abort();
    }
    MaybeFetch(key, block, status);
    if (TF_GetCode(status) != TF_OK) return -1;
    UpdateLRU(key, block, status);
    if (TF_GetCode(status) != TF_OK) return -1;
    // Copy the relevant portion of the block into the result buffer.
    const auto& data = block->data;
    if (offset >= pos + data.size()) {
      // The requested offset is at or beyond the end of the file. This can