Merge pull request #39 from miloyip/LocalCopyOptimization

Fixes local copy optimization

include/rapidjson/filereadstream.h

@@ -69,11 +69,6 @@ private:
 	bool eof_;
 };
 
-template<>
-struct StreamTraits<FileReadStream> {
-	typedef FileReadStream StreamCopyType;	// Enable stream copy optimization.
-};
-
 } // namespace rapidjson
 
 #endif // RAPIDJSON_FILESTREAM_H_

include/rapidjson/rapidjson.h

@@ -203,12 +203,42 @@ template<typename Stream>
 struct StreamTraits {
 	//! Whether to make local copy of stream for optimization during parsing.
 	/*!
-		If it is defined as Stream&, it will not make a local copy.
-		If it is defined as Stream, it will make a local copy for optimization.
-		By default, for safety, streams do not use local copy optimization, i.e. it is defined as Stream&.
+		By default, for safety, streams do not use local copy optimization.
 		Stream that can be copied fast should specialize this, like StreamTraits<StringStream>.
 	*/
-	typedef Stream& StreamCopyType;
+	enum { copyOptimization = 0 };
+};
+
+template<typename Stream, bool>
+class StreamLocalCopy;
+
+template<typename Stream>
+class StreamLocalCopy<Stream, 1> {
+public:
+	StreamLocalCopy(Stream& original) : original_(original), s_(original) {}
+	~StreamLocalCopy() { original_ = s_; }
+	Stream* operator->() { return &s_; }
+	Stream& operator*() { return s_; }
+
+private:
+	StreamLocalCopy& operator=(const StreamLocalCopy&);
+
+	Stream& original_;
+	Stream s_;
+};
+
+template<typename Stream>
+class StreamLocalCopy<Stream, 0> {
+public:
+	StreamLocalCopy(Stream& original) : s_(original) {}
+	~StreamLocalCopy() {}
+	Stream* operator->() { return &s_; }
+	Stream& operator*() { return s_; }
+
+private:
+	StreamLocalCopy& operator=(const StreamLocalCopy&);
+
+	Stream& s_;
 };
 
 //! Put N copies of a character to a stream.
@@ -245,7 +275,7 @@ struct GenericStringStream {
 
 template <typename Encoding>
 struct StreamTraits<GenericStringStream<Encoding> > {
-	typedef GenericStringStream<Encoding> StreamCopyType;	// Enable stream copy optimization.
+	enum { copyOptimization = 1 };
 };
 
 typedef GenericStringStream<UTF8<> > StringStream;
@@ -281,7 +311,7 @@ struct GenericInsituStringStream {
 
 template <typename Encoding>
 struct StreamTraits<GenericInsituStringStream<Encoding> > {
-	typedef GenericInsituStringStream<Encoding> StreamCopyType;	// Enable stream copy optimization.
+	enum { copyOptimization = 1 };
 };
 
 typedef GenericInsituStringStream<UTF8<> > InsituStringStream;

include/rapidjson/reader.h

@@ -135,10 +135,9 @@ struct BaseReaderHandler {
 */
 template<typename InputStream>
 void SkipWhitespace(InputStream& is) {
-	typename StreamTraits<InputStream>::StreamCopyType s = is;	// Use a local copy for optimization
-	while (s.Peek() == ' ' || s.Peek() == '\n' || s.Peek() == '\r' || s.Peek() == '\t')
-		s.Take();
-	is = s;
+	StreamLocalCopy<InputStream, StreamTraits<InputStream>::copyOptimization> s(is);
+	while (s->Peek() == ' ' || s->Peek() == '\n' || s->Peek() == '\r' || s->Peek() == '\t')
+		s->Take();
 }
 
 #ifdef RAPIDJSON_SSE42
@@ -295,6 +294,10 @@ public:
 	size_t GetErrorOffset() const { return errorOffset_; }
 
 private:
+	// Prohibit copy constructor & assignment operator.
+	GenericReader(const GenericReader&);
+	GenericReader& operator=(const GenericReader&);
+
 	// Parse object: { string : value, ... }
 	template<unsigned parseFlags, typename InputStream, typename Handler>
 	void ParseObject(InputStream& is, Handler& handler) {
@@ -406,10 +409,9 @@ private:
 	// Helper function to parse four hexidecimal digits in \uXXXX in ParseString().
 	template<typename InputStream>
 	unsigned ParseHex4(InputStream& is) {
-		typename StreamTraits<InputStream>::StreamCopyType s = is;	// Use a local copy for optimization
 		unsigned codepoint = 0;
 		for (int i = 0; i < 4; i++) {
-			Ch c = s.Take();
+			Ch c = is.Take();
 			codepoint <<= 4;
 			codepoint += static_cast<unsigned>(c);
 			if (c >= '0' && c <= '9')
@@ -419,11 +421,10 @@ private:
 			else if (c >= 'a' && c <= 'f')
 				codepoint -= 'a' - 10;
 			else {
-				RAPIDJSON_PARSE_ERROR_NORETURN(kParseErrorStringUnicodeEscapeInvalidHex, s.Tell() - 1);
+				RAPIDJSON_PARSE_ERROR_NORETURN(kParseErrorStringUnicodeEscapeInvalidHex, is.Tell() - 1);
 				return 0;
 			}
 		}
-		is = s; // Restore is
 		return codepoint;
 	}
 
@@ -447,24 +448,23 @@ private:
 	// Parse string and generate String event. Different code paths for kParseInsituFlag.
 	template<unsigned parseFlags, typename InputStream, typename Handler>
 	void ParseString(InputStream& is, Handler& handler) {
-		typename StreamTraits<InputStream>::StreamCopyType  s = is;	// Local copy for optimization
+		StreamLocalCopy<InputStream, StreamTraits<InputStream>::copyOptimization> s(is);
 		if (parseFlags & kParseInsituFlag) {
-			Ch *head = s.PutBegin();
-			ParseStringToStream<parseFlags, SourceEncoding, SourceEncoding>(s, s);
+			Ch *head = s->PutBegin();
+			ParseStringToStream<parseFlags, SourceEncoding, SourceEncoding>(*s, *s);
 			if (HasParseError())
 				return;
-			size_t length = s.PutEnd(head) - 1;
+			size_t length = s->PutEnd(head) - 1;
 			RAPIDJSON_ASSERT(length <= 0xFFFFFFFF);
 			handler.String((typename TargetEncoding::Ch*)head, SizeType(length), false);
 		}
 		else {
 			StackStream stackStream(stack_);
-			ParseStringToStream<parseFlags, SourceEncoding, TargetEncoding>(s, stackStream);
+			ParseStringToStream<parseFlags, SourceEncoding, TargetEncoding>(*s, stackStream);
 			if (HasParseError())
 				return;
 			handler.String(stack_.template Pop<typename TargetEncoding::Ch>(stackStream.length_), stackStream.length_ - 1, true);
 		}
-		is = s;		// Restore is
 	}
 
 	// Parse string to an output is
@@ -527,43 +527,43 @@ private:
 
 	template<unsigned parseFlags, typename InputStream, typename Handler>
 	void ParseNumber(InputStream& is, Handler& handler) {
-		typename StreamTraits<InputStream>::StreamCopyType s = is; // Local copy for optimization
+		StreamLocalCopy<InputStream, StreamTraits<InputStream>::copyOptimization> s(is);
 		// Parse minus
 		bool minus = false;
-		if (s.Peek() == '-') {
+		if (s->Peek() == '-') {
 			minus = true;
-			s.Take();
+			s->Take();
 		}
 
 		// Parse int: zero / ( digit1-9 *DIGIT )
 		unsigned i;
 		bool try64bit = false;
-		if (s.Peek() == '0') {
+		if (s->Peek() == '0') {
 			i = 0;
-			s.Take();
+			s->Take();
 		}
-		else if (s.Peek() >= '1' && s.Peek() <= '9') {
-			i = static_cast<unsigned>(s.Take() - '0');
+		else if (s->Peek() >= '1' && s->Peek() <= '9') {
+			i = static_cast<unsigned>(s->Take() - '0');
 
 			if (minus)
-				while (s.Peek() >= '0' && s.Peek() <= '9') {
+				while (s->Peek() >= '0' && s->Peek() <= '9') {
 					if (i >= 214748364) { // 2^31 = 2147483648
-						if (i != 214748364 || s.Peek() > '8') {
+						if (i != 214748364 || s->Peek() > '8') {
 							try64bit = true;
 							break;
 						}
 					}
-					i = i * 10 + static_cast<unsigned>(s.Take() - '0');
+					i = i * 10 + static_cast<unsigned>(s->Take() - '0');
 				}
 			else
-				while (s.Peek() >= '0' && s.Peek() <= '9') {
+				while (s->Peek() >= '0' && s->Peek() <= '9') {
 					if (i >= 429496729) { // 2^32 - 1 = 4294967295
-						if (i != 429496729 || s.Peek() > '5') {
+						if (i != 429496729 || s->Peek() > '5') {
 							try64bit = true;
 							break;
 						}
 					}
-					i = i * 10 + static_cast<unsigned>(s.Take() - '0');
+					i = i * 10 + static_cast<unsigned>(s->Take() - '0');
 				}
 		}
 		else
@@ -575,22 +575,22 @@ private:
 		if (try64bit) {
 			i64 = i;
 			if (minus) 
-				while (s.Peek() >= '0' && s.Peek() <= '9') {					
+				while (s->Peek() >= '0' && s->Peek() <= '9') {					
 					if (i64 >= UINT64_C(922337203685477580)) // 2^63 = 9223372036854775808
-						if (i64 != UINT64_C(922337203685477580) || s.Peek() > '8') {
+						if (i64 != UINT64_C(922337203685477580) || s->Peek() > '8') {
 							useDouble = true;
 							break;
 						}
-					i64 = i64 * 10 + static_cast<unsigned>(s.Take() - '0');
+					i64 = i64 * 10 + static_cast<unsigned>(s->Take() - '0');
 				}
 			else
-				while (s.Peek() >= '0' && s.Peek() <= '9') {					
+				while (s->Peek() >= '0' && s->Peek() <= '9') {					
 					if (i64 >= UINT64_C(1844674407370955161)) // 2^64 - 1 = 18446744073709551615
-						if (i64 != UINT64_C(1844674407370955161) || s.Peek() > '5') {
+						if (i64 != UINT64_C(1844674407370955161) || s->Peek() > '5') {
 							useDouble = true;
 							break;
 						}
-					i64 = i64 * 10 + static_cast<unsigned>(s.Take() - '0');
+					i64 = i64 * 10 + static_cast<unsigned>(s->Take() - '0');
 				}
 		}
 
@@ -598,65 +598,65 @@ private:
 		double d = 0.0;
 		if (useDouble) {
 			d = (double)i64;
-			while (s.Peek() >= '0' && s.Peek() <= '9') {
+			while (s->Peek() >= '0' && s->Peek() <= '9') {
 				if (d >= 1E307)
 					RAPIDJSON_PARSE_ERROR(kParesErrorNumberTooBig, is.Tell());
-				d = d * 10 + (s.Take() - '0');
+				d = d * 10 + (s->Take() - '0');
 			}
 		}
 
 		// Parse frac = decimal-point 1*DIGIT
 		int expFrac = 0;
-		if (s.Peek() == '.') {
+		if (s->Peek() == '.') {
 			if (!useDouble) {
 				d = try64bit ? (double)i64 : (double)i;
 				useDouble = true;
 			}
-			s.Take();
+			s->Take();
 
-			if (s.Peek() >= '0' && s.Peek() <= '9') {
-				d = d * 10 + (s.Take() - '0');
+			if (s->Peek() >= '0' && s->Peek() <= '9') {
+				d = d * 10 + (s->Take() - '0');
 				--expFrac;
 			}
 			else
 				RAPIDJSON_PARSE_ERROR(kParseErrorNumberMissFraction, is.Tell());
 
-			while (s.Peek() >= '0' && s.Peek() <= '9') {
+			while (s->Peek() >= '0' && s->Peek() <= '9') {
 				if (expFrac > -16) {
-					d = d * 10 + (s.Peek() - '0');
+					d = d * 10 + (s->Peek() - '0');
 					--expFrac;
 				}
-				s.Take();
+				s->Take();
 			}
 		}
 
 		// Parse exp = e [ minus / plus ] 1*DIGIT
 		int exp = 0;
-		if (s.Peek() == 'e' || s.Peek() == 'E') {
+		if (s->Peek() == 'e' || s->Peek() == 'E') {
 			if (!useDouble) {
 				d = try64bit ? (double)i64 : (double)i;
 				useDouble = true;
 			}
-			s.Take();
+			s->Take();
 
 			bool expMinus = false;
-			if (s.Peek() == '+')
-				s.Take();
-			else if (s.Peek() == '-') {
-				s.Take();
+			if (s->Peek() == '+')
+				s->Take();
+			else if (s->Peek() == '-') {
+				s->Take();
 				expMinus = true;
 			}
 
-			if (s.Peek() >= '0' && s.Peek() <= '9') {
-				exp = s.Take() - '0';
-				while (s.Peek() >= '0' && s.Peek() <= '9') {
-					exp = exp * 10 + (s.Take() - '0');
+			if (s->Peek() >= '0' && s->Peek() <= '9') {
+				exp = s->Take() - '0';
+				while (s->Peek() >= '0' && s->Peek() <= '9') {
+					exp = exp * 10 + (s->Take() - '0');
 					if (exp > 308)
 						RAPIDJSON_PARSE_ERROR(kParesErrorNumberTooBig, is.Tell());
 				}
 			}
 			else
-				RAPIDJSON_PARSE_ERROR(kParseErrorNumberMissExponent, s.Tell());
+				RAPIDJSON_PARSE_ERROR(kParseErrorNumberMissExponent, is.Tell());
 
 			if (expMinus)
 				exp = -exp;
@@ -689,8 +689,6 @@ private:
 					handler.Uint(i);
 			}
 		}
-
-		is = s; // restore is
 	}
 
 	// Parse any JSON value

test/unittest/readertest.cpp

@@ -623,8 +623,9 @@ public:
 	size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }
 
 private:
-	// Not support copy constructor.
+	// Prohibit copy constructor & assignment operator.
 	CustomStringStream(const CustomStringStream&);
+	CustomStringStream& operator=(const CustomStringStream&);
 
 	const Ch* src_;		//!< Current read position.
 	const Ch* head_;	//!< Original head of the string.
@@ -637,7 +638,7 @@ namespace rapidjson {
 
 template <typename Encoding>
 struct StreamTraits<CustomStringStream<Encoding> > {
-	typedef CustomStringStream<Encoding> StreamCopyType;
+	enum { copyOptimization = 1 };
 };
 
 } // namespace rapdijson