base/internal/errno_saver.h

0001 // Copyright 2017 The Abseil Authors.
0002 //
0003 // Licensed under the Apache License, Version 2.0 (the "License");
0004 // you may not use this file except in compliance with the License.
0005 // You may obtain a copy of the License at
0006 //
0007 //      https://www.apache.org/licenses/LICENSE-2.0
0008 //
0009 // Unless required by applicable law or agreed to in writing, software
0010 // distributed under the License is distributed on an "AS IS" BASIS,
0011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
0012 // See the License for the specific language governing permissions and
0013 // limitations under the License.
0014
0015 #ifndef ABSL_BASE_INTERNAL_ERRNO_SAVER_H_
0016 #define ABSL_BASE_INTERNAL_ERRNO_SAVER_H_
0017
0018 #include <cerrno>
0019
0020 #include "absl/base/config.h"
0021
0022 namespace absl {
0023 ABSL_NAMESPACE_BEGIN
0024 namespace base_internal {
0025
0026 // `ErrnoSaver` captures the value of `errno` upon construction and restores it
0027 // upon deletion.  It is used in low-level code and must be super fast.  Do not
0028 // add instrumentation, even in debug modes.
0029 class ErrnoSaver {
0030  public:
0031   ErrnoSaver() : saved_errno_(errno) {}
0032   ~ErrnoSaver() { errno = saved_errno_; }
0033   int operator()() const { return saved_errno_; }
0034
0035  private:
0036   const int saved_errno_;
0037 };
0038
0039 }  // namespace base_internal
0040 ABSL_NAMESPACE_END
0041 }  // namespace absl
0042
0043 #endif  // ABSL_BASE_INTERNAL_ERRNO_SAVER_H_