do_lzx_decompress: handle uncompressed chunks

maharmstone · Jan 5, 2021 · c346ade · c346ade
1 parent 83f2100
commit c346ade
Showing 1 changed file with 22 additions and 8 deletions.
diff --git a/src/decomp.cpp b/src/decomp.cpp
@@ -161,17 +161,31 @@ string do_lzx_decompress(const string_view& compdata, uint64_t size) {
 
  ret.resize(size);
 
+ auto data = string_view(compdata.data() + ((num_chunks - 1) * sizeof(uint32_t)),
+ compdata.length() - ((num_chunks - 1) * sizeof(uint32_t)));
+
  for (uint64_t i = 0; i < num_chunks; i++) {
- uint64_t off = (num_chunks - 1) * sizeof(uint32_t);
- if (i != 0)
- off += offsets[i - 1];
+ 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];
 
- auto err = lzx_decompress(ctx, compdata.data() + off, compdata.length() - off, ret.data() + (i * LZX_CHUNK_SIZE),
- i == num_chunks - 1 ? (ret.length() - (i * LZX_CHUNK_SIZE)) : LZX_CHUNK_SIZE);
+ if (complen == (i == num_chunks - 1 ? (ret.length() - (i * LZX_CHUNK_SIZE)) : LZX_CHUNK_SIZE)) {
+ // stored uncompressed
+ memcpy(ret.data() + (i * LZX_CHUNK_SIZE), data.data() + off, complen);
+ } else {
+ auto err = lzx_decompress(ctx, data.data() + off, complen, ret.data() + (i * LZX_CHUNK_SIZE),
+ i == num_chunks - 1 ? (ret.length() - (i * LZX_CHUNK_SIZE)) : LZX_CHUNK_SIZE);
 
- if (err != 0) {
- lzx_free_decompressor(ctx);
- throw formatted_error(FMT_STRING("lzx_decompress returned {}."), err);
+ if (err != 0) {
+ lzx_free_decompressor(ctx);
+ throw formatted_error(FMT_STRING("lzx_decompress returned {}."), err);
+ }
  }
  }