69 lines
2.6 KiB
C
69 lines
2.6 KiB
C
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/****************************************************************
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* *
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* Copyright 2005, 2009 Fidelity Information Services, Inc *
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* *
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* This source code contains the intellectual property *
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* of its copyright holder(s), and is made available *
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* under a license. If you do not know the terms of *
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* the license, please stop and do not read further. *
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* *
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****************************************************************/
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#include "mdef.h"
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#include "gdsroot.h"
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#include "gdsbt.h"
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#include "gdsfhead.h"
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#include "jnl_get_checksum.h"
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/*
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* Input :
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* buff : Pointer to the input buffer whose checksum needs to be computed.
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* bufflen : Buffer size in bytes
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*
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* Returns:
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* Computed checksum.
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*
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* Algorithm:
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* For every 512 (DISK_BLOCK_SIZE) byte block of the input buffer, the first 16 and last 16 bytes are considered for checksum.
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* The way this is implemented is as follows.
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* For the 0th 512-byte block, the first 16 bytes are considered.
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* For the 1st 512-byte block, the last 16 bytes of the 0th block and the first 16 bytes of the 1st block are considered.
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* This is taken as a contiguous sequence of 32-bytes (i.e. CHKSUM_SEGLEN4 uint4s)
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* For the 2nd 512-byte block, the last 16 bytes of the 1st block and the first 16 bytes of the 2nd block are considered.
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* This is taken as a contiguous sequence of 32-bytes (i.e. CHKSUM_SEGLEN4 uint4s)
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* And so on until the input buffer length is exceeded.
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* If bufflen is not divisible by 4, it is ROUNDED DOWN to the nearest 4-byte (uint4) multiple.
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*/
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uint4 jnl_get_checksum(uint4 *buff, sgmnt_addrs *csa, int bufflen)
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{
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uint4 *top, *blk_base, *blk_top, blen, checksum;
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# ifdef GTM_CRYPT
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DEBUG_ONLY(
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sm_uc_ptr_t orig_buff = NULL;
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)
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if (NULL != csa && (csa->hdr->is_encrypted))
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{
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DBG_ENSURE_PTR_IS_VALID_GLOBUFF(csa, csa->hdr, (sm_uc_ptr_t)buff);
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DEBUG_ONLY(orig_buff = (unsigned char *)buff;)
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buff = (uint4 *)GDS_ANY_ENCRYPTGLOBUF(buff, csa);
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DBG_ENSURE_PTR_IS_VALID_ENCTWINGLOBUFF(csa, csa->hdr, (sm_uc_ptr_t)buff);
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}
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# endif
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checksum = INIT_CHECKSUM_SEED;
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for (blen = bufflen / SIZEOF(*buff), top = buff + blen, blk_top = buff + CHKSUM_SEGLEN4 / 2; buff < top ;)
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{
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if (blk_top > top)
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blk_top = top;
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for ( ; buff < blk_top; buff++)
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checksum = ADJUST_CHECKSUM(checksum, *buff);
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blk_top = (uint4 *)((sm_uc_ptr_t)buff + DISK_BLOCK_SIZE);
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buff = blk_top - CHKSUM_SEGLEN4;
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}
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/* It is theoretically possible the computed checksum calculates to 0. Since we use a 0 to imply checksum
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* was never computed, we need to return a non-zero value so in this case return INIT_CHECKSUM_SEED
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*/
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if (!checksum)
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checksum = INIT_CHECKSUM_SEED;
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return checksum;
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}
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