+static int dry_run, quiet;
+static const char unpack_usage[] = "git-unpack-objects [-n] [-q] < pack-file";
+
+/* We always read in 4kB chunks. */
+static unsigned char buffer[4096];
+static unsigned long offset, len, eof;
+static SHA_CTX ctx;
+
+/*
+ * Make sure at least "min" bytes are available in the buffer, and
+ * return the pointer to the buffer.
+ */
+static void * fill(int min)
+{
+ if (min <= len)
+ return buffer + offset;
+ if (eof)
+ die("unable to fill input");
+ if (min > sizeof(buffer))
+ die("cannot fill %d bytes", min);
+ if (offset) {
+ SHA1_Update(&ctx, buffer, offset);
+ memcpy(buffer, buffer + offset, len);
+ offset = 0;
+ }
+ do {
+ int ret = xread(0, buffer + len, sizeof(buffer) - len);
+ if (ret <= 0) {
+ if (!ret)
+ die("early EOF");
+ die("read error on input: %s", strerror(errno));
+ }
+ len += ret;
+ } while (len < min);
+ return buffer;
+}
+
+static void use(int bytes)
+{
+ if (bytes > len)
+ die("used more bytes than were available");
+ len -= bytes;
+ offset += bytes;
+}
+
+static void *get_data(unsigned long size)
+{
+ z_stream stream;
+ void *buf = xmalloc(size);
+
+ memset(&stream, 0, sizeof(stream));
+
+ stream.next_out = buf;
+ stream.avail_out = size;
+ stream.next_in = fill(1);
+ stream.avail_in = len;
+ inflateInit(&stream);
+
+ for (;;) {
+ int ret = inflate(&stream, 0);
+ use(len - stream.avail_in);
+ if (stream.total_out == size && ret == Z_STREAM_END)
+ break;
+ if (ret != Z_OK)
+ die("inflate returned %d\n", ret);
+ stream.next_in = fill(1);
+ stream.avail_in = len;
+ }
+ inflateEnd(&stream);
+ return buf;
+}
+
+struct delta_info {
+ unsigned char base_sha1[20];
+ unsigned long size;
+ void *delta;
+ struct delta_info *next;