1 /*
2  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 // This is a highly stripped-down version of libjingle's talk/base/logging.h.
12 // It is a thin wrapper around WEBRTC_TRACE, maintaining the libjingle log
13 // semantics to ease a transition to that format.
14 
15 // NOTE: LS_INFO maps to a new trace level which should be reserved for
16 // infrequent, non-verbose logs. The other levels below kTraceWarning have been
17 // rendered essentially useless due to their verbosity. Carefully consider the
18 // impact of adding a new LS_INFO log. If it will be logged at anything
19 // approaching a frame or packet frequency, use LS_VERBOSE if necessary, or
20 // preferably, do not log at all.
21 
22 //   LOG(...) an ostream target that can be used to send formatted
23 // output to a variety of logging targets, such as debugger console, stderr,
24 // file, or any StreamInterface.
25 //   The severity level passed as the first argument to the LOGging
26 // functions is used as a filter, to limit the verbosity of the logging.
27 //   Static members of LogMessage documented below are used to control the
28 // verbosity and target of the output.
29 //   There are several variations on the LOG macro which facilitate logging
30 // of common error conditions, detailed below.
31 
32 // LOG(sev) logs the given stream at severity "sev", which must be a
33 //     compile-time constant of the LoggingSeverity type, without the namespace
34 //     prefix.
35 // LOG_V(sev) Like LOG(), but sev is a run-time variable of the LoggingSeverity
36 //     type (basically, it just doesn't prepend the namespace).
37 // LOG_F(sev) Like LOG(), but includes the name of the current function.
38 
39 // Additional helper macros added by WebRTC:
40 // LOG_API is a shortcut for API call logging. Pass in the input parameters of
41 // the method. For example:
42 //   Foo(int bar, int baz) {
43 //     LOG_API2(bar, baz);
44 //   }
45 //
46 // LOG_FERR is a shortcut for logging a failed function call. For example:
47 //   if (!Foo(bar)) {
48 //     LOG_FERR1(LS_WARNING, Foo, bar);
49 //   }
50 
51 #ifndef WEBRTC_SYSTEM_WRAPPERS_INTERFACE_LOGGING_H_
52 #define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_LOGGING_H_
53 
54 #include <sstream>
55 
56 namespace webrtc {
57 
58 //////////////////////////////////////////////////////////////////////
59 
60 // Note that the non-standard LoggingSeverity aliases exist because they are
61 // still in broad use.  The meanings of the levels are:
62 //  LS_SENSITIVE: Information which should only be logged with the consent
63 //   of the user, due to privacy concerns.
64 //  LS_VERBOSE: This level is for data which we do not want to appear in the
65 //   normal debug log, but should appear in diagnostic logs.
66 //  LS_INFO: Chatty level used in debugging for all sorts of things, the default
67 //   in debug builds.
68 //  LS_WARNING: Something that may warrant investigation.
69 //  LS_ERROR: Something that should not have occurred.
70 enum LoggingSeverity {
71   LS_SENSITIVE, LS_VERBOSE, LS_INFO, LS_WARNING, LS_ERROR
72 };
73 
74 class LogMessage {
75  public:
76   LogMessage(const char* file, int line, LoggingSeverity sev);
77   ~LogMessage();
78 
79   static bool Loggable(LoggingSeverity sev);
stream()80   std::ostream& stream() { return print_stream_; }
81 
82  private:
83   // The ostream that buffers the formatted message before output
84   std::ostringstream print_stream_;
85 
86   // The severity level of this message
87   LoggingSeverity severity_;
88 };
89 
90 //////////////////////////////////////////////////////////////////////
91 // Macros which automatically disable logging when WEBRTC_LOGGING == 0
92 //////////////////////////////////////////////////////////////////////
93 
94 #ifndef LOG
95 // The following non-obvious technique for implementation of a
96 // conditional log stream was stolen from google3/base/logging.h.
97 
98 // This class is used to explicitly ignore values in the conditional
99 // logging macros.  This avoids compiler warnings like "value computed
100 // is not used" and "statement has no effect".
101 
102 class LogMessageVoidify {
103  public:
LogMessageVoidify()104   LogMessageVoidify() { }
105   // This has to be an operator with a precedence lower than << but
106   // higher than ?:
107   void operator&(std::ostream&) { }
108 };
109 
110 #if defined(WEBRTC_RESTRICT_LOGGING)
111 // This should compile away logs matching the following condition.
112 #define RESTRICT_LOGGING_PRECONDITION(sev)  \
113   sev < webrtc::LS_INFO ? (void) 0 :
114 #else
115 #define RESTRICT_LOGGING_PRECONDITION(sev)
116 #endif
117 
118 #define LOG_SEVERITY_PRECONDITION(sev) \
119   RESTRICT_LOGGING_PRECONDITION(sev) !(webrtc::LogMessage::Loggable(sev)) \
120     ? (void) 0 \
121     : webrtc::LogMessageVoidify() &
122 
123 #define LOG(sev) \
124   LOG_SEVERITY_PRECONDITION(webrtc::sev) \
125     webrtc::LogMessage(__FILE__, __LINE__, webrtc::sev).stream()
126 
127 // The _V version is for when a variable is passed in.  It doesn't do the
128 // namespace concatination.
129 #define LOG_V(sev) \
130   LOG_SEVERITY_PRECONDITION(sev) \
131     webrtc::LogMessage(__FILE__, __LINE__, sev).stream()
132 
133 // The _F version prefixes the message with the current function name.
134 #if (defined(__GNUC__) && defined(_DEBUG)) || defined(WANT_PRETTY_LOG_F)
135 #define LOG_F(sev) LOG(sev) << __PRETTY_FUNCTION__ << ": "
136 #else
137 #define LOG_F(sev) LOG(sev) << __FUNCTION__ << ": "
138 #endif
139 
140 #define LOG_API0() LOG_F(LS_VERBOSE)
141 #define LOG_API1(v1) LOG_API0() << #v1 << "=" << v1
142 #define LOG_API2(v1, v2) LOG_API1(v1) \
143     << ", " << #v2 << "=" << v2
144 #define LOG_API3(v1, v2, v3) LOG_API2(v1, v2) \
145     << ", " << #v3 << "=" << v3
146 
147 #define LOG_FERR0(sev, func) LOG(sev) << #func << " failed"
148 #define LOG_FERR1(sev, func, v1) LOG_FERR0(sev, func) \
149     << ": " << #v1 << "=" << v1
150 #define LOG_FERR2(sev, func, v1, v2) LOG_FERR1(sev, func, v1) \
151     << ", " << #v2 << "=" << v2
152 #define LOG_FERR3(sev, func, v1, v2, v3) LOG_FERR2(sev, func, v1, v2) \
153     << ", " << #v3 << "=" << v3
154 #define LOG_FERR4(sev, func, v1, v2, v3, v4) LOG_FERR3(sev, func, v1, v2, v3) \
155     << ", " << #v4 << "=" << v4
156 
157 #endif  // LOG
158 
159 }  // namespace webrtc
160 
161 #endif  // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_LOGGING_H_
162