do_xpress_decompress: handle uncompressed chunks

src/decomp.cpp

@@ -198,13 +198,26 @@ string do_xpress_decompress(const string_view& compdata, uint64_t size, uint32_t
 
  for (uint64_t i = 0; i < num_chunks; i++) {
  uint64_t off = i == 0 ? 0 : offsets[i - 1];
+ uint64_t complen;
+
+ if (i == 0)
+ complen = num_chunks > 1 ? offsets[0] : data.length();
+ else if (i == num_chunks - 1)
+ complen = data.length() - offsets[i - 1];
+ else
+ complen = offsets[i] - offsets[i - 1];
+
+ if (complen == (i == num_chunks - 1 ? (ret.length() - (i * chunk_size)) : chunk_size)) {
+ // stored uncompressed
+ memcpy(ret.data() + (i * chunk_size), data.data() + off, complen);
+ } else {
+ auto err = xpress_decompress(ctx, data.data() + off, complen, ret.data() + (i * chunk_size),
+ i == num_chunks - 1 ? (ret.length() - (i * chunk_size)) : chunk_size);
 
- auto err = xpress_decompress(ctx, data.data() + off, data.length() - off, ret.data() + (i * chunk_size),
- i == num_chunks - 1 ? (ret.length() - (i * chunk_size)) : chunk_size);
-
- if (err != 0) {
- xpress_free_decompressor(ctx);
- throw formatted_error(FMT_STRING("xpress_decompress returned {}."), err);
+ if (err != 0) {
+ xpress_free_decompressor(ctx);
+ throw formatted_error(FMT_STRING("xpress_decompress returned {}."), err);
+ }
  }
  }