c/include/mojo/environment/logger.h

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MOJO_PUBLIC_C_INCLUDE_MOJO_ENVIRONMENT_LOGGER_H_
#define MOJO_PUBLIC_C_INCLUDE_MOJO_ENVIRONMENT_LOGGER_H_

#include <stdint.h>

// |MojoLogLevel|: Used to specify the type of log message. Values are ordered
// by severity (i.e., higher numerical values are more severe).

typedef int32_t MojoLogLevel;

#ifdef __cplusplus
const MojoLogLevel MOJO_LOG_LEVEL_VERBOSE = -1;
const MojoLogLevel MOJO_LOG_LEVEL_INFO = 0;
const MojoLogLevel MOJO_LOG_LEVEL_WARNING = 1;
const MojoLogLevel MOJO_LOG_LEVEL_ERROR = 2;
const MojoLogLevel MOJO_LOG_LEVEL_FATAL = 3;
#else
#define MOJO_LOG_LEVEL_VERBOSE ((MojoLogLevel)-1)
#define MOJO_LOG_LEVEL_INFO ((MojoLogLevel)0)
#define MOJO_LOG_LEVEL_WARNING ((MojoLogLevel)1)
#define MOJO_LOG_LEVEL_ERROR ((MojoLogLevel)2)
#define MOJO_LOG_LEVEL_FATAL ((MojoLogLevel)3)
#endif

// Structure with basic logging functions (on top of which more friendly logging
// macros may be built). The functions are thread-safe, except for
// |SetMinimumLogLevel()| (see below).
struct MojoLogger {
  // Logs |message| (which must not be null) at level |log_level| if |log_level|
  // is at least the current minimum log level. If |log_level| is
  // |MOJO_LOG_LEVEL_FATAL| (or greater), aborts the application/process.
  // |source_file| and |source_line| indicate the source file and (1-based) line
  // number, respectively; they are optional: |source_file| may be null and
  // |source_line| may be zero (if |source_file| is null, then |source_line| may
  // be ignored).
  void (*LogMessage)(MojoLogLevel log_level,
                     const char* source_file,
                     uint32_t source_line,
                     const char* message);

  // Gets the minimum log level (see above), which will always be at most
  // |MOJO_LOG_LEVEL_FATAL|. (Though |LogMessage()| will automatically avoid
  // logging messages below the minimum log level, this may be used to avoid
  // extra work.)
  MojoLogLevel (*GetMinimumLogLevel)(void);

  // Sets the minimum log level (see above) to the lesser of |minimum_log_level|
  // and |MOJO_LOG_LEVEL_FATAL|.
  //
  // Warning: This function may not be thread-safe, and should not be called
  // concurrently with other |MojoLogger| functions. (In some environments --
  // such as Chromium -- that share a logger across applications, this may mean
  // that it is almost never safe to call this.)
  void (*SetMinimumLogLevel)(MojoLogLevel minimum_log_level);
};

#endif  // MOJO_PUBLIC_C_INCLUDE_MOJO_ENVIRONMENT_LOGGER_H_