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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* 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. *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#include "H5Zmodule.h" /* This source code file is part of the H5Z module */
#include "H5private.h" /* Generic Functions */
#include "H5Eprivate.h" /* Error handling */
#include "H5Fprivate.h" /* File access */
#include "H5MMprivate.h" /* Memory management */
#include "H5Zpkg.h" /* Data filters */
/* Local function prototypes */
static size_t H5Z__filter_fletcher32(unsigned flags, size_t cd_nelmts, const unsigned cd_values[],
size_t nbytes, size_t *buf_size, void **buf);
/* This message derives from H5Z */
const H5Z_class2_t H5Z_FLETCHER32[1] = {{
H5Z_CLASS_T_VERS, /* H5Z_class_t version */
H5Z_FILTER_FLETCHER32, /* Filter id number */
1, /* encoder_present flag (set to true) */
1, /* decoder_present flag (set to true) */
"fletcher32", /* Filter name for debugging */
NULL, /* The "can apply" callback */
NULL, /* The "set local" callback */
H5Z__filter_fletcher32, /* The actual filter function */
}};
#define FLETCHER_LEN 4
/*-------------------------------------------------------------------------
* Function: H5Z__filter_fletcher32
*
* Purpose: Implement an I/O filter of Fletcher32 Checksum
*
* Return: Success: Size of buffer filtered
* Failure: 0
*
*-------------------------------------------------------------------------
*/
static size_t
H5Z__filter_fletcher32(unsigned flags, size_t H5_ATTR_UNUSED cd_nelmts,
const unsigned H5_ATTR_UNUSED cd_values[], size_t nbytes, size_t *buf_size, void **buf)
{
void *outbuf = NULL; /* Pointer to new buffer */
unsigned char *src = (unsigned char *)(*buf);
uint32_t fletcher; /* Checksum value */
uint32_t reversed_fletcher; /* Possible wrong checksum value */
uint8_t c[4];
uint8_t tmp;
size_t ret_value = 0; /* Return value */
FUNC_ENTER_PACKAGE
assert(sizeof(uint32_t) >= 4);
if (flags & H5Z_FLAG_REVERSE) { /* Read */
/* Do checksum if it's enabled for read; otherwise skip it
* to save performance. */
if (!(flags & H5Z_FLAG_SKIP_EDC)) {
unsigned char *tmp_src; /* Pointer to checksum in buffer */
size_t src_nbytes = nbytes; /* Original number of bytes */
uint32_t stored_fletcher; /* Stored checksum value */
/* Get the stored checksum */
src_nbytes -= FLETCHER_LEN;
tmp_src = src + src_nbytes;
UINT32DECODE(tmp_src, stored_fletcher);
/* Compute checksum (can't fail) */
fletcher = H5_checksum_fletcher32(src, src_nbytes);
/* The reversed checksum. There was a bug in the calculating code of
* the Fletcher32 checksum in the library before v1.6.3. The checksum
* value wasn't consistent between big-endian and little-endian systems.
* This bug was fixed in Release 1.6.3. However, after fixing the bug,
* the checksum value is no longer the same as before on little-endian
* system. We'll check both the correct checksum and the wrong
* checksum to be consistent with Release 1.6.2 and before.
*/
H5MM_memcpy(c, &fletcher, (size_t)4);
tmp = c[1];
c[1] = c[0];
c[0] = tmp;
tmp = c[3];
c[3] = c[2];
c[2] = tmp;
H5MM_memcpy(&reversed_fletcher, c, (size_t)4);
/* Verify computed checksum matches stored checksum */
if (stored_fletcher != fletcher && stored_fletcher != reversed_fletcher)
HGOTO_ERROR(H5E_STORAGE, H5E_READERROR, 0, "data error detected by Fletcher32 checksum");
}
/* Set return values */
/* (Reuse the input buffer, just note that the size is smaller by the size of the checksum) */
ret_value = nbytes - FLETCHER_LEN;
}
else { /* Write */
unsigned char *dst; /* Temporary pointer to destination buffer */
/* Compute checksum (can't fail) */
fletcher = H5_checksum_fletcher32(src, nbytes);
if (NULL == (outbuf = H5MM_malloc(nbytes + FLETCHER_LEN)))
HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, 0,
"unable to allocate Fletcher32 checksum destination buffer");
dst = (unsigned char *)outbuf;
/* Copy raw data */
H5MM_memcpy((void *)dst, (void *)(*buf), nbytes);
/* Append checksum to raw data for storage */
dst += nbytes;
UINT32ENCODE(dst, fletcher);
/* Free input buffer */
H5MM_xfree(*buf);
/* Set return values */
*buf_size = nbytes + FLETCHER_LEN;
*buf = outbuf;
outbuf = NULL;
ret_value = *buf_size;
}
done:
if (outbuf)
H5MM_xfree(outbuf);
FUNC_LEAVE_NOAPI(ret_value)
}
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