pg_crc32c_sb8.c File Reference

#include "c.h"
#include "port/pg_crc32c.h"

Include dependency graph for pg_crc32c_sb8.c:

Go to the source code of this file.

Macros
#define	CRC8(x)   pg_crc32c_table[0][(crc ^ (x)) & 0xFF] ^ (crc >> 8)

Functions
pg_crc32c	pg_comp_crc32c_sb8 (pg_crc32c crc, const void *data, size_t len)

Variables
static const uint32	pg_crc32c_table [8][256]

Macro Definition Documentation

CRC8

#define CRC8

(

x

)

pg_crc32c_table[0][(crc ^ (x)) & 0xFF] ^ (crc >> 8)

Definition at line 31 of file pg_crc32c_sb8.c.

Function Documentation

pg_comp_crc32c_sb8()

pg_crc32c pg_comp_crc32c_sb8	(	pg_crc32c	crc,
		const void *	data,
		size_t	len
	)

Definition at line 35 of file pg_crc32c_sb8.c.

{
    const unsigned char *p = data;
    const uint32 *p4;
 
    /*
     * Handle 0-3 initial bytes one at a time, so that the loop below starts
     * with a pointer aligned to four bytes.
     */
    while (len > 0 && ((uintptr_t) p & 3))
    {
        crc = CRC8(*p++);
        len--;
    }
 
    /*
     * Process eight bytes of data at a time.
     */
    p4 = (const uint32 *) p;
    while (len >= 8)
    {
        uint32      a = *p4++ ^ crc;
        uint32      b = *p4++;
 
#ifdef WORDS_BIGENDIAN
        const uint8 c0 = b;
        const uint8 c1 = b >> 8;
        const uint8 c2 = b >> 16;
        const uint8 c3 = b >> 24;
        const uint8 c4 = a;
        const uint8 c5 = a >> 8;
        const uint8 c6 = a >> 16;
        const uint8 c7 = a >> 24;
#else
        const uint8 c0 = b >> 24;
        const uint8 c1 = b >> 16;
        const uint8 c2 = b >> 8;
        const uint8 c3 = b;
        const uint8 c4 = a >> 24;
        const uint8 c5 = a >> 16;
        const uint8 c6 = a >> 8;
        const uint8 c7 = a;
#endif
 
        crc =
            pg_crc32c_table[0][c0] ^ pg_crc32c_table[1][c1] ^
            pg_crc32c_table[2][c2] ^ pg_crc32c_table[3][c3] ^
            pg_crc32c_table[4][c4] ^ pg_crc32c_table[5][c5] ^
            pg_crc32c_table[6][c6] ^ pg_crc32c_table[7][c7];
 
        len -= 8;
    }
 
    /*
     * Handle any remaining bytes one at a time.
     */
    p = (const unsigned char *) p4;
    while (len > 0)
    {
        crc = CRC8(*p++);
        len--;
    }
 
    return crc;
}

References a, b, crc, CRC8, data, len, and pg_crc32c_table.

Referenced by pg_comp_crc32c_choose().

Variable Documentation

pg_crc32c_table

static const uint32 pg_crc32c_table

static

Definition at line 25 of file pg_crc32c_sb8.c.

Referenced by pg_comp_crc32c_sb8().