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/*
* patch-delta.c:
* recreate a buffer from a source and the delta produced by diff-delta.c
*
* (C) 2005 Nicolas Pitre <nico@fluxnic.net>
*
* 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 "git-compat-util.h"
#include "delta.h"
void *patch_delta(const void *src_buf, unsigned long src_size,
const 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;
if (delta_size < DELTA_SIZE_MIN)
return NULL;
data = delta_buf;
top = (const unsigned char *) delta_buf + delta_size;
/* make sure the orig file size matches what we expect */
size = get_delta_hdr_size(&data, top);
if (size != src_size)
return NULL;
/* now the result size */
size = get_delta_hdr_size(&data, top);
dst_buf = xmallocz(size);
out = dst_buf;
while (data < top) {
cmd = *data++;
if (cmd & 0x80) {
unsigned long cp_off = 0, cp_size = 0;
#define PARSE_CP_PARAM(bit, var, shift) do { \
if (cmd & (bit)) { \
if (data >= top) \
goto bad_length; \
var |= ((unsigned) *data++ << (shift)); \
} } while (0)
PARSE_CP_PARAM(0x01, cp_off, 0);
PARSE_CP_PARAM(0x02, cp_off, 8);
PARSE_CP_PARAM(0x04, cp_off, 16);
PARSE_CP_PARAM(0x08, cp_off, 24);
PARSE_CP_PARAM(0x10, cp_size, 0);
PARSE_CP_PARAM(0x20, cp_size, 8);
PARSE_CP_PARAM(0x40, cp_size, 16);
#undef PARSE_CP_PARAM
if (cp_size == 0) cp_size = 0x10000;
if (unsigned_add_overflows(cp_off, cp_size) ||
cp_off + cp_size > src_size ||
cp_size > size)
goto bad_length;
memcpy(out, (char *) src_buf + cp_off, cp_size);
out += cp_size;
size -= cp_size;
} else if (cmd) {
if (cmd > size || cmd > top - data)
goto bad_length;
memcpy(out, data, cmd);
out += cmd;
data += cmd;
size -= cmd;
} else {
/*
* cmd == 0 is reserved for future encoding
* extensions. In the mean time we must fail when
* encountering them (might be data corruption).
*/
error("unexpected delta opcode 0");
goto bad;
}
}
/* sanity check */
if (data != top || size != 0) {
bad_length:
error("delta replay has gone wild");
bad:
free(dst_buf);
return NULL;
}
*dst_size = out - dst_buf;
return dst_buf;
}
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