#include "storage/bufpage.h"

Include dependency graph for checksum_impl.h:

This graph shows which files directly or indirectly include this file:

Data Structures
union	PGChecksummablePage

Macros
#define	N_SUMS 32

#define	FNV_PRIME 16777619

#define	CHECKSUM_COMP(checksum, value)

Functions
static uint32	pg_checksum_block (const PGChecksummablePage *page)

uint16	pg_checksum_page (char *page, BlockNumber blkno)

Variables
static const uint32	checksumBaseOffsets [N_SUMS]

Macro Definition Documentation

◆ CHECKSUM_COMP

#define CHECKSUM_COMP	(	checksum,
		value
	)

Value:

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

Definition at line 135 of file checksum_impl.h.

◆ FNV_PRIME

#define FNV_PRIME 16777619

Definition at line 108 of file checksum_impl.h.

◆ N_SUMS

#define N_SUMS 32

Definition at line 106 of file checksum_impl.h.

Function Documentation

◆ pg_checksum_block()

static uint32 pg_checksum_block ( const PGChecksummablePage * page )

static

Definition at line 146 of file checksum_impl.h.

 {
     uint32      sums[N_SUMS];
     uint32      result = 0;
     uint32      i,
                 j;
  
     /* ensure that the size is compatible with the algorithm */
     Assert(sizeof(PGChecksummablePage) == BLCKSZ);
  
     /* initialize partial checksums to their corresponding offsets */
     memcpy(sums, checksumBaseOffsets, sizeof(checksumBaseOffsets));
  
     /* main checksum calculation */
     for (i = 0; i < (uint32) (BLCKSZ / (sizeof(uint32) * N_SUMS)); i++)
         for (j = 0; j < N_SUMS; j++)
             CHECKSUM_COMP(sums[j], page->data[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;
 }

References Assert, CHECKSUM_COMP, checksumBaseOffsets, PGChecksummablePage::data, i, j, and N_SUMS.

Referenced by pg_checksum_page().

◆ pg_checksum_page()

uint16 pg_checksum_page	(	char *	page,
		BlockNumber	blkno
	)

Definition at line 187 of file checksum_impl.h.

 {
     PGChecksummablePage *cpage = (PGChecksummablePage *) page;
     uint16      save_checksum;
     uint32      checksum;
  
     /* We only calculate the checksum for properly-initialized pages */
     Assert(!PageIsNew((Page) page));
  
     /*
      * Save pd_checksum and temporarily set it to zero, so that the checksum
      * calculation isn't affected by the old checksum stored on the page.
      * Restore it after, because actually updating the checksum is NOT part of
      * the API of this function.
      */
     save_checksum = cpage->phdr.pd_checksum;
     cpage->phdr.pd_checksum = 0;
     checksum = pg_checksum_block(cpage);
     cpage->phdr.pd_checksum = save_checksum;
  
     /* Mix in the block number to detect transposed pages */
     checksum ^= blkno;
  
     /*
      * Reduce to a uint16 (to fit in the pd_checksum field) with an offset of
      * one. That avoids checksums of zero, which seems like a good idea.
      */
     return (uint16) ((checksum % 65535) + 1);
 }

References Assert, PageIsNew(), PageHeaderData::pd_checksum, pg_checksum_block(), and PGChecksummablePage::phdr.

Referenced by page_checksum_internal(), PageIsVerifiedExtended(), PageSetChecksumCopy(), PageSetChecksumInplace(), rewriteVisibilityMap(), scan_file(), and verify_page_checksum().

Variable Documentation

◆ checksumBaseOffsets

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 121 of file checksum_impl.h.

Referenced by pg_checksum_block().

Data Structures

Macros

Functions

Variables