1 // Copyright 2022 The Abseil Authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 // ----------------------------------------------------------------------------- 16 // File: log/internal/nullguard.h 17 // ----------------------------------------------------------------------------- 18 // 19 // NullGuard exists such that NullGuard<T>::Guard(v) returns v, unless passed a 20 // nullptr_t, or a null char* or const char*, in which case it returns "(null)". 21 // This allows streaming NullGuard<T>::Guard(v) to an output stream without 22 // hitting undefined behavior for null values. 23 24 #ifndef ABSL_LOG_INTERNAL_NULLGUARD_H_ 25 #define ABSL_LOG_INTERNAL_NULLGUARD_H_ 26 27 #include <cstddef> 28 29 #include "absl/base/config.h" 30 31 namespace absl { 32 ABSL_NAMESPACE_BEGIN 33 namespace log_internal { 34 35 template <typename T> 36 struct NullGuard final { Guardfinal37 static const T& Guard(const T& v) { return v; } 38 }; 39 template <> 40 struct NullGuard<char*> final { 41 static const char* Guard(const char* v) { return v ? v : "(null)"; } 42 }; 43 template <> 44 struct NullGuard<const char*> final { 45 static const char* Guard(const char* v) { return v ? v : "(null)"; } 46 }; 47 template <> 48 struct NullGuard<std::nullptr_t> final { 49 static const char* Guard(const std::nullptr_t&) { return "(null)"; } 50 }; 51 52 } // namespace log_internal 53 ABSL_NAMESPACE_END 54 } // namespace absl 55 56 #endif // ABSL_LOG_INTERNAL_NULLGUARD_H_ 57