NEW FILE HEADER / COPYRIGHT FORMAT

[senf.git] / Packets / PacketParser.ih

diff --git a/Packets/PacketParser.ih b/Packets/PacketParser.ih
index 0c6131e..250c1fa 100644 (file)
--- a/Packets/PacketParser.ih
+++ b/Packets/PacketParser.ih
@@ -1,6 +1,8 @@
+// $Id$
+//
 // Copyright (C) 2007 
-// Fraunhofer Institut fuer offene Kommunikationssysteme (FOKUS)
-// Kompetenzzentrum fuer Satelitenkommunikation (SatCom)
+// Fraunhofer Institute for Open Communication Systems (FOKUS) 
+// Competence Center NETwork research (NET), St. Augustin, GERMANY 
 //     Stefan Bund <g0dil@berlios.de>
 //
 // This program is free software; you can redistribute it and/or modify
@@ -25,6 +27,7 @@
 #define IH_PacketParser_ 1
 
 // Custom includes
+#include "../Utils/mpl.hh"
 
 ///////////////////////////////ih.p////////////////////////////////////////
 
@@ -35,35 +38,51 @@ namespace detail {
 
 #   ifndef DOXYGEN
 
-    template <PacketParserBase::size_type i>
-    struct Parser_TakeNum {};
-
+    // Use SFINAE to check, if Parser has an integer-valued fixed_bytes member. If not,
+    // 'Parser_TakeNum<Parser::fixed_bytes>' fails and the overload is removed from the overload
+    // set. 
     template <class Parser>
     PacketParserBase::size_type packetParserSize(
-        Parser p, int, Parser_TakeNum<Parser::fixed_bytes> * = 0);
+        Parser p, int, senf::mpl::take_uint<Parser::fixed_bytes> * = 0);
 
+    // An ellipsis is always the worst match. A call 'packetParserSize(p,0) will prefer above
+    // overload if that is not disabled by SFINAE.
     template <class Parser>
     PacketParserBase::size_type packetParserSize(Parser p, ...);
 
-    template <unsigned n> struct ParserInitBytes_RV { char _[16][n]; };
-
+    // Same as above: This overload is only enabled, if Parser has an integer values 'init_bytes'
+    // member.
     template <class Parser>
-    ParserInitBytes_RV<1> ParserInitBytes_Choose_(Parser_TakeNum<Parser::init_bytes> *);
-    
+    senf::mpl::rv<0> ParserInitBytes_Choose_(senf::mpl::take_uint<Parser::init_bytes> *);
+
     template <class Parser>
-    ParserInitBytes_RV<2> ParserInitBytes_Choose_(...);
+    senf::mpl::rv<1> ParserInitBytes_Choose_(...);
 
-    template <class Parser, unsigned size>
+    // This version of ParserInitBytes_Choose uses 'Parser::init_bytes' to provide 'value' (via
+    // 'boost::integral_constant')
+    template <class Parser, unsigned _>
     struct ParserInitBytes_Choose 
         : public boost::integral_constant<PacketParserBase::size_type, Parser::init_bytes> {};
-
+    // ^^-- g++ error signaled here:
+    //    error: 'fixed_bytes' is not a member of 'some-class-name'
+    //
+    // The 'some-class-name' class (as given in the error message) does not seem to be a parser at
+    // all (it has neither a 'fixed_bytes' nor an 'init_bytes' member).
+    //
+    // Either 'some-class-name' is not the class you wanted to use (it really is no parser) or you
+    // left out either 'init_bytes' or 'fixed_bytes' when defining the parser. This will also
+    // happen, if you forget to call 'SENF_PARSER_FINALIZE()' when defining a composite parser.
+    ///////////////////////////////////////////////////////////////////////////////////////////////
+
+    // If Parser::init_bytes is not defined, this specialization is chosen which instead uses
+    // 'Parser::fixed_bytes'
     template <class Parser>
-    struct ParserInitBytes_Choose<Parser, sizeof(ParserInitBytes_RV<2>)>
+    struct ParserInitBytes_Choose<Parser, 1>
         : public boost::integral_constant<PacketParserBase::size_type, Parser::fixed_bytes> {};
 
     template <class Parser>
     struct ParserInitBytes
-        : public ParserInitBytes_Choose<Parser, sizeof(ParserInitBytes_Choose_<Parser>(0))> {};
+        : public ParserInitBytes_Choose<Parser,SENF_MPL_RV(ParserInitBytes_Choose_<Parser>(0))> {};
 
 #   endif
 
@@ -80,4 +99,5 @@ namespace detail {
 // indent-tabs-mode: nil
 // ispell-local-dictionary: "american"
 // compile-command: "scons -u test"
+// comment-column: 40
 // End: