Release the Abseil Logging library

PiperOrigin-RevId: 470080638
Change-Id: I8d9ddfabc7704c383ed5a73abf0411f4c58a4bf7

1 files changed, 134 insertions, 0 deletions

diff --git a/absl/log/internal/nullstream.h b/absl/log/internal/nullstream.h
new file mode 100644
index 00000000..80c62c9e
--- /dev/null
+++ b/absl/log/internal/nullstream.h
@@ -0,0 +1,134 @@
+// Copyright 2022 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// -----------------------------------------------------------------------------
+// File: log/internal/nullstream.h
+// -----------------------------------------------------------------------------
+//
+// Classes `NullStream`, `NullStreamMaybeFatal ` and `NullStreamFatal`
+// implement a subset of the `LogMessage` API and are used instead when logging
+// of messages has been disabled.
+
+#ifndef ABSL_LOG_INTERNAL_NULLSTREAM_H_
+#define ABSL_LOG_INTERNAL_NULLSTREAM_H_
+
+#ifdef _WIN32
+#include <cstdlib>
+#else
+#include <unistd.h>
+#endif
+#include <ios>
+#include <ostream>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/log_severity.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace log_internal {
+
+// A `NullStream` implements the API of `LogMessage` (a few methods and
+// `operator<<`) but does nothing.  All methods are defined inline so the
+// compiler can eliminate the whole instance and discard anything that's
+// streamed in.
+class NullStream {
+ public:
+  NullStream& AtLocation(absl::string_view, int) { return *this; }
+  template <typename SourceLocationType>
+  NullStream& AtLocation(SourceLocationType) {
+    return *this;
+  }
+  NullStream& NoPrefix() { return *this; }
+  NullStream& WithVerbosity(int) { return *this; }
+  template <typename TimeType>
+  NullStream& WithTimestamp(TimeType) {
+    return *this;
+  }
+  template <typename Tid>
+  NullStream& WithThreadID(Tid) {
+    return *this;
+  }
+  template <typename LogEntryType>
+  NullStream& WithMetadataFrom(const LogEntryType&) {
+    return *this;
+  }
+  NullStream& WithPerror() { return *this; }
+  template <typename LogSinkType>
+  NullStream& ToSinkAlso(LogSinkType*) {
+    return *this;
+  }
+  template <typename LogSinkType>
+  NullStream& ToSinkOnly(LogSinkType*) {
+    return *this;
+  }
+  template <typename LogSinkType>
+  NullStream& OutputToSink(LogSinkType*, bool) {
+    return *this;
+  }
+  NullStream& InternalStream() { return *this; }
+};
+template <typename T>
+inline NullStream& operator<<(NullStream& str, const T&) {
+  return str;
+}
+inline NullStream& operator<<(NullStream& str,
+                              std::ostream& (*)(std::ostream& os)) {
+  return str;
+}
+inline NullStream& operator<<(NullStream& str,
+                              std::ios_base& (*)(std::ios_base& os)) {
+  return str;
+}
+
+// `NullStreamMaybeFatal` implements the process termination semantics of
+// `LogMessage`, which is used for `DFATAL` severity and expression-defined
+// severity e.g. `LOG(LEVEL(HowBadIsIt()))`.  Like `LogMessage`, it terminates
+// the process when destroyed if the passed-in severity equals `FATAL`.
+class NullStreamMaybeFatal final : public NullStream {
+ public:
+  explicit NullStreamMaybeFatal(absl::LogSeverity severity)
+      : fatal_(severity == absl::LogSeverity::kFatal) {}
+  ~NullStreamMaybeFatal() {
+    if (fatal_) _exit(1);
+  }
+
+ private:
+  bool fatal_;
+};
+
+// `NullStreamFatal` implements the process termination semantics of
+// `LogMessageFatal`, which means it always terminates the process.  `DFATAL`
+// and expression-defined severity use `NullStreamMaybeFatal` above.
+class NullStreamFatal final : public NullStream {
+ public:
+  NullStreamFatal() {}
+  // ABSL_ATTRIBUTE_NORETURN doesn't seem to work on destructors with msvc, so
+  // disable msvc's warning about the d'tor never returning.
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4722)
+#endif
+  ABSL_ATTRIBUTE_NORETURN ~NullStreamFatal() { _exit(1); }
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+};
+
+}  // namespace log_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_LOG_INTERNAL_GLOBALS_H_