path: root/utils/unittest/googletest/include/gtest/gtest-printers.h

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// 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.).
  *<