// // GTMLogger.h // // Copyright 2007-2008 Google Inc. // // Licensed under the Apache License, Version 2.0 (the "License"); you may not // use this file except in compliance with the License. You may obtain a copy // of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the // License for the specific language governing permissions and limitations under // the License. // // Key Abstractions // ---------------- // // This file declares multiple classes and protocols that are used by the // GTMLogger logging system. The 4 main abstractions used in this file are the // following: // // * logger (GTMLogger) - The main logging class that users interact with. It // has methods for logging at different levels and uses a log writer, a log // formatter, and a log filter to get the job done. // // * log writer (GTMLogWriter) - Writes a given string to some log file, where // a "log file" can be a physical file on disk, a POST over HTTP to some URL, // or even some in-memory structure (e.g., a ring buffer). // // * log formatter (GTMLogFormatter) - Given a format string and arguments as // a va_list, returns a single formatted NSString. A "formatted string" could // be a string with the date prepended, a string with values in a CSV format, // or even a string of XML. // // * log filter (GTMLogFilter) - Given a formatted log message as an NSString // and the level at which the message is to be logged, this class will decide // whether the given message should be logged or not. This is a flexible way // to filter out messages logged at a certain level, messages that contain // certain text, or filter nothing out at all. This gives the caller the // flexibility to dynamically enable debug logging in Release builds. // // This file also declares some classes to handle the common log writer, log // formatter, and log filter cases. Callers can also create their own writers, // formatters, and filters and they can even build them on top of the ones // declared here. Keep in mind that your custom writer/formatter/filter may be // called from multiple threads, so it must be thread-safe. #import #import "GTMDefines.h" // Predeclaration of used protocols that are declared later in this file. @protocol GTMLogWriter, GTMLogFormatter, GTMLogFilter; // GTMLogger // // GTMLogger is the primary user-facing class for an object-oriented logging // system. It is built on the concept of log formatters (GTMLogFormatter), log // writers (GTMLogWriter), and log filters (GTMLogFilter). When a message is // sent to a GTMLogger to log a message, the message is formatted using the log // formatter, then the log filter is consulted to see if the message should be // logged, and if so, the message is sent to the log writer to be written out. // // GTMLogger is intended to be a flexible and thread-safe logging solution. Its // flexibility comes from the fact that GTMLogger instances can be customized // with user defined formatters, filters, and writers. And these writers, // filters, and formatters can be combined, stacked, and customized in arbitrary // ways to suit the needs at hand. For example, multiple writers can be used at // the same time, and a GTMLogger instance can even be used as another // GTMLogger's writer. This allows for arbitrarily deep logging trees. // // A standard GTMLogger uses a writer that sends messages to standard out, a // formatter that smacks a timestamp and a few other bits of interesting // information on the message, and a filter that filters out debug messages from // release builds. Using the standard log settings, a log message will look like // the following: // // 2007-12-30 10:29:24.177 myapp[4588/0xa07d0f60] [lvl=1] foo= // // The output contains the date and time of the log message, the name of the // process followed by its process ID/thread ID, the log level at which the // message was logged (in the previous example the level was 1: // kGTMLoggerLevelDebug), and finally, the user-specified log message itself (in // this case, the log message was @"foo=%@", foo). // // Multiple instances of GTMLogger can be created, each configured their own // way. Though GTMLogger is not a singleton (in the GoF sense), it does provide // access to a shared (i.e., globally accessible) GTMLogger instance. This makes // it convenient for all code in a process to use the same GTMLogger instance. // The shared GTMLogger instance can also be configured in an arbitrary, and // these configuration changes will affect all code that logs through the shared // instance. // // Log Levels // ---------- // GTMLogger has 3 different log levels: Debug, Info, and Error. GTMLogger // doesn't take any special action based on the log level; it simply forwards // this information on to formatters, filters, and writers, each of which may // optionally take action based on the level. Since log level filtering is // performed at runtime, log messages are typically not filtered out at compile // time. The exception to this rule is that calls to the GTMLoggerDebug() macro // *ARE* filtered out of non-DEBUG builds. This is to be backwards compatible // with behavior that many developers are currently used to. Note that this // means that GTMLoggerDebug(@"hi") will be compiled out of Release builds, but // [[GTMLogger sharedLogger] logDebug:@"hi"] will NOT be compiled out. // // Standard loggers are created with the GTMLogLevelFilter log filter, which // filters out certain log messages based on log level, and some other settings. // // In addition to the -logDebug:, -logInfo:, and -logError: methods defined on // GTMLogger itself, there are also C macros that make usage of the shared // GTMLogger instance very convenient. These macros are: // // GTMLoggerDebug(...) // GTMLoggerInfo(...) // GTMLoggerError(...) // // Again, a notable feature of these macros is that GTMLogDebug() calls *will be // compiled out of non-DEBUG builds*. // // Standard Loggers // ---------------- // GTMLogger has the concept of "standard loggers". A standard logger is simply // a logger that is pre-configured with some standard/common writer, formatter, // and filter combination. Standard loggers are created using the creation // methods beginning with "standard". The alternative to a standard logger is a // regular logger, which will send messages to stdout, with no special // formatting, and no filtering. // // How do I use GTMLogger? // ---------------------- // The typical way you will want to use GTMLogger is to simply use the // GTMLogger*() macros for logging from code. That way we can easily make // changes to the GTMLogger class and simply update the macros accordingly. Only // your application startup code (perhaps, somewhere in main()) should use the // GTMLogger class directly in order to configure the shared logger, which all // of the code using the macros will be using. Again, this is just the typical // situation. // // To be complete, there are cases where you may want to use GTMLogger directly, // or even create separate GTMLogger instances for some reason. That's fine, // too. // // Examples // -------- // The following show some common GTMLogger use cases. // // 1. You want to log something as simply as possible. Also, this call will only // appear in debug builds. In non-DEBUG builds it will be completely removed. // // GTMLoggerDebug(@"foo = %@", foo); // // 2. The previous example is similar to the following. The major difference is // that the previous call (example 1) will be compiled out of Release builds // but this statement will not be compiled out. // // [[GTMLogger sharedLogger] logDebug:@"foo = %@", foo]; // // 3. Send all logging output from the shared logger to a file. We do this by // creating an NSFileHandle for writing associated with a file, and setting // that file handle as the logger's writer. // // NSFileHandle *f = [NSFileHandle fileHandleForWritingAtPath:@"/tmp/f.log" // create:YES]; // [[GTMLogger sharedLogger] setWriter:f]; // GTMLoggerError(@"hi"); // This will be sent to /tmp/f.log // // 4. Create a new GTMLogger that will log to a file. This example differs from // the previous one because here we create a new GTMLogger that is different // from the shared logger. // // GTMLogger *logger = [GTMLogger standardLoggerWithPath:@"/tmp/temp.log"]; // [logger logInfo:@"hi temp log file"]; // // 5. Create a logger that writes to stdout and does NOT do any formatting to // the log message. This might be useful, for example, when writing a help // screen for a command-line tool to standard output. // // GTMLogger *logger = [GTMLogger logger]; // [logger logInfo:@"%@ version 0.1 usage", progName]; // // 6. Send log output to stdout AND to a log file. The trick here is that // NSArrays function as composite log writers, which means when an array is // set as the log writer, it forwards all logging messages to all of its // contained GTMLogWriters. // // // Create array of GTMLogWriters // NSArray *writers = [NSArray arrayWithObjects: // [NSFileHandle fileHandleForWritingAtPath:@"/tmp/f.log" create:YES], // [NSFileHandle fileHandleWithStandardOutput], nil]; // // GTMLogger *logger = [GTMLogger standardLogger]; // [logger setWriter:writers]; // [logger logInfo:@"hi"]; // Output goes to stdout and /tmp/f.log // // For futher details on log writers, formatters, and filters, see the // documentation below. // // NOTE: GTMLogger is application level logging. By default it does nothing // with _GTMDevLog/_GTMDevAssert (see GTMDefines.h). An application can choose // to bridge _GTMDevLog/_GTMDevAssert to GTMLogger by providing macro // definitions in its prefix header (see GTMDefines.h for how one would do // that). // @interface GTMLogger : NSObject { @private id writer_; id formatter_; id filter_; } // // Accessors for the shared logger instance // // Returns a shared/global standard GTMLogger instance. Callers should typically // use this method to get a GTMLogger instance, unless they explicitly want // their own instance to configure for their own needs. This is the only method // that returns a shared instance; all the rest return new GTMLogger instances. + (id)sharedLogger; // Sets the shared logger instance to |logger|. Future calls to +sharedLogger // will return |logger| instead. + (void)setSharedLogger:(GTMLogger *)logger; // // Creation methods // // Returns a new autoreleased GTMLogger instance that will log to stdout, using // the GTMLogStandardFormatter, and the GTMLogLevelFilter filter. + (id)standardLogger; // Same as +standardLogger, but logs to stderr. + (id)standardLoggerWithStderr; // Same as +standardLogger but levels >= kGTMLoggerLevelError are routed to // stderr, everything else goes to stdout. + (id)standardLoggerWithStdoutAndStderr; // Returns a new standard GTMLogger instance with a log writer that will // write to the file at |path|, and will use the GTMLogStandardFormatter and // GTMLogLevelFilter classes. If |path| does not exist, it will be created. + (id)standardLoggerWithPath:(NSString *)path; // Returns an autoreleased GTMLogger instance that will use the specified // |writer|, |formatter|, and |filter|. + (id)loggerWithWriter:(id)writer formatter:(id)formatter filter:(id)filter; // Returns an autoreleased GTMLogger instance that logs to stdout, with the // basic formatter, and no filter. The returned logger differs from the logger // returned by +standardLogger because this one does not do any filtering and // does not do any special log formatting; this is the difference between a // "regular" logger and a "standard" logger. + (id)logger; // Designated initializer. This method returns a GTMLogger initialized with the // specified |writer|, |formatter|, and |filter|. See the setter methods below // for what values will be used if nil is passed for a parameter. - (id)initWithWriter:(id)writer formatter:(id)formatter filter:(id)filter; // // Logging methods // // Logs a message at the debug level (kGTMLoggerLevelDebug). - (void)logDebug:(NSString *)fmt, ... NS_FORMAT_FUNCTION(1, 2); // Logs a message at the info level (kGTMLoggerLevelInfo). - (void)logInfo:(NSString *)fmt, ... NS_FORMAT_FUNCTION(1, 2); // Logs a message at the error level (kGTMLoggerLevelError). - (void)logError:(NSString *)fmt, ... NS_FORMAT_FUNCTION(1, 2); // Logs a message at the assert level (kGTMLoggerLevelAssert). - (void)logAssert:(NSString *)fmt, ... NS_FORMAT_FUNCTION(1, 2); // // Accessors // // Accessor methods for the log writer. If the log writer is set to nil, // [NSFileHandle fileHandleWithStandardOutput] is used. - (id)writer; - (void)setWriter:(id)writer; // Accessor methods for the log formatter. If the log formatter is set to nil, // GTMLogBasicFormatter is used. This formatter will format log messages in a // plain printf style. - (id)formatter; - (void)setFormatter:(id)formatter; // Accessor methods for the log filter. If the log filter is set to nil, // GTMLogNoFilter is used, which allows all log messages through. - (id)filter; - (void)setFilter:(id)filter; @end // GTMLogger // Helper functions that are used by the convenience GTMLogger*() macros that // enable the logging of function names. @interface GTMLogger (GTMLoggerMacroHelpers) - (void)logFuncDebug:(const char *)func msg:(NSString *)fmt, ... NS_FORMAT_FUNCTION(2, 3); - (void)logFuncInfo:(const char *)func msg:(NSString *)fmt, ... NS_FORMAT_FUNCTION(2, 3); - (void)logFuncError:(const char *)func msg:(NSString *)fmt, ... NS_FORMAT_FUNCTION(2, 3); - (void)logFuncAssert:(const char *)func msg:(NSString *)fmt, ... NS_FORMAT_FUNCTION(2, 3); @end // GTMLoggerMacroHelpers // The convenience macros are only defined if they haven't already been defined. #ifndef GTMLoggerInfo // Convenience macros that log to the shared GTMLogger instance. These macros // are how users should typically log to GTMLogger. Notice that GTMLoggerDebug() // calls will be compiled out of non-Debug builds. #define GTMLoggerDebug(...) \ [[GTMLogger sharedLogger] logFuncDebug:__func__ msg:__VA_ARGS__] #define GTMLoggerInfo(...) \ [[GTMLogger sharedLogger] logFuncInfo:__func__ msg:__VA_ARGS__] #define GTMLoggerError(...) \ [[GTMLogger sharedLogger] logFuncError:__func__ msg:__VA_ARGS__] #define GTMLoggerAssert(...) \ [[GTMLogger sharedLogger] logFuncAssert:__func__ msg:__VA_ARGS__] // If we're not in a debug build, remove the GTMLoggerDebug statements. This // makes calls to GTMLoggerDebug "compile out" of Release builds #ifndef DEBUG #undef GTMLoggerDebug #define GTMLoggerDebug(...) do {} while(0) #endif #endif // !defined(GTMLoggerInfo) // Log levels. typedef enum { kGTMLoggerLevelUnknown, kGTMLoggerLevelDebug, kGTMLoggerLevelInfo, kGTMLoggerLevelError, kGTMLoggerLevelAssert, } GTMLoggerLevel; // // Log Writers // // Protocol to be implemented by a GTMLogWriter instance. @protocol GTMLogWriter // Writes the given log message to where the log writer is configured to write. - (void)logMessage:(NSString *)msg level:(GTMLoggerLevel)level; @end // GTMLogWriter // Simple category on NSFileHandle that makes NSFileHandles valid log writers. // This is convenient because something like, say, +fileHandleWithStandardError // now becomes a valid log writer. Log messages are written to the file handle // with a newline appended. @interface NSFileHandle (GTMFileHandleLogWriter) // Opens the file at |path| in append mode, and creates the file with |mode| // if it didn't previously exist. + (id)fileHandleForLoggingAtPath:(NSString *)path mode:(mode_t)mode; @end // NSFileHandle // This category makes NSArray a GTMLogWriter that can be composed of other // GTMLogWriters. This is the classic Composite GoF design pattern. When the // GTMLogWriter -logMessage:level: message is sent to the array, the array // forwards the message to all of its elements that implement the GTMLogWriter // protocol. // // This is useful in situations where you would like to send log output to // multiple log writers at the same time. Simply create an NSArray of the log // writers you wish to use, then set the array as the "writer" for your // GTMLogger instance. @interface NSArray (GTMArrayCompositeLogWriter) @end // GTMArrayCompositeLogWriter // This category adapts the GTMLogger interface so that it can be used as a log // writer; it's an "adapter" in the GoF Adapter pattern sense. // // This is useful when you want to configure a logger to log to a specific // writer with a specific formatter and/or filter. But you want to also compose // that with a different log writer that may have its own formatter and/or // filter. @interface GTMLogger (GTMLoggerLogWriter) @end // GTMLoggerLogWriter // // Log Formatters // // Protocol to be implemented by a GTMLogFormatter instance. @protocol GTMLogFormatter // Returns a formatted string using the format specified in |fmt| and the va // args specified in |args|. - (NSString *)stringForFunc:(NSString *)func withFormat:(NSString *)fmt valist:(va_list)args level:(GTMLoggerLevel)level NS_FORMAT_FUNCTION(2, 0); @end // GTMLogFormatter // A basic log formatter that formats a string the same way that NSLog (or // printf) would. It does not do anything fancy, nor does it add any data of its // own. @interface GTMLogBasicFormatter : NSObject // Helper method for prettying C99 __func__ and GCC __PRETTY_FUNCTION__ - (NSString *)prettyNameForFunc:(NSString *)func; @end // GTMLogBasicFormatter // A log formatter that formats the log string like the basic formatter, but // also prepends a timestamp and some basic process info to the message, as // shown in the following sample output. // 2007-12-30 10:29:24.177 myapp[4588/0xa07d0f60] [lvl=1] log mesage here @interface GTMLogStandardFormatter : GTMLogBasicFormatter { @private NSDateFormatter *dateFormatter_; // yyyy-MM-dd HH:mm:ss.SSS NSString *pname_; pid_t pid_; } @end // GTMLogStandardFormatter // // Log Filters // // Protocol to be imlemented by a GTMLogFilter instance. @protocol GTMLogFilter // Returns YES if |msg| at |level| should be filtered out; NO otherwise. - (BOOL)filterAllowsMessage:(NSString *)msg level:(GTMLoggerLevel)level; @end // GTMLogFilter // A log filter that filters messages at the kGTMLoggerLevelDebug level out of // non-debug builds. Messages at the kGTMLoggerLevelInfo level are also filtered // out of non-debug builds unless GTMVerboseLogging is set in the environment or // the processes's defaults. Messages at the kGTMLoggerLevelError level are // never filtered. @interface GTMLogLevelFilter : NSObject @end // GTMLogLevelFilter // A simple log filter that does NOT filter anything out; // -filterAllowsMessage:level will always return YES. This can be a convenient // way to enable debug-level logging in release builds (if you so desire). @interface GTMLogNoFilter : NSObject @end // GTMLogNoFilter // Base class for custom level filters. Not for direct use, use the minimum // or maximum level subclasses below. @interface GTMLogAllowedLevelFilter : NSObject { @private NSIndexSet *allowedLevels_; } @end // A log filter that allows you to set a minimum log level. Messages below this // level will be filtered. @interface GTMLogMininumLevelFilter : GTMLogAllowedLevelFilter // Designated initializer, logs at levels < |level| will be filtered. - (id)initWithMinimumLevel:(GTMLoggerLevel)level; @end // A log filter that allows you to set a maximum log level. Messages whose level // exceeds this level will be filtered. This is really only useful if you have // a composite GTMLogger that is sending the other messages elsewhere. @interface GTMLogMaximumLevelFilter : GTMLogAllowedLevelFilter // Designated initializer, logs at levels > |level| will be filtered. - (id)initWithMaximumLevel:(GTMLoggerLevel)level; @end // For subclasses only @interface GTMLogger (PrivateMethods) - (void)logInternalFunc:(const char *)func format:(NSString *)fmt valist:(va_list)args level:(GTMLoggerLevel)level NS_FORMAT_FUNCTION(2, 0); @end