Support arbitrary loggers.

While the defaults (logd or stderr) make sense for most use cases,
there are places that can only log to the kernel, or need to log to a
file, etc.

Allow the user to pass in an arbitrary logging object, and provide
LogdLogger and StderrLogger as defaults.

Change-Id: I62368acc795ff313242bb205d65017404bf64e88

1 files changed, 45 insertions, 15 deletions

diff --git a/base/include/base/logging.h b/base/include/base/logging.h
index 346099781..19c1b647b 100644
--- a/base/include/base/logging.h
+++ b/base/include/base/logging.h
@@ -17,6 +17,7 @@
 #ifndef BASE_LOGGING_H
 #define BASE_LOGGING_H
 
+#include <functional>
 #include <memory>
 #include <ostream>
 
@@ -35,10 +36,32 @@ enum LogSeverity {
 };
 
 enum LogId {
+  DEFAULT,
   MAIN,
   SYSTEM,
 };
 
+typedef std::function<void(LogId, LogSeverity, const char*, const char*,
+                           unsigned int, const char*)> LogFunction;
+
+extern void StderrLogger(LogId, LogSeverity, const char*, const char*,
+                         unsigned int, const char*);
+
+#ifdef __ANDROID__
+// We expose this even though it is the default because a user that wants to
+// override the default log buffer will have to construct this themselves.
+class LogdLogger {
+ public:
+  explicit LogdLogger(LogId default_log_id = android::base::MAIN);
+
+  void operator()(LogId, LogSeverity, const char* tag, const char* file,
+                  unsigned int line, const char* message);
+
+ private:
+  LogId default_log_id_;
+};
+#endif
+
 // Configure logging based on ANDROID_LOG_TAGS environment variable.
 // We need to parse a string that looks like
 //
@@ -47,8 +70,15 @@ enum LogId {
 // The tag (or '*' for the global level) comes first, followed by a colon and a
 // letter indicating the minimum priority level we're expected to log.  This can
 // be used to reveal or conceal logs with specific tags.
+extern void InitLogging(char* argv[], LogFunction&& logger);
+
+// Configures logging using the default logger (logd for the device, stderr for
+// the host).
 extern void InitLogging(char* argv[]);
 
+// Replace the current logger.
+extern void SetLogger(LogFunction&& logger);
+
 // Returns the command line used to invoke the current tool or nullptr if
 // InitLogging hasn't been performed.
 extern const char* GetCmdLine();
@@ -65,8 +95,8 @@ extern const char* ProgramInvocationShortName();
 // FATAL it also causes an abort. For example:
 //
 //     LOG(FATAL) << "We didn't expect to reach here";
-#define LOG(severity)                                                    \
-  ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::MAIN, \
+#define LOG(severity)                                                       \
+  ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::DEFAULT, \
                               ::android::base::severity, -1).stream()
 
 // Logs a message to logcat with the specified log ID on Android otherwise to
@@ -77,8 +107,8 @@ extern const char* ProgramInvocationShortName();
 
 // A variant of LOG that also logs the current errno value. To be used when
 // library calls fail.
-#define PLOG(severity)                                                   \
-  ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::MAIN, \
+#define PLOG(severity)                                                      \
+  ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::DEFAULT, \
                               ::android::base::severity, errno).stream()
 
 // Behaves like PLOG, but logs to the specified log ID.
@@ -96,20 +126,20 @@ extern const char* ProgramInvocationShortName();
 //
 //     CHECK(false == true) results in a log message of
 //       "Check failed: false == true".
-#define CHECK(x)                                                         \
-  if (UNLIKELY(!(x)))                                                    \
-  ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::MAIN, \
-                              ::android::base::FATAL, -1).stream()       \
+#define CHECK(x)                                                            \
+  if (UNLIKELY(!(x)))                                                       \
+  ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::DEFAULT, \
+                              ::android::base::FATAL, -1).stream()          \
       << "Check failed: " #x << " "
 
 // Helper for CHECK_xx(x,y) macros.
-#define CHECK_OP(LHS, RHS, OP)                                           \
-  for (auto _values = ::android::base::MakeEagerEvaluator(LHS, RHS);     \
-       UNLIKELY(!(_values.lhs OP _values.rhs));                          \
-       /* empty */)                                                      \
-  ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::MAIN, \
-                              ::android::base::FATAL, -1).stream()       \
-      << "Check failed: " << #LHS << " " << #OP << " " << #RHS           \
+#define CHECK_OP(LHS, RHS, OP)                                              \
+  for (auto _values = ::android::base::MakeEagerEvaluator(LHS, RHS);        \
+       UNLIKELY(!(_values.lhs OP _values.rhs));                             \
+       /* empty */)                                                         \
+  ::android::base::LogMessage(__FILE__, __LINE__, ::android::base::DEFAULT, \
+                              ::android::base::FATAL, -1).stream()          \
+      << "Check failed: " << #LHS << " " << #OP << " " << #RHS              \
       << " (" #LHS "=" << _values.lhs << ", " #RHS "=" << _values.rhs << ") "
 
 // Check whether a condition holds between x and y, LOG(FATAL) if not. The value