/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_logging_h

#define mozilla_logging_h

#include <string.h>

#include <stdarg.h>

#include "mozilla/Assertions.h"

#include "mozilla/Atomics.h"

#include "mozilla/Attributes.h"

#include "mozilla/Likely.h"

#include "mozilla/Poison.h"

// We normally have logging enabled everywhere, but measurements showed that

// having logging enabled on Android is quite expensive (hundreds of kilobytes

// for both the format strings for logging and the code to perform all the

// logging calls).  Because retrieving logs from a mobile device is

// comparatively more difficult for Android than it is for desktop and because

// desktop machines tend to be less space/bandwidth-constrained than Android

// devices, we've chosen to leave logging enabled on desktop, but disabled on

// Android.  Given that logging can still be useful for development purposes,

// however, we leave logging enabled on Android developer builds.

#if !defined(ANDROID) || !defined(RELEASE_OR_BETA)

#define MOZ_LOGGING_ENABLED 1

#else

#define MOZ_LOGGING_ENABLED 0

#endif

namespace mozilla {

// While not a 100% mapping to PR_LOG's numeric values, mozilla::LogLevel does

// maintain a direct mapping for the Disabled, Debug and Verbose levels.

//

// Mappings of LogLevel to PR_LOG's numeric values:

//

//   +---------+------------------+-----------------+

//   | Numeric | NSPR Logging     | Mozilla Logging |

//   +---------+------------------+-----------------+

//   |       0 | PR_LOG_NONE      | Disabled        |

//   |       1 | PR_LOG_ALWAYS    | Error           |

//   |       2 | PR_LOG_ERROR     | Warning         |

//   |       3 | PR_LOG_WARNING   | Info            |

//   |       4 | PR_LOG_DEBUG     | Debug           |

//   |       5 | PR_LOG_DEBUG + 1 | Verbose         |

//   +---------+------------------+-----------------+

//

enum class LogLevel {

  Disabled = 0,

  Error,

  Warning,

  Info,

  Debug,

  Verbose,

};

/**

 * Safely converts an integer into a valid LogLevel.

 */

LogLevel ToLogLevel(int32_t aLevel);

class LogModule

{

public:

  ~LogModule() { ::free(mName); }

  /**

   * Retrieves the module with the given name. If it does not already exist

   * it will be created.

   *

   * @param aName The name of the module.

   * @return A log module for the given name. This may be shared.

   */

  static LogModule* Get(const char* aName);

  /**

   * Logging processes -MOZ_LOG and -MOZ_LOG_FILE command line arguments

   * to override or set modules and the file as if passed through MOZ_LOG

   * and MOZ_LOG_FILE env vars.  It's fine to pass (0, nullptr) if args

   * are not accessible in the caller's context, it will just do nothing.

   * Note that the args take effect (are processed) only when this function

   * is called the first time.

   */

  static void Init(int argc, char* argv[]);

  /**

   * Sets the log file to the given filename.

   */

  static void SetLogFile(const char* aFilename);

  /**

   * @param aBuffer - pointer to a buffer

   * @param aLength - the length of the buffer

   *

   * @return the actual length of the filepath.

   */

  static uint32_t GetLogFile(char *aBuffer, size_t aLength);

  /**

   * @param aAddTimestamp If we should log a time stamp with every message.

   */

  static void SetAddTimestamp(bool aAddTimestamp);

  /**

   * @param aIsSync If we should flush the file after every logged message.

   */

  static void SetIsSync(bool aIsSync);

  /**

   * Indicates whether or not the given log level is enabled.

   */

  bool ShouldLog(LogLevel aLevel) const { return mLevel >= aLevel; }

  /**

   * Retrieves the log module's current level.

   */

  LogLevel Level() const { return mLevel; }

  /**

   * Sets the log module's level.

   */

  void SetLevel(LogLevel level) { mLevel = level; }

  /**

   * Print a log message for this module.

   */

  void Printv(LogLevel aLevel, const char* aFmt, va_list aArgs) const MOZ_FORMAT_PRINTF(3, 0);

  /**

   * Retrieves the module name.

   */

  const char* Name() const { return mName; }

private:

  friend class LogModuleManager;

  explicit LogModule(const char* aName, LogLevel aLevel)

    : mName(strdup(aName)), mLevel(aLevel)

  {

  }

  LogModule(LogModule&) = delete;

  LogModule& operator=(const LogModule&) = delete;

  char* mName;

  // Logging atomics and other state are not preserved by web replay, as they

  // may be accessed during the GC and other areas where recorded events are

  // not allowed.

  Atomic<LogLevel, Relaxed, recordreplay::Behavior::DontPreserve> mLevel;

};

/**

 * Helper class that lazy loads the given log module. This is safe to use for

 * declaring static references to log modules and can be used as a replacement

 * for accessing a LogModule directly.

 *

 * Example usage:

 *   static LazyLogModule sLayoutLog("layout");

 *

 *   void Foo() {

 *     MOZ_LOG(sLayoutLog, LogLevel::Verbose, ("Entering foo"));

 *   }

 */

class LazyLogModule final

{

public:

  explicit constexpr LazyLogModule(const char* aLogName)

    : mLogName(aLogName)

    , mLog(nullptr)

  {

  }

  operator LogModule*();

private:

  const char* const mLogName;

  const CorruptionCanaryForStatics mCanary;

  // As for LogModule::mLevel, don't preserve behavior for this atomic when

  // recording/replaying.

  Atomic<LogModule*, ReleaseAcquire, recordreplay::Behavior::DontPreserve> mLog;

};

namespace detail {

inline bool log_test(const LogModule* module, LogLevel level) {

  MOZ_ASSERT(level != LogLevel::Disabled);

  return module && module->ShouldLog(level);

}

void log_print(const LogModule* aModule,

               LogLevel aLevel,

               const char* aFmt, ...) MOZ_FORMAT_PRINTF(3, 4);

} // namespace detail

} // namespace mozilla

// Helper macro used convert MOZ_LOG's third parameter, |_args|, from a

// parenthesized form to a varargs form. For example:

//   ("%s", "a message") => "%s", "a message"

#define MOZ_LOG_EXPAND_ARGS(...) __VA_ARGS__

#if MOZ_LOGGING_ENABLED

#define MOZ_LOG_TEST(_module,_level) mozilla::detail::log_test(_module, _level)

#else

// Define away MOZ_LOG_TEST here so the compiler will fold away entire

// logging blocks via dead code elimination, e.g.:

//

//   if (MOZ_LOG_TEST(...)) {

//     ...compute things to log and log them...

//   }

#define MOZ_LOG_TEST(_module,_level) false

#endif

// The natural definition of the MOZ_LOG macro would expand to:

//

//   do {

//     if (MOZ_LOG_TEST(_module, _level)) {

//       mozilla::detail::log_print(_module, ...);

//     }

//   } while (0)

//

// However, since _module is a LazyLogModule, and we need to call

// LazyLogModule::operator() to get a LogModule* for the MOZ_LOG_TEST

// macro and for the logging call, we'll wind up doing *two* calls, one

// for each, rather than a single call.  The compiler is not able to

// fold the two calls into one, and the extra call can have a

// significant effect on code size.  (Making LazyLogModule::operator() a

// `const` function does not have any effect.)

//

// Therefore, we will have to make a single call ourselves.  But again,

// the natural definition:

//

//   do {

//     ::mozilla::LogModule* real_module = _module;

//     if (MOZ_LOG_TEST(real_module, _level)) {

//       mozilla::detail::log_print(real_module, ...);

//     }

//   } while (0)

//

// also has a problem: if logging is disabled, then we will call

// LazyLogModule::operator() unnecessarily, and the compiler will not be

// able to optimize away the call as dead code.  We would like to avoid

// such a scenario, as the whole point of disabling logging is for the

// logging statements to not generate any code.

//

// Therefore, we need different definitions of MOZ_LOG, depending on

// whether logging is enabled or not.  (We need an actual definition of

// MOZ_LOG even when logging is disabled to ensure the compiler sees that

// variables only used during logging code are actually used, even if the

// code will never be executed.)  Hence, the following code.

#if MOZ_LOGGING_ENABLED

#define MOZ_LOG(_module,_level,_args)                                         \

  do {                                                                        \

    const ::mozilla::LogModule* moz_real_module = _module;                    \

    if (MOZ_LOG_TEST(moz_real_module,_level)) {                               \

      mozilla::detail::log_print(moz_real_module, _level, MOZ_LOG_EXPAND_ARGS _args); \

    }                                                                         \

  } while (0)

#else

#define MOZ_LOG(_module,_level,_args)                                         \

  do {                                                                        \

    if (MOZ_LOG_TEST(_module,_level)) {                        \

      mozilla::detail::log_print(_module, _level, MOZ_LOG_EXPAND_ARGS _args); \

    }                                                                         \

  } while (0)

#endif

// This #define is a Logging.h-only knob!  Don't encourage people to get fancy

// with their log definitions by exporting it outside of Logging.h.

#undef MOZ_LOGGING_ENABLED

#endif // mozilla_logging_h