X-Git-Url: http://g0dil.de/git?a=blobdiff_plain;f=Utils%2FSafeBool.hh;h=c0b7163f0983f319da540e0a8b56fc4452d6964d;hb=9a988902090d28007578e93bffd809f6bd913155;hp=5bde302818a4f03e2f13e095185792b7a99b0682;hpb=9248350bdd5a59799e603936d98241a1bb4591f9;p=senf.git

diff --git a/Utils/SafeBool.hh b/Utils/SafeBool.hh
index 5bde302..c0b7163 100644
--- a/Utils/SafeBool.hh
+++ b/Utils/SafeBool.hh
@@ -1,6 +1,6 @@
 // $Id$
 //
-// Copyright (C) 2006 
+// Copyright (C) 2006
 
 #ifndef HH_SafeBool_
 #define HH_SafeBool_ 1
@@ -10,64 +10,93 @@
 //#include "SafeBool.mpp"
 ///////////////////////////////hh.p////////////////////////////////////////
 
-namespace satcom {
-namespace lib {
-    
-    // This is a direct copy of a safe bool solution by Bjorn Karlsson 
-    // from http://www.artima.com/cppsource/safebool.html
-    //
-    // Usage:
-    //    class TestableWithVirtual 
-    //        : public safe_bool<> 
-    //    {
-    //    protected:
-    //        bool boolean_test() const 
-    //        {
-    //            // Perform Boolean logic here
-    //        }
-    //    };
-    //
-    //    class TestableWithoutVirtual 
-    //        : public safe_bool <TestableWithoutVirtual> 
-    //    {
-    //    public:
-    //        bool boolean_test() const 
-    //        {
-    //            // Perform Boolean logic here
-    //        }
-    //    };
-
-    class SafeBoolBase 
+namespace senf {
+
+    /** \brief internal SafeBool base class
+        \internal
+     */
+    class SafeBoolBase
     {
     protected:
-	typedef void (SafeBoolBase::*bool_type)() const;
-	void this_type_does_not_support_comparisons() const;
+        typedef void (SafeBoolBase::*bool_type)() const;
+        void this_type_does_not_support_comparisons() const;
+
+        // Just here to make them protected ...
 
-	SafeBoolBase();
-	SafeBoolBase(const SafeBoolBase&);
-	SafeBoolBase& operator=(const SafeBoolBase&);
-	~SafeBoolBase();
+        SafeBoolBase();
+        SafeBoolBase(const SafeBoolBase&);
+        SafeBoolBase& operator=(const SafeBoolBase&);
+        ~SafeBoolBase();
     };
 
-    template <typename T=void> 
-    class SafeBool 
-	: public SafeBoolBase 
+    /** \brief Mixin class for safe boolean conversion support
+
+        This is a direct yet simplified copy of a safe bool solution
+        by Bjorn Karlsson from
+        http://www.artima.com/cppsource/safebool.html
+
+        This mixin provides the client class with safe boolean
+        testing. It is a safe replacement for <tt>operator
+        bool</tt>. <tt>operator bool</tt> is problematic since \c bool
+        is an integer type. This conversion operator makes the class
+        usable in any numeric context, which can be quite
+        dangerous. The <tt>operator void *</tt> solution is much
+        better in this respect but still allows two instances of any
+        class having such a <tt>void *</tt> conversion to be compared
+        for equality. This again will produce absolutely unexpected
+        results since it will not check whether the objects are
+        identical, it will only check, that both return the same
+        boolean state.
+
+        This solutions solves all these problems by returning a
+        pointer-to-member which cannot be converted to any other
+        type. By providing explicit implementations of \c operator==
+        and \c operator!= which fail in an obvious way at compile
+        time, this hazard is removed.
+
+        To make a class boolean testable, just inherit from the mixin
+        and implement \c boolean_test:
+
+        \code
+        class Testable
+            : public SafeBool<Testable>
+        {
+        public:
+            bool boolean_test() const
+            {
+                // Perform Boolean logic here
+            }
+        };
+
+        Testable t = ...;
+
+        if (t) {
+           ...
+        }
+        \endcode
+
+        \todo Either rename intrusive_refcount to IntrusiveRefcount or
+        SafeBool to safe_bool (I tend to the latter ...)
+     */
+    template <typename T>
+    class SafeBool
+        : public SafeBoolBase
     {
     public:
-	operator bool_type() const;
-	bool operator !() const;
+        operator bool_type() const;
+        bool operator !() const;
 
     protected:
-	~SafeBool();
+        ~SafeBool();
     };
 
-    template <typename T, typename U> 
+    template <typename T, typename U>
     void operator==(const SafeBool<T>& lhs,const SafeBool<U>& rhs);
 
-    template <typename T,typename U> 
+    template <typename T,typename U>
     void operator!=(const SafeBool<T>& lhs,const SafeBool<U>& rhs);
 
-}}
+}
 
 ///////////////////////////////hh.e////////////////////////////////////////
 #include "SafeBool.cci"
@@ -79,4 +108,8 @@ namespace lib {
 
 // Local Variables:
 // mode: c++
+// fill-column: 100
+// c-file-style: "senf"
+// indent-tabs-mode: nil
+// ispell-local-dictionary: "american"
 // End: