////////////////////////////////////////////////////////////////////////////////
// Copyright 2016 Google Inc.
//
// This software is licensed under the terms defined in the Widevine Master
// License Agreement. For a copy of this agreement, please contact
// widevine-licensing@google.com.
////////////////////////////////////////////////////////////////////////////////

#ifndef BASE_MACROS_H_
#define BASE_MACROS_H_

#include <stddef.h>  // For size_t

// DISALLOW_COPY_AND_ASSIGN disallows the copy constructor and copy assignment
// operator. DISALLOW_IMPLICIT_CONSTRUCTORS is like DISALLOW_COPY_AND_ASSIGN,
// but also disallows the default constructor, intended to help make a
// class uninstantiable.
//
// These must be placed in the private: declarations for a class.
//
// Note: New code should prefer static_assert over COMPILE_ASSERT.
#define DISALLOW_COPY_AND_ASSIGN(TypeName) \
  TypeName(const TypeName&) = delete;      \
  TypeName& operator=(const TypeName&) = delete
#define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \
  TypeName() = delete;                           \
  DISALLOW_COPY_AND_ASSIGN(TypeName)

// The arraysize(arr) macro returns the # of elements in an array arr.
// The expression is a compile-time constant, and therefore can be
// used in defining new arrays, for example.  If you use arraysize on
// a pointer by mistake, you will get a compile-time error.
//
// This template function declaration is used in defining arraysize.
// Note that the function doesn't need an implementation, as we only
// use its type.
template <typename T, size_t N>
char (&ArraySizeHelper(T (&array)[N]))[N];

// That gcc wants both of these prototypes seems mysterious. VC, for
// its part, can't decide which to use (another mystery). Matching of
// template overloads: the final frontier.
#ifndef COMPILER_MSVC
template <typename T, size_t N>
char (&ArraySizeHelper(const T (&array)[N]))[N];
#endif

#define arraysize(array) (sizeof(ArraySizeHelper(array)))

// A macro to turn a symbol into a std::string
#define AS_STRING(x)   AS_STRING_INTERNAL(x)
#define AS_STRING_INTERNAL(x)   #x

// The following enum should be used only as a constructor argument to indicate
// that the variable has static storage class, and that the constructor should
// do nothing to its state.  It indicates to the reader that it is legal to
// declare a static instance of the class, provided the constructor is given
// the base::LINKER_INITIALIZED argument.  Normally, it is unsafe to declare a
// static variable that has a constructor or a destructor because invocation
// order is undefined.  However, IF the type can be initialized by filling with
// zeroes (which the loader does for static variables), AND the type's
// destructor does nothing to the storage, then a constructor for static
// initialization can be declared as
//       explicit MyClass(base::LinkerInitialized x) {}
// and invoked as
//       static MyClass my_variable_name(base::LINKER_INITIALIZED);
namespace base {
enum LinkerInitialized { LINKER_INITIALIZED };
}

// The FALLTHROUGH_INTENDED macro can be used to annotate implicit fall-through
// between switch labels:
//  switch (x) {
//    case 40:
//    case 41:
//      if (truth_is_out_there) {
//        ++x;
//        FALLTHROUGH_INTENDED;  // Use instead of/along with annotations in
//                               // comments.
//      } else {
//        return x;
//      }
//    case 42:
//      ...
//
//  As shown in the example above, the FALLTHROUGH_INTENDED macro should be
//  followed by a semicolon. It is designed to mimic control-flow statements
//  like 'break;', so it can be placed in most places where 'break;' can, but
//  only if there are no statements on the execution path between it and the
//  next switch label.
//
//  When compiled with clang in C++11 mode, the FALLTHROUGH_INTENDED macro is
//  expanded to [[clang::fallthrough]] attribute, which is analysed when
//  performing switch labels fall-through diagnostic ('-Wimplicit-fallthrough').
//  See clang documentation on language extensions for details:
//  http://clang.llvm.org/docs/LanguageExtensions.html#clang__fallthrough
//
//  When used with unsupported compilers, the FALLTHROUGH_INTENDED macro has no
//  effect on diagnostics.
//
//  In either case this macro has no effect on runtime behavior and performance
//  of code.
#if defined(__clang__) && defined(LANG_CXX11) && defined(__has_warning)
#if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
#define FALLTHROUGH_INTENDED [[clang::fallthrough]]  // NOLINT
#endif
#endif

#ifndef FALLTHROUGH_INTENDED
#define FALLTHROUGH_INTENDED do { } while (0)
#endif

#endif  // BASE_MACROS_H_