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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 <stdint.h>
+#include <stdlib.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
+
+// The mandatory extension we add to log files. Note that rotate will append
+// the file piece number still at the end.
+#define MOZ_LOG_FILE_EXTENSION ".moz_log"
+
+// Token for Process ID substitution.
+#define MOZ_LOG_PID_TOKEN "%PID"
+
+namespace mozilla {
+
+class TimeStamp;
+
+// 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);
+
+ /**
+ * Print a log message for this module.
+ */
+ void Printv(LogLevel aLevel, const char* aFmt, va_list aArgs) const
+ MOZ_FORMAT_PRINTF(3, 0);
+
+ void Printv(LogLevel aLevel, const TimeStamp* aStart, const char* aFmt,
+ va_list aArgs) const MOZ_FORMAT_PRINTF(4, 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;
+
+ 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) {}
+
+ MOZ_NEVER_INLINE_DEBUG 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);
+
+void log_print(const LogModule* aModule, LogLevel aLevel, TimeStamp* aStart,
+ const char* aFmt, ...) MOZ_FORMAT_PRINTF(4, 5);
+} // 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) \
+ MOZ_UNLIKELY(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.
+//
+// MOZ_LOG_DURATION takes a start time, and will generate a time range
+// in the logs. Also, if 'profilermarkers' is used in the env var
+// MOZ_LOG, MOZ_LOG_DURATION will generate a marker with a time
+// duration instead of a single point in time.
+#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)
+# define MOZ_LOG_DURATION(_module, _level, start, _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, start, \
+ 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)
+# define MOZ_LOG_DURATION(_module, _level, start, _args) \
+ do { \
+ if (MOZ_LOG_TEST(_module, _level)) { \
+ mozilla::detail::log_print(_module, _level, start, \
+ 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
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