mirror of
https://github.com/git/git.git
synced 2024-10-31 14:27:54 +01:00
04fe2a1706
Since we already depend on zlib, we don't need to define our own adler32(). Spotted by oprofile. Signed-off-by: Peter Eriksen <s022018@student.dtu.dk> Signed-off-by: Junio C Hamano <junkio@cox.net>
287 lines
6.1 KiB
C
287 lines
6.1 KiB
C
/*
|
|
* 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"
|
|
#include "zlib.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)))
|
|
|
|
static unsigned int hashbits(unsigned int size)
|
|
{
|
|
unsigned int val = 1, bits = 0;
|
|
while (val < size && bits < 32) {
|
|
val <<= 1;
|
|
bits++;
|
|
}
|
|
return bits ? bits: 1;
|
|
}
|
|
|
|
typedef struct s_chanode {
|
|
struct s_chanode *next;
|
|
int icurr;
|
|
} chanode_t;
|
|
|
|
typedef struct s_chastore {
|
|
int isize, nsize;
|
|
chanode_t *ancur;
|
|
} chastore_t;
|
|
|
|
static void cha_init(chastore_t *cha, int isize, int icount)
|
|
{
|
|
cha->isize = isize;
|
|
cha->nsize = icount * isize;
|
|
cha->ancur = NULL;
|
|
}
|
|
|
|
static void *cha_alloc(chastore_t *cha)
|
|
{
|
|
chanode_t *ancur;
|
|
void *data;
|
|
|
|
ancur = cha->ancur;
|
|
if (!ancur || ancur->icurr == cha->nsize) {
|
|
ancur = malloc(sizeof(chanode_t) + cha->nsize);
|
|
if (!ancur)
|
|
return NULL;
|
|
ancur->icurr = 0;
|
|
ancur->next = cha->ancur;
|
|
cha->ancur = ancur;
|
|
}
|
|
|
|
data = (void *)ancur + sizeof(chanode_t) + ancur->icurr;
|
|
ancur->icurr += cha->isize;
|
|
return data;
|
|
}
|
|
|
|
static void cha_free(chastore_t *cha)
|
|
{
|
|
chanode_t *cur = cha->ancur;
|
|
while (cur) {
|
|
chanode_t *tmp = cur;
|
|
cur = cur->next;
|
|
free(tmp);
|
|
}
|
|
}
|
|
|
|
typedef struct s_bdrecord {
|
|
struct s_bdrecord *next;
|
|
unsigned int fp;
|
|
const unsigned char *ptr;
|
|
} bdrecord_t;
|
|
|
|
typedef struct s_bdfile {
|
|
chastore_t cha;
|
|
unsigned int fphbits;
|
|
bdrecord_t **fphash;
|
|
} bdfile_t;
|
|
|
|
static int delta_prepare(const unsigned char *buf, int bufsize, bdfile_t *bdf)
|
|
{
|
|
unsigned int fphbits;
|
|
int i, hsize;
|
|
const unsigned char *data, *top;
|
|
bdrecord_t *brec;
|
|
bdrecord_t **fphash;
|
|
|
|
fphbits = hashbits(bufsize / BLK_SIZE + 1);
|
|
hsize = 1 << fphbits;
|
|
fphash = malloc(hsize * sizeof(bdrecord_t *));
|
|
if (!fphash)
|
|
return -1;
|
|
for (i = 0; i < hsize; i++)
|
|
fphash[i] = NULL;
|
|
cha_init(&bdf->cha, sizeof(bdrecord_t), hsize / 4 + 1);
|
|
|
|
top = buf + bufsize;
|
|
data = buf + (bufsize / BLK_SIZE) * BLK_SIZE;
|
|
if (data == top)
|
|
data -= BLK_SIZE;
|
|
|
|
for ( ; data >= buf; data -= BLK_SIZE) {
|
|
brec = cha_alloc(&bdf->cha);
|
|
if (!brec) {
|
|
cha_free(&bdf->cha);
|
|
free(fphash);
|
|
return -1;
|
|
}
|
|
brec->fp = adler32(0, data, MIN(BLK_SIZE, top - data));
|
|
brec->ptr = data;
|
|
i = HASH(brec->fp, fphbits);
|
|
brec->next = fphash[i];
|
|
fphash[i] = brec;
|
|
}
|
|
|
|
bdf->fphbits = fphbits;
|
|
bdf->fphash = fphash;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void delta_cleanup(bdfile_t *bdf)
|
|
{
|
|
free(bdf->fphash);
|
|
cha_free(&bdf->cha);
|
|
}
|
|
|
|
#define COPYOP_SIZE(o, s) \
|
|
(!!(o & 0xff) + !!(o & 0xff00) + !!(o & 0xff0000) + !!(o & 0xff000000) + \
|
|
!!(s & 0xff) + !!(s & 0xff00) + 1)
|
|
|
|
void *diff_delta(void *from_buf, unsigned long from_size,
|
|
void *to_buf, unsigned long to_size,
|
|
unsigned long *delta_size,
|
|
unsigned long max_size)
|
|
{
|
|
int i, outpos, outsize, inscnt, csize, msize, moff;
|
|
unsigned int fp;
|
|
const unsigned char *ref_data, *ref_top, *data, *top, *ptr1, *ptr2;
|
|
unsigned char *out, *orig;
|
|
bdrecord_t *brec;
|
|
bdfile_t bdf;
|
|
|
|
if (!from_size || !to_size || delta_prepare(from_buf, from_size, &bdf))
|
|
return NULL;
|
|
|
|
outpos = 0;
|
|
outsize = 8192;
|
|
out = malloc(outsize);
|
|
if (!out) {
|
|
delta_cleanup(&bdf);
|
|
return NULL;
|
|
}
|
|
|
|
ref_data = from_buf;
|
|
ref_top = from_buf + from_size;
|
|
data = to_buf;
|
|
top = to_buf + to_size;
|
|
|
|
/* store reference buffer size */
|
|
out[outpos++] = from_size;
|
|
from_size >>= 7;
|
|
while (from_size) {
|
|
out[outpos - 1] |= 0x80;
|
|
out[outpos++] = from_size;
|
|
from_size >>= 7;
|
|
}
|
|
|
|
/* store target buffer size */
|
|
out[outpos++] = to_size;
|
|
to_size >>= 7;
|
|
while (to_size) {
|
|
out[outpos - 1] |= 0x80;
|
|
out[outpos++] = to_size;
|
|
to_size >>= 7;
|
|
}
|
|
|
|
inscnt = 0;
|
|
moff = 0;
|
|
while (data < top) {
|
|
msize = 0;
|
|
fp = adler32(0, data, MIN(top - data, BLK_SIZE));
|
|
i = HASH(fp, bdf.fphbits);
|
|
for (brec = bdf.fphash[i]; brec; brec = brec->next) {
|
|
if (brec->fp == fp) {
|
|
csize = ref_top - brec->ptr;
|
|
if (csize > top - data)
|
|
csize = top - data;
|
|
for (ptr1 = brec->ptr, ptr2 = data;
|
|
csize && *ptr1 == *ptr2;
|
|
csize--, ptr1++, ptr2++);
|
|
|
|
csize = ptr1 - brec->ptr;
|
|
if (csize > msize) {
|
|
moff = brec->ptr - ref_data;
|
|
msize = csize;
|
|
if (msize >= 0x10000) {
|
|
msize = 0x10000;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!msize || msize < COPYOP_SIZE(moff, msize)) {
|
|
if (!inscnt)
|
|
outpos++;
|
|
out[outpos++] = *data++;
|
|
inscnt++;
|
|
if (inscnt == 0x7f) {
|
|
out[outpos - inscnt - 1] = inscnt;
|
|
inscnt = 0;
|
|
}
|
|
} else {
|
|
if (inscnt) {
|
|
out[outpos - inscnt - 1] = inscnt;
|
|
inscnt = 0;
|
|
}
|
|
|
|
data += msize;
|
|
orig = out + outpos++;
|
|
i = 0x80;
|
|
|
|
if (moff & 0xff) { out[outpos++] = moff; i |= 0x01; }
|
|
moff >>= 8;
|
|
if (moff & 0xff) { out[outpos++] = moff; i |= 0x02; }
|
|
moff >>= 8;
|
|
if (moff & 0xff) { out[outpos++] = moff; i |= 0x04; }
|
|
moff >>= 8;
|
|
if (moff & 0xff) { out[outpos++] = moff; i |= 0x08; }
|
|
|
|
if (msize & 0xff) { out[outpos++] = msize; i |= 0x10; }
|
|
msize >>= 8;
|
|
if (msize & 0xff) { out[outpos++] = msize; i |= 0x20; }
|
|
|
|
*orig = i;
|
|
}
|
|
|
|
if (max_size && outpos > max_size) {
|
|
free(out);
|
|
delta_cleanup(&bdf);
|
|
return NULL;
|
|
}
|
|
|
|
/* next time around the largest possible output is 1 + 4 + 3 */
|
|
if (outpos > outsize - 8) {
|
|
void *tmp = out;
|
|
outsize = outsize * 3 / 2;
|
|
out = realloc(out, outsize);
|
|
if (!out) {
|
|
free(tmp);
|
|
delta_cleanup(&bdf);
|
|
return NULL;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (inscnt)
|
|
out[outpos - inscnt - 1] = inscnt;
|
|
|
|
delta_cleanup(&bdf);
|
|
*delta_size = outpos;
|
|
return out;
|
|
}
|