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TMessagesProj/jni/voip/webrtc/absl/log/log.h

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+// 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/log.h
+// -----------------------------------------------------------------------------
+//
+// This header declares a family of LOG macros.
+//
+// Basic invocation looks like this:
+//
+//   LOG(INFO) << "Found " << num_cookies << " cookies";
+//
+// Most `LOG` macros take a severity level argument.  The severity levels are
+// `INFO`, `WARNING`, `ERROR`, and `FATAL`.  They are defined
+// in absl/base/log_severity.h.
+// * The `FATAL` severity level terminates the program with a stack trace after
+//   logging its message.  Error handlers registered with `RunOnFailure`
+//   (process_state.h) are run, but exit handlers registered with `atexit(3)`
+//   are not.
+// * The `QFATAL` pseudo-severity level is equivalent to `FATAL` but triggers
+//   quieter termination messages, e.g. without a full stack trace, and skips
+//   running registered error handlers.
+// * The `DFATAL` pseudo-severity level is defined as `FATAL` in debug mode and
+//   as `ERROR` otherwise.
+// Some preprocessor shenanigans are used to ensure that e.g. `LOG(INFO)` has
+// the same meaning even if a local symbol or preprocessor macro named `INFO` is
+// defined.  To specify a severity level using an expression instead of a
+// literal, use `LEVEL(expr)`.
+// Example:
+//
+//   LOG(LEVEL(stale ? absl::LogSeverity::kWarning : absl::LogSeverity::kInfo))
+//       << "Cookies are " << days << " days old";
+
+// `LOG` macros evaluate to an unterminated statement.  The value at the end of
+// the statement supports some chainable methods:
+//
+//   * .AtLocation(absl::string_view file, int line)
+//     .AtLocation(absl::SourceLocation loc)
+//     Overrides the location inferred from the callsite.  The string pointed to
+//     by `file` must be valid until the end of the statement.
+//   * .NoPrefix()
+//     Omits the prefix from this line.  The prefix includes metadata about the
+//     logged data such as source code location and timestamp.
+//   * .WithVerbosity(int verbose_level)
+//     Sets the verbosity field of the logged message as if it was logged by
+//     `VLOG(verbose_level)`.  Unlike `VLOG`, this method does not affect
+//     evaluation of the statement when the specified `verbose_level` has been
+//     disabled.  The only effect is on `LogSink` implementations which make use
+//     of the `absl::LogSink::verbosity()` value.  The value
+//     `absl::LogEntry::kNoVerbosityLevel` can be specified to mark the message
+//     not verbose.
+//   * .WithTimestamp(absl::Time timestamp)
+//     Uses the specified timestamp instead of one collected at the time of
+//     execution.
+//   * .WithThreadID(absl::LogEntry::tid_t tid)
+//     Uses the specified thread ID instead of one collected at the time of
+//     execution.
+//   * .WithMetadataFrom(const absl::LogEntry &entry)
+//     Copies all metadata (but no data) from the specified `absl::LogEntry`.
+//     This can be used to change the severity of a message, but it has some
+//     limitations:
+//     * `ABSL_MIN_LOG_LEVEL` is evaluated against the severity passed into
+//       `LOG` (or the implicit `FATAL` level of `CHECK`).
+//     * `LOG(FATAL)` and `CHECK` terminate the process unconditionally, even if
+//       the severity is changed later.
+//     `.WithMetadataFrom(entry)` should almost always be used in combination
+//     with `LOG(LEVEL(entry.log_severity()))`.
+//   * .WithPerror()
+//     Appends to the logged message a colon, a space, a textual description of
+//     the current value of `errno` (as by `strerror(3)`), and the numerical
+//     value of `errno`.
+//   * .ToSinkAlso(absl::LogSink* sink)
+//     Sends this message to `*sink` in addition to whatever other sinks it
+//     would otherwise have been sent to.  `sink` must not be null.
+//   * .ToSinkOnly(absl::LogSink* sink)
+//     Sends this message to `*sink` and no others.  `sink` must not be null.
+//
+// No interfaces in this header are async-signal-safe; their use in signal
+// handlers is unsupported and may deadlock your program or eat your lunch.
+//
+// Many logging statements are inherently conditional.  For example,
+// `LOG_IF(INFO, !foo)` does nothing if `foo` is true.  Even seemingly
+// unconditional statements like `LOG(INFO)` might be disabled at
+// compile-time to minimize binary size or for security reasons.
+//
+// * Except for the condition in a `CHECK` or `QCHECK` statement, programs must
+//   not rely on evaluation of expressions anywhere in logging statements for
+//   correctness.  For example, this is ok:
+//
+//     CHECK((fp = fopen("config.ini", "r")) != nullptr);
+//
+//   But this is probably not ok:
+//
+//     LOG(INFO) << "Server status: " << StartServerAndReturnStatusString();
+//
+//   The example below is bad too; the `i++` in the `LOG_IF` condition might
+//   not be evaluated, resulting in an infinite loop:
+//
+//     for (int i = 0; i < 1000000;)
+//       LOG_IF(INFO, i++ % 1000 == 0) << "Still working...";
+//
+// * Except where otherwise noted, conditions which cause a statement not to log
+//   also cause expressions not to be evaluated.  Programs may rely on this for
+//   performance reasons, e.g. by streaming the result of an expensive function
+//   call into a `DLOG` or `LOG_EVERY_N` statement.
+// * Care has been taken to ensure that expressions are parsed by the compiler
+//   even if they are never evaluated.  This means that syntax errors will be
+//   caught and variables will be considered used for the purposes of
+//   unused-variable diagnostics.  For example, this statement won't compile
+//   even if `INFO`-level logging has been compiled out:
+//
+//     int number_of_cakes = 40;
+//     LOG(INFO) << "Number of cakes: " << number_of_cake;  // Note the typo!
+//
+//   Similarly, this won't produce unused-variable compiler diagnostics even
+//   if `INFO`-level logging is compiled out:
+//
+//     {
+//       char fox_line1[] = "Hatee-hatee-hatee-ho!";
+//       LOG_IF(ERROR, false) << "The fox says " << fox_line1;
+//       char fox_line2[] = "A-oo-oo-oo-ooo!";
+//       LOG(INFO) << "The fox also says " << fox_line2;
+//     }
+//
+//   This error-checking is not perfect; for example, symbols that have been
+//   declared but not defined may not produce link errors if used in logging
+//   statements that compile away.
+//
+// Expressions streamed into these macros are formatted using `operator<<` just
+// as they would be if streamed into a `std::ostream`, however it should be
+// noted that their actual type is unspecified.
+//
+// To implement a custom formatting operator for a type you own, there are two
+// options: `AbslStringify()` or `std::ostream& operator<<(std::ostream&, ...)`.
+// It is recommended that users make their types loggable through
+// `AbslStringify()` as it is a universal stringification extension that also
+// enables `absl::StrFormat` and `absl::StrCat` support. If both
+// `AbslStringify()` and `std::ostream& operator<<(std::ostream&, ...)` are
+// defined, `AbslStringify()` will be used.
+//
+// To use the `AbslStringify()` API, define a friend function template in your
+// type's namespace with the following signature:
+//
+//   template <typename Sink>
+//   void AbslStringify(Sink& sink, const UserDefinedType& value);
+//
+// `Sink` has the same interface as `absl::FormatSink`, but without
+// `PutPaddedString()`.
+//
+// Example:
+//
+//   struct Point {
+//     template <typename Sink>
+//     friend void AbslStringify(Sink& sink, const Point& p) {
+//       absl::Format(&sink, "(%v, %v)", p.x, p.y);
+//     }
+//
+//     int x;
+//     int y;
+//   };
+//
+// To use `std::ostream& operator<<(std::ostream&, ...)`, define
+// `std::ostream& operator<<(std::ostream&, ...)` in your type's namespace (for
+// ADL) just as you would to stream it to `std::cout`.
+//
+// Currently `AbslStringify()` ignores output manipulators but this is not
+// guaranteed behavior and may be subject to change in the future. If you would
+// like guaranteed behavior regarding output manipulators, please use
+// `std::ostream& operator<<(std::ostream&, ...)` to make custom types loggable
+// instead.
+//
+// Those macros that support streaming honor output manipulators and `fmtflag`
+// changes that output data (e.g. `std::ends`) or control formatting of data
+// (e.g. `std::hex` and `std::fixed`), however flushing such a stream is
+// ignored.  The message produced by a log statement is sent to registered
+// `absl::LogSink` instances at the end of the statement; those sinks are
+// responsible for their own flushing (e.g. to disk) semantics.
+//
+// Flag settings are not carried over from one `LOG` statement to the next; this
+// is a bit different than e.g. `std::cout`:
+//
+//   LOG(INFO) << std::hex << 0xdeadbeef;  // logs "0xdeadbeef"
+//   LOG(INFO) << 0xdeadbeef;              // logs "3735928559"
+
+#ifndef ABSL_LOG_LOG_H_
+#define ABSL_LOG_LOG_H_
+
+#include "absl/log/internal/log_impl.h"
+
+// LOG()
+//
+// `LOG` takes a single argument which is a severity level.  Data streamed in
+// comprise the logged message.
+// Example:
+//
+//   LOG(INFO) << "Found " << num_cookies << " cookies";
+#define LOG(severity) ABSL_LOG_INTERNAL_LOG_IMPL(_##severity)
+
+// PLOG()
+//
+// `PLOG` behaves like `LOG` except that a description of the current state of
+// `errno` is appended to the streamed message.
+#define PLOG(severity) ABSL_LOG_INTERNAL_PLOG_IMPL(_##severity)
+
+// DLOG()
+//
+// `DLOG` behaves like `LOG` in debug mode (i.e. `#ifndef NDEBUG`).  Otherwise
+// it compiles away and does nothing.  Note that `DLOG(FATAL)` does not
+// terminate the program if `NDEBUG` is defined.
+#define DLOG(severity) ABSL_LOG_INTERNAL_DLOG_IMPL(_##severity)
+
+// `VLOG` uses numeric levels to provide verbose logging that can configured at
+// runtime, including at a per-module level.  `VLOG` statements are logged at
+// `INFO` severity if they are logged at all; the numeric levels are on a
+// different scale than the proper severity levels.  Positive levels are
+// disabled by default.  Negative levels should not be used.
+// Example:
+//
+//   VLOG(1) << "I print when you run the program with --v=1 or higher";
+//   VLOG(2) << "I print when you run the program with --v=2 or higher";
+//
+// See vlog_is_on.h for further documentation, including the usage of the
+// --vmodule flag to log at different levels in different source files.
+//
+// `VLOG` does not produce any output when verbose logging is not enabled.
+// However, simply testing whether verbose logging is enabled can be expensive.
+// If you don't intend to enable verbose logging in non-debug builds, consider
+// using `DVLOG` instead.
+#define VLOG(severity) ABSL_LOG_INTERNAL_VLOG_IMPL(severity)
+
+// `DVLOG` behaves like `VLOG` in debug mode (i.e. `#ifndef NDEBUG`).
+// Otherwise, it compiles away and does nothing.
+#define DVLOG(severity) ABSL_LOG_INTERNAL_DVLOG_IMPL(severity)
+
+// `LOG_IF` and friends add a second argument which specifies a condition.  If
+// the condition is false, nothing is logged.
+// Example:
+//
+//   LOG_IF(INFO, num_cookies > 10) << "Got lots of cookies";
+//
+// There is no `VLOG_IF` because the order of evaluation of the arguments is
+// ambiguous and the alternate spelling with an `if`-statement is trivial.
+#define LOG_IF(severity, condition) \
+  ABSL_LOG_INTERNAL_LOG_IF_IMPL(_##severity, condition)
+#define PLOG_IF(severity, condition) \
+  ABSL_LOG_INTERNAL_PLOG_IF_IMPL(_##severity, condition)
+#define DLOG_IF(severity, condition) \
+  ABSL_LOG_INTERNAL_DLOG_IF_IMPL(_##severity, condition)
+
+// LOG_EVERY_N
+// LOG_FIRST_N
+// LOG_EVERY_POW_2
+// LOG_EVERY_N_SEC
+//
+// These "stateful" macros log conditionally based on a hidden counter or timer.
+// When the condition is false and no logging is done, streamed operands aren't
+// evaluated either.  Each instance has its own state (i.e. counter, timer)
+// that's independent of other instances of the macros.  The macros in this
+// family are thread-safe in the sense that they are meant to be called
+// concurrently and will not invoke undefined behavior, however their
+// implementation prioritizes efficiency over exactness and may occasionally log
+// more or less often than specified.
+//
+//   * `LOG_EVERY_N` logs the first time and once every `n` times thereafter.
+//   * `LOG_FIRST_N` logs the first `n` times and then stops.
+//   * `LOG_EVERY_POW_2` logs the first, second, fourth, eighth, etc. times.
+//   * `LOG_EVERY_N_SEC` logs the first time and no more than once every `n`
+//     seconds thereafter.  `n` is passed as a floating point value.
+//
+// The `LOG_IF`... variations with an extra condition evaluate the specified
+// condition first and short-circuit if it is false.  For example, an evaluation
+// of `LOG_IF_FIRST_N` does not count against the first `n` if the specified
+// condition is false.  Stateful `VLOG`... variations likewise short-circuit
+// if `VLOG` is disabled.
+//
+// An approximate count of the number of times a particular instance's stateful
+// condition has been evaluated (i.e. excluding those where a specified `LOG_IF`
+// condition was false) can be included in the logged message by streaming the
+// symbol `COUNTER`.
+//
+// The `n` parameter need not be a constant.  Conditional logging following a
+// change to `n` isn't fully specified, but it should converge on the new value
+// within roughly `max(old_n, new_n)` evaluations or seconds.
+//
+// Examples:
+//
+//   LOG_EVERY_N(WARNING, 1000) << "Got a packet with a bad CRC (" << COUNTER
+//                              << " total)";
+//
+//   LOG_EVERY_N_SEC(INFO, 2.5) << "Got " << COUNTER << " cookies so far";
+//
+//   LOG_IF_EVERY_N(INFO, (size > 1024), 10) << "Got the " << COUNTER
+//                                           << "th big cookie";
+#define LOG_EVERY_N(severity, n) \
+  ABSL_LOG_INTERNAL_LOG_EVERY_N_IMPL(_##severity, n)
+#define LOG_FIRST_N(severity, n) \
+  ABSL_LOG_INTERNAL_LOG_FIRST_N_IMPL(_##severity, n)
+#define LOG_EVERY_POW_2(severity) \
+  ABSL_LOG_INTERNAL_LOG_EVERY_POW_2_IMPL(_##severity)
+#define LOG_EVERY_N_SEC(severity, n_seconds) \
+  ABSL_LOG_INTERNAL_LOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
+
+#define PLOG_EVERY_N(severity, n) \
+  ABSL_LOG_INTERNAL_PLOG_EVERY_N_IMPL(_##severity, n)
+#define PLOG_FIRST_N(severity, n) \
+  ABSL_LOG_INTERNAL_PLOG_FIRST_N_IMPL(_##severity, n)
+#define PLOG_EVERY_POW_2(severity) \
+  ABSL_LOG_INTERNAL_PLOG_EVERY_POW_2_IMPL(_##severity)
+#define PLOG_EVERY_N_SEC(severity, n_seconds) \
+  ABSL_LOG_INTERNAL_PLOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
+
+#define DLOG_EVERY_N(severity, n) \
+  ABSL_LOG_INTERNAL_DLOG_EVERY_N_IMPL(_##severity, n)
+#define DLOG_FIRST_N(severity, n) \
+  ABSL_LOG_INTERNAL_DLOG_FIRST_N_IMPL(_##severity, n)
+#define DLOG_EVERY_POW_2(severity) \
+  ABSL_LOG_INTERNAL_DLOG_EVERY_POW_2_IMPL(_##severity)
+#define DLOG_EVERY_N_SEC(severity, n_seconds) \
+  ABSL_LOG_INTERNAL_DLOG_EVERY_N_SEC_IMPL(_##severity, n_seconds)
+
+#define VLOG_EVERY_N(severity, n) \
+  ABSL_LOG_INTERNAL_VLOG_EVERY_N_IMPL(severity, n)
+#define VLOG_FIRST_N(severity, n) \
+  ABSL_LOG_INTERNAL_VLOG_FIRST_N_IMPL(severity, n)
+#define VLOG_EVERY_POW_2(severity) \
+  ABSL_LOG_INTERNAL_VLOG_EVERY_POW_2_IMPL(severity)
+#define VLOG_EVERY_N_SEC(severity, n_seconds) \
+  ABSL_LOG_INTERNAL_VLOG_EVERY_N_SEC_IMPL(severity, n_seconds)
+
+#define LOG_IF_EVERY_N(severity, condition, n) \
+  ABSL_LOG_INTERNAL_LOG_IF_EVERY_N_IMPL(_##severity, condition, n)
+#define LOG_IF_FIRST_N(severity, condition, n) \
+  ABSL_LOG_INTERNAL_LOG_IF_FIRST_N_IMPL(_##severity, condition, n)
+#define LOG_IF_EVERY_POW_2(severity, condition) \
+  ABSL_LOG_INTERNAL_LOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
+#define LOG_IF_EVERY_N_SEC(severity, condition, n_seconds) \
+  ABSL_LOG_INTERNAL_LOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
+
+#define PLOG_IF_EVERY_N(severity, condition, n) \
+  ABSL_LOG_INTERNAL_PLOG_IF_EVERY_N_IMPL(_##severity, condition, n)
+#define PLOG_IF_FIRST_N(severity, condition, n) \
+  ABSL_LOG_INTERNAL_PLOG_IF_FIRST_N_IMPL(_##severity, condition, n)
+#define PLOG_IF_EVERY_POW_2(severity, condition) \
+  ABSL_LOG_INTERNAL_PLOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
+#define PLOG_IF_EVERY_N_SEC(severity, condition, n_seconds) \
+  ABSL_LOG_INTERNAL_PLOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
+
+#define DLOG_IF_EVERY_N(severity, condition, n) \
+  ABSL_LOG_INTERNAL_DLOG_IF_EVERY_N_IMPL(_##severity, condition, n)
+#define DLOG_IF_FIRST_N(severity, condition, n) \
+  ABSL_LOG_INTERNAL_DLOG_IF_FIRST_N_IMPL(_##severity, condition, n)
+#define DLOG_IF_EVERY_POW_2(severity, condition) \
+  ABSL_LOG_INTERNAL_DLOG_IF_EVERY_POW_2_IMPL(_##severity, condition)
+#define DLOG_IF_EVERY_N_SEC(severity, condition, n_seconds) \
+  ABSL_LOG_INTERNAL_DLOG_IF_EVERY_N_SEC_IMPL(_##severity, condition, n_seconds)
+
+#endif  // ABSL_LOG_LOG_H_