.

High Level C APIs: H5LT: The following functions have been added to the HDF5 Lite (H5LT) API:

- H5LTtext_to_dtype `hid_t H5LTtext_to_datatype( const char *text, H5LT_lang_t lang_type)`
- H5LTdtype_to_text `herr_t H5LTdtype_to_text( hid_t datatype, char *str, H5LT_lang_t lang_type, size_t *len)`
- H5LTset_attribute_long_long `herr_t H5LTset_attribute_long_long( hid_t loc_id, const char *obj_name, const char *attr_name, const long_long *data, size_t *size)`
- H5LTget_attribute_long_long `herr_t H5LTget_attribute_long_long( hid_t loc_id, const char *obj_name, const char *attr_name, long_long *data)`

Two high-level C APIs are distributed for the first time with this release:

- H5PT, the HDF5 Packet Table interface
- H5DS, the HDF5 Dimension Scale interface Full documentation for these interfaces can be accessed directly from the High Level APIs overview page.

The new functions included in the packet table (H5PT) high-level APIs are as follows:

- H5PTcreate_fl `hid_t H5PTcreate_fl( hid_t loc_id, const char * dset_name, hid_t dtype_id, hsize_t chunk_size )`
- H5PTcreate_vl `hid_t H5PTcreate_vl( hid_t loc_id, const char *dset_name, hsize_t chunk_size )`
- H5PTopen `hid_t H5PTopen( hid_t loc_id, const char *dset_name )`
- H5PTclose `herr_t H5PTclose( hid_t table_id )`
- H5PTappend `herr_t H5PTappend( hid_t table_id, hsize_t nrecords, const void *data)`
- H5PTcreate_index `herr_t H5PTcreate_index( hid_t table_id)`
- H5PTset_index `herr_t H5PTset_index( hid_t table_id, hsize_t pt_index)`
- H5PTread_packets `herr_t H5PTread_packets( hid_t table_id, hsize_t start, hsize_t nrecords, void *data)`
- H5PTget_next `herr_t H5PTget_next( hid_t table_id, hsize_t nrecords, void *data)`
- H5PTget_num_packets `herr_t H5PTget_num_packets( hid_t table_id, hsize_t * nrecords)`
- H5PTis_valid `herr_t H5PTis_valid( hid_t table_id)`
- H5PTis_varlen `herr_t H5PTis_varlen( hid_t table_id)`
- H5PTfree_vlen_readbuff `herr_t H5PTfree_vlen_readbuff( hid_t table_id, hsize_t bufflen, void * buff)`

The new functions included in the dimension scale (H5DS) high-level APIs are as follows:

- H5DSset_scale `herr_t H5DSset_scale(hid_t did, const char *dimname, hid_t dimscale_id)`
- H5DSattach_scale `herr_t H5DSattach_scale(hid_t did, hid_t dsid, unsigned int idx)`
- H5DSdetach_scale `herr_t H5DSdetach_scale(hid_t did, hid_t dsid, unsigned int idx)`
- H5DSis_attached `htri_t H5DSis_attached(hid_t did, hid_t dsid, unsigned int idx)`
- H5DSis_scale `htri_t H5DSis_scale(hid_t did)`
- H5DSiterate_scales `herr_t H5DSiterate_scales(hid_t did, unsigned dim, int *idx, H5DS_iterate_t visitor, void *visitor_data)`
- H5DSset_label `herr_t H5DSset_label(hid_t did, unsigned int idx, const char *label)`
- H5DSget_label `ssize_t H5DSget_label(hid_t did, unsigned int idx, char *label, size_t size)`
- H5DSget_scale_name `hssize_t H5DSget_scale_name(hid_t did, char name, size_t *size)`
- H5DSget_num_scales `int H5DSget_num_scales(hid_t did, unsigned int idx)`

High Level Fortan90 APIs:

Fortran90 subroutines are now available for the following high-level APIs:

- H5LT: HDF5 Lite
- H5IM: HDF5 Image
- H5TB: HDF5 Table

Tools:

- h5stat

#### Deprecated and Deleted Functions

The following functions, subroutines and wrappers have been removed in this release:

C functions: HDF5 no longer provides GASS support.

- H5Pset_fapl_gass
- H5Pget_fapl_gass

HDF5 no longer provides SRB support. SRB functionality is now supported through the mechanism described in SRB - The DICE Storage Resource Broker.

- H5Pset_fapl_srb
- H5Pget_fapl_srb

The stream virtual file driver (H5FD_STREAM) has been removed from the HDF5 distribution. The functionality was last available from `hdf5-addons.origo.ethz.ch/`.

- H5Pset_fapl_stream
- H5Pget_fapl_stream

These two functions are replaced by H5Pget_type_conv_cb and H5Pset_type_conv_cb.

- H5Tset_overflow
- H5Tget_overflow

Several functions, subroutines, and wrappers are deprecated in this HDF5 release and may eventually be removed from the HDF5 distribution and from the HDF5 Reference Manual. A Release 1.6.x compatibility mode is provided enabling these and other Release 1.6.x compatibility features, but is available only if the HDF5 Library is configured with the default settings or with the flag `--with-default-api-version=v16`. Release 1.8.0 also provides macros that can be mapped selectively to 1.6.x and 1.8.0 function versions according to the needs of a user application. The backward compatibility mode is enabled in the Release 1.8.0 binaries distributed by NCSA. See API Compatibility Macros for full details.

Deprecated functions are marked in the function index at the beginning of each API section in the HDF5 Reference Manual.

Virtual File Driver Removed The stream virtual file driver (H5FD_STREAM) have been removed in this release. This affects the functions H5Pset_fapl_stream and H5Pget_fapl_stream and the constant H5FD_STREAM.

This virtual file driver will remain available at `hdf5-addons.origo.ethz.ch/`. Note that as of this writing, this transition is still in progress; the necessary integration tools may not be available when HDF5 Release 1.8.0 first comes out.

#### Functions with New or Changed Symbols or Fixed Values

Symbols and preset values associated with the following functions, subroutines or wrappers have changed as noted.

C functions:

- H5Tregister - Null is no longer a valid value for the parameter func.
- H5Pget_filter_by_id
- H5Pmodify_filter
- H5Premove_filter
- H5Pset_filter
- H5Zfilter_avail
- H5Zget_filter_info - Two new filter identifiers are available for the filter parameter:
  - H5Z_FILTER_NBIT
  - H5Z_FILTER_SCALEOFFSET
- H5Pget_filter - Two new filter identifiers are available as the return value:
  - H5Z_FILTER_NBIT
  - H5Z_FILTER_SCALEOFFSET

Fortran90 subroutines:

- h5pget_filter_f
- h5pget_filter_by_id_f
- h5pmodify_filter_f
- h5premove_filter_f
- h5pset_filter_f
- h5zfilter_avail_f
- h5zget_filter_info_f - Two new filter identifiers are available for the filter or filter_id parameters:
  - H5Z_FILTER_NBIT_F
  - H5Z_FILTER_SCALEOFFSET_F

Functions with Changed Syntax Function syntax changes in this release are handled through the mechanism described in API Compatibility Macros.

Exceptions: The function H5Eget_minor is not governed by the above-mentioned macros and its return type has changed:

- H5Eget_minor `char *H5Eget_minor (H5E_minor_t n)`

An application calling H5Eget_minor from an HDF5 Library of Release 1.8.0 or later will have to free the memory associated with the return value to prevent a memory leak. (This note added at Release 1.8.4, November 2009.)

In the function H5Dextend, the size parameter signature was changed.

- H5Dextend `herr_t H5Dextend( hid_t dataset_id, const hsize_t size[] )`
  see the Release 1.6 entry for the old signature.

The new function signature is generally considered equivalent to the old signature, but some compilers require an exact match. (This note added in February 2010, following Release 1.8.4.)

Renamed Functions The following C functions have been renamed. The original function names remain available under certain circumstances; see API Compatibility Macros for full details.

Original Function | New Function
--- | ---
H5Acreate | H5Acreate1
H5Aiterate | H5Aiterate1
H5Dcreate | H5Dcreate1
H5Dopen | H5Dopen1
H5Eclear | H5Eclear1
H5Eget_auto | H5Eget_auto1
H5Eprint | H5Eprint1
H5Epush | H5Epush1
H5Eset_auto | H5Eset_auto1
H5Ewalk | H5Ewalk1
H5Gcreate | H5Gcreate1
H5Gopen | H5Gopen1
H5Pget_filter | H5Pget_filter1
H5Pget_filter_by_id | H5Pget_filter_by_id1
H5Pinsert | H5Pinsert1
H5Pregister | H5Pregister1
H5Rget_obj_type | H5Rget_obj_type1
H5Tarray_create | H5Tarray_create1
H5Tcommit | H5Tcommit1
H5Tget_array_dims | H5Tget_array_dims1
H5Topen | H5Topen1

Changed Library Structures The following library structures have changed as follows: C API:

- H5FD_t - In this struct, the field fileno[2] has changed to fileno. The struct is otherwise unchanged.
- H5Z_class_t - This struct contains three new fields:
  - int version
  - unsigned encoder_present
  - unsigned decoder_present
  The struct is now defined as follows:`typedef struct H5Z_class_t { int version; H5Z_filter_t filter_id; unsigned encoder_present unsigned decoder_present const char *comment; H5Z_can_apply_func_t can_apply_func; H5Z_set_local_func_t set_local_func; H5Z_func_t filter_func;
  } H5Z_class_t;`

Changed ENUMs The following enumerated datatypes used by the library are discontinued in this release:

- H5E_major_t - Major error numbers
- H5E_minor_t - Minor error numbers

HDF5 error codes have changed from the ENUM format used in earlier releases to an identifier format. As ENUMs, error codes were constants defined at compile time; as identifiers, error codes are defined at runtime, in the same manner as HDF5 object identifiers (file, dataset, group, etc.).

Under normal circumstances, this change should be transparent to user applications.

The following enumerated datatypes used by the library have changed in the C and Fortran APIs as follows:

H5G_obj_t - Object types This ENUM has reordered as follows:

- H5G_GROUP
- H5G_DATASET
- H5G_TYPE
- H5G_LINK

H5I_type_t - Identifier types The following symbols have been added to this ENUM:

- H5I_UNINIT
- H5I_ERROR_CLASS
- H5I_ERROR_MSG
- H5I_ERROR_STACK

Another new symbol

- H5I_NTYPES replaces the old symbol H5I_NGROUPS

While visible in the public API, H5I_NTYPES functions as a limit value for the HDF5 Library and is not generally used at the application level. The same was true of H5I_NGROUPS.

H5S_class_t - Dataspace type identifiers The following symbol has been added:

- H5S_NULL

H5T_cset_t - Character set encoding identifiers The following symbol has been added:

- H5T_CSET_UTF8

H5Z_filter_t - Filters identifiers The following symbols have been added:

- H5Z_FILTER_NBIT
- H5Z_FILTER_SCALEOFFSET

### New Datatypes

The following OpenVMS-specific floating point datatypes are new with this release:

- H5T_VAX_F32
- H5T_VAX_F64

### New Property Lists

The following property lists are new with this release:

- H5P_DATASET_ACCESS
- H5P_GROUP_CREATE
- H5P_GROUP_ACCESS
- H5P_DATATYPE_CREATE
- H5P_DATATYPE_ACCESS
- H5P_ATTRIBUTE_CREATE

### Changed Library Configuration

The following configuration features have changed as follows.

New with this release:

- `--disable-dependency-tracking`
- `--enable-hdf5v1_6`
- `--enable-dconv-exception`
- `--disable-dconv-exception`
- `--enable-dconv-accuracy`
- `--disable-dconv-accuracy`
- `--program-prefix=PREFIX`
- `--program-prefix=SUFFIX`
- `--program-transform-name=PROGRAM`
- `--enable-maintainer-mode`
- `--disable-dependency-tracking`
- `--enable-dependency-tracking`
- `--enable-codestack`
- `--enable-direct-vfd`
- `--with-tags[=TAGS]`

New with this release, but expected to be useful only to those working inside the HDF5 Library or working very closely with HDF5 developers:

- `--enable-build-all`
- `--enable-metadata-trace-file`

New with this release, but not actively supported:

- `--enable-fphdf5`

Changed in this release:

- `--enable-shared[=PKGS]`
- `--enable-static[=PKGS]`
- `--enable-fast-install[=PKGS]`

Removed in this release:

- `--enable-hdf5v1_4`
- `--enable-funcstack`
- `--with-ssl=LIB`
- `--with-gass=DIR`
- `--with-srb=DIR`

The environment variables, which are deprecated in this release.

- FC replaces F9X
- FCFLAGS replaces F9XFLAGS

Additional new "influential environment variables" in this release include the following:

- CXX
- CXXFLAGS
- CXXCPP
- F77
- FFLAGS

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