greenplumn pg_crc32c_armv8 源码
greenplumn pg_crc32c_armv8 代码
文件路径：/src/port/pg_crc32c_armv8.c
/*-------------------------------------------------------------------------
*
* pg_crc32c_armv8.c
* Compute CRC-32C checksum using ARMv8 CRC Extension instructions
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/port/pg_crc32c_armv8.c
*
*-------------------------------------------------------------------------
*/
#include "c.h"
#include "port/pg_crc32c.h"
#include <arm_acle.h>
pg_crc32c
pg_comp_crc32c_armv8(pg_crc32c crc, const void *data, size_t len)
{
const unsigned char *p = data;
const unsigned char *pend = p + len;
/*
* ARMv8 doesn't require alignment, but aligned memory access is
* significantly faster. Process leading bytes so that the loop below
* starts with a pointer aligned to eight bytes.
*/
if (!PointerIsAligned(p, uint16) &&
p + 1 <= pend)
{
crc = __crc32cb(crc, *p);
p += 1;
}
if (!PointerIsAligned(p, uint32) &&
p + 2 <= pend)
{
crc = __crc32ch(crc, *(uint16 *) p);
p += 2;
}
if (!PointerIsAligned(p, uint64) &&
p + 4 <= pend)
{
crc = __crc32cw(crc, *(uint32 *) p);
p += 4;
}
/* Process eight bytes at a time, as far as we can. */
while (p + 8 <= pend)
{
crc = __crc32cd(crc, *(uint64 *) p);
p += 8;
}
/* Process remaining 0-7 bytes. */
if (p + 4 <= pend)
{
crc = __crc32cw(crc, *(uint32 *) p);
p += 4;
}
if (p + 2 <= pend)
{
crc = __crc32ch(crc, *(uint16 *) p);
p += 2;
}
if (p < pend)
{
crc = __crc32cb(crc, *p);
}
return crc;
}
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