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// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// This header provides functions which make it easier to work generically
// with string-like objects such as fbl::StringPiece, fbl::String, std::string,
// and std::string_view.
#include <stddef.h>
#include <type_traits>
namespace trace {
namespace internal {
// Macro for defining a trait that checks if a type T has a method with the
// given name. See fbl/macros.h.
// Example:
// has_c_str, c_str, const char* (C::*)() const);
template <typename T> \
struct trait_name { \
private: \
template <typename C> \
static std::true_type test(decltype(static_cast<sig>(&C::fn_name))); \
template <typename C> \
static std::false_type test(...); \
public: \
static constexpr bool value = decltype(test<T>(nullptr))::value; \
}; \
template <typename T> \
static /*inline*/ constexpr bool trait_name##_v = trait_name<T>::value
TRACE_INTERNAL_DECLARE_HAS_MEMBER_FN_WITH_SIGNATURE(has_data, data, const char* (C::*)() const);
TRACE_INTERNAL_DECLARE_HAS_MEMBER_FN_WITH_SIGNATURE(has_length, length, size_t (C::*)() const);
// Gets the character data from a string-like object.
template <typename T>
constexpr const char* GetStringData(const T& value) {
// Gets the length (in characters) of a string-like object.
template <typename T>
constexpr size_t GetStringLength(const T& value) {
return value.length();
// is_string_like_v<T>
// Evaluates to true if GetStringData() and GetStringLength() are supported
// instances of type T.
template <typename T>
using is_string_like = std::integral_constant<bool, has_data_v<T> && has_length_v<T>>;
} // namespace internal
} // namespace trace