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
56namespace 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.
70enum LoggingSeverity {
71  LS_SENSITIVE, LS_VERBOSE, LS_INFO, LS_WARNING, LS_ERROR
72};
73
74class LogMessage {
75 public:
76  LogMessage(const char* file, int line, LoggingSeverity sev);
77  ~LogMessage();
78
79  static bool Loggable(LoggingSeverity sev);
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
102class LogMessageVoidify {
103 public:
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