Added safe HttpMsg pointer wrapper that locks and unlocks the message.

This class will not be needed if we switch to refcounting HttpMsg. Meanwhile,
it allows to pass message pointers in AsyncCalls and avoid auto_ptr<> in
exception-sensitive code.

=== modified file 'src/HttpMsg.h'
--- src/HttpMsg.h	2010-08-19 00:12:43 +0000
+++ src/HttpMsg.h	2010-08-30 22:06:01 +0000
@@ -167,4 +167,41 @@
 #define HTTPMSGUNLOCK(a) if(a){(a)->_unlock();(a)=NULL;}
 #define HTTPMSGLOCK(a) (a)->_lock()
 
+// TODO: replace HTTPMSGLOCK with general RefCounting and delete this class
+/// safe HttpMsg pointer wrapper that locks and unlocks the message
+template <class Msg>
+class HttpMsgPointerT
+{
+public:
+    HttpMsgPointerT(): msg(NULL) {}
+    explicit HttpMsgPointerT(Msg *m): msg(m) { lock(); }
+    virtual ~HttpMsgPointerT() { unlock(); }
+
+    HttpMsgPointerT(const HttpMsgPointerT &p): msg(p.msg) { lock(); }
+    HttpMsgPointerT &operator =(const HttpMsgPointerT &p)
+        { if (msg != p.msg) { unlock(); msg = p.msg; lock(); } return *this; }
+
+    Msg &operator *() { return *msg; }
+    const Msg &operator *() const { return *msg; }
+    Msg *operator ->() { return msg; }
+    const Msg *operator ->() const { return msg; }
+    operator Msg *() { return msg; }
+    operator const Msg *() const { return msg; }
+    // add more as needed
+
+    void lock() { if (msg) HTTPMSGLOCK(msg); } ///< prevent msg destruction
+    void unlock() { HTTPMSGUNLOCK(msg); } ///< allows/causes msg destruction
+
+private:
+    Msg *msg;
+};
+
+/// convenience wrapper to create HttpMsgPointerT<> object based on msg type
+template <class Msg>
+inline
+HttpMsgPointerT<Msg> HttpMsgPointer(Msg *msg)
+{
+    return HttpMsgPointerT<Msg>(msg);
+}
+
 #endif /* SQUID_HTTPMSG_H */