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(void *src_buf, unsigned long src_size,
  17                  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        int i;
  24
  25        /* the smallest delta size possible is 6 bytes */
  26        if (delta_size < 6)
  27                return NULL;
  28
  29        data = delta_buf;
  30        top = delta_buf + delta_size;
  31
  32        /* make sure the orig file size matches what we expect */
  33        size = i = 0;
  34        cmd = *data++;
  35        while (cmd) {
  36                if (cmd & 1)
  37                        size |= *data++ << i;
  38                i += 8;
  39                cmd >>= 1;
  40        }
  41        if (size != src_size)
  42                return NULL;
  43
  44        /* now the result size */
  45        size = i = 0;
  46        cmd = *data++;
  47        while (cmd) {
  48                if (cmd & 1)
  49                        size |= *data++ << i;
  50                i += 8;
  51                cmd >>= 1;
  52        }
  53        dst_buf = malloc(size);
  54        if (!dst_buf)
  55                return NULL;
  56
  57        out = dst_buf;
  58        while (data < top) {
  59                cmd = *data++;
  60                if (cmd & 0x80) {
  61                        unsigned long cp_off = 0, cp_size = 0;
  62                        const unsigned char *buf;
  63                        if (cmd & 0x01) cp_off = *data++;
  64                        if (cmd & 0x02) cp_off |= (*data++ << 8);
  65                        if (cmd & 0x04) cp_off |= (*data++ << 16);
  66                        if (cmd & 0x08) cp_off |= (*data++ << 24);
  67                        if (cmd & 0x10) cp_size = *data++;
  68                        if (cmd & 0x20) cp_size |= (*data++ << 8);
  69                        if (cp_size == 0) cp_size = 0x10000;
  70                        buf = (cmd & 0x40) ? dst_buf : src_buf;
  71                        memcpy(out, buf + cp_off, cp_size);
  72                        out += cp_size;
  73                } else {
  74                        memcpy(out, data, cmd);
  75                        out += cmd;
  76                        data += cmd;
  77                }
  78        }
  79
  80        /* sanity check */
  81        if (data != top || out - dst_buf != size) {
  82                free(dst_buf);
  83                return NULL;
  84        }
  85
  86        *dst_size = size;
  87        return dst_buf;
  88}