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Use optimized byte swap operations for Microsoft and GNU [Snyder].

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This commit is contained in:
Mark Adler
2012-02-11 00:26:38 -08:00
parent 1a4ba8cd91
commit 7d45cf5a1d
3 changed files with 19 additions and 13 deletions
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10
crc32.c
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@@ -59,8 +59,6 @@
/* Definitions for doing the crc four data bytes at a time. */
#ifdef BYFOUR
typedef u4 crc_table_t;
# define REV(w) ((((w)>>24)&0xff)+(((w)>>8)&0xff00)+ \
(((w)&0xff00)<<8)+(((w)&0xff)<<24))
local unsigned long crc32_little OF((unsigned long,
const unsigned char FAR *, unsigned));
local unsigned long crc32_big OF((unsigned long,
@@ -145,11 +143,11 @@ local void make_crc_table()
and then the byte reversal of those as well as the first table */
for (n = 0; n < 256; n++) {
c = crc_table[0][n];
crc_table[4][n] = REV(c);
crc_table[4][n] = ZSWAP32(c);
for (k = 1; k < 4; k++) {
c = crc_table[0][c & 0xff] ^ (c >> 8);
crc_table[k][n] = c;
crc_table[k + 4][n] = REV(c);
crc_table[k + 4][n] = ZSWAP32(c);
}
}
#endif /* BYFOUR */
@@ -317,7 +315,7 @@ local unsigned long crc32_big(crc, buf, len)
register u4 c;
register const u4 FAR *buf4;
c = REV((u4)crc);
c = ZSWAP32((u4)crc);
c = ~c;
while (len && ((ptrdiff_t)buf & 3)) {
c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
@@ -341,7 +339,7 @@ local unsigned long crc32_big(crc, buf, len)
c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
} while (--len);
c = ~c;
return (unsigned long)(REV(c));
return (unsigned long)(ZSWAP32(c));
}
#endif /* BYFOUR */