gtest-printers.h
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gtest-printers.h
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	// Copyright 2007, Google Inc.
	// All rights reserved.
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are
	// met:
	//
	// * Redistributions of source code must retain the above copyright
	// notice, this list of conditions and the following disclaimer.
	// * Redistributions in binary form must reproduce the above
	// copyright notice, this list of conditions and the following disclaimer
	// in the documentation and/or other materials provided with the
	// distribution.
	// * Neither the name of Google Inc. nor the names of its
	// contributors may be used to endorse or promote products derived from
	// this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	//
	// Author: wan@google.com (Zhanyong Wan)

	// Google Test - The Google C++ Testing Framework
	//
	// This file implements a universal value printer that can print a
	// value of any type T:
	//
	// void ::testing::internal::UniversalPrinter<T>::Print(value, ostream_ptr);
	//
	// A user can teach this function how to print a class type T by
	// defining either operator<<() or PrintTo() in the namespace that
	// defines T. More specifically, the FIRST defined function in the
	// following list will be used (assuming T is defined in namespace
	// foo):
	//
	// 1. foo::PrintTo(const T&, ostream*)
	// 2. operator<<(ostream&, const T&) defined in either foo or the
	// global namespace.
	//
	// If none of the above is defined, it will print the debug string of
	// the value if it is a protocol buffer, or print the raw bytes in the
	// value otherwise.
	//
	// To aid debugging: when T is a reference type, the address of the
	// value is also printed; when T is a (const) char pointer, both the
	// pointer value and the NUL-terminated string it points to are
	// printed.
	//
	// We also provide some convenient wrappers:
	//
	// // Prints a value to a string. For a (const or not) char
	// // pointer, the NUL-terminated string (but not the pointer) is
	// // printed.
	// std::string ::testing::PrintToString(const T& value);
	//
	// // Prints a value tersely: for a reference type, the referenced
	// // value (but not the address) is printed; for a (const or not) char
	// // pointer, the NUL-terminated string (but not the pointer) is
	// // printed.
	// void ::testing::internal::UniversalTersePrint(const T& value, ostream*);
	//
	// // Prints value using the type inferred by the compiler. The difference
	// // from UniversalTersePrint() is that this function prints both the
	// // pointer and the NUL-terminated string for a (const or not) char pointer.
	// void ::testing::internal::UniversalPrint(const T& value, ostream*);
	//
	// // Prints the fields of a tuple tersely to a string vector, one
	// // element for each field. Tuple support must be enabled in
	// // gtest-port.h.
	// std::vector<string> UniversalTersePrintTupleFieldsToStrings(
	// const Tuple& value);
	//
	// Known limitation:
	//
	// The print primitives print the elements of an STL-style container
	// using the compiler-inferred type of *iter where iter is a
	// const_iterator of the container. When const_iterator is an input
	// iterator but not a forward iterator, this inferred type may not
	// match value_type, and the print output may be incorrect. In
	// practice, this is rarely a problem as for most containers
	// const_iterator is a forward iterator. We'll fix this if there's an
	// actual need for it. Note that this fix cannot rely on value_type
	// being defined as many user-defined container types don't have
	// value_type.

	#ifndef GTEST_INCLUDE_GTEST_GTEST_PRINTERS_H_
	#define GTEST_INCLUDE_GTEST_GTEST_PRINTERS_H_

	#include <ostream> // NOLINT
	#include <sstream>
	#include <string>
	#include <utility>
	#include <vector>
	#include <gtest/internal/gtest-port.h>
	#include <gtest/internal/gtest-internal.h>

	namespace testing {

	// Definitions in the 'internal' and 'internal2' name spaces are
	// subject to change without notice. DO NOT USE THEM IN USER CODE!
	namespace internal2 {

	// Prints the given number of bytes in the given object to the given
	// ostream.
	GTEST_API_ void PrintBytesInObjectTo(const unsigned char* obj_bytes,
	size_t count,
	::std::ostream* os);

	// For selecting which printer to use when a given type has neither <<
	// nor PrintTo().
	enum TypeKind {
	kProtobuf, // a protobuf type
	kConvertibleToInteger, // a type implicitly convertible to BiggestInt
	// (e.g. a named or unnamed enum type)
	kOtherType, // anything else
	};

	// TypeWithoutFormatter<T, kTypeKind>::PrintValue(value, os) is called
	// by the universal printer to print a value of type T when neither
	// operator<< nor PrintTo() is defined for T, where kTypeKind is the
	// "kind" of T as defined by enum TypeKind.
	template <typename T, TypeKind kTypeKind>
	class TypeWithoutFormatter {
	public:
	// This default version is called when kTypeKind is kOtherType.
	static void PrintValue(const T& value, ::std::ostream* os) {
	PrintBytesInObjectTo(reinterpret_cast<const unsigned char*>(&value),
	sizeof(value), os);
	}
	};

	// We print a protobuf using its ShortDebugString() when the string
	// doesn't exceed this many characters; otherwise we print it using
	// DebugString() for better readability.
	const size_t kProtobufOneLinerMaxLength = 50;

	template <typename T>
	class TypeWithoutFormatter<T, kProtobuf> {
	public:
	static void PrintValue(const T& value, ::std::ostream* os) {
	const ::testing::internal::string short_str = value.ShortDebugString();
	const ::testing::internal::string pretty_str =
	short_str.length() <= kProtobufOneLinerMaxLength ?
	short_str : ("\n" + value.DebugString());
	*os << ("<" + pretty_str + ">");
	}
	};

	template <typename T>
	class TypeWithoutFormatter<T, kConvertibleToInteger> {
	public:
	// Since T has no << operator or PrintTo() but can be implicitly
	// converted to BiggestInt, we print it as a BiggestInt.
	//
	// Most likely T is an enum type (either named or unnamed), in which
	// case printing it as an integer is the desired behavior. In case
	// T is not an enum, printing it as an integer is the best we can do
	// given that it has no user-defined printer.
	static void PrintValue(const T& value, ::std::ostream* os) {
	const internal::BiggestInt kBigInt = value;
	*os << kBigInt;
	}
	};

	// Prints the given value to the given ostream. If the value is a
	// protocol message, its debug string is printed; if it's an enum or
	// of a type implicitly convertible to BiggestInt, it's printed as an
	// integer; otherwise the bytes in the value are printed. This is
	// what UniversalPrinter<T>::Print() does when it knows nothing about
	// type T and T has neither << operator nor PrintTo().
	//
	// A user can override this behavior for a class type Foo by defining
	// a << operator in the namespace where Foo is defined.
	//
	// We put this operator in namespace 'internal2' instead of 'internal'
	// to simplify the implementation, as much code in 'internal' needs to
	// use << in STL, which would conflict with our own << were it defined
	// in 'internal'.
	//
	// Note that this operator<< takes a generic std::basic_ostream<Char,
	// CharTraits> type instead of the more restricted std::ostream. If
	// we define it to take an std::ostream instead, we'll get an
	// "ambiguous overloads" compiler error when trying to print a type
	// Foo that supports streaming to std::basic_ostream<Char,
	// CharTraits>, as the compiler cannot tell whether
	// operator<<(std::ostream&, const T&) or
	// operator<<(std::basic_stream<Char, CharTraits>, const Foo&) is more
	// specific.
	template <typename Char, typename CharTraits, typename T>
	::std::basic_ostream<Char, CharTraits>& operator<<(
	::std::basic_ostream<Char, CharTraits>& os, const T& x) {
	TypeWithoutFormatter<T,
	(internal::IsAProtocolMessage<T>::value ? kProtobuf :
	internal::ImplicitlyConvertible<const T&, internal::BiggestInt>::value ?
	kConvertibleToInteger : kOtherType)>::PrintValue(x, &os);
	return os;
	}

	} // namespace internal2
	} // namespace testing

	// This namespace MUST NOT BE NESTED IN ::testing, or the name look-up
	// magic needed for implementing UniversalPrinter won't work.
	namespace testing_internal {

	// Used to print a value that is not an STL-style container when the
	// user doesn't define PrintTo() for it.
	template <typename T>
	void DefaultPrintNonContainerTo(const T& value, ::std::ostream* os) {
	// With the following statement, during unqualified name lookup,
	// testing::internal2::operator<< appears as if it was declared in
	// the nearest enclosing namespace that contains both
	// ::testing_internal and ::testing::internal2, i.e. the global
	// namespace. For more details, refer to the C++ Standard section
	// 7.3.4-1 [namespace.udir]. This allows us to fall back onto
	// testing::internal2::operator<< in case T doesn't come with a <<
	// operator.
	//
	// We cannot write 'using ::testing::internal2::operator<<;', which
	// gcc 3.3 fails to compile due to a compiler bug.
	using namespace ::testing::internal2; // NOLINT

	// Assuming T is defined in namespace foo, in the next statement,
	// the compiler will consider all of:
	//
	// 1. foo::operator<< (thanks to Koenig look-up),
	// 2. ::operator<< (as the current namespace is enclosed in ::),
	// 3. testing::internal2::operator<< (thanks to the using statement above).
	//
	// The operator<< whose type matches T best will be picked.
	//
	// We deliberately allow #2 to be a candidate, as sometimes it's
	// impossible to define #1 (e.g. when foo is ::std, defining
	// anything in it is undefined behavior unless you are a compiler
	// vendor.).
	*os << value;
	}

	} // namespace testing_internal

	namespace testing {
	namespace internal {

	// UniversalPrinter<T>::Print(value, ostream_ptr) prints the given
	// value to the given ostream. The caller must ensure that
	// 'ostream_ptr' is not NULL, or the behavior is undefined.
	//
	// We define UniversalPrinter as a class template (as opposed to a
	// function template), as we need to partially specialize it for
	// reference types, which cannot be done with function templates.
	template <typename T>
	class UniversalPrinter;

	template <typename T>
	void UniversalPrint(const T& value, ::std::ostream* os);

	// Used to print an STL-style container when the user doesn't define
	// a PrintTo() for it.
	template <typename C>
	void DefaultPrintTo(IsContainer /* dummy */,
	false_type /* is not a pointer */,
	const C& container, ::std::ostream* os) {
	const size_t kMaxCount = 32; // The maximum number of elements to print.
	*os << '{';
	size_t count = 0;
	for (typename C::const_iterator it = container.begin();
	it != container.end(); ++it, ++count) {
	if (count > 0) {
	*os << ',';
	if (count == kMaxCount) { // Enough has been printed.
	*os << " ...";
	break;
	}
	}
	*os << ' ';
	// We cannot call PrintTo(*it, os) here as PrintTo() doesn't
	// handle *it being a native array.
	internal::UniversalPrint(*it, os);
	}

	if (count > 0) {
	*os << ' ';
	}
	*os << '}';
	}

	// Used to print a pointer that is neither a char pointer nor a member
	// pointer, when the user doesn't define PrintTo() for it. (A member
	// variable pointer or member function pointer doesn't really point to
	// a location in the address space. Their representation is
	// implementation-defined. Therefore they will be printed as raw
	// bytes.)
	template <typename T>
	void DefaultPrintTo(IsNotContainer /* dummy */,
	true_type /* is a pointer */,
	T* p, ::std::ostream* os) {
	if (p == NULL) {
	*os << "NULL";
	} else {
	// C++ doesn't allow casting from a function pointer to any object
	// pointer.
	if (ImplicitlyConvertible<T, const void>::value) {
	// T is not a function type. We just call << to print p,
	// relying on ADL to pick up user-defined << for their pointer
	// types, if any.
	*os << p;
	} else {
	// T is a function type, so '*os << p' doesn't do what we want
	// (it just prints p as bool). We want to print p as a const
	// void. However, we cannot cast it to const void directly,
	// even using reinterpret_cast, as earlier versions of gcc
	// (e.g. 3.4.5) cannot compile the cast when p is a function
	// pointer. Casting to UInt64 first solves the problem.
	os << reinterpret_cast<const void>(
	reinterpret_cast<internal::UInt64>(p));
	}
	}
	}

	// Used to print a non-container, non-pointer value when the user
	// doesn't define PrintTo() for it.
	template <typename T>
	void DefaultPrintTo(IsNotContainer /* dummy */,
	false_type /* is not a pointer */,
	const T& value, ::std::ostream* os) {
	::testing_internal::DefaultPrintNonContainerTo(value, os);
	}

	// Prints the given value using the << operator if it has one;
	// otherwise prints the bytes in it. This is what
	// UniversalPrinter<T>::Print() does when PrintTo() is not specialized
	// or overloaded for type T.
	//
	// A user can override this behavior for a class type Foo by defining
	// an overload of PrintTo() in the namespace where Foo is defined. We
	// give the user this option as sometimes defining a << operator for
	// Foo is not desirable (e.g. the coding style may prevent doing it,
	// or there is already a << operator but it doesn't do what the user
	// wants).
	template <typename T>
	void PrintTo(const T& value, ::std::ostream* os) {
	// DefaultPrintTo() is overloaded. The type of its first two
	// arguments determine which version will be picked. If T is an
	// STL-style container, the version for container will be called; if
	// T is a pointer, the pointer version will be called; otherwise the
	// generic version will be called.
	//
	// Note that we check for container types here, prior to we check
	// for protocol message types in our operator<<. The rationale is:
	//
	// For protocol messages, we want to give people a chance to
	// override Google Mock's format by defining a PrintTo() or
	// operator<<. For STL containers, other formats can be
	// incompatible with Google Mock's format for the container
	// elements; therefore we check for container types here to ensure
	// that our format is used.
	//
	// The second argument of DefaultPrintTo() is needed to bypass a bug
	// in Symbian's C++ compiler that prevents it from picking the right
	// overload between:
	//
	// PrintTo(const T& x, ...);
	// PrintTo(T* x, ...);
	DefaultPrintTo(IsContainerTest<T>(0), is_pointer<T>(), value, os);
	}

	// The following list of PrintTo() overloads tells
	// UniversalPrinter<T>::Print() how to print standard types (built-in
	// types, strings, plain arrays, and pointers).

	// Overloads for various char types.
	GTEST_API_ void PrintTo(unsigned char c, ::std::ostream* os);
	GTEST_API_ void PrintTo(signed char c, ::std::ostream* os);
	inline void PrintTo(char c, ::std::ostream* os) {
	// When printing a plain char, we always treat it as unsigned. This
	// way, the output won't be affected by whether the compiler thinks
	// char is signed or not.
	PrintTo(static_cast<unsigned char>(c), os);
	}

	// Overloads for other simple built-in types.
	inline void PrintTo(bool x, ::std::ostream* os) {
	*os << (x ? "true" : "false");
	}

	// Overload for wchar_t type.
	// Prints a wchar_t as a symbol if it is printable or as its internal
	// code otherwise and also as its decimal code (except for L'\0').
	// The L'\0' char is printed as "L'\\0'". The decimal code is printed
	// as signed integer when wchar_t is implemented by the compiler
	// as a signed type and is printed as an unsigned integer when wchar_t
	// is implemented as an unsigned type.
	GTEST_API_ void PrintTo(wchar_t wc, ::std::ostream* os);

	// Overloads for C strings.
	GTEST_API_ void PrintTo(const char* s, ::std::ostream* os);
	inline void PrintTo(char* s, ::std::ostream* os) {
	PrintTo(implicit_cast<const char*>(s), os);
	}

	// signed/unsigned char is often used for representing binary data, so
	// we print pointers to it as void* to be safe.
	inline void PrintTo(const signed char* s, ::std::ostream* os) {
	PrintTo(implicit_cast<const void*>(s), os);
	}
	inline void PrintTo(signed char* s, ::std::ostream* os) {
	PrintTo(implicit_cast<const void*>(s), os);
	}
	inline void PrintTo(const unsigned char* s, ::std::ostream* os) {
	PrintTo(implicit_cast<const void*>(s), os);
	}
	inline void PrintTo(unsigned char* s, ::std::ostream* os) {
	PrintTo(implicit_cast<const void*>(s), os);
	}

	// MSVC can be configured to define wchar_t as a typedef of unsigned
	// short. It defines _NATIVE_WCHAR_T_DEFINED when wchar_t is a native
	// type. When wchar_t is a typedef, defining an overload for const
	// wchar_t* would cause unsigned short* be printed as a wide string,
	// possibly causing invalid memory accesses.
	#if !defined(_MSC_VER) \|\| defined(_NATIVE_WCHAR_T_DEFINED)
	// Overloads for wide C strings
	GTEST_API_ void PrintTo(const wchar_t* s, ::std::ostream* os);
	inline void PrintTo(wchar_t* s, ::std::ostream* os) {
	PrintTo(implicit_cast<const wchar_t*>(s), os);
	}
	#endif

	// Overload for C arrays. Multi-dimensional arrays are printed
	// properly.

	// Prints the given number of elements in an array, without printing
	// the curly braces.
	template <typename T>
	void PrintRawArrayTo(const T a[], size_t count, ::std::ostream* os) {
	UniversalPrint(a[0], os);
	for (size_t i = 1; i != count; i++) {
	*os << ", ";
	UniversalPrint(a[i], os);
	}
	}

	// Overloads for ::string and ::std::string.
	#if GTEST_HAS_GLOBAL_STRING
	GTEST_API_ void PrintStringTo(const ::string&s, ::std::ostream* os);
	inline void PrintTo(const ::string& s, ::std::ostream* os) {
	PrintStringTo(s, os);
	}
	#endif // GTEST_HAS_GLOBAL_STRING

	GTEST_API_ void PrintStringTo(const ::std::string&s, ::std::ostream* os);
	inline void PrintTo(const ::std::string& s, ::std::ostream* os) {
	PrintStringTo(s, os);
	}

	// Overloads for ::wstring and ::std::wstring.
	#if GTEST_HAS_GLOBAL_WSTRING
	GTEST_API_ void PrintWideStringTo(const ::wstring&s, ::std::ostream* os);
	inline void PrintTo(const ::wstring& s, ::std::ostream* os) {
	PrintWideStringTo(s, os);
	}
	#endif // GTEST_HAS_GLOBAL_WSTRING

	#if GTEST_HAS_STD_WSTRING
	GTEST_API_ void PrintWideStringTo(const ::std::wstring&s, ::std::ostream* os);
	inline void PrintTo(const ::std::wstring& s, ::std::ostream* os) {
	PrintWideStringTo(s, os);
	}
	#endif // GTEST_HAS_STD_WSTRING

	#if GTEST_HAS_TR1_TUPLE
	// Overload for ::std::tr1::tuple. Needed for printing function arguments,
	// which are packed as tuples.

	// Helper function for printing a tuple. T must be instantiated with
	// a tuple type.
	template <typename T>
	void PrintTupleTo(const T& t, ::std::ostream* os);

	// Overloaded PrintTo() for tuples of various arities. We support
	// tuples of up-to 10 fields. The following implementation works
	// regardless of whether tr1::tuple is implemented using the
	// non-standard variadic template feature or not.

	inline void PrintTo(const ::std::tr1::tuple<>& t, ::std::ostream* os) {
	PrintTupleTo(t, os);
	}

	template <typename T1>
	void PrintTo(const ::std::tr1::tuple<T1>& t, ::std::ostream* os) {
	PrintTupleTo(t, os);
	}

	template <typename T1, typename T2>
	void PrintTo(const ::std::tr1::tuple<T1, T2>& t, ::std::ostream* os) {
	PrintTupleTo(t, os);
	}

	template <typename T1, typename T2, typename T3>
	void PrintTo(const ::std::tr1::tuple<T1, T2, T3>& t, ::std::ostream* os) {
	PrintTupleTo(t, os);
	}

	template <typename T1, typename T2, typename T3, typename T4>
	void PrintTo(const ::std::tr1::tuple<T1, T2, T3, T4>& t, ::std::ostream* os) {
	PrintTupleTo(t, os);
	}

	template <typename T1, typename T2, typename T3, typename T4, typename T5>
	void PrintTo(const ::std::tr1::tuple<T1, T2, T3, T4, T5>& t,
	::std::ostream* os) {
	PrintTupleTo(t, os);
	}

	template <typename T1, typename T2, typename T3, typename T4, typename T5,
	typename T6>
	void PrintTo(const ::std::tr1::tuple<T1, T2, T3, T4, T5, T6>& t,
	::std::ostream* os) {
	PrintTupleTo(t, os);
	}

	template <typename T1, typename T2, typename T3, typename T4, typename T5,
	typename T6, typename T7>
	void PrintTo(const ::std::tr1::tuple<T1, T2, T3, T4, T5, T6, T7>& t,
	::std::ostream* os) {
	PrintTupleTo(t, os);
	}

	template <typename T1, typename T2, typename T3, typename T4, typename T5,
	typename T6, typename T7, typename T8>
	void PrintTo(const ::std::tr1::tuple<T1, T2, T3, T4, T5, T6, T7, T8>& t,
	::std::ostream* os) {
	PrintTupleTo(t, os);
	}

	template <typename T1, typename T2, typename T3, typename T4, typename T5,
	typename T6, typename T7, typename T8, typename T9>
	void PrintTo(const ::std::tr1::tuple<T1, T2, T3, T4, T5, T6, T7, T8, T9>& t,
	::std::ostream* os) {
	PrintTupleTo(t, os);
	}

	template <typename T1, typename T2, typename T3, typename T4, typename T5,
	typename T6, typename T7, typename T8, typename T9, typename T10>
	void PrintTo(
	const ::std::tr1::tuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>& t,
	::std::ostream* os) {
	PrintTupleTo(t, os);
	}
	#endif // GTEST_HAS_TR1_TUPLE

	// Overload for std::pair.
	template <typename T1, typename T2>
	void PrintTo(const ::std::pair<T1, T2>& value, ::std::ostream* os) {
	*os << '(';
	// We cannot use UniversalPrint(value.first, os) here, as T1 may be
	// a reference type. The same for printing value.second.
	UniversalPrinter<T1>::Print(value.first, os);
	*os << ", ";
	UniversalPrinter<T2>::Print(value.second, os);
	*os << ')';
	}

	// Implements printing a non-reference type T by letting the compiler
	// pick the right overload of PrintTo() for T.
	template <typename T>
	class UniversalPrinter {
	public:
	// MSVC warns about adding const to a function type, so we want to
	// disable the warning.
	#ifdef _MSC_VER
	#pragma warning(push) // Saves the current warning state.
	#pragma warning(disable:4180) // Temporarily disables warning 4180.
	#endif // _MSC_VER

	// Note: we deliberately don't call this PrintTo(), as that name
	// conflicts with ::testing::internal::PrintTo in the body of the
	// function.
	static void Print(const T& value, ::std::ostream* os) {
	// By default, ::testing::internal::PrintTo() is used for printing
	// the value.
	//
	// Thanks to Koenig look-up, if T is a class and has its own
	// PrintTo() function defined in its namespace, that function will
	// be visible here. Since it is more specific than the generic ones
	// in ::testing::internal, it will be picked by the compiler in the
	// following statement - exactly what we want.
	PrintTo(value, os);
	}

	#ifdef _MSC_VER
	#pragma warning(pop) // Restores the warning state.
	#endif // _MSC_VER
	};

	// UniversalPrintArray(begin, len, os) prints an array of 'len'
	// elements, starting at address 'begin'.
	template <typename T>
	void UniversalPrintArray(const T* begin, size_t len, ::std::ostream* os) {
	if (len == 0) {
	*os << "{}";
	} else {
	*os << "{ ";
	const size_t kThreshold = 18;
	const size_t kChunkSize = 8;
	// If the array has more than kThreshold elements, we'll have to
	// omit some details by printing only the first and the last
	// kChunkSize elements.
	// TODO(wan@google.com): let the user control the threshold using a flag.
	if (len <= kThreshold) {
	PrintRawArrayTo(begin, len, os);
	} else {
	PrintRawArrayTo(begin, kChunkSize, os);
	*os << ", ..., ";
	PrintRawArrayTo(begin + len - kChunkSize, kChunkSize, os);
	}
	*os << " }";
	}
	}
	// This overload prints a (const) char array compactly.
	GTEST_API_ void UniversalPrintArray(const char* begin,
	size_t len,
	::std::ostream* os);

	// Implements printing an array type T[N].
	template <typename T, size_t N>
	class UniversalPrinter<T[N]> {
	public:
	// Prints the given array, omitting some elements when there are too
	// many.
	static void Print(const T (&a)[N], ::std::ostream* os) {
	UniversalPrintArray(a, N, os);
	}
	};

	// Implements printing a reference type T&.
	template <typename T>
	class UniversalPrinter<T&> {
	public:
	// MSVC warns about adding const to a function type, so we want to
	// disable the warning.
	#ifdef _MSC_VER
	#pragma warning(push) // Saves the current warning state.
	#pragma warning(disable:4180) // Temporarily disables warning 4180.
	#endif // _MSC_VER

	static void Print(const T& value, ::std::ostream* os) {
	// Prints the address of the value. We use reinterpret_cast here
	// as static_cast doesn't compile when T is a function type.
	os << "@" << reinterpret_cast<const void>(&value) << " ";

	// Then prints the value itself.
	UniversalPrint(value, os);
	}

	#ifdef _MSC_VER
	#pragma warning(pop) // Restores the warning state.
	#endif // _MSC_VER
	};

	// Prints a value tersely: for a reference type, the referenced value
	// (but not the address) is printed; for a (const) char pointer, the
	// NUL-terminated string (but not the pointer) is printed.
	template <typename T>
	void UniversalTersePrint(const T& value, ::std::ostream* os) {
	UniversalPrint(value, os);
	}
	inline void UniversalTersePrint(const char* str, ::std::ostream* os) {
	if (str == NULL) {
	*os << "NULL";
	} else {
	UniversalPrint(string(str), os);
	}
	}
	inline void UniversalTersePrint(char* str, ::std::ostream* os) {
	UniversalTersePrint(static_cast<const char*>(str), os);
	}

	// Prints a value using the type inferred by the compiler. The
	// difference between this and UniversalTersePrint() is that for a
	// (const) char pointer, this prints both the pointer and the
	// NUL-terminated string.
	template <typename T>
	void UniversalPrint(const T& value, ::std::ostream* os) {
	UniversalPrinter<T>::Print(value, os);
	}

	#if GTEST_HAS_TR1_TUPLE
	typedef ::std::vector<string> Strings;

	// This helper template allows PrintTo() for tuples and
	// UniversalTersePrintTupleFieldsToStrings() to be defined by
	// induction on the number of tuple fields. The idea is that
	// TuplePrefixPrinter<N>::PrintPrefixTo(t, os) prints the first N
	// fields in tuple t, and can be defined in terms of
	// TuplePrefixPrinter<N - 1>.

	// The inductive case.
	template <size_t N>
	struct TuplePrefixPrinter {
	// Prints the first N fields of a tuple.
	template <typename Tuple>
	static void PrintPrefixTo(const Tuple& t, ::std::ostream* os) {
	TuplePrefixPrinter<N - 1>::PrintPrefixTo(t, os);
	*os << ", ";
	UniversalPrinter<typename ::std::tr1::tuple_element<N - 1, Tuple>::type>
	::Print(::std::tr1::get<N - 1>(t), os);
	}

	// Tersely prints the first N fields of a tuple to a string vector,
	// one element for each field.
	template <typename Tuple>
	static void TersePrintPrefixToStrings(const Tuple& t, Strings* strings) {
	TuplePrefixPrinter<N - 1>::TersePrintPrefixToStrings(t, strings);
	::std::stringstream ss;
	UniversalTersePrint(::std::tr1::get<N - 1>(t), &ss);
	strings->push_back(ss.str());
	}
	};

	// Base cases.
	template <>
	struct TuplePrefixPrinter<0> {
	template <typename Tuple>
	static void PrintPrefixTo(const Tuple&, ::std::ostream*) {}

	template <typename Tuple>
	static void TersePrintPrefixToStrings(const Tuple&, Strings*) {}
	};
	template <>
	template <typename Tuple>
	void TuplePrefixPrinter<1>::PrintPrefixTo(const Tuple& t, ::std::ostream* os) {
	UniversalPrinter<typename ::std::tr1::tuple_element<0, Tuple>::type>::
	Print(::std::tr1::get<0>(t), os);
	}

	// Helper function for printing a tuple. T must be instantiated with
	// a tuple type.
	template <typename T>
	void PrintTupleTo(const T& t, ::std::ostream* os) {
	*os << "(";
	TuplePrefixPrinter< ::std::tr1::tuple_size<T>::value>::
	PrintPrefixTo(t, os);
	*os << ")";
	}

	// Prints the fields of a tuple tersely to a string vector, one
	// element for each field. See the comment before
	// UniversalTersePrint() for how we define "tersely".
	template <typename Tuple>
	Strings UniversalTersePrintTupleFieldsToStrings(const Tuple& value) {
	Strings result;
	TuplePrefixPrinter< ::std::tr1::tuple_size<Tuple>::value>::
	TersePrintPrefixToStrings(value, &result);
	return result;
	}
	#endif // GTEST_HAS_TR1_TUPLE

	} // namespace internal

	template <typename T>
	::std::string PrintToString(const T& value) {
	::std::stringstream ss;
	internal::UniversalTersePrint(value, &ss);
	return ss.str();
	}

	} // namespace testing

	#endif // GTEST_INCLUDE_GTEST_GTEST_PRINTERS_H_

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