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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Copyright by The HDF Group. *
* Copyright by the Board of Trustees of the University of Illinois. *
* 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. *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*
* Programmer: Raymond Lu
* Wednesday, 20 September 2006
*
* Purpose: The public header file for the direct driver.
*/
#ifndef H5FDdirect_H
#define H5FDdirect_H
#ifdef H5_HAVE_DIRECT
#define H5FD_DIRECT (H5FD_direct_init())
#else
#define H5FD_DIRECT (H5I_INVALID_HID)
#endif /* H5_HAVE_DIRECT */
#ifdef H5_HAVE_DIRECT
#ifdef __cplusplus
extern "C" {
#endif
/* Default values for memory boundary, file block size, and maximal copy buffer size.
* Application can set these values through the function H5Pset_fapl_direct. */
#define MBOUNDARY_DEF 4096
#define FBSIZE_DEF 4096
#define CBSIZE_DEF 16 * 1024 * 1024
H5_DLL hid_t H5FD_direct_init(void);
/**
* \ingroup FAPL
*
* \brief Sets up use of the direct I/O driver
*
* \fapl_id
* \param[in] alignment Required memory alignment boundary
* \param[in] block_size File system block size
* \param[in] cbuf_size Copy buffer size
* \returns \herr_t
*
* \details H5Pset_fapl_direct() sets the file access property list, \p fapl_id,
* to use the direct I/O driver, #H5FD_DIRECT. With this driver, data
* is written to or read from the file synchronously without being
* cached by the system.
*
* File systems usually require the data address in memory, the file
* address, and the size of the data to be aligned. The HDF5 library’s
* direct I/O driver is able to handle unaligned data, though that will
* consume some additional memory resources and may slow
* performance. To get better performance, use the system function \p
* posix_memalign to align the data buffer in memory and the HDF5
* function H5Pset_alignment() to align the data in the file. Be aware,
* however, that aligned data I/O may cause the HDF5 file to be bigger
* than the actual data size would otherwise require because the
* alignment may leave some holes in the file.
*
* \p alignment specifies the required alignment boundary in memory.
*
* \p block_size specifies the file system block size. A value of 0
* (zero) means to use HDF5 library’s default value of 4KB.
*
* \p cbuf_size specifies the copy buffer size.
*
* \since 1.8.0
*
*/
H5_DLL herr_t H5Pset_fapl_direct(hid_t fapl_id, size_t alignment, size_t block_size, size_t cbuf_size);
/**
* \ingroup FAPL
*
* \brief Retrieves direct I/O driver settings
*
* \fapl_id
* \param[out] boundary Required memory alignment boundary
* \param[out] block_size File system block size
* \param[out] cbuf_size Copy buffer size
* \returns \herr_t
*
* \details H5Pget_fapl_direct() retrieves the required memory alignment (\p
* alignment), file system block size (\p block_size), and copy buffer
* size (\p cbuf_size) settings for the direct I/O driver, #H5FD_DIRECT,
* from the file access property list \p fapl_id.
*
* See H5Pset_fapl_direct() for discussion of these values,
* requirements, and important considerations.
*
* \since 1.8.0
*
*/
H5_DLL herr_t H5Pget_fapl_direct(hid_t fapl_id, size_t *boundary /*out*/, size_t *block_size /*out*/,
size_t *cbuf_size /*out*/);
#ifdef __cplusplus
}
#endif
#endif /* H5_HAVE_DIRECT */
#endif
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