/* * patch-delta.c: * recreate a buffer from a source and the delta produced by diff-delta.c * * (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 "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 = xmalloc(size + 1); dst_buf[size] = 0; out = dst_buf; while (data < top) { cmd = *data++; if (cmd & 0x80) { unsigned long cp_off = 0, cp_size = 0; if (cmd & 0x01) cp_off = *data++; if (cmd & 0x02) cp_off |= (*data++ << 8); if (cmd & 0x04) cp_off |= (*data++ << 16); if (cmd & 0x08) cp_off |= (*data++ << 24); if (cmd & 0x10) cp_size = *data++; if (cmd & 0x20) cp_size |= (*data++ << 8); if (cmd & 0x40) cp_size |= (*data++ << 16); if (cp_size == 0) cp_size = 0x10000; if (cp_off + cp_size < cp_size || cp_off + cp_size > src_size || cp_size > size) break; memcpy(out, (char *) src_buf + cp_off, cp_size); out += cp_size; size -= cp_size; } else if (cmd) { if (cmd > size) break; 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) { error("delta replay has gone wild"); bad: free(dst_buf); return NULL; } *dst_size = out - dst_buf; return dst_buf; }