65 lines
2.0 KiB
C++
65 lines
2.0 KiB
C++
// Copyright 2022 The Abseil Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ABSL_STRINGS_HAS_ABSL_STRINGIFY_H_
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#define ABSL_STRINGS_HAS_ABSL_STRINGIFY_H_
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#include <type_traits>
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#include <utility>
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#include "absl/base/config.h"
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#include "absl/strings/string_view.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace strings_internal {
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// This is an empty class not intended to be used. It exists so that
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// `HasAbslStringify` can reference a universal class rather than needing to be
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// copied for each new sink.
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class UnimplementedSink {
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public:
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void Append(size_t count, char ch);
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void Append(string_view v);
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// Support `absl::Format(&sink, format, args...)`.
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friend void AbslFormatFlush(UnimplementedSink* sink, absl::string_view v);
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};
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} // namespace strings_internal
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// `HasAbslStringify<T>` detects if type `T` supports the `AbslStringify()`
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// customization point (see
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// https://abseil.io/docs/cpp/guides/format#abslstringify for the
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// documentation).
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//
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// Note that there are types that can be `StrCat`-ed that do not use the
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// `AbslStringify` customization point (for example, `int`).
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template <typename T, typename = void>
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struct HasAbslStringify : std::false_type {};
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template <typename T>
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struct HasAbslStringify<
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T, std::enable_if_t<std::is_void<decltype(AbslStringify(
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std::declval<strings_internal::UnimplementedSink&>(),
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std::declval<const T&>()))>::value>> : std::true_type {};
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_STRINGS_HAS_ABSL_STRINGIFY_H_
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