checksum.c File Reference

#include "postgres.h"
#include "storage/checksum.h"

Include dependency graph for checksum.c:

Go to the source code of this file.

Defines
#define	N_SUMS   32
#define	FNV_PRIME   16777619
#define	CHECKSUM_COMP(checksum, value)
Functions
uint32	checksum_block (char *data, uint32 size)
Variables
static const uint32	checksumBaseOffsets [N_SUMS]

---

Define Documentation

#define CHECKSUM_COMP	(		checksum,
			value
	)

Value:

do {\
    uint32 __tmp = (checksum) ^ (value);\
    (checksum) = __tmp * FNV_PRIME ^ (__tmp >> 17);\
} while (0)

Definition at line 126 of file checksum.c.

Referenced by checksum_block().

#define FNV_PRIME   16777619

Definition at line 106 of file checksum.c.

#define N_SUMS   32

Definition at line 104 of file checksum.c.

Referenced by checksum_block().

---

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;
}

---

Variable Documentation

const uint32 checksumBaseOffsets[N_SUMS] [static]

Initial value:

 {
    0x5B1F36E9, 0xB8525960, 0x02AB50AA, 0x1DE66D2A,
    0x79FF467A, 0x9BB9F8A3, 0x217E7CD2, 0x83E13D2C,
    0xF8D4474F, 0xE39EB970, 0x42C6AE16, 0x993216FA,
    0x7B093B5D, 0x98DAFF3C, 0xF718902A, 0x0B1C9CDB,
    0xE58F764B, 0x187636BC, 0x5D7B3BB1, 0xE73DE7DE,
    0x92BEC979, 0xCCA6C0B2, 0x304A0979, 0x85AA43D4,
    0x783125BB, 0x6CA8EAA2, 0xE407EAC6, 0x4B5CFC3E,
    0x9FBF8C76, 0x15CA20BE, 0xF2CA9FD3, 0x959BD756
}

Definition at line 112 of file checksum.c.

Referenced by checksum_block().