137 lines
4.2 KiB
C++
137 lines
4.2 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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//
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// -----------------------------------------------------------------------------
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// File: log/internal/nullstream.h
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// -----------------------------------------------------------------------------
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//
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// Classes `NullStream`, `NullStreamMaybeFatal ` and `NullStreamFatal`
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// implement a subset of the `LogMessage` API and are used instead when logging
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// of messages has been disabled.
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#ifndef ABSL_LOG_INTERNAL_NULLSTREAM_H_
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#define ABSL_LOG_INTERNAL_NULLSTREAM_H_
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#ifdef _WIN32
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#include <cstdlib>
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#else
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#include <unistd.h>
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#endif
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#include <ios>
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#include <ostream>
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#include "absl/base/attributes.h"
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#include "absl/base/config.h"
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#include "absl/base/log_severity.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 log_internal {
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// A `NullStream` implements the API of `LogMessage` (a few methods and
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// `operator<<`) but does nothing. All methods are defined inline so the
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// compiler can eliminate the whole instance and discard anything that's
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// streamed in.
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class NullStream {
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public:
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NullStream& AtLocation(absl::string_view, int) { return *this; }
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template <typename SourceLocationType>
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NullStream& AtLocation(SourceLocationType) {
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return *this;
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}
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NullStream& NoPrefix() { return *this; }
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NullStream& WithVerbosity(int) { return *this; }
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template <typename TimeType>
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NullStream& WithTimestamp(TimeType) {
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return *this;
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}
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template <typename Tid>
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NullStream& WithThreadID(Tid) {
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return *this;
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}
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template <typename LogEntryType>
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NullStream& WithMetadataFrom(const LogEntryType&) {
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return *this;
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}
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NullStream& WithPerror() { return *this; }
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template <typename LogSinkType>
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NullStream& ToSinkAlso(LogSinkType*) {
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return *this;
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}
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template <typename LogSinkType>
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NullStream& ToSinkOnly(LogSinkType*) {
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return *this;
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}
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template <typename LogSinkType>
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NullStream& OutputToSink(LogSinkType*, bool) {
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return *this;
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}
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NullStream& InternalStream() { return *this; }
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};
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template <typename T>
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inline NullStream& operator<<(NullStream& str, const T&) {
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return str;
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}
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inline NullStream& operator<<(NullStream& str,
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std::ostream& (*)(std::ostream& os)) {
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return str;
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}
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inline NullStream& operator<<(NullStream& str,
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std::ios_base& (*)(std::ios_base& os)) {
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return str;
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}
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// `NullStreamMaybeFatal` implements the process termination semantics of
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// `LogMessage`, which is used for `DFATAL` severity and expression-defined
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// severity e.g. `LOG(LEVEL(HowBadIsIt()))`. Like `LogMessage`, it terminates
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// the process when destroyed if the passed-in severity equals `FATAL`.
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class NullStreamMaybeFatal final : public NullStream {
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public:
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explicit NullStreamMaybeFatal(absl::LogSeverity severity)
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: fatal_(severity == absl::LogSeverity::kFatal) {}
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~NullStreamMaybeFatal() {
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if (fatal_) {
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_exit(1);
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}
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}
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private:
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bool fatal_;
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};
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// `NullStreamFatal` implements the process termination semantics of
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// `LogMessageFatal`, which means it always terminates the process. `DFATAL`
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// and expression-defined severity use `NullStreamMaybeFatal` above.
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class NullStreamFatal final : public NullStream {
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public:
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NullStreamFatal() = default;
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// ABSL_ATTRIBUTE_NORETURN doesn't seem to work on destructors with msvc, so
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// disable msvc's warning about the d'tor never returning.
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#if defined(_MSC_VER) && !defined(__clang__)
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#pragma warning(push)
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#pragma warning(disable : 4722)
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#endif
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ABSL_ATTRIBUTE_NORETURN ~NullStreamFatal() { _exit(1); }
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#if defined(_MSC_VER) && !defined(__clang__)
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#pragma warning(pop)
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#endif
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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_GLOBALS_H_
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