/*
* Deltafication of a GIT database.
*
* (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 "cache.h"
#include "delta.h"
static int replace_object(char *buf, unsigned long size, unsigned char *sha1)
{
char tmpfile[PATH_MAX];
int fd;
snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
fd = mkstemp(tmpfile);
if (fd < 0)
return error("%s: %s\n", tmpfile, strerror(errno));
if (write(fd, buf, size) != size) {
perror("unable to write file");
close(fd);
unlink(tmpfile);
return -1;
}
fchmod(fd, 0444);
close(fd);
if (rename(tmpfile, sha1_file_name(sha1))) {
perror("unable to replace original object");
unlink(tmpfile);
return -1;
}
return 0;
}
static void *create_object(char *buf, unsigned long len, char *hdr, int hdrlen,
unsigned long *retsize)
{
char *compressed;
unsigned long size;
z_stream stream;
/* Set it up */
memset(&stream, 0, sizeof(stream));
deflateInit(&stream, Z_BEST_COMPRESSION);
size = deflateBound(&stream, len+hdrlen);
compressed = xmalloc(size);
/* Compress it */
stream.next_out = compressed;
stream.avail_out = size;
/* First header.. */
stream.next_in = hdr;
stream.avail_in = hdrlen;
while (deflate(&stream, 0) == Z_OK)
/* nothing */;
/* Then the data itself.. */
stream.next_in = buf;
stream.avail_in = len;
while (deflate(&stream, Z_FINISH) == Z_OK)
/* nothing */;
deflateEnd(&stream);
*retsize = stream.total_out;
return compressed;
}
static int restore_original_object(char *buf, unsigned long len,
char *type, unsigned char *sha1)
{
char hdr[50];
int hdrlen, ret;
void *compressed;
unsigned long size;
hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
compressed = create_object(buf, len, hdr, hdrlen, &size);
ret = replace_object(compressed, size, sha1);
free(compressed);
return ret;
}
static void *create_delta_object(char *buf, unsigned long len,
unsigned char *sha1_ref, unsigned long *size)
{
char hdr[50];
int hdrlen;
/* Generate the header + sha1 of reference for delta */
hdrlen = sprintf(hdr, "delta %lu", len+20)+1;
memcpy(hdr + hdrlen, sha1_ref, 20);
hdrlen += 20;
return create_object(buf, len, hdr, hdrlen, size);
}
static unsigned long get_object_size(unsigned char *sha1)
{
struct stat st;
if (stat(sha1_file_name(sha1), &st))
die("%s: %s", sha1_to_hex(sha1), strerror(errno));
return st.st_size;
}
static void *get_buffer(unsigned char *sha1, char *type, unsigned long *size)
{
unsigned long mapsize;
void *map = map_sha1_file(sha1, &mapsize);
if (map) {
void *buffer = unpack_sha1_file(map, mapsize, type, size);
munmap(map, mapsize);
if (buffer)
return buffer;
}
error("unable to get object %s", sha1_to_hex(sha1));
return NULL;
}
static void *expand_delta(void *delta, unsigned long delta_size, char *type,
unsigned long *size, unsigned int *depth, char *head)
{
void *buf = NULL;
*depth++;
if (delta_size < 20) {
error("delta object is bad");
free(delta);
} else {
unsigned long ref_size;
void *ref = get_buffer(delta, type, &ref_size);
if (ref && !strcmp(type, "delta"))
ref = expand_delta(ref, ref_size, type, &ref_size,
depth, head);
else
memcpy(head, delta, 20);
if (ref)
buf = patch_delta(ref, ref_size, delta+20,
delta_size-20, size);
free(ref);
free(delta);
}
return buf;
}
static char *mkdelta_usage =
"mkdelta [ --max-depth=N ] <reference_sha1> <target_sha1> [ <next_sha1> ... ]";
int main(int argc, char **argv)
{
unsigned char sha1_ref[20], sha1_trg[20], head_ref[20], head_trg[20];
char type_ref[20], type_trg[20];
void *buf_ref, *buf_trg, *buf_delta;
unsigned long size_ref, size_trg, size_orig, size_delta;
unsigned int depth_ref, depth_trg, depth_max = -1;
int i, verbose = 0;
for (i = 1; i < argc; i++) {
if (!strcmp(argv[i], "-v")) {
verbose = 1;
} else if (!strcmp(argv[i], "-d") && i+1 < argc) {
depth_max = atoi(argv[++i]);
} else if (!strncmp(argv[i], "--max-depth=", 12)) {
depth_max = atoi(argv[i]+12);
} else
break;
}
if (i + (depth_max != 0) >= argc)
usage(mkdelta_usage);
if (get_sha1(argv[i], sha1_ref))
die("bad sha1 %s", argv[i]);
depth_ref = 0;
buf_ref = get_buffer(sha1_ref, type_ref, &size_ref);
if (buf_ref && !strcmp(type_ref, "delta"))
buf_ref = expand_delta(buf_ref, size_ref, type_ref,
&size_ref, &depth_ref, head_ref);
else
memcpy(head_ref, sha1_ref, 20);
if (!buf_ref)
die("unable to obtain initial object %s", argv[i]);
if (depth_ref > depth_max) {
if (restore_original_object(buf_ref, size_ref, type_ref, sha1_ref))
die("unable to restore %s", argv[i]);
if (verbose)
printf("undelta %s (depth was %d)\n", argv[i], depth_ref);
depth_ref = 0;
}
/*
* TODO: deltafication should be tried against any early object
* in the object list and not only the previous object.
*/
while (++i < argc) {
if (get_sha1(argv[i], sha1_trg))
die("bad sha1 %s", argv[i]);
depth_trg = 0;
buf_trg = get_buffer(sha1_trg, type_trg, &size_trg);
if (buf_trg && !size_trg) {
if (verbose)
printf("skip %s (object is empty)\n", argv[i]);
continue;
}
size_orig = size_trg;
if (buf_trg && !strcmp(type_trg, "delta")) {
if (!memcmp(buf_trg, sha1_ref, 20)) {
/* delta already in place */
depth_ref++;
memcpy(sha1_ref, sha1_trg, 20);
buf_ref = patch_delta(buf_ref, size_ref,
buf_trg+20, size_trg-20,
&size_ref);
if (!buf_ref)
die("unable to apply delta %s", argv[i]);
if (depth_ref > depth_max) {
if (restore_original_object(buf_ref, size_ref,
type_ref, sha1_ref))
die("unable to restore %s", argv[i]);
if (verbose)
printf("undelta %s (depth was %d)\n", argv[i], depth_ref);
depth_ref = 0;
continue;
}
if (verbose)
printf("skip %s (delta already in place)\n", argv[i]);
continue;
}
buf_trg = expand_delta(buf_trg, size_trg, type_trg,
&size_trg, &depth_trg, head_trg);
} else
memcpy(head_trg, sha1_trg, 20);
if (!buf_trg)
die("unable to read target object %s", argv[i]);
if (depth_trg > depth_max) {
if (restore_original_object(buf_trg, size_trg, type_trg, sha1_trg))
die("unable to restore %s", argv[i]);
if (verbose)
printf("undelta %s (depth was %d)\n", argv[i], depth_trg);
depth_trg = 0;
size_orig = size_trg;
}
if (depth_max == 0)
goto skip;
if (strcmp(type_ref, type_trg))
die("type mismatch for object %s", argv[i]);
if (!size_ref) {
if (verbose)
printf("skip %s (initial object is empty)\n", argv[i]);
goto skip;
}
if (depth_ref + 1 > depth_max) {
if (verbose)
printf("skip %s (exceeding max link depth)\n", argv[i]);
goto skip;
}
if (!memcmp(head_ref, sha1_trg, 20)) {
if (verbose)
printf("skip %s (would create a loop)\n", argv[i]);
goto skip;
}
buf_delta = diff_delta(buf_ref, size_ref, buf_trg, size_trg, &size_delta);
if (!buf_delta)
die("out of memory");
/* no need to even try to compress if original
uncompressed is already smaller */
if (size_delta+20 < size_orig) {
void *buf_obj;
unsigned long size_obj;
buf_obj = create_delta_object(buf_delta, size_delta,
sha1_ref, &size_obj);
free(buf_delta);
size_orig = get_object_size(sha1_trg);
if (size_obj >= size_orig) {
free(buf_obj);
if (verbose)
printf("skip %s (original is smaller)\n", argv[i]);
goto skip;
}
if (replace_object(buf_obj, size_obj, sha1_trg))
die("unable to write delta for %s", argv[i]);
free(buf_obj);
depth_ref++;
if (verbose)
printf("delta %s (size=%ld.%02ld%%, depth=%d)\n",
argv[i], size_obj*100 / size_orig,
(size_obj*10000 / size_orig)%100,
depth_ref);
} else {
free(buf_delta);
if (verbose)
printf("skip %s (original is smaller)\n", argv[i]);
skip:
depth_ref = depth_trg;
memcpy(head_ref, head_trg, 20);
}
free(buf_ref);
buf_ref = buf_trg;
size_ref = size_trg;
memcpy(sha1_ref, sha1_trg, 20);
}
return 0;
}