Merge pull request #97 from miloyip/issue72customdtoa

Fix #72

doc/sax.md

@@ -225,7 +225,7 @@ You may doubt that, why not just using `sprintf()` or `std::stringstream` to bui
 There are various reasons:
 1. `Writer` must output a well-formed JSON. If there is incorrect event sequence (e.g. `Int()` just after `StartObject()`), it generates assertion fail in debug mode.
 2. `Writer::String()` can handle string escaping (e.g. converting code point `U+000A` to `\n`) and Unicode transcoding.
-3. `Writer` handles number output consistently. For example, user can set precision for `Double()`.
+3. `Writer` handles number output consistently.
 4. `Writer` implements the event handler concept. It can be used to handle events from `Reader`, `Document` or other event publisher.
 5. `Writer` can be optimized for different platforms.
 
@@ -258,20 +258,6 @@ The last one, `Allocator` is the type of allocator, which is used for allocating
 
 Besides, the constructor of `Writer` has a `levelDepth` parameter. This parameter affects the initial memory allocated for storing information per hierarchy level.
 
-## Precision (#WriterPrecision)
-
-When using `Double()`, the precision of output can be specified, for example:
-
-~~~~~~~~~~cpp
-writer.SetDoublePrecision(4);
-writer.StartArary();
-writer.Double(3.14159265359);
-writer.EndArray();
-~~~~~~~~~~
-~~~~~~~~~~
-[3.1416]
-~~~~~~~~~~
-
 ## PrettyWriter {#PrettyWriter}
 
 While the output of `Writer` is the most condensed JSON without white-spaces, suitable for network transfer or storage, it is not easily readable by human.

include/rapidjson/internal/pow10.h

@@ -6,27 +6,12 @@ namespace internal {
 
 //! Computes integer powers of 10 in double (10.0^n).
 /*! This function uses lookup table for fast and accurate results.
-	\param n positive/negative exponent. Must <= 308.
+	\param n non-negative exponent. Must <= 308.
 	\return 10.0^n
 */
 inline double Pow10(int n) {
-	static const double e[] = { // 1e-308...1e308: 617 * 8 bytes = 4936 bytes
-		1e-308,1e-307,1e-306,1e-305,1e-304,1e-303,1e-302,1e-301,1e-300,
-		1e-299,1e-298,1e-297,1e-296,1e-295,1e-294,1e-293,1e-292,1e-291,1e-290,1e-289,1e-288,1e-287,1e-286,1e-285,1e-284,1e-283,1e-282,1e-281,1e-280,
-		1e-279,1e-278,1e-277,1e-276,1e-275,1e-274,1e-273,1e-272,1e-271,1e-270,1e-269,1e-268,1e-267,1e-266,1e-265,1e-264,1e-263,1e-262,1e-261,1e-260,
-		1e-259,1e-258,1e-257,1e-256,1e-255,1e-254,1e-253,1e-252,1e-251,1e-250,1e-249,1e-248,1e-247,1e-246,1e-245,1e-244,1e-243,1e-242,1e-241,1e-240,
-		1e-239,1e-238,1e-237,1e-236,1e-235,1e-234,1e-233,1e-232,1e-231,1e-230,1e-229,1e-228,1e-227,1e-226,1e-225,1e-224,1e-223,1e-222,1e-221,1e-220,
-		1e-219,1e-218,1e-217,1e-216,1e-215,1e-214,1e-213,1e-212,1e-211,1e-210,1e-209,1e-208,1e-207,1e-206,1e-205,1e-204,1e-203,1e-202,1e-201,1e-200,
-		1e-199,1e-198,1e-197,1e-196,1e-195,1e-194,1e-193,1e-192,1e-191,1e-190,1e-189,1e-188,1e-187,1e-186,1e-185,1e-184,1e-183,1e-182,1e-181,1e-180,
-		1e-179,1e-178,1e-177,1e-176,1e-175,1e-174,1e-173,1e-172,1e-171,1e-170,1e-169,1e-168,1e-167,1e-166,1e-165,1e-164,1e-163,1e-162,1e-161,1e-160,
-		1e-159,1e-158,1e-157,1e-156,1e-155,1e-154,1e-153,1e-152,1e-151,1e-150,1e-149,1e-148,1e-147,1e-146,1e-145,1e-144,1e-143,1e-142,1e-141,1e-140,
-		1e-139,1e-138,1e-137,1e-136,1e-135,1e-134,1e-133,1e-132,1e-131,1e-130,1e-129,1e-128,1e-127,1e-126,1e-125,1e-124,1e-123,1e-122,1e-121,1e-120,
-		1e-119,1e-118,1e-117,1e-116,1e-115,1e-114,1e-113,1e-112,1e-111,1e-110,1e-109,1e-108,1e-107,1e-106,1e-105,1e-104,1e-103,1e-102,1e-101,1e-100,
-		1e-99, 1e-98, 1e-97, 1e-96, 1e-95, 1e-94, 1e-93, 1e-92, 1e-91, 1e-90, 1e-89, 1e-88, 1e-87, 1e-86, 1e-85, 1e-84, 1e-83, 1e-82, 1e-81, 1e-80, 
-		1e-79, 1e-78, 1e-77, 1e-76, 1e-75, 1e-74, 1e-73, 1e-72, 1e-71, 1e-70, 1e-69, 1e-68, 1e-67, 1e-66, 1e-65, 1e-64, 1e-63, 1e-62, 1e-61, 1e-60, 
-		1e-59, 1e-58, 1e-57, 1e-56, 1e-55, 1e-54, 1e-53, 1e-52, 1e-51, 1e-50, 1e-49, 1e-48, 1e-47, 1e-46, 1e-45, 1e-44, 1e-43, 1e-42, 1e-41, 1e-40, 
-		1e-39, 1e-38, 1e-37, 1e-36, 1e-35, 1e-34, 1e-33, 1e-32, 1e-31, 1e-30, 1e-29, 1e-28, 1e-27, 1e-26, 1e-25, 1e-24, 1e-23, 1e-22, 1e-21, 1e-20, 
-		1e-19, 1e-18, 1e-17, 1e-16, 1e-15, 1e-14, 1e-13, 1e-12, 1e-11, 1e-10, 1e-9,  1e-8,  1e-7,  1e-6,  1e-5,  1e-4,  1e-3,  1e-2,  1e-1,  1e+0,  
+	static const double e[] = { // 1e-0...1e308: 309 * 8 bytes = 2472 bytes
+		1e+0,  
 		1e+1,  1e+2,  1e+3,  1e+4,  1e+5,  1e+6,  1e+7,  1e+8,  1e+9,  1e+10, 1e+11, 1e+12, 1e+13, 1e+14, 1e+15, 1e+16, 1e+17, 1e+18, 1e+19, 1e+20, 
 		1e+21, 1e+22, 1e+23, 1e+24, 1e+25, 1e+26, 1e+27, 1e+28, 1e+29, 1e+30, 1e+31, 1e+32, 1e+33, 1e+34, 1e+35, 1e+36, 1e+37, 1e+38, 1e+39, 1e+40,
 		1e+41, 1e+42, 1e+43, 1e+44, 1e+45, 1e+46, 1e+47, 1e+48, 1e+49, 1e+50, 1e+51, 1e+52, 1e+53, 1e+54, 1e+55, 1e+56, 1e+57, 1e+58, 1e+59, 1e+60,
@@ -44,8 +29,8 @@ inline double Pow10(int n) {
 		1e+281,1e+282,1e+283,1e+284,1e+285,1e+286,1e+287,1e+288,1e+289,1e+290,1e+291,1e+292,1e+293,1e+294,1e+295,1e+296,1e+297,1e+298,1e+299,1e+300,
 		1e+301,1e+302,1e+303,1e+304,1e+305,1e+306,1e+307,1e+308
 	};
-	RAPIDJSON_ASSERT(n <= 308);
-	return n < -308 ? 0.0 : e[n + 308];
+	RAPIDJSON_ASSERT(n >= 0 && n <= 308);
+	return e[n];
 }
 
 } // namespace internal

include/rapidjson/prettywriter.h

@@ -31,9 +31,6 @@ public:
 	PrettyWriter(OutputStream& os, Allocator* allocator = 0, size_t levelDepth = Base::kDefaultLevelDepth) : 
 		Base(os, allocator, levelDepth), indentChar_(' '), indentCharCount_(4) {}
 
-	//! Overridden for fluent API, see \ref Writer::SetDoublePrecision()
-	PrettyWriter& SetDoublePrecision(int p) { Base::SetDoublePrecision(p); return *this; }
-
 	//! Set custom indentation.
 	/*! \param indentChar		Character for indentation. Must be whitespace character (' ', '\\t', '\\n', '\\r').
 		\param indentCharCount	Number of indent characters for each indentation level.
@@ -119,15 +116,6 @@ public:
 	//! Simpler but slower overload.
 	bool String(const Ch* str) { return String(str, internal::StrLen(str)); }
 
-	//! Overridden for fluent API, see \ref Writer::Double()
-	bool Double(double d, int precision) {
-		int oldPrecision = Base::GetDoublePrecision();
-		SetDoublePrecision(precision);
-		bool ret = Double(d);
-		SetDoublePrecision(oldPrecision);
-		return ret;
-	}
-
 	//@}
 protected:
 	void PrettyPrefix(Type type) {

include/rapidjson/reader.h

@@ -668,6 +668,18 @@ private:
 		}
 	}
 
+	inline double StrtodFastPath(double significand, int exp) {
+		// Fast path only works on limited range of values.
+		// But for simplicity and performance, currently only implement this.
+		// see http://www.exploringbinary.com/fast-path-decimal-to-floating-point-conversion/
+		if (exp < -308)
+			return 0.0;
+		else if (exp >= 0)
+			return significand * internal::Pow10(exp);
+		else
+			return significand / internal::Pow10(-exp);
+	}
+
 	template<unsigned parseFlags, typename InputStream, typename Handler>
 	void ParseNumber(InputStream& is, Handler& handler) {
 		internal::StreamLocalCopy<InputStream> copy(is);
@@ -813,11 +825,11 @@ private:
 			int expSum = exp + expFrac;
 			if (expSum < -308) {
 				// Prevent expSum < -308, making Pow10(expSum) = 0
-				d *= internal::Pow10(exp);
-				d *= internal::Pow10(expFrac);
+				d = StrtodFastPath(d, exp);
+				d = StrtodFastPath(d, expFrac);
 			}
 			else
-				d *= internal::Pow10(expSum);
+				d = StrtodFastPath(d, expSum);
 
 			cont = handler.Double(minus ? -d : d);
 		}

include/rapidjson/writer.h

@@ -4,9 +4,9 @@
 #include "rapidjson.h"
 #include "internal/stack.h"
 #include "internal/strfunc.h"
+#include "internal/dtoa.h"
 #include "internal/itoa.h"
 #include "stringbuffer.h"
-#include <cstdio>	// snprintf() or _sprintf_s()
 #include <new>		// placement new
 
 #ifdef _MSC_VER
@@ -43,12 +43,10 @@ public:
 		\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), hasRoot_(false) {}
+		os_(&os), level_stack_(allocator, levelDepth * sizeof(Level)), hasRoot_(false) {}
 
 	Writer(Allocator* allocator = 0, size_t levelDepth = kDefaultLevelDepth) :
-		os_(0), level_stack_(allocator, levelDepth * sizeof(Level)),
-		doublePrecision_(kDefaultDoublePrecision), hasRoot_(false) {}
+		os_(0), level_stack_(allocator, levelDepth * sizeof(Level)), hasRoot_(false) {}
 
 	//! Reset the writer with a new stream.
 	/*!
@@ -70,7 +68,6 @@ public:
 	*/
 	void Reset(OutputStream& os) {
 		os_ = &os;
-		doublePrecision_ = kDefaultDoublePrecision;
 		hasRoot_ = false;
 		level_stack_.Clear();
 	}
@@ -83,21 +80,6 @@ public:
 		return hasRoot_ && level_stack_.Empty();
 	}
 
-	//! 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
 	*/
@@ -112,12 +94,6 @@ public:
 
 	//! 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 Whether it is succeed.
 	*/
@@ -167,23 +143,6 @@ public:
 	/*! @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 Whether it is succeeded.
-	*/
-	bool Double(double d, int precision) {
-		int oldPrecision = GetDoublePrecision();
-		SetDoublePrecision(precision);
-		bool ret = Double(d);
-		SetDoublePrecision(oldPrecision);
-		return ret;
-	}
-
 	//! Simpler but slower overload.
 	bool String(const Ch* str) { return String(str, internal::StrLen(str)); }
 
@@ -239,25 +198,17 @@ protected:
 
 	bool WriteUint64(uint64_t u64) {
 		char buffer[20];
-		const char* end = internal::u64toa(u64, buffer);
-		for (const char* p = buffer; p != end; ++p)
+		char* end = internal::u64toa(u64, buffer);
+		for (char* p = buffer; p != end; ++p)
 			os_->Put(*p);
 		return true;
 	}
 
-#ifdef _MSC_VER
-#define RAPIDJSON_SNPRINTF sprintf_s
-#else
-#define RAPIDJSON_SNPRINTF snprintf
-#endif
-
-	//! \todo Optimization with custom double-to-string converter.
 	bool 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]);
+		char buffer[25];
+		char* end = internal::dtoa(d, buffer);
+		for (char* p = buffer; p != end; ++p)
+			os_->Put(*p);
 		return true;
 	}
 #undef RAPIDJSON_SNPRINTF
@@ -358,11 +309,8 @@ protected:
 
 	OutputStream* os_;
 	internal::Stack<Allocator> level_stack_;
-	int doublePrecision_;
 	bool hasRoot_;
 
-	static const int kDefaultDoublePrecision = 6;
-
 private:
 	// Prohibit copy constructor & assignment operator.
 	Writer(const Writer&);
@@ -403,6 +351,14 @@ inline bool Writer<StringBuffer>::WriteUint64(uint64_t u) {
 	return true;
 }
 
+template<>
+inline bool Writer<StringBuffer>::WriteDouble(double d) {
+	char *buffer = os_->Push(25);
+	char* end = internal::dtoa(d, buffer);
+	os_->Pop(25 - (end - buffer));
+	return true;
+}
+
 } // namespace rapidjson
 
 #ifdef _MSC_VER

test/unittest/writertest.cpp

@@ -60,60 +60,9 @@ TEST(Writer, String) {
 	TEST_ROUNDTRIP("[\"\\\"\\\\/\\b\\f\\n\\r\\t\"]");
 }
 
-TEST(Writer,DoublePrecision) {
-	const char json[] = "[1.2345,1.2345678,0.123456789012,1234567.8]";
+TEST(Writer, Double) {
+	TEST_ROUNDTRIP("[1.2345,1.2345678,0.123456789012,1234567.8]");
 
-	StringBuffer buffer;
-	Writer<StringBuffer> writer(buffer);
-
-	const int kDefaultDoublePrecision = 6;
-	// handling the double precision
-	EXPECT_EQ(writer.GetDoublePrecision(), kDefaultDoublePrecision);
-	writer.SetDoublePrecision(17);
-	EXPECT_EQ(writer.GetDoublePrecision(), 17);
-	writer.SetDoublePrecision(-1); // negative equivalent to reset
-	EXPECT_EQ(writer.GetDoublePrecision(), kDefaultDoublePrecision);
-	writer.SetDoublePrecision(1);
-	writer.SetDoublePrecision();   // reset again
-	EXPECT_EQ(writer.GetDoublePrecision(), kDefaultDoublePrecision);
-
-	{ // write with explicitly increased precision
-		StringStream s(json);
-		Reader reader;
-		reader.Parse<0>(s, writer.SetDoublePrecision(12));
-		EXPECT_EQ(writer.GetDoublePrecision(), 12);
-		EXPECT_STREQ(json, buffer.GetString());
-	}
-	{ // explicit individual double precisions
-		buffer.Clear();
-		writer.Reset(buffer);
-		writer.SetDoublePrecision(2);
-		writer.StartArray();
-		writer.Double(1.2345, 5);
-		writer.Double(1.2345678, 9);
-		writer.Double(0.123456789012, 12);
-		writer.Double(1234567.8, 8);
-		writer.EndArray();
-
-		EXPECT_EQ(writer.GetDoublePrecision(), 2);
-		EXPECT_STREQ(json, buffer.GetString());
-	}
-	{ // write with default precision (output with precision loss)
-		Document d;
-		d.Parse<0>(json);
-		buffer.Clear();
-		writer.Reset(buffer);
-		d.Accept(writer.SetDoublePrecision());
-
-		// parsed again to avoid platform-dependent floating point outputs
-		// (e.g. width of exponents)
-		d.Parse<0>(buffer.GetString());
-		EXPECT_EQ(writer.GetDoublePrecision(), kDefaultDoublePrecision);
-		EXPECT_DOUBLE_EQ(d[0u].GetDouble(), 1.2345);
-		EXPECT_DOUBLE_EQ(d[1u].GetDouble(), 1.23457);
-		EXPECT_DOUBLE_EQ(d[2u].GetDouble(), 0.123457);
-		EXPECT_DOUBLE_EQ(d[3u].GetDouble(), 1234570);
-	}
 }
 
 TEST(Writer, Transcode) {