adds optional LogStream for cpp iostream-style logging

interface/src/LogStream.h

@@ -0,0 +1,106 @@
+//
+// LogStream.h
+// interface
+//
+// Created by Tobias Schwinger on 4/17/13.
+// Copyright (c) 2013 High Fidelity, Inc. All rights reserved.
+//
+
+#ifndef __interface__LogStream__
+#define __interface__LogStream__
+
+#include <sstream>
+
+#include "Log.h"
+
+//
+// Makes the logging facility accessible as a C++ stream.
+//
+// Example: 
+//
+//      // somewhere central - ideally one per thread (else pass 'true' as
+//      // second constructor argument and compromise some efficiency)
+//      LogStream lOut(printLog); 
+//
+//      // elsewhere:
+//      lOut << "Hello there!" << std::endl;
+//
+class LogStream {
+    std::ostringstream  _objOutStream;
+    Log&                _refLog;
+    bool                _flgThreadSafe;
+public:
+    inline LogStream(Log& log, bool threadSafe = false);
+
+    class StreamRef; friend class StreamRef;
+
+    template< typename T > friend inline LogStream::StreamRef const operator<<(LogStream&, T const&);
+
+private:
+    // don't
+    LogStream(LogStream const&); // = delete;
+    LogStream& operator=(LogStream const&); // = delete;
+
+    inline void ostreamBegin();
+    inline void ostreamEnd();
+};
+
+inline LogStream::LogStream(Log& log, bool threadSafe) :
+    _objOutStream(std::ios_base::out), _refLog(log), _flgThreadSafe(threadSafe) { }
+
+inline void LogStream::ostreamBegin() {
+
+    if (_flgThreadSafe) {
+        // the user wants to share this LogStream among threads,
+        // so lock the global log here, already
+        pthread_mutex_lock(& _refLog._mtx);
+    }
+    _objOutStream.str("");
+}
+
+inline void LogStream::ostreamEnd() {
+
+    if (! _flgThreadSafe) {
+        // haven't locked, so far (we have memory for each thread)
+        pthread_mutex_lock(& _refLog._mtx);
+    }
+    _refLog.addMessage(_objOutStream.str().c_str());
+    pthread_mutex_unlock(& _refLog._mtx);
+}
+
+
+//
+// The Log::StreamRef class makes operator<< work. It...
+//
+class LogStream::StreamRef {
+    mutable LogStream* _ptrLogStream;
+    typedef std::ostream& (*manipulator)(std::ostream&);
+
+    friend class LogStream;
+
+    template< typename T > friend inline LogStream::StreamRef const operator<<(LogStream&, T const&);
+    StreamRef(LogStream* log) : _ptrLogStream(log) { }
+public:
+    // ...forwards << operator calls to stringstream...
+    template< typename T > StreamRef const operator<<(T const& x) const { _ptrLogStream->_objOutStream << x; return *this; }
+    // ...has to dance around to make manipulators (such as std::hex, std::endl) work...
+    StreamRef const operator<<(manipulator x) const { _ptrLogStream->_objOutStream << x; return *this; }
+    // ...informs the logger that a stream has ended when it has the responsibility...
+    ~StreamRef() { if (_ptrLogStream != 0l) { _ptrLogStream->ostreamEnd(); } }
+    // ...which is passed on upon copy. 
+    StreamRef(StreamRef const& other) : _ptrLogStream(other._ptrLogStream) { other._ptrLogStream = 0l; }
+
+private:
+    // don't
+    StreamRef& operator=(StreamRef const&); // = delete; 
+};
+
+template< typename T > inline LogStream::StreamRef const operator<<(LogStream& s, T const& x) {
+    
+    s.ostreamBegin(); 
+    s._objOutStream << x;
+    return LogStream::StreamRef(& s); // calls streamEnd at the end of the stream expression
+}
+
+
+#endif