+static void* map_pack(unsigned long offset)
+{
+ if (offset >= pack_size)
+ die("object offset outside of pack file");
+ if (offset >= pack_mlen) {
+ if (pack_base)
+ munmap(pack_base, pack_mlen);
+ /* round out how much we map to 16 MB units */
+ pack_mlen = pack_size;
+ if (pack_mlen & ((1 << 24) - 1))
+ pack_mlen = ((pack_mlen >> 24) + 1) << 24;
+ pack_base = mmap(NULL,pack_mlen,PROT_READ,MAP_SHARED,pack_fd,0);
+ if (pack_base == MAP_FAILED)
+ die("Failed to map generated pack: %s", strerror(errno));
+ remap_count++;
+ }
+ return (char*)pack_base + offset;
+}
+
+static unsigned long unpack_object_header(unsigned long offset,
+ enum object_type *type,
+ unsigned long *sizep)
+{
+ unsigned shift;
+ unsigned char c;
+ unsigned long size;
+
+ c = *(unsigned char*)map_pack(offset++);
+ *type = (c >> 4) & 7;
+ size = c & 15;
+ shift = 4;
+ while (c & 0x80) {
+ c = *(unsigned char*)map_pack(offset++);
+ size += (c & 0x7f) << shift;
+ shift += 7;
+ }
+ *sizep = size;
+ return offset;
+}
+
+static void *unpack_non_delta_entry(unsigned long o, unsigned long sz)
+{
+ z_stream stream;
+ unsigned char *result;
+
+ result = xmalloc(sz + 1);
+ result[sz] = 0;
+
+ memset(&stream, 0, sizeof(stream));
+ stream.next_in = map_pack(o);
+ stream.avail_in = pack_mlen - o;
+ stream.next_out = result;
+ stream.avail_out = sz;
+
+ inflateInit(&stream);
+ for (;;) {
+ int st = inflate(&stream, Z_FINISH);
+ if (st == Z_STREAM_END)
+ break;
+ if (st == Z_OK) {
+ o = stream.next_in - (unsigned char*)pack_base;
+ stream.next_in = map_pack(o);
+ stream.avail_in = pack_mlen - o;
+ continue;
+ }
+ die("Error from zlib during inflate.");
+ }
+ inflateEnd(&stream);
+ if (stream.total_out != sz)
+ die("Error after inflate: sizes mismatch");
+ return result;
+}
+
+static void *unpack_entry(unsigned long offset, unsigned long *sizep);
+
+static void *unpack_delta_entry(unsigned long offset,
+ unsigned long delta_size,
+ unsigned long *sizep)
+{
+ struct object_entry *base_oe;
+ unsigned char *base_sha1;
+ void *delta_data, *base, *result;
+ unsigned long base_size, result_size;
+
+ base_sha1 = (unsigned char*)map_pack(offset + 20) - 20;
+ base_oe = find_object(base_sha1);
+ if (!base_oe)
+ die("I'm broken; I can't find a base I know must be here.");
+ base = unpack_entry(base_oe->offset, &base_size);
+ delta_data = unpack_non_delta_entry(offset + 20, delta_size);
+ result = patch_delta(base, base_size,
+ delta_data, delta_size,
+ &result_size);
+ if (!result)
+ die("failed to apply delta");
+ free(delta_data);
+ free(base);
+ *sizep = result_size;
+ return result;
+}
+
+static void *unpack_entry(unsigned long offset, unsigned long *sizep)
+{
+ unsigned long size;
+ enum object_type kind;
+
+ offset = unpack_object_header(offset, &kind, &size);
+ switch (kind) {
+ case OBJ_DELTA:
+ return unpack_delta_entry(offset, size, sizep);
+ case OBJ_COMMIT:
+ case OBJ_TREE:
+ case OBJ_BLOB:
+ case OBJ_TAG:
+ *sizep = size;
+ return unpack_non_delta_entry(offset, size);
+ default:
+ die("I created an object I can't read!");
+ }
+}
+