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diff-delta.c
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Nicolas Pitre authored
This is a wrap-up patch including all the cleanups I've done to the delta code and its usage. The most important change is the factorization of the delta header handling code. Signed-off-by:
Nicolas Pitre <nico@cam.org> Signed-off-by:
Linus Torvalds <torvalds@osdl.org>
Nicolas Pitre authoredThis is a wrap-up patch including all the cleanups I've done to the delta code and its usage. The most important change is the factorization of the delta header handling code. Signed-off-by:
Nicolas Pitre <nico@cam.org> Signed-off-by:
Linus Torvalds <torvalds@osdl.org>
diff-delta.c 7.14 KiB
/*
* diff-delta.c: generate a delta between two buffers
*
* Many parts of this file have been lifted from LibXDiff version 0.10.
* http://www.xmailserver.org/xdiff-lib.html
*
* LibXDiff was written by Davide Libenzi <davidel@xmailserver.org>
* Copyright (C) 2003 Davide Libenzi
*
* Many mods for GIT usage by Nicolas Pitre <nico@cam.org>, (C) 2005.
*
* This file is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* Use of this within git automatically means that the LGPL
* licensing gets turned into GPLv2 within this project.
*/
#include <stdlib.h>
#include "delta.h"
/* block size: min = 16, max = 64k, power of 2 */
#define BLK_SIZE 16
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define GR_PRIME 0x9e370001
#define HASH(v, b) (((unsigned int)(v) * GR_PRIME) >> (32 - (b)))
/* largest prime smaller than 65536 */
#define BASE 65521
/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
#define NMAX 5552
#define DO1(buf, i) { s1 += buf[i]; s2 += s1; }
#define DO2(buf, i) DO1(buf, i); DO1(buf, i + 1);
#define DO4(buf, i) DO2(buf, i); DO2(buf, i + 2);
#define DO8(buf, i) DO4(buf, i); DO4(buf, i + 4);
#define DO16(buf) DO8(buf, 0); DO8(buf, 8);
static unsigned int adler32(unsigned int adler, const unsigned char *buf, int len)
{
int k;
unsigned int s1 = adler & 0xffff;
unsigned int s2 = adler >> 16;
while (len > 0) {
k = MIN(len, NMAX);
len -= k;
while (k >= 16) {
DO16(buf);
buf += 16;
k -= 16;
}
if (k != 0)
do {
s1 += *buf++;
s2 += s1;
} while (--k);
s1 %= BASE;
s2 %= BASE;
}
return (s2 << 16) | s1;
}