/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Copyright by The HDF Group. * * All rights reserved. * * * * This file is part of HDF5. The full HDF5 copyright notice, including * * terms governing use, modification, and redistribution, is contained in * * the COPYING file, which can be found at the root of the source code * * distribution tree, or in https://www.hdfgroup.org/licenses. * * If you do not have access to either file, you may request a copy from * * help@hdfgroup.org. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ /* * Purpose: This file contains declarations which define macros for the * H5VL package. Including this header means that the source file * is part of the H5VL package. */ #ifndef H5VLmodule_H #define H5VLmodule_H /* Define the proper control macros for the generic FUNC_ENTER/LEAVE and error * reporting macros. */ #define H5VL_MODULE #define H5_MY_PKG H5VL #define H5_MY_PKG_ERR H5E_VOL /** \page H5VL_UG The HDF5 Virtual Object Layer (VOL) * * \section sec_vol The HDF5 Virtual Object Layer (VOL) * * \subsection subsec_vol_intro Introduction * The virtual object layer is an abstraction layer in the HDF5 library that intercepts all API calls * that could potentially access objects in an HDF5 container and forwards those calls to a VOL * connector, which implements the storage. The user or application gets the benefit of using the * familiar and widely-used HDF5 data model and API, but can map the physical storage of the HDF5 file * and objects to storage that better meets the application’s data needs. * * \subsection subsec_vol_abstract_layer The VOL Abstraction Layer * The VOL lies just under the public API. When a storage-oriented public APIcall is made, the library * performs a few sanity checks on the input parameters and then immediately invokes a VOL callback, * which resolves to an implementation in the VOL connector that was selected when opening or creating * the file. The VOL connector then performs whatever operations are needed before control returns to the * library, where any final library operations such as assigning IDs for newly created/opened datasets are * performed before returning. This means that, for calls that utilize the VOL, all of the functionality * is deferred to the VOL connector and the HDF5 library does very little work. An important consideration * of this is that most of the HDF5 caching layers (metadata and chunk caches, page buffering, etc.) will * not be available as those are implemented in the HDF5 native VOL connector and cannot be easily reused * by external connectors. * * * * * *
* \image html vol_architecture.png "The VOL Architecture" *
* * Not all public HDF5 API calls pass through the VOL. Only calls which require manipulating storage go * through the VOL and require a VOL connector author to implement the appropriate callback. Dataspace, * property list, error stack, etc. calls have nothing to do with storage manipulation or querying and * do not use the VOL. This may be confusing when it comes to property list calls, since many of those * calls set properties for storage. Property lists are just collections of key-value pairs, though, so * a particular VOL connector is not required to set or get properties. * * Another thing to keep in mind is that not every VOL connector will implement the full HDF5 public API. * In some cases, a particular feature like variable-length types may not have been developed yet or may * not have an equivalent in the target storage system. Also, many HDF5 public API calls are specific to * the native HDF5 file format and are unlikely to have any use in other VOL connectors. A * feature/capabilities flag scheme is being developed to help navigate this. * * For more information about which calls go through the VOL and the mechanism by which this is implemented, * see the connector author and library internals documentation. * * \subsection subsec_vol_connect VOL Connectors * A VOL connector can be implemented in several ways: * \li as a shared or static library linked to an application * \li as a dynamically loaded plugin, implemented as a shared library * \li and even as an internal connector, built into the HDF5 library itself * * This section mostly focuses on external connectors, both libraries and plugins, as those are expected * to be much more common than internal implementations. * * A list of VOL connectors can be found here: * * Registered VOL Connectors * * This list is incomplete and only includes the VOL connectors that have been registered with * The HDF Group. * * Not every connector in this collection is actively maintained by The HDF Group. It simply serves as a * single location where important VOL connectors can be found. See the documentation in a connector's * repository to determine its development status and the parties responsible for it. * * A VOL template that contains build scripts (Autotools and CMake) and an empty VOL connector "shell" * which can be copied and used as a starting point for building new connectors is located here: * VOL Connector Template * * This template VOL connector is for use in constructing terminal VOL connectors that do not forward * calls to an underlying connector. The external pass-through VOL connector listed on the registered * connector page can be used as a starting point for pass-through connectors. * * The only current (non-test) internal VOL connector distributed with the library is the native file * format connector (the "native VOL connector") which contains the code that handles native HDF5 (*.h5/hdf5) * files. In other words, even the canonical HDF5 file format is implemented via the VOL, making it a core * part of the HDF5 library and not an optional component which could be disabled. * * It has not been completely abstracted from the HDF5 library, though, and is treated as a special case. * For example, it cannot be unloaded and is always present. * * \subsection subsec_vol_quickstart Quickstart * The following steps summarize how one would go about using a VOL connector * with an application. More information on particular steps can be found later * on in this document. * * \subsubsection subsubsec_vol_quick_read Read The Documentation For The New VOL Connector * Many VOL connectors will require specific setup and configuration of both the application and the * storage. Specific permissions may have to be set, configuration files constructed, and * connector-specific setup calls may need to be invoked in the application. In many cases, converting * software to use a new VOL connector will be more than just a straightforward drop-in replacement done by * specifying a name in the VOL plugin environment variable. * * \subsubsection subsubsec_vol_quick_use Use A VOL-Enabled HDF5 Library * The virtual object layer was introduced in HDF5 1.12.0, however that version of the VOL is deprecated * due to inadequate support for pass-through connectors. These deficiencies have been addressed * in HDF5 1.14.0, so VOL users and connector authors should target the 1.14.0 VOL API. * * On Windows, it’s probably best to use the same debug vs release configuration for the application and * all libraries in order to avoid C runtime (CRT) issues. Pre-2015 versions of Visual Studio are not * supported. * * \subsubsection subsubsec_vol_quick_set Determine How You Will Set The VOL Connector * Fundamentally, setting a VOL connector involves modifying the file access property list (fapl) that will * be used to open or create the file. * * There are essentially three ways to do this: * \li Direct use of \ref H5Pset_vol() * \li Library-specific API calls that call \ref H5Pset_vol() for you * \li Use the VOL environment variable, which will also call \ref H5Pset_vol() for you * * Exactly how you go about setting a VOL connector in a fapl, will depend on * the complexity of the VOL connector and how much control you have over the * application’s source code. Note that the environment variable method, though * convenient, has some limitations in its implementation, which are discussed * below. * * \subsubsection subsubsec_vol_quick_update If Needed: Update Your Code To Load And Use A VOL Connector * There are two concerns when modifying the application: * * * In some cases, using the VOL environment variable will work well for setting the * connector and any associated storage setup and the application will not use API * calls that are not supported by the VOL connector. In this case, no application * modification will be necessary. * * \subsubsection subsubsec_vol_quick_plugin If Using A Plugin: Make Sure The VOL Connector Is In The Search * Path The default location for all HDF5 plugins is set at configure time when building the HDF5 library. * This is true for both CMake and the Autotools. The default locations for the plugins on both Windows and * POSIX systems is listed further on in this document. * * \subsubsection subsubsec_vol_quick_opt Optional: Set The VOL Connector Via The Environment Variable * In place of modifying the source code of your application, you may be able * to simply set the #HDF5_VOL_CONNECTOR environment variable (see below). This * will automatically use the specified VOL in place of the native VOL connector. * * \subsection subsec_vol_use Connector Use * Before a VOL connector can be set in a fapl, it must be registered with the * library (\ref H5Pset_vol requires the connector’s #hid_t ID) and, if a plugin, it * must be discoverable by the library at run time. * * \subsubsection subsubsec_vol_connect_register Registration * Before a connector can be used, it must be registered. This loads the connector * into the library and give it an HDF5 hid_t ID. The \ref H5VLregister_connector * API calls are used for this. * \code * hid_t H5VLregister_connector_by_name(const char *connector_name, hid_t vipl_id) * hid_t H5VLregister_connector_by_value(H5VL_class_value_t connector_value, hid_t vipl_id) * \endcode * When used with a plugin, these functions will check to see if an appropriate * plugin with a matching name, value, etc. is already loaded and check the plugin * path (see above) for matching plugins if this is not true. The functions return * #H5I_INVALID_HID if they are unable to register the connector. Many VOL connectors will provide * a connector-specific init call that will load and register the * connector for you. * * Note the two ways that a VOL connector can be identified: by a name or by * a connector-specific numerical value (#H5VL_class_value_t is typedef’d to an * integer). The name and value for a connector can be found in the connector’s * documentation or public header file. * * Each call also takes a VOL initialization property list (vipl). The library adds * no properties to this list, so it is entirely for use by connector authors. Set this * to #H5P_DEFAULT unless instructed differently by the documentation for the VOL * connector. * * As far as the library is concerned, connectors do not need to be explicitly unregistered as the * library will unload the plugin and close the ID when the library is * closed. If you want to close a VOL connector ID, either \ref H5VLunregister_connector() * or \ref H5VLclose() can be used (they have the same internal code path). The library maintains a * reference count on all open IDs and will not do the actual * work of closing an ID until its reference count drops to zero, so it’s safe to close * IDs anytime after they are used, even while an HDF5 file that was opened with * that connector is still open. * * Note that it’s considered an error to unload the native VOL connector. The * library will prevent this. This means that, for the time being, the native VOL * connector will always be available. This may change in the future so that * the memory footprint of the native VOL connector goes away when not in * use. * * \subsubsection subsubsec_vol_connect_version Connector Versioning * The VOL connector struct provides a \b conn_version field for versioning connectors. The library * developers are working on some best practices for versioning connectors. * * \subsubsection subsubsec_vol_connect_reg_calls Connector-Specific Registration Calls * Most connectors will provide a special API call which will set the connector * in the fapl. These will often be in the form of \b H5Pset_fapl_(). For * example, the DAOS VOL connector * provides a \b H5Pset_fapl_daos() API call which will take MPI parameters and * make this call. See the connector’s documentation or public header file(s) for * more information. * * \subsubsection subsubsec_vol_connect_set_vol H5Pset_vol() * The is the main library API call for setting the VOL connector in a file access * property list. Its signature is: * \code * herr_t H5Pset_vol(hid_t plist_id, hid_t new_vol_id, const void new_vol_info) * \endcode * * It takes the ID of the file access property list, the ID of the registered VOL * connector, and a pointer to whatever connector-specific data the connector is * expecting. This will usually be a data struct specified in the connector’s header * or a NULL pointer if the connecter requires no special information (as in the * native VOL connector). * * As mentioned above, many connectors will provide their own replacement for * this call. See the connector’s documentation for more information. * * \subsubsection subsubsec_vol_connect_search VOL Connector Search Path * Dynamically loaded VOL connector plugins are discovered and loaded by the * library using the same mechanism as dataset/group filter plugins. The default * locations are: * * Default locations * \code * POSIX systems: /usr/local/hdf5/lib/plugin * Windows: %ALLUSERSPROFILE%/hdf5/lib/plugin * \endcode * * These default locations can be overridden by setting the #HDF5_PLUGIN_PATH * environment variable. There are also public H5PL API calls which can be used * to add, modify, and remove search paths. The library will only look for plugins * in the specified plugin paths. By default, it will NOT find plugins that are * simply located in the same directory as the executable. * * \subsubsection subsubsec_vol_connect_param Parameter Strings * Each VOL connector is allowed to take in a parameter string which can be * parsed via \ref H5VLconnector_str_to_info() to get an info struct which can be * passed to \ref H5Pset_vol(). * \code * herr_t H5VLconnector_str_to_info(const char *str, hid_t connector_id, void **info) * \endcode * * And the obtained info can be freed via: * \code * herr_t H5VLfree_connector_info(hid_t connector_id, void *vol_info) * \endcode * * Most users will not need this functionality as they will be using either connector- * specific setup calls which will handle registering and configuring the connector * for them or they will be using the environment variable (see below). * * \subsubsection subsubsec_vol_connect_env Environment Variable * The HDF5 library allows specifying a default VOL connector via an environment * variable: #HDF5_VOL_CONNECTOR. The value of this environment variable should * be set to ”vol connector name \”. * * This will perform the equivalent of: *
    *
  1. \ref H5VLregister_connector_by_name() using the specified connector name
    2. *
  2. \ref H5VLconnector_str_to_info() using the specified parameters. This will * go through the connector we got from the previous step and should return * a VOL info struct from the parameter string in the environment variable.
    3. *
  3. \ref H5Pset_vol() on the default fapl using the obtained ID and info.
    4. *
* * The environment variable is parsed once, at library startup. Since the environment variable scheme * just changes the default connector, it can be overridden * by subsequent calls to \ref H5Pset_vol(). The \ is optional, so for * connectors which do not require any special configuration parameters you can * just set the environment variable to the name. * * NOTE: Implementing the environment variable in this way means that setting * the native VOL connector becomes somewhat awkward as there is no explicit * HDF5 API call to do this. Instead you will need to get the native VOL connector’s ID via * \ref H5VLget_connector_id_by_value(#H5_VOL_NATIVE) and set it manually in the fapl * using \ref H5Pset_vol(). * * \subsection subsec_vol_adapt Adapting HDF5 Software to Use the VOL * The VOL was engineered to be as unobtrusive as possible and, when a connector * which implements most/all of the data model functionality is in use, many applications * will require little, if any, modification. As mentioned in the quick start * section, most modifications will probably consist of connector setup code (which * can usually be accomplished via the environment variable), adapting code to use * the new token-based API calls, and protecting native-VOL-connector-specific * functions. * * \subsubsection subsubsec_vol_adapt_token haddr_t → H5O_token_t * Some HDF5 API calls and data structures refer to addresses in the HDF5 using * the #haddr_t type. Unfortunately, the concept of an ”address” will make no * sense for many connectors, though they may still have some sort of location key * (e.g.: a key in a key-value pair store). * * As a part of the VOL work, the HDF5 API was updated to replace the #haddr_t * type with a new #H5O_token_t type that represents a more generic object location. * These tokens appear as an opaque byte array of #H5O_MAX_TOKEN_SIZE bytes * that is only meaningful for a particular VOL connector. They are not intended * for interpretation outside of a VOL connector, though a connector author may * provide an API call to convert their tokens to something meaningful for the * storage. * \code * typedef struct H5O_token_t { * uint8_t __data[H5O_MAX_TOKEN_SIZE]; * } H5O_token_t; * \endcode * * As an example, in the native VOL connector, the token stores an #haddr_t address and * addresses can be converted to and from tokens using #H5VLnative_addr_to_token() * and #H5VLnative_token_to_addr(). * * \code * herr_t H5VLnative_addr_to_token(hid_t loc_id, haddr_t addr, H5O_token_t *token) * herr_t H5VLnative_token_to_addr(hid_t loc_id, H5O_token_t token, haddr_t *addr) * \endcode * * Several API calls have also been added to compare tokens and convert tokens * to and from strings. * * \code * herr_t H5Otoken_cmp(hid_t loc_id, const H5O_token_t *token1, const H5O_token_t *token2, * int *cmp_value) * herr_t H5Otoken_to_str(hid_t loc_id, const H5O_token_t *token, char **token_str) * herr_t H5Otoken_from_str(hid_t loc_id, const char *token_str, H5O_token_t *token) * \endcode * * \subsubsection subsubsec_vol_adapt_api Specific API Call Substitutions *

H5Fis_hdf5() → H5Fis_accessible()

* \ref H5Fis_hdf5() does not take a file access property list (fapl). As this is where the * VOL connector is specified, this call cannot be used with arbitrary connectors. * As a VOL-enabled replacement, \ref H5Fis_accessible() has been added to the * library. It has the same semantics as \ref H5Fis_hdf5(), but takes a fapl so it can * work with any VOL connector. * * Note that, at this time, \ref H5Fis_hdf5() always uses the native VOL connector, * regardless of the settings of environment variables, etc. * \code * htri_t H5Fis_accessible(const char *container_name, hid_t fapl_id) * \endcode * *

H5Oget_info[1|2]() → H5Oget_info3() and H5Oget_native_info()

* The \ref H5Oget_info1() and \ref H5Oget_info2() family of HDF5 API calls are often * used by user code to obtain information about an object in the file, however * these calls returned a struct which contained native information and are thus * unsuitable for use with arbitrary VOL connectors. * * A new \ref H5Oget_info3() family of API calls has been added to the library which * only return data model information via a new \ref H5O_info2_t struct. This struct * also returns #H5O_token_t tokens in place of #haddr_t addresses. * \code * H5Oget_info3(hid_t loc_id, H5O_info2_t *oinfo, unsigned fields) * * herr_t H5Oget_info_by_name3(hid_t loc_id, const char *name, H5O_info2_t *oinfo, * unsigned fields, hid_t lapl_id) * herr_t H5Oget_info_by_idx3(hid_t loc_id, const char *group_name, H5_index_t idx_type, * H5_iter_order_t order, hsize_t n, H5O_info2_t *oinfo, * unsigned fields, hid_t lapl_id) * \endcode * * \code * typedef struct H5O_info2_t { * unsigned long fileno; // File number that object is located in * H5O_token_t token; // Token representing the object * H5O_type_t type; // Basic object type (group, dataset, etc.) * unsigned rc; // Reference count of object * time_t atime; // Access time * time_t mtime; // Modification time * time_t ctime; // Change time * time_t btime; // Birth time * hsize_t num_attrs; // # of attributes attached to object * } H5O_info2_t; * \endcode * * To return the native file format information, \ref H5Oget_native_info() calls have * been added which can return such data separate from the data model data. * \code * herr_t H5Oget_native_info(hid_t loc_id, H5O_native_info_t *oinfo, unsigned fields) * * herr_t H5Oget_native_info_by_name(hid_t loc_id, const char *name, H5O_native_info_t *oinfo, * unsigned fields, hid_t lapl_id) * * herr_t H5Oget_native_info_by_idx(hid_t loc_id, const char *group_name, H5_index_t idx_type, * H5_iter_order_t order, hsize_t n, H5O_native_info_t *oinfo, * unsigned fields, hid_t lapl_id) * \endcode * * \code * typedef struct H5O_native_info_t { * H5O_hdr_info_t hdr; // Object header information * // Extra metadata storage for obj & attributes * struct { * H5_ih_info_t obj; // v1/v2 B-tree & local/fractal heap for groups, * // B-tree for chunked datasets * H5_ih_info_t attr; // v2 B-tree & heap for attributes * } meta_size; * } H5O_native_info_t; * \endcode * *

H5Ovisit[1|2]() → H5Ovisit3()

* The callback used in the \ref H5Ovisit() family of API calls took an H5O info t * struct parameter. As in \ref H5Oget_info(), this both commingled data model and * native file format information and also used native HDF5 file addresses. * * New \ref H5Ovisit3() API calls have been created which use the token-based, data-model-only * #H5O_info_t struct in the callback. * * \code * herr_t H5Ovisit3(hid_t obj_id, H5_index_t idx_type, H5_iter_order_t order, H5O_iterate2_t op, * void *op_data, unsigned fields) * * herr_t H5Ovisit_by_name3(hid_t loc_id, const char *obj_name, H5_index_t idx_type, * H5_iter_order_t order, H5O_iterate2_t op, void *op_data, * unsigned fields, hid_t lapl_id) * \endcode * * \code * typedef herr_t (*H5O_iterate2_t)(hid_t obj, const char *name, const H5O_info2_t *info, void *op_data) * \endcode * *

H5Lget_info() → H5Lget_info2()

* The \ref H5Lget_info() API calls were updated to use tokens instead of addresses * in the #H5L_info_t struct. * \code * herr_t H5Lget_info2(hid_t loc_id, const char *name, H5L_info2_t *linfo, hid_t lapl_id) * * herr_t H5Lget_info_by_idx2(hid_t loc_id, const char *group_name, H5_index_t idx_type, * H5_iter_order_t order, hsize_t n, H5L_info2_t *linfo, hid_t lapl_id) * \endcode * * \code * typedef struct { * H5L_type_t type; // Type of link * hbool_t corder_valid; // Indicate if creation order is valid * int64_t corder; // Creation order * H5T_cset_t cset; // Character set of link name * union { * H5O_token_t token; // Token of location that hard link points to * size_t val_size; // Size of a soft link or UD link value * } u; * } H5L_info2_t; * \endcode * *

H5Literate() and H5Lvisit() → H5Literte2() and H5Lvisit2()

* The callback used in these API calls used the old #H5L_info_t struct, which used * addresses instead of tokens. These callbacks were versioned in the C library and * now take modified #H5L_iterate2_t callbacks which use the new token-based info * structs. * \code * herr_t H5Literate2(hid_t grp_id, H5_index_t idx_type, H5_iter_order_t order, hsize_t *idx, * H5L_iterate2_t op, void *op_data) * * herr_t H5Literate_by_name2(hid_t loc_id, const char *group_name, H5_index_t idx_type, * H5_iter_order_t order, hsize_t *idx, H5L_iterate2_t op, * void *op_data, hid_t lapl_id) * * herr_t H5Lvisit2(hid_t grp_id, H5_index_t idx_type, H5_iter_order_t order, H5L_iterate2_t op, * void *op_data) * * herr_t H5Lvisit_by_name2(hid_t loc_id, const char *group_name, H5_index_t idx_type, * H5_iter_order_t order, H5L_iterate2_t op, void *op_data, hid_t lapl_id) * \endcode * * \code * typedef herr_t (*H5L_iterate2_t)(hid_t group, const char *name, const H5L_info2_t *info, * void *op_data); * \endcode * *

H5Oopen by addr() → H5Oopen by token()

* The new \ref H5Oopen_by_token() API call can be used to open objects by the * tokens that are returned by the various ”get info”, et al. API calls. * \code * hid_t H5Oopen_by_token(hid_t loc_id, H5O_token_t token) * \endcode * * \subsubsection subsubsec_vol_adapt_native Protect Native-Only API Calls * In HDF5 1.14.0, a way to determine support for optional calls has been added. * \code * herr_t H5VLquery_optional(hid_t obj_id, H5VL_subclass_t subcls, int opt_type, uint64_t *flags) * \endcode * * The call takes an object that is VOL managed (i.e.; file, group, dataset, attribute, * object, committed datatype), the VOL subclass (an enum documented * in H5VLpublic.h), an operation ”type” (discussed below), and an out parameter for the * bitwise capabilities flags (also discussed below). Code that needs * to protect a VOL-specific API call can call the function to see if the API * call is supported, which will be reported via the flags. Specifically, if the * #H5VL_OPT_QUERY_SUPPORTED bit is set, the feature is supported. The other flags * are more useful for VOL connector authors than end users. * * In the case of the native VOL connector, the opt type operations are documented in * H5VLnative.h. The current list of native operations is given at the * end of this document, along with a list of native-only connector calls. * * \subsection subsec_vol_lang Language Wrappers * Due to the parameter type and callback changes that were required in the * C library API regarding the update from #haddr_t addresses to #H5O_token_t * tokens and the difficulty in versioning the wrapper APIs, it was decided to * update all of the wrappers to use tokens instead of addresses. This will allow * the language wrappers to make use of the VOL, but at the expense of backward * compatibility. * * Information on the C API changes can be found above. * * Affected API calls, by language: * * \subsubsection subsubsec_vol_lang_c C++ * * * The C++ wrappers do not allow opening HDF5 file objects by address or token. * * The public H5VL API calls found in H5VLpublic.h were NOT added to the C++ API. * * \subsubsection subsubsec_vol_lang_fort Fortran * As in the C API, these API calls had their structs updated to the token version * so the h5o_info_t, etc. structs no longer contain native file format information * and the callbacks will need to match the non-deprecated, token-enabled versions. * * * Additionally, h5fis_hdf5_f was updated to use \ref H5Fis_accessible internally, * though with the same caveat as the C++ implementation: the default fapl is * always passed in so arbitrary VOL connectors will only work if the default VOL * connector is changed via the environment variable. * * The public H5VL API calls found in H5VLpublic.h were also added to the * Fortran wrappers. * * \subsubsection subsubsec_vol_lang_java Java/JNI * * * \subsection subsec_vol_cl Using VOL Connectors With The HDF5 Command-Line Tools * The following command-line tools are VOL-aware and can be used with arbitrary VOL connectors: * \li (p)h5diff * \li h5dump * \li h5ls * \li h5mkgrp * \li h5repack * * The VOL connector can be set either using the #HDF5_VOL_CONNECTOR environment variable * (see above) or via the command line. Each of the above tools * takes command-line options to set the VOL connector by name or value and * the VOL connector string, usually in the form of * \code * --vol-(name|value|info) * \endcode * See the individual tool’s help for the options specific to that tool. * * \subsection subsec_vol_compat Compatibility * * \subsubsection subsubsec_vol_compat_native List of HDF5 Native VOL API Calls * These API calls will probably fail when used with terminal VOL connectors * other than the native HDF5 file format connector. Their use should be protected * in code that uses arbitrary VOL connectors. Note that some connectors may, in * fact, implement some of this functionality as it is possible to mimic the native * HDF5 connector, however this will probably not be true for most non-native * VOL connectors. * \snippet{doc} tables/volAPIs.dox vol_native_table * * \subsubsection subsubsec_vol_compat_indep List of HDF5 VOL-Independent API Calls * These HDF5 API calls do not depend on a particular VOL connector being loaded. * \snippet{doc} tables/volAPIs.dox vol_independent_table * * \subsubsection subsubsec_vol_compat_opt List of Native VOL Optional Operation Values By Subclass * These values can be passed to the opt type parameter of H5VLquery optional(). * \snippet{doc} tables/volAPIs.dox vol_optional_table * * * * Previous Chapter \ref sec_plist - Next Chapter \ref sec_async * */ /** *\defgroup H5VL VOL connector (H5VL) * * \todo Describe the VOL plugin life cycle. * * \defgroup ASYNC Asynchronous Functions * \brief List of the asynchronous functions. * \note The argument \p es_id associated with the asynchronous APIs is the \Emph{event set id}. See H5ES for *context. * * \defgroup H5VLDEF Definitions * \ingroup H5VL * \defgroup H5VLDEV VOL Developer * \ingroup H5VL * \defgroup H5VLNAT Native VOL * \ingroup H5VL * \defgroup H5VLPT Pass-through VOL * \ingroup H5VL */ #endif /* H5VLmodule_H */