gecko-dev/xpcom/base/Logging.h

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4.6 KiB
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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 "prlog.h"
#include "mozilla/Assertions.h"
#include "mozilla/Atomics.h"
#include "mozilla/Likely.h"
// This file is a placeholder for a replacement to the NSPR logging framework
// that is defined in prlog.h. Currently it is just a pass through, but as
// work progresses more functionality will be swapped out in favor of
// mozilla logging implementations.
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,
};
class LogModule
{
public:
/**
* 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.
*/
#if !defined(MOZILLA_XPCOMRT_API)
static LogModule* Get(const char* aName);
#else
// For simplicity, libxpcomrt doesn't supoort logging.
static LogModule* Get(const char* aName) { return nullptr; }
#endif
static void Init();
/**
* 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; }
private:
friend class LogModuleManager;
explicit LogModule(LogLevel aLevel) : mLevel(aLevel) {}
LogModule(LogModule&) = delete;
LogModule& operator=(const LogModule&) = delete;
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 MOZ_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 PRLogModuleInfo* module, LogLevel level) {
MOZ_ASSERT(level != LogLevel::Disabled);
return module && module->level >= static_cast<int>(level);
}
inline bool log_test(const LogModule* module, LogLevel level) {
MOZ_ASSERT(level != LogLevel::Disabled);
return module && module->ShouldLog(level);
}
} // namespace detail
} // namespace mozilla
#define MOZ_LOG_TEST(_module,_level) mozilla::detail::log_test(_module, _level)
#define MOZ_LOG(_module,_level,_args) \
PR_BEGIN_MACRO \
if (MOZ_LOG_TEST(_module,_level)) { \
PR_LogPrint _args; \
} \
PR_END_MACRO
#undef PR_LOG
#undef PR_LOG_TEST
/*
* __func__ was standardized in C++11 and is supported by clang, gcc, and MSVC
* 2015. Here we polyfill __func__ for earlier versions of MSVC.
* http://blogs.msdn.com/b/vcblog/archive/2015/06/19/c-11-14-17-features-in-vs-2015-rtm.aspx
*/
#ifdef _MSC_VER
# if _MSC_VER < 1900
# define __func__ __FUNCTION__
# endif
#endif
#endif // mozilla_logging_h