Module Name: src
Committed By: riastradh
Date: Mon Apr 27 03:26:10 UTC 2020
Modified Files:
src/usr.bin/cksum: crc.c
Log Message:
Speed up cksum word-by-word with a 15 KB table generated dynamically.
(Really we could generate the main table dynamically too.)
>From anonymous.
To generate a diff of this commit:
cvs rdiff -u -r1.19 -r1.20 src/usr.bin/cksum/crc.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/usr.bin/cksum/crc.c
diff -u src/usr.bin/cksum/crc.c:1.19 src/usr.bin/cksum/crc.c:1.20
--- src/usr.bin/cksum/crc.c:1.19 Wed Oct 29 18:09:35 2014
+++ src/usr.bin/cksum/crc.c Mon Apr 27 03:26:09 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: crc.c,v 1.19 2014/10/29 18:09:35 uebayasi Exp $ */
+/* $NetBSD: crc.c,v 1.20 2020/04/27 03:26:09 riastradh Exp $ */
/*-
* Copyright (c) 1991, 1993
@@ -41,11 +41,13 @@
#if 0
static char sccsid[] = "@(#)crc.c 8.1 (Berkeley) 6/17/93";
#else
-__RCSID("$NetBSD: crc.c,v 1.19 2014/10/29 18:09:35 uebayasi Exp $");
+__RCSID("$NetBSD: crc.c,v 1.20 2020/04/27 03:26:09 riastradh Exp $");
#endif
#endif /* not lint */
#include <sys/types.h>
+#include <sys/endian.h>
+
#include <unistd.h>
#include "extern.h"
@@ -114,20 +116,17 @@ static const u_int32_t crctab[] = {
int
crc(int fd, u_int32_t *cval, off_t *clen)
{
- u_char *p;
ssize_t nr;
u_int32_t thecrc;
off_t len;
u_char buf[16 * 1024];
-#define COMPUTE(var, ch) (var) = (var) << 8 ^ crctab[(var) >> 24 ^ (ch)]
-
thecrc = 0;
len = 0;
- while ((nr = read(fd, buf, sizeof(buf))) > 0)
- for (len += nr, p = buf; nr--; ++p) {
- COMPUTE(thecrc, *p);
- }
+ while ((nr = read(fd, buf, sizeof(buf))) > 0) {
+ thecrc = crc_buf(thecrc, buf, nr);
+ len += nr;
+ }
if (nr < 0)
return 1;
@@ -135,13 +134,31 @@ crc(int fd, u_int32_t *cval, off_t *clen
/* Include the length of the file. */
for (; len != 0; len >>= 8) {
- COMPUTE(thecrc, len & 0xff);
+ thecrc = crc_byte(thecrc, len & 0xff);
}
*cval = ~thecrc;
return 0;
}
+#define COMPUTE(var, ch) (var) = (var) << 8 ^ crctab[(var) >> 24 ^ (ch)]
+
+static uint32_t crcslice[15][256];
+
+static void
+tables(void)
+{
+ int a, b;
+
+ for (a = 0; a < 256; a++) {
+ uint32_t crc = crctab[a];
+ for (b = 0; b < 15; b++) {
+ COMPUTE(crc, 0);
+ crcslice[b][a] = crc;
+ }
+ }
+}
+
/* These two are rather more useful to the outside world */
uint32_t
@@ -149,8 +166,37 @@ crc_buf(uint32_t thecrc, const void *buf
{
const uint8_t *p = buf;
- for (p = buf; len; p++, len--)
+ /* Compute the tables once. */
+ if (crcslice[14][255] == 0)
+ tables();
+
+ for (; len >= 16; p += 16, len -= 16) {
+ uint32_t a = be32dec(p + 0) ^ thecrc;
+ uint32_t b = be32dec(p + 4);
+ uint32_t c = be32dec(p + 8);
+ uint32_t d = be32dec(p + 12);
+ thecrc =
+ crcslice[14][a >> 24 & 0xff] ^
+ crcslice[13][a >> 16 & 0xff] ^
+ crcslice[12][a >> 8 & 0xff] ^
+ crcslice[11][a >> 0 & 0xff] ^
+ crcslice[10][b >> 24 & 0xff] ^
+ crcslice[9][b >> 16 & 0xff] ^
+ crcslice[8][b >> 8 & 0xff] ^
+ crcslice[7][b >> 0 & 0xff] ^
+ crcslice[6][c >> 24 & 0xff] ^
+ crcslice[5][c >> 16 & 0xff] ^
+ crcslice[4][c >> 8 & 0xff] ^
+ crcslice[3][c >> 0 & 0xff] ^
+ crcslice[2][d >> 24 & 0xff] ^
+ crcslice[1][d >> 16 & 0xff] ^
+ crcslice[0][d >> 8 & 0xff] ^
+ crctab[d >> 0 & 0xff];
+ }
+
+ for (; len; p++, len--)
COMPUTE(thecrc, *p);
+
return thecrc;
}
