Re: [Plib-devel] psl copy constructor.

[Jonathan W. <jtw...@in...>]

On Tue, 2004-04-20 at 21:29, Steve Baker wrote:
> We need to be careful around the bytecode stuff because it would be
> very easy to introduce something that would clobber performance.
> Reading the bytecode array happens at the innermost levels of the
> runtime interpreter - so tread VERY carefully!

OK, I've got a patch that implements ref counting for the pslCompiler
class and i've set it to delete the code array when it's destructor is
called - This does feel like a hack though, cleaning up an array created
by a seperate class.  Could the array creation be moved into the
pslCompiler constructor?

I've written a program that compiles a simple psl script, runs it, makes
a copy, deletes the first one and then repeats the process.  All three
scripts seem to run without a hitch, so I guess the patch does work. 
Once again I'd appreciate any feedback.

Jonathan.


Index: pslCompiler.h
===================================================================
RCS file: /cvsroot/plib/plib/src/psl/pslCompiler.h,v
retrieving revision 1.33
diff -u -r1.33 pslCompiler.h
--- pslCompiler.h	6 Jan 2003 05:10:13 -0000	1.33
+++ pslCompiler.h	20 Apr 2004 12:37:52 -0000
@@ -51,6 +51,8 @@
 
 class pslCompiler
 {
+  int ref_count; // reference count.  Clean up when this reaches zero 
+  
   /* File I/O and preprocessor */
 
   int  getChar               () ;
@@ -313,6 +315,7 @@
                 const pslExtension *_extn,
                 const char   *_progName )
   {
+    ref_count = 1;
     program  = prog ;
     progName = ulStrDup ( _progName ) ;
 
@@ -341,6 +344,21 @@
       delete [] symtab      [ i ] . symbol ; symtab      [ i ] . symbol
= NULL ;
       delete [] code_symtab [ i ] . symbol ; code_symtab [ i ] . symbol
= NULL ;
       delete [] forward_ref [ i ] . symbol ; forward_ref [ i ] . symbol
= NULL ;
+    }
+  }
+
+  void ref()
+  {
+    ref_count++;
+  }
+
+  void deref()
+  {
+    ref_count--;
+    if(ref_count < 1)
+    {
+      delete [] code;
+      delete this;
     }
   }
 
Index: pslProgram.cxx
===================================================================
RCS file: /cvsroot/plib/plib/src/psl/pslProgram.cxx,v
retrieving revision 1.17
diff -u -r1.17 pslProgram.cxx
--- pslProgram.cxx	6 Jan 2003 05:10:14 -0000	1.17
+++ pslProgram.cxx	20 Apr 2004 12:37:52 -0000
@@ -29,7 +29,7 @@
   if ( ! _pslInitialised )
     ulSetError ( UL_FATAL,
           "PSL: You didn't call pslInit() before using PSL functions."
) ;
-
+ 
   code = new pslOpcode [ MAX_CODE ] ;
 
   extensions = ext ;
@@ -64,17 +64,17 @@
   progName = NULL ;
 
   if ( _prgnm == NULL ) _prgnm = src -> getProgName () ;
-
+  
   setProgName ( _prgnm ) ;
 
   /* This will fail if this pslProgram is ever deleted */
   /* We need ref-counting on code/compiler */
-
+ 
   code       = src -> getCode       () ;
   compiler   = src -> getCompiler   () ;
   extensions = src -> getExtensions () ;
   userData   = src -> getUserData   () ;
-
+  compiler -> ref();
   context = new pslContext ( this ) ;
   context -> reset () ;
 }
@@ -86,9 +86,9 @@
   /* We need ref-counting on code/compiler */
   /* DEBUG-ME! */
   delete [] progName ;
-  delete    compiler ;
   delete    context  ;
-  delete [] code     ;
+  compiler -> deref();
+  
 }