include/gtest/gtest-message.h

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// The Google C++ Testing and Mocking 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!

// IWYU pragma: private, include "gtest/gtest.h"
// IWYU pragma: friend gtest/.*
// IWYU pragma: friend gmock/.*

#ifndef GOOGLETEST_INCLUDE_GTEST_GTEST_MESSAGE_H_
#define GOOGLETEST_INCLUDE_GTEST_GTEST_MESSAGE_H_

#include <limits>
#include <memory>
#include <ostream>
#include <sstream>
#include <string>

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

#ifdef GTEST_HAS_ABSL
#include <type_traits>

#include "absl/strings/internal/has_absl_stringify.h"
#include "absl/strings/str_cat.h"
#endif  // GTEST_HAS_ABSL

GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
/* class A needs to have dll-interface to be used by clients of class B */)

// 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;
  }

  // Streams a non-pointer value to this object. If building a version of
  // GoogleTest with ABSL, this overload is only enabled if the value does not
  // have an AbslStringify definition.
  template <typename T
#ifdef GTEST_HAS_ABSL
            ,
            typename std::enable_if<
                !absl::strings_internal::HasAbslStringify<T>::value,  // NOLINT
                int>::type = 0
#endif  // GTEST_HAS_ABSL
            >
  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;
  }

#ifdef GTEST_HAS_ABSL
  // Streams a non-pointer value with an AbslStringify definition to this
  // object.
  template <typename T,
            typename std::enable_if<
                absl::strings_internal::HasAbslStringify<T>::value,  // NOLINT
                int>::type = 0>
  inline Message& operator<<(const T& val) {
    // ::operator<< is needed here for a similar reason as with the non-Abseil
    // version above
    using ::operator<<;
    *ss_ << absl::StrCat(val);
    return *this;
  }
#endif  // GTEST_HAS_ABSL

  // 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 == nullptr) {
      *ss_ << "(null)";
    } else {
      *ss_ << pointer;
    }
    return *this;
  }

  // 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

  // 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:
  // We'll hold the text streamed to this object here.
  const std::unique_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

GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251

#endif  // GOOGLETEST_INCLUDE_GTEST_GTEST_MESSAGE_H_