Commit a310d434 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Linus Torvalds

[PATCH] Deltification library work by Nicolas Pitre.

This patch adds the basic library functions to create and replay delta
information.  Also included is a test-delta utility to validate the
code.

diff-delta was based on LibXDiff written by Davide Libenzi
Signed-off-by: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarDavide Libenzi <davidel@xmailserver.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 21949255
......@@ -36,9 +36,9 @@ install: $(PROG) $(SCRIPTS)
$(INSTALL) $(PROG) $(SCRIPTS) $(dest)$(bin)
LIB_OBJS=read-cache.o sha1_file.o usage.o object.o commit.o tree.o blob.o \
tag.o date.o
tag.o date.o diff-delta.o patch-delta.o
LIB_FILE=libgit.a
LIB_H=cache.h object.h blob.h tree.h commit.h tag.h
LIB_H=cache.h object.h blob.h tree.h commit.h tag.h delta.h
LIB_H += strbuf.h
LIB_OBJS += strbuf.o
......@@ -72,6 +72,9 @@ $(LIB_FILE): $(LIB_OBJS)
test-date: test-date.c date.o
$(CC) $(CFLAGS) -o $@ test-date.c date.o
test-delta: test-delta.c diff-delta.o patch-delta.o
$(CC) $(CFLAGS) -o $@ $^
git-%: %.c $(LIB_FILE)
$(CC) $(CFLAGS) -o $@ $(filter %.c,$^) $(LIBS)
......
extern void *diff_delta(void *from_buf, unsigned long from_size,
void *to_buf, unsigned long to_size,
unsigned long *delta_size);
extern void *patch_delta(void *src_buf, unsigned long src_size,
void *delta_buf, unsigned long delta_size,
unsigned long *dst_size);
/*
* 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;
}
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 {
chanode_t *head, *tail;
int isize, nsize;
chanode_t *ancur;
chanode_t *sncur;
int scurr;
} chastore_t;
static void cha_init(chastore_t *cha, int isize, int icount)
{
cha->head = cha->tail = NULL;
cha->isize = isize;
cha->nsize = icount * isize;
cha->ancur = cha->sncur = NULL;
cha->scurr = 0;
}
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 = NULL;
if (cha->tail)
cha->tail->next = ancur;
if (!cha->head)
cha->head = ancur;
cha->tail = 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->head;
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 {
const unsigned char *data, *top;
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 *base, *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);
bdf->data = data = base = buf;
bdf->top = top = buf + bufsize;
data += (bufsize / BLK_SIZE) * BLK_SIZE;
if (data == top)
data -= BLK_SIZE;
for ( ; data >= base; 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)
{
int i, outpos, outsize, inscnt, csize, msize, moff;
unsigned int fp;
const unsigned char *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;
}
data = to_buf;
top = to_buf + to_size;
/* store reference buffer size */
orig = out + outpos++;
*orig = i = 0;
do {
if (from_size & 0xff) {
*orig |= (1 << i);
out[outpos++] = from_size;
}
i++;
from_size >>= 8;
} while (from_size);
/* store target buffer size */
orig = out + outpos++;
*orig = i = 0;
do {
if (to_size & 0xff) {
*orig |= (1 << i);
out[outpos++] = to_size;
}
i++;
to_size >>= 8;
} while (to_size);
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 = bdf.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 - bdf.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;
}
/* 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;
}
/*
* patch-delta.c:
* recreate a buffer from a source and the delta produced by diff-delta.c
*
* (C) 2005 Nicolas Pitre <nico@cam.org>
*
* This code is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <stdlib.h>
#include <string.h>
#include "delta.h"
void *patch_delta(void *src_buf, unsigned long src_size,
void *delta_buf, unsigned long delta_size,
unsigned long *dst_size)
{
const unsigned char *data, *top;
unsigned char *dst_buf, *out, cmd;
unsigned long size;
int i;
/* the smallest delta size possible is 6 bytes */
if (delta_size < 6)
return NULL;
data = delta_buf;
top = delta_buf + delta_size;
/* make sure the orig file size matches what we expect */
size = i = 0;
cmd = *data++;
while (cmd) {
if (cmd & 1)
size |= *data++ << i;
i += 8;
cmd >>= 1;
}
if (size != src_size)
return NULL;
/* now the result size */
size = i = 0;
cmd = *data++;
while (cmd) {
if (cmd & 1)
size |= *data++ << i;
i += 8;
cmd >>= 1;
}
dst_buf = malloc(size);
if (!dst_buf)
return NULL;
out = dst_buf;
while (data < top) {
cmd = *data++;
if (cmd & 0x80) {
unsigned long cp_off = 0, cp_size = 0;
const unsigned char *buf;
if (cmd & 0x01) cp_off = *data++;
if (cmd & 0x02) cp_off |= (*data++ << 8);
if (cmd & 0x04) cp_off |= (*data++ << 16);
if (cmd & 0x08) cp_off |= (*data++ << 24);
if (cmd & 0x10) cp_size = *data++;
if (cmd & 0x20) cp_size |= (*data++ << 8);
if (cp_size == 0) cp_size = 0x10000;
buf = (cmd & 0x40) ? dst_buf : src_buf;
memcpy(out, buf + cp_off, cp_size);
out += cp_size;
} else {
memcpy(out, data, cmd);
out += cmd;
data += cmd;
}
}
/* sanity check */
if (data != top || out - dst_buf != size) {
free(dst_buf);
return NULL;
}
*dst_size = size;
return dst_buf;
}
/*
* test-delta.c: test code to exercise diff-delta.c and patch-delta.c
*
* (C) 2005 Nicolas Pitre <nico@cam.org>
*
* This code is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include "delta.h"
static const char *usage =
"test-delta (-d|-p) <from_file> <data_file> <out_file>";
int main(int argc, char *argv[])
{
int fd;
struct stat st;
void *from_buf, *data_buf, *out_buf;
unsigned long from_size, data_size, out_size;
if (argc != 5 || (strcmp(argv[1], "-d") && strcmp(argv[1], "-p"))) {
fprintf(stderr, "Usage: %s\n", usage);
return 1;
}
fd = open(argv[2], O_RDONLY);
if (fd < 0 || fstat(fd, &st)) {
perror(argv[2]);
return 1;
}
from_size = st.st_size;
from_buf = mmap(NULL, from_size, PROT_READ, MAP_PRIVATE, fd, 0);
if (from_buf == MAP_FAILED) {
perror(argv[2]);
return 1;
}
close(fd);
fd = open(argv[3], O_RDONLY);
if (fd < 0 || fstat(fd, &st)) {
perror(argv[3]);
return 1;
}
data_size = st.st_size;
data_buf = mmap(NULL, data_size, PROT_READ, MAP_PRIVATE, fd, 0);
if (data_buf == MAP_FAILED) {
perror(argv[3]);
return 1;
}
close(fd);
if (argv[1][1] == 'd')
out_buf = diff_delta(from_buf, from_size,
data_buf, data_size, &out_size);
else
out_buf = patch_delta(from_buf, from_size,
data_buf, data_size, &out_size);
if (!out_buf) {
fprintf(stderr, "delta operation failed (returned NULL)\n");
return 1;
}
fd = open (argv[4], O_WRONLY|O_CREAT|O_TRUNC, 0666);
if (fd < 0 || write(fd, out_buf, out_size) != out_size) {
perror(argv[4]);
return 1;
}
return 0;
}
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