Andrew's git - gitweb.git/blob

   1/*
   2 * patch-delta.c:
   3 * recreate a buffer from a source and the delta produced by diff-delta.c
   4 *
   5 * (C) 2005 Nicolas Pitre <nico@cam.org>
   6 *
   7 * This code is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 */
  11
  12#include <stdlib.h>
  13#include <string.h>
  14#include "delta.h"
  15
  16void *patch_delta(const void *src_buf, unsigned long src_size,
  17                  const void *delta_buf, unsigned long delta_size,
  18                  unsigned long *dst_size)
  19{
  20        const unsigned char *data, *top;
  21        unsigned char *dst_buf, *out, cmd;
  22        unsigned long size;
  23
  24        if (delta_size < DELTA_SIZE_MIN)
  25                return NULL;
  26
  27        data = delta_buf;
  28        top = delta_buf + delta_size;
  29
  30        /* make sure the orig file size matches what we expect */
  31        size = get_delta_hdr_size(&data, top);
  32        if (size != src_size)
  33                return NULL;
  34
  35        /* now the result size */
  36        size = get_delta_hdr_size(&data, top);
  37        dst_buf = malloc(size + 1);
  38        if (!dst_buf)
  39                return NULL;
  40        dst_buf[size] = 0;
  41
  42        out = dst_buf;
  43        while (data < top) {
  44                cmd = *data++;
  45                if (cmd & 0x80) {
  46                        unsigned long cp_off = 0, cp_size = 0;
  47                        if (cmd & 0x01) cp_off = *data++;
  48                        if (cmd & 0x02) cp_off |= (*data++ << 8);
  49                        if (cmd & 0x04) cp_off |= (*data++ << 16);
  50                        if (cmd & 0x08) cp_off |= (*data++ << 24);
  51                        if (cmd & 0x10) cp_size = *data++;
  52                        if (cmd & 0x20) cp_size |= (*data++ << 8);
  53                        if (cmd & 0x40) cp_size |= (*data++ << 16);
  54                        if (cp_size == 0) cp_size = 0x10000;
  55                        if (cp_off + cp_size < cp_size ||
  56                            cp_off + cp_size > src_size ||
  57                            cp_size > size)
  58                                goto bad;
  59                        memcpy(out, src_buf + cp_off, cp_size);
  60                        out += cp_size;
  61                        size -= cp_size;
  62                } else if (cmd) {
  63                        if (cmd > size)
  64                                goto bad;
  65                        memcpy(out, data, cmd);
  66                        out += cmd;
  67                        data += cmd;
  68                        size -= cmd;
  69                } else {
  70                        /*
  71                         * cmd == 0 is reserved for future encoding
  72                         * extensions. In the mean time we must fail when
  73                         * encountering them (might be data corruption).
  74                         */
  75                        goto bad;
  76                }
  77        }
  78
  79        /* sanity check */
  80        if (data != top || size != 0) {
  81                bad:
  82                free(dst_buf);
  83                return NULL;
  84        }
  85
  86        *dst_size = out - dst_buf;
  87        return dst_buf;
  88}