rapidjson/include/rapidjson/writer.h

#ifndef RAPIDJSON_WRITER_H_
#define RAPIDJSON_WRITER_H_

#include "rapidjson.h"
#include "internal/stack.h"
#include "internal/strfunc.h"
#include <cstdio>	// snprintf() or _sprintf_s()
#include <new>		// placement new

#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable : 4127) // conditional expression is constant
#endif

namespace rapidjson {

//! JSON writer
/*! Writer implements the concept Handler.
	It generates JSON text by events to an output os.

	User may programmatically calls the functions of a writer to generate JSON text.

	On the other side, a writer can also be passed to objects that generates events, 

	for example Reader::Parse() and Document::Accept().

	\tparam OutputStream Type of output stream.
	\tparam SourceEncoding Encoding of source string.
	\tparam TargetEncoding Encoding of output stream.
	\tparam Allocator Type of allocator for allocating memory of stack.
	\note implements Handler concept
*/
template<typename OutputStream, typename SourceEncoding = UTF8<>, typename TargetEncoding = UTF8<>, typename Allocator = MemoryPoolAllocator<> >
class Writer {
public:
	typedef typename SourceEncoding::Ch Ch;

	//! Constructor
	/*! \param os Output stream.
		\param allocator User supplied allocator. If it is null, it will create a private one.
		\param levelDepth Initial capacity of stack.
	*/
	Writer(OutputStream& os, Allocator* allocator = 0, size_t levelDepth = kDefaultLevelDepth) : 
		os_(os), level_stack_(allocator, levelDepth * sizeof(Level)),
		doublePrecision_(kDefaultDoublePrecision) {}

	//! Set the number of significant digits for \c double values
	/*! When writing a \c double value to the \c OutputStream, the number
		of significant digits is limited to 6 by default.
		\param p maximum number of significant digits (default: 6)
		\return The Writer itself for fluent API.
	*/
	Writer& SetDoublePrecision(int p = kDefaultDoublePrecision) {
		if (p < 0) p = kDefaultDoublePrecision; // negative precision is ignored
		doublePrecision_ = p;
		return *this;
	}

	//! \see SetDoublePrecision()
	int GetDoublePrecision() const { return doublePrecision_; }

	/*!@name Implementation of Handler
		\see Handler
	*/
	//@{

	Writer& Null()					{ Prefix(kNullType);   WriteNull();			return *this; }
	Writer& Bool(bool b)			{ Prefix(b ? kTrueType : kFalseType); WriteBool(b); return *this; }
	Writer& Int(int i)				{ Prefix(kNumberType); WriteInt(i);			return *this; }
	Writer& Uint(unsigned u)		{ Prefix(kNumberType); WriteUint(u);		return *this; }
	Writer& Int64(int64_t i64)		{ Prefix(kNumberType); WriteInt64(i64);		return *this; }
	Writer& Uint64(uint64_t u64)	{ Prefix(kNumberType); WriteUint64(u64);	return *this; }

	//! Writes the given \c double value to the stream
	/*!
		The number of significant digits (the precision) to be written
		can be set by \ref SetDoublePrecision() for the Writer:
		\code
		Writer<...> writer(...);
		writer.SetDoublePrecision(12).Double(M_PI);
		\endcode
		\param d The value to be written.
		\return The Writer itself for fluent API.
	*/
	Writer& Double(double d)		{ Prefix(kNumberType); WriteDouble(d);		return *this; }

	Writer& String(const Ch* str, SizeType length, bool copy = false) {
		(void)copy;
		Prefix(kStringType);
		WriteString(str, length);
		return *this;
	}

	Writer& StartObject() {
		Prefix(kObjectType);
		new (level_stack_.template Push<Level>()) Level(false);
		WriteStartObject();
		return *this;
	}

	Writer& EndObject(SizeType memberCount = 0) {
		(void)memberCount;
		RAPIDJSON_ASSERT(level_stack_.GetSize() >= sizeof(Level));
		RAPIDJSON_ASSERT(!level_stack_.template Top<Level>()->inArray);
		level_stack_.template Pop<Level>(1);
		WriteEndObject();
		if (level_stack_.Empty())	// end of json text
			os_.Flush();
		return *this;
	}

	Writer& StartArray() {
		Prefix(kArrayType);
		new (level_stack_.template Push<Level>()) Level(true);
		WriteStartArray();
		return *this;
	}

	Writer& EndArray(SizeType elementCount = 0) {
		(void)elementCount;
		RAPIDJSON_ASSERT(level_stack_.GetSize() >= sizeof(Level));
		RAPIDJSON_ASSERT(level_stack_.template Top<Level>()->inArray);
		level_stack_.template Pop<Level>(1);
		WriteEndArray();
		if (level_stack_.Empty())	// end of json text
			os_.Flush();
		return *this;
	}
	//@}

	/*! @name Convenience extensions */
	//@{

	//! Writes the given \c double value to the stream (explicit precision)
	/*!
		The currently set double precision is ignored in favor of the explicitly
		given precision for this value.
		\see Double(), SetDoublePrecision(), GetDoublePrecision()
		\param d The value to be written
		\param precision The number of significant digits for this value
		\return The Writer itself for fluent API.
	*/
	Writer& Double(double d, int precision) {
		int oldPrecision = GetDoublePrecision();
		return SetDoublePrecision(precision).Double(d).SetDoublePrecision(oldPrecision);
	}

	//! Simpler but slower overload.
	Writer& String(const Ch* str) { return String(str, internal::StrLen(str)); }

	//@}

protected:
	//! Information for each nested level
	struct Level {
		Level(bool inArray_) : valueCount(0), inArray(inArray_) {}
		size_t valueCount;	//!< number of values in this level
		bool inArray;		//!< true if in array, otherwise in object
	};

	static const size_t kDefaultLevelDepth = 32;

	void WriteNull()  {
		os_.Put('n'); os_.Put('u'); os_.Put('l'); os_.Put('l');
	}

	void WriteBool(bool b)  {
		if (b) {
			os_.Put('t'); os_.Put('r'); os_.Put('u'); os_.Put('e');
		}
		else {
			os_.Put('f'); os_.Put('a'); os_.Put('l'); os_.Put('s'); os_.Put('e');
		}
	}

	void WriteInt(int i) {
		if (i < 0) {
			os_.Put('-');
			i = -i;
		}
		WriteUint((unsigned)i);
	}

	void WriteUint(unsigned u) {
		char buffer[10];
		char *p = buffer;
		do {
			*p++ = (u % 10) + '0';
			u /= 10;
		} while (u > 0);

		do {
			--p;
			os_.Put(*p);
		} while (p != buffer);
	}

	void WriteInt64(int64_t i64) {
		if (i64 < 0) {
			os_.Put('-');
			i64 = -i64;
		}
		WriteUint64((uint64_t)i64);
	}

	void WriteUint64(uint64_t u64) {
		char buffer[20];
		char *p = buffer;
		do {
			*p++ = char(u64 % 10) + '0';
			u64 /= 10;
		} while (u64 > 0);

		do {
			--p;
			os_.Put(*p);
		} while (p != buffer);
	}

#ifdef _MSC_VER
#define RAPIDJSON_SNPRINTF sprintf_s
#else
#define RAPIDJSON_SNPRINTF snprintf
#endif

	//! \todo Optimization with custom double-to-string converter.
	void WriteDouble(double d) {
		char buffer[100];
		int ret = RAPIDJSON_SNPRINTF(buffer, sizeof(buffer), "%.*g", doublePrecision_, d);
		RAPIDJSON_ASSERT(ret >= 1);
		for (int i = 0; i < ret; i++)
			os_.Put(buffer[i]);
	}
#undef RAPIDJSON_SNPRINTF

	void WriteString(const Ch* str, SizeType length)  {
		static const char hexDigits[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
		static const char escape[256] = {
#define Z16 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
			//0    1    2    3    4    5    6    7    8    9    A    B    C    D    E    F
			'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'b', 't', 'n', 'u', 'f', 'r', 'u', 'u', // 00
			'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', // 10
			  0,   0, '"',   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, // 20
			Z16, Z16,																		// 30~4F
			  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,'\\',   0,   0,   0, // 50
			Z16, Z16, Z16, Z16, Z16, Z16, Z16, Z16, Z16, Z16								// 60~FF
#undef Z16
		};

		os_.Put('\"');
		GenericStringStream<SourceEncoding> is(str);
		while (is.Tell() < length) {
			const Ch c = is.Peek();
			if ((sizeof(Ch) == 1 || (unsigned)c < 256) && escape[(unsigned char)c])  {
				is.Take();
				os_.Put('\\');
				os_.Put(escape[(unsigned char)c]);
				if (escape[(unsigned char)c] == 'u') {
					os_.Put('0');
					os_.Put('0');
					os_.Put(hexDigits[(unsigned char)c >> 4]);
					os_.Put(hexDigits[(unsigned char)c & 0xF]);
				}
			}
			else
				Transcoder<SourceEncoding, TargetEncoding>::Transcode(is, os_);
		}
		os_.Put('\"');
	}

	void WriteStartObject()	{ os_.Put('{'); }
	void WriteEndObject()	{ os_.Put('}'); }
	void WriteStartArray()	{ os_.Put('['); }
	void WriteEndArray()	{ os_.Put(']'); }

	void Prefix(Type type) {
		(void)type;
		if (level_stack_.GetSize() != 0) { // this value is not at root
			Level* level = level_stack_.template Top<Level>();
			if (level->valueCount > 0) {
				if (level->inArray) 
					os_.Put(','); // add comma if it is not the first element in array
				else  // in object
					os_.Put((level->valueCount % 2 == 0) ? ',' : ':');
			}
			if (!level->inArray && level->valueCount % 2 == 0)
				RAPIDJSON_ASSERT(type == kStringType);  // if it's in object, then even number should be a name
			level->valueCount++;
		}
		else
			RAPIDJSON_ASSERT(type == kObjectType || type == kArrayType);
	}

	OutputStream& os_;
	internal::Stack<Allocator> level_stack_;
	int doublePrecision_;

	static const int kDefaultDoublePrecision = 6;

private:
	// Prohibit copy constructor & assignment operator.
	Writer(const Writer&);
	Writer& operator=(const Writer&);
};

} // namespace rapidjson

#ifdef _MSC_VER
#pragma warning(pop)
#endif

#endif // RAPIDJSON_RAPIDJSON_H_