Abseil Common Libraries (C++) (grcp 依赖)
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57 lines
1.8 KiB
57 lines
1.8 KiB
2 years ago
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// 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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//
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// -----------------------------------------------------------------------------
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// File: log/internal/nullguard.h
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// -----------------------------------------------------------------------------
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//
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// NullGuard exists such that NullGuard<T>::Guard(v) returns v, unless passed a
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// nullptr_t, or a null char* or const char*, in which case it returns "(null)".
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// This allows streaming NullGuard<T>::Guard(v) to an output stream without
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// hitting undefined behavior for null values.
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#ifndef ABSL_LOG_INTERNAL_NULLGUARD_H_
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#define ABSL_LOG_INTERNAL_NULLGUARD_H_
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#include <cstddef>
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#include "absl/base/config.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace log_internal {
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template <typename T>
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struct NullGuard final {
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static const T& Guard(const T& v) { return v; }
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};
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template <>
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struct NullGuard<char*> final {
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static const char* Guard(const char* v) { return v ? v : "(null)"; }
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};
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template <>
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struct NullGuard<const char*> final {
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static const char* Guard(const char* v) { return v ? v : "(null)"; }
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};
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template <>
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struct NullGuard<std::nullptr_t> final {
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static const char* Guard(const std::nullptr_t&) { return "(null)"; }
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};
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} // namespace log_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_LOG_INTERNAL_NULLGUARD_H_
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