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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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* Copyright by The HDF Group. *
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* All rights reserved. *
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* *
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* This file is part of HDF5. The full HDF5 copyright notice, including *
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* terms governing use, modification, and redistribution, is contained in *
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* the COPYING file, which can be found at the root of the source code *
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* distribution tree, or in https://www.hdfgroup.org/licenses. *
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* If you do not have access to either file, you may request a copy from *
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* help@hdfgroup.org. *
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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/*
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* Programmer: Raymond Lu
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* Wednesday, 20 September 2006
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*
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* Purpose: The public header file for the direct driver.
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*/
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#ifndef H5FDdirect_H
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#define H5FDdirect_H
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#ifdef H5_HAVE_DIRECT
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#define H5FD_DIRECT (H5FDperform_init(H5FD_direct_init))
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#define H5FD_DIRECT_VALUE H5_VFD_DIRECT
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#else
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#define H5FD_DIRECT (H5I_INVALID_HID)
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#define H5FD_DIRECT_VALUE H5_VFD_INVALID
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#endif /* H5_HAVE_DIRECT */
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#ifdef H5_HAVE_DIRECT
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Default values for memory boundary, file block size, and maximal copy buffer size.
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* Application can set these values through the function H5Pset_fapl_direct. */
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#define MBOUNDARY_DEF 4096
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#define FBSIZE_DEF 4096
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#define CBSIZE_DEF 16 * 1024 * 1024
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H5_DLL hid_t H5FD_direct_init(void);
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/**
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* \ingroup FAPL
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*
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* \brief Sets up use of the direct I/O driver
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*
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* \fapl_id
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* \param[in] alignment Required memory alignment boundary
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* \param[in] block_size File system block size
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* \param[in] cbuf_size Copy buffer size
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* \returns \herr_t
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*
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* \details H5Pset_fapl_direct() sets the file access property list, \p fapl_id,
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* to use the direct I/O driver, #H5FD_DIRECT. With this driver, data
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* is written to or read from the file synchronously without being
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* cached by the system.
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*
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* File systems usually require the data address in memory, the file
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* address, and the size of the data to be aligned. The HDF5 library’s
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* direct I/O driver is able to handle unaligned data, though that will
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* consume some additional memory resources and may slow
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* performance. To get better performance, use the system function \p
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* posix_memalign to align the data buffer in memory and the HDF5
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* function H5Pset_alignment() to align the data in the file. Be aware,
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* however, that aligned data I/O may cause the HDF5 file to be bigger
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* than the actual data size would otherwise require because the
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* alignment may leave some holes in the file.
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*
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* \p alignment specifies the required alignment boundary in memory.
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*
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* \p block_size specifies the file system block size. A value of 0
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* (zero) means to use HDF5 library’s default value of 4KB.
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*
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* \p cbuf_size specifies the copy buffer size.
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*
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* \since 1.8.0
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*
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*/
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H5_DLL herr_t H5Pset_fapl_direct(hid_t fapl_id, size_t alignment, size_t block_size, size_t cbuf_size);
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/**
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* \ingroup FAPL
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*
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* \brief Retrieves direct I/O driver settings
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*
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* \fapl_id
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* \param[out] boundary Required memory alignment boundary
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* \param[out] block_size File system block size
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* \param[out] cbuf_size Copy buffer size
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* \returns \herr_t
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*
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* \details H5Pget_fapl_direct() retrieves the required memory alignment (\p
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* alignment), file system block size (\p block_size), and copy buffer
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* size (\p cbuf_size) settings for the direct I/O driver, #H5FD_DIRECT,
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* from the file access property list \p fapl_id.
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*
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* See H5Pset_fapl_direct() for discussion of these values,
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* requirements, and important considerations.
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*
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* \since 1.8.0
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*
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*/
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H5_DLL herr_t H5Pget_fapl_direct(hid_t fapl_id, size_t *boundary /*out*/, size_t *block_size /*out*/,
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size_t *cbuf_size /*out*/);
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#ifdef __cplusplus
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}
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#endif
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#endif /* H5_HAVE_DIRECT */
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#endif
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