Features

General

• Cross-platform
• Compilers: Visual Studio, gcc, clang, etc.
• Architectures: x86, x64, ARM, etc.
• Operating systems: Windows, Mac OS X, Linux, iOS, Android, etc.
• Easy installation
• Header files only library. Just copy the headers to your project.
• Self-contained, minimal dependences
• No STL, BOOST, etc.
• Only included <cstdio>, <cstdlib>, <cstring>, <inttypes.h>, <new>, <stdint.h>.
• Without C++ exception, RTTI
• High performance
• Use template and inline functions to reduce function call overheads.
• Internal optimized Grisu2 and floating point parsing implementations.
• Optional SSE2/SSE4.2 support.

Standard compliance

• RapidJSON should be fully RFC4627/ECMA-404 compliance.
• Support JSON Pointer (RFC6901).
• Support JSON Schema Draft v4.
• Support Unicode surrogate.
• Support null character ("\u0000")
• For example, ["Hello\u0000World"] can be parsed and handled gracefully. There is API for getting/setting lengths of string.
• Support optional relaxed syntax.
• Single line (// ...) and multiple line (/* ... */) comments (kParseCommentsFlag).
• Trailing commas at the end of objects and arrays (kParseTrailingCommasFlag).
• NaN, Inf, Infinity, -Inf and -Infinity as double values (kParseNanAndInfFlag)
• NPM compliant.

Unicode

• Support UTF-8, UTF-16, UTF-32 encodings, including little endian and big endian.
• These encodings are used in input/output streams and in-memory representation.
• Support automatic detection of encodings in input stream.
• Support transcoding between encodings internally.
• For example, you can read a UTF-8 file and let RapidJSON transcode the JSON strings into UTF-16 in the DOM.
• Support encoding validation internally.
• For example, you can read a UTF-8 file, and let RapidJSON check whether all JSON strings are valid UTF-8 byte sequence.
• Support custom character types.
• By default the character types are char for UTF8, wchar_t for UTF16, uint32_t for UTF32.
• Support custom encodings.

API styles

• SAX (Simple API for XML) style API
• Similar to SAX, RapidJSON provides a event sequential access parser API (rapidjson::GenericReader). It also provides a generator API (rapidjson::Writer) which consumes the same set of events.
• DOM (Document Object Model) style API
• Similar to DOM for HTML/XML, RapidJSON can parse JSON into a DOM representation (rapidjson::GenericDocument), for easy manipulation, and finally stringify back to JSON if needed.
• The DOM style API (rapidjson::GenericDocument) is actually implemented with SAX style API (rapidjson::GenericReader). SAX is faster but sometimes DOM is easier. Users can pick their choices according to scenarios.

Parsing

• Recursive (default) and iterative parser
• Recursive parser is faster but prone to stack overflow in extreme cases.
• Iterative parser use custom stack to keep parsing state.
• Support in situ parsing.
• Parse JSON string values in-place at the source JSON, and then the DOM points to addresses of those strings.
• Faster than convention parsing: no allocation for strings, no copy (if string does not contain escapes), cache-friendly.
• Support 32-bit/64-bit signed/unsigned integer and double for JSON number type.
• Support parsing multiple JSONs in input stream (kParseStopWhenDoneFlag).
• Error Handling
• Support comprehensive error code if parsing failed.
• Support error message localization.

DOM (Document)

• RapidJSON checks range of numerical values for conversions.
• Optimization for string literal
• Only store pointer instead of copying
• Optimization for "short" strings
• Store short string in Value internally without additional allocation.
• For UTF-8 string: maximum 11 characters in 32-bit, 21 characters in 64-bit (13 characters in x86-64).
• Optionally support std::string (define RAPIDJSON_HAS_STDSTRING=1)

Generation

• Support rapidjson::PrettyWriter for adding newlines and indentations.

Stream

• Support rapidjson::GenericStringBuffer for storing the output JSON as string.
• Support rapidjson::FileReadStream and rapidjson::FileWriteStream for input/output FILE object.
• Support custom streams.

Memory

• Minimize memory overheads for DOM.
• Each JSON value occupies exactly 16/20 bytes for most 32/64-bit machines (excluding text string).
• Support fast default allocator.
• A stack-based allocator (allocate sequentially, prohibit to free individual allocations, suitable for parsing).
• User can provide a pre-allocated buffer. (Possible to parse a number of JSONs without any CRT allocation)
• Support standard CRT(C-runtime) allocator.
• Support custom allocators.

Miscellaneous

• Some C++11 support (optional)
• Rvalue reference
• noexcept specifier
• Range-based for loop