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# 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.
* Optional SSE2/SSE4.1 support.
## Standard compliance
* RapidJSON should be fully RFC4627/ECMA-404 compliance.
* 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.
## 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](http://en.wikipedia.org/wiki/Simple_API_for_XML), 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](http://en.wikipedia.org/wiki/Document_Object_Model) 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.
## DOM (Document)
* 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.
* RapidJSON checks range of numerical values for conversions.
## SAX (Reader)
* Support comprehensive error code if parsing failed.
* Support error message localization.
## SAX (Writer)
* Support `rapidjson::PrettyWriter` for adding newlines and indentations.
* Support custom precision for floating point values.
## 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.
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