mirror of
https://git.proxmox.com/git/libgit2
synced 2025-05-05 13:48:41 +00:00
135 lines
3.1 KiB
C
135 lines
3.1 KiB
C
/*
|
|
* Copyright (C) the libgit2 contributors. All rights reserved.
|
|
*
|
|
* This file is part of libgit2, distributed under the GNU GPL v2 with
|
|
* a Linking Exception. For full terms see the included COPYING file.
|
|
*/
|
|
#include "common.h"
|
|
#include "git2/odb.h"
|
|
#include "delta-apply.h"
|
|
|
|
/*
|
|
* This file was heavily cribbed from BinaryDelta.java in JGit, which
|
|
* itself was heavily cribbed from <code>patch-delta.c</code> in the
|
|
* GIT project. The original delta patching code was written by
|
|
* Nicolas Pitre <nico@cam.org>.
|
|
*/
|
|
|
|
static int hdr_sz(
|
|
size_t *size,
|
|
const unsigned char **delta,
|
|
const unsigned char *end)
|
|
{
|
|
const unsigned char *d = *delta;
|
|
size_t r = 0;
|
|
unsigned int c, shift = 0;
|
|
|
|
do {
|
|
if (d == end)
|
|
return -1;
|
|
c = *d++;
|
|
r |= (c & 0x7f) << shift;
|
|
shift += 7;
|
|
} while (c & 0x80);
|
|
*delta = d;
|
|
*size = r;
|
|
return 0;
|
|
}
|
|
|
|
int git__delta_read_header(
|
|
const unsigned char *delta,
|
|
size_t delta_len,
|
|
size_t *base_sz,
|
|
size_t *res_sz)
|
|
{
|
|
const unsigned char *delta_end = delta + delta_len;
|
|
if ((hdr_sz(base_sz, &delta, delta_end) < 0) ||
|
|
(hdr_sz(res_sz, &delta, delta_end) < 0))
|
|
return -1;
|
|
return 0;
|
|
}
|
|
|
|
int git__delta_apply(
|
|
git_rawobj *out,
|
|
const unsigned char *base,
|
|
size_t base_len,
|
|
const unsigned char *delta,
|
|
size_t delta_len)
|
|
{
|
|
const unsigned char *delta_end = delta + delta_len;
|
|
size_t base_sz, res_sz;
|
|
unsigned char *res_dp;
|
|
|
|
/* Check that the base size matches the data we were given;
|
|
* if not we would underflow while accessing data from the
|
|
* base object, resulting in data corruption or segfault.
|
|
*/
|
|
if ((hdr_sz(&base_sz, &delta, delta_end) < 0) || (base_sz != base_len)) {
|
|
giterr_set(GITERR_INVALID, "Failed to apply delta. Base size does not match given data");
|
|
return -1;
|
|
}
|
|
|
|
if (hdr_sz(&res_sz, &delta, delta_end) < 0) {
|
|
giterr_set(GITERR_INVALID, "Failed to apply delta. Base size does not match given data");
|
|
return -1;
|
|
}
|
|
|
|
res_dp = git__malloc(res_sz + 1);
|
|
GITERR_CHECK_ALLOC(res_dp);
|
|
|
|
res_dp[res_sz] = '\0';
|
|
out->data = res_dp;
|
|
out->len = res_sz;
|
|
|
|
while (delta < delta_end) {
|
|
unsigned char cmd = *delta++;
|
|
if (cmd & 0x80) {
|
|
/* cmd is a copy instruction; copy from the base.
|
|
*/
|
|
size_t off = 0, len = 0;
|
|
|
|
if (cmd & 0x01) off = *delta++;
|
|
if (cmd & 0x02) off |= *delta++ << 8;
|
|
if (cmd & 0x04) off |= *delta++ << 16;
|
|
if (cmd & 0x08) off |= *delta++ << 24;
|
|
|
|
if (cmd & 0x10) len = *delta++;
|
|
if (cmd & 0x20) len |= *delta++ << 8;
|
|
if (cmd & 0x40) len |= *delta++ << 16;
|
|
if (!len) len = 0x10000;
|
|
|
|
if (base_len < off + len || res_sz < len)
|
|
goto fail;
|
|
memcpy(res_dp, base + off, len);
|
|
res_dp += len;
|
|
res_sz -= len;
|
|
|
|
} else if (cmd) {
|
|
/* cmd is a literal insert instruction; copy from
|
|
* the delta stream itself.
|
|
*/
|
|
if (delta_end - delta < cmd || res_sz < cmd)
|
|
goto fail;
|
|
memcpy(res_dp, delta, cmd);
|
|
delta += cmd;
|
|
res_dp += cmd;
|
|
res_sz -= cmd;
|
|
|
|
} else {
|
|
/* cmd == 0 is reserved for future encodings.
|
|
*/
|
|
goto fail;
|
|
}
|
|
}
|
|
|
|
if (delta != delta_end || res_sz)
|
|
goto fail;
|
|
return 0;
|
|
|
|
fail:
|
|
git__free(out->data);
|
|
out->data = NULL;
|
|
giterr_set(GITERR_INVALID, "Failed to apply delta");
|
|
return -1;
|
|
}
|