Merge "imgdiff: skip spurious gzip headers in image files"

  while (pos < sz) {

    unsigned char* p = img+pos;

    bool processed_deflate = false;

    if (sz - pos >= 4 &&

        p[0] == 0x1f && p[1] == 0x8b &&

        p[2] == 0x08 &&    // deflate compression

        strm.next_out = curr->data + curr->len;

        ret = inflate(&strm, Z_NO_FLUSH);

        if (ret < 0) {

          if (!processed_deflate) {

            // This is the first chunk, assume that it's just a spurious

            // gzip header instead of a real one.

            break;

          }

          printf("Error: inflate failed [%s] at file offset [%zu]\n"

                 "imgdiff only supports gzip kernel compression,"

                 " did you try CONFIG_KERNEL_LZO?\n",

          allocated *= 2;

          curr->data = reinterpret_cast<unsigned char*>(realloc(curr->data, allocated));

        }

        processed_deflate = true;

      } while (ret != Z_STREAM_END);

      curr->deflate_len = sz - strm.avail_in - pos;