gecko-dev/xpcom/base/Logging.h

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/* -*- 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"
// 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);
static void Init();
/**
* 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;
/**
* 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;
Atomic<LogLevel, Relaxed> 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*()
{
// NB: The use of an atomic makes the reading and assignment of mLog
// thread-safe. There is a small chance that mLog will be set more
// than once, but that's okay as it will be set to the same LogModule
// instance each time. Also note LogModule::Get is thread-safe.
LogModule* tmp = mLog;
if (MOZ_UNLIKELY(!tmp)) {
tmp = LogModule::Get(mLogName);
mLog = tmp;
}
return tmp;
}
private:
const char* const mLogName;
Atomic<LogModule*, ReleaseAcquire> 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...
// }
//
// This also has the nice property that no special definition of MOZ_LOG is
// required when logging is disabled.
#define MOZ_LOG_TEST(_module,_level) false
#endif
#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)
// 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