include/gtest/gtest-message.h

// Copyright 2005, 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)
//
// The Google C++ Testing Framework (Google Test)
//
// This header file defines the Message class.
//
// IMPORTANT NOTE: Due to limitation of the C++ language, we have to
// leave some internal implementation details in this header file.
// They are clearly marked by comments like this:
//
//   // INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
//
// Such code is NOT meant to be used by a user directly, and is subject
// to CHANGE WITHOUT NOTICE.  Therefore DO NOT DEPEND ON IT in a user
// program!

#ifndef GTEST_INCLUDE_GTEST_GTEST_MESSAGE_H_
#define GTEST_INCLUDE_GTEST_GTEST_MESSAGE_H_

#include <limits>

#include "gtest/internal/gtest-port.h"

// Ensures that there is at least one operator<< in the global namespace.
// See Message& operator<<(...) below for why.
void operator<<(const testing::internal::Secret&, int);

namespace testing
{
// The Message class works like an ostream repeater.
//
// Typical usage:
//
//   1. You stream a bunch of values to a Message object.
//      It will remember the text in a stringstream.
//   2. Then you stream the Message object to an ostream.
//      This causes the text in the Message to be streamed
//      to the ostream.
//
// For example;
//
//   testing::Message foo;
//   foo << 1 << " != " << 2;
//   std::cout << foo;
//
// will print "1 != 2".
//
// Message is not intended to be inherited from.  In particular, its
// destructor is not virtual.
//
// Note that stringstream behaves differently in gcc and in MSVC.  You
// can stream a NULL char pointer to it in the former, but not in the
// latter (it causes an access violation if you do).  The Message
// class hides this difference by treating a NULL char pointer as
// "(null)".
class GTEST_API_ Message
{
private:
	// The type of basic IO manipulators (endl, ends, and flush) for
	// narrow streams.
	typedef std::ostream& (*BasicNarrowIoManip)(std::ostream&);

public:
	// Constructs an empty Message.
	Message();

	// Copy constructor.
	Message(const Message& msg) : ss_(new ::std::stringstream)
	{  // NOLINT
		*ss_ << msg.GetString();
	}

	// Constructs a Message from a C-string.
	explicit Message(const char* str) : ss_(new ::std::stringstream)
	{
		*ss_ << str;
	}

#if GTEST_OS_SYMBIAN
	// Streams a value (either a pointer or not) to this object.
	template <typename T>
	inline Message& operator<<(const T& value)
	{
		StreamHelper(typename internal::is_pointer<T>::type(), value);
		return *this;
	}
#else
	// Streams a non-pointer value to this object.
	template <typename T>
	inline Message& operator<<(const T& val)
	{
		// Some libraries overload << for STL containers.  These
		// overloads are defined in the global namespace instead of ::std.
		//
		// C++'s symbol lookup rule (i.e. Koenig lookup) says that these
		// overloads are visible in either the std namespace or the global
		// namespace, but not other namespaces, including the testing
		// namespace which Google Test's Message class is in.
		//
		// To allow STL containers (and other types that has a << operator
		// defined in the global namespace) to be used in Google Test
		// assertions, testing::Message must access the custom << operator
		// from the global namespace.  With this using declaration,
		// overloads of << defined in the global namespace and those
		// visible via Koenig lookup are both exposed in this function.
		using ::operator<<;
		*ss_ << val;
		return *this;
	}

	// Streams a pointer value to this object.
	//
	// This function is an overload of the previous one.  When you
	// stream a pointer to a Message, this definition will be used as it
	// is more specialized.  (The C++ Standard, section
	// [temp.func.order].)  If you stream a non-pointer, then the
	// previous definition will be used.
	//
	// The reason for this overload is that streaming a NULL pointer to
	// ostream is undefined behavior.  Depending on the compiler, you
	// may get "0", "(nil)", "(null)", or an access violation.  To
	// ensure consistent result across compilers, we always treat NULL
	// as "(null)".
	template <typename T>
	inline Message& operator<<(T* const& pointer)
	{  // NOLINT
		if (pointer == NULL)
		{
			*ss_ << "(null)";
		}
		else
		{
			*ss_ << pointer;
		}
		return *this;
	}
#endif  // GTEST_OS_SYMBIAN

	// Since the basic IO manipulators are overloaded for both narrow
	// and wide streams, we have to provide this specialized definition
	// of operator <<, even though its body is the same as the
	// templatized version above.  Without this definition, streaming
	// endl or other basic IO manipulators to Message will confuse the
	// compiler.
	Message& operator<<(BasicNarrowIoManip val)
	{
		*ss_ << val;
		return *this;
	}

	// Instead of 1/0, we want to see true/false for bool values.
	Message& operator<<(bool b)
	{
		return *this << (b ? "true" : "false");
	}

	// These two overloads allow streaming a wide C string to a Message
	// using the UTF-8 encoding.
	Message& operator<<(const wchar_t* wide_c_str);
	Message& operator<<(wchar_t* wide_c_str);

#if GTEST_HAS_STD_WSTRING
	// Converts the given wide string to a narrow string using the UTF-8
	// encoding, and streams the result to this Message object.
	Message& operator<<(const ::std::wstring& wstr);
#endif  // GTEST_HAS_STD_WSTRING

#if GTEST_HAS_GLOBAL_WSTRING
	// Converts the given wide string to a narrow string using the UTF-8
	// encoding, and streams the result to this Message object.
	Message& operator<<(const ::wstring& wstr);
#endif  // GTEST_HAS_GLOBAL_WSTRING

	// Gets the text streamed to this object so far as an std::string.
	// Each '\0' character in the buffer is replaced with "\\0".
	//
	// INTERNAL IMPLEMENTATION - DO NOT USE IN A USER PROGRAM.
	std::string GetString() const;

private:
#if GTEST_OS_SYMBIAN
	// These are needed as the Nokia Symbian Compiler cannot decide between
	// const T& and const T* in a function template. The Nokia compiler _can_
	// decide between class template specializations for T and T*, so a
	// tr1::type_traits-like is_pointer works, and we can overload on that.
	template <typename T>
	inline void StreamHelper(internal::true_type /*is_pointer*/, T* pointer)
	{
		if (pointer == NULL)
		{
			*ss_ << "(null)";
		}
		else
		{
			*ss_ << pointer;
		}
	}
	template <typename T>
	inline void StreamHelper(internal::false_type /*is_pointer*/,
							 const T& value)
	{
		// See the comments in Message& operator <<(const T&) above for why
		// we need this using statement.
		using ::operator<<;
		*ss_ << value;
	}
#endif  // GTEST_OS_SYMBIAN

	// We'll hold the text streamed to this object here.
	const internal::scoped_ptr< ::std::stringstream> ss_;

	// We declare (but don't implement) this to prevent the compiler
	// from implementing the assignment operator.
	void operator=(const Message&);
};

// Streams a Message to an ostream.
inline std::ostream& operator<<(std::ostream& os, const Message& sb)
{
	return os << sb.GetString();
}

namespace internal
{
// Converts a streamable value to an std::string.  A NULL pointer is
// converted to "(null)".  When the input value is a ::string,
// ::std::string, ::wstring, or ::std::wstring object, each NUL
// character in it is replaced with "\\0".
template <typename T>
std::string StreamableToString(const T& streamable)
{
	return (Message() << streamable).GetString();
}

}  // namespace internal
}  // namespace testing

#endif  // GTEST_INCLUDE_GTEST_GTEST_MESSAGE_H_