rapidjson-dev binary package in Ubuntu Focal amd64

 RapidJSON is an attempt to create the fastest JSON parser and generator.
 .
  - Small but complete. Supports both SAX and DOM style API. SAX parser only a
    few hundred lines of code.
  - Fast. In the order of magnitude of strlen(). Optionally supports
    SSE2/SSE4.2 for acceleration.
  - Self-contained. Minimal dependency on standard libraries. No BOOST, not
    even STL.
  - Compact. Each JSON value is 16 or 20 bytes for 32 or 64-bit machines
    respectively (excluding text string storage). With the custom memory
    allocator, parser allocates memory compactly during parsing.
  - Full RFC7159 compliance. Supports UTF-8, UTF-16 and UTF-32.
  - Support both in-situ parsing (directly decode strings into the source JSON
    text) and non-destructive parsing (decode strings into new buffers).
  - Parse number to int/unsigned/int64_t/uint64_t/double depending on input
  - Support custom memory allocation. Also, the default memory pool allocator
    can also be supplied with a user buffer (such as a buffer allocated on
    user's heap or programme stack) to minimize allocation.

Source package