checksum.h File Reference

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Functions
uint32	checksum_block (char *data, uint32 size)

---

Function Documentation

uint32 checksum_block	(	char *	data,
		uint32	size
	)

Definition at line 132 of file checksum.c.

References Assert, CHECKSUM_COMP, checksumBaseOffsets, i, and N_SUMS.

Referenced by PageCalcChecksum16().

{
    uint32 sums[N_SUMS];
    uint32 (*dataArr)[N_SUMS] = (uint32 (*)[N_SUMS]) data;
    uint32 result = 0;
    int i, j;

    /* ensure that the size is compatible with the algorithm */
    Assert((size % (sizeof(uint32)*N_SUMS)) == 0);

    /* initialize partial checksums to their corresponding offsets */
    memcpy(sums, checksumBaseOffsets, sizeof(checksumBaseOffsets));

    /* main checksum calculation */
    for (i = 0; i < size/sizeof(uint32)/N_SUMS; i++)
        for (j = 0; j < N_SUMS; j++)
            CHECKSUM_COMP(sums[j], dataArr[i][j]);

    /* finally add in two rounds of zeroes for additional mixing */
    for (i = 0; i < 2; i++)
        for (j = 0; j < N_SUMS; j++)
            CHECKSUM_COMP(sums[j], 0);

    /* xor fold partial checksums together */
    for (i = 0; i < N_SUMS; i++)
        result ^= sums[i];

    return result;
}