performace issue in Tk

From: Khamis Abuelkomboz (khamis_at_wellcode.com)
Date: 11/29/04 

Date: Mon, 29 Nov 2004 22:15:50 +0100

Hi

I have found a performance and memory usage issue in the function ObjectIsEmpty implemented in
tk8.4.6\generic\tkConfig.c:2229

To test if an object is empty it just convert every object into a string. this is pretty ugly, if
you have lists in the options list. it converts all lists, integers and so on into strings. as
example, with my fix I reduced memory usage from 200MB to 110MB by large amount of data. It got even
  some factors faster.

here is the origin

static int
ObjectIsEmpty(objPtr)
     Tcl_Obj *objPtr; /* Object to test. May be NULL. */
{
     int length;

     if (objPtr == NULL) {
        return 1;
     }
     if (objPtr->bytes != NULL) {
        return (objPtr->length == 0);
     }
     Tcl_GetStringFromObj(objPtr, &length);
     return (length == 0);
}

and the modified version

static int
ObjectIsEmpty(objPtr)
     Tcl_Obj *objPtr; /* Object to test. May be NULL. */
{
     int length;

     if (objPtr == NULL) {
        return 1;
     }
     if (objPtr->bytes != NULL) {
        return (objPtr->length == 0);
     }
++++++>>>>>>>
     if (objPtr->typePtr != NULL)
     {
        if (stricmp(objPtr->typePtr->name, "list") == 0)
        {
            List *listRepPtr = (List *) objPtr->internalRep.twoPtrValue.ptr1;
            int numElems = listRepPtr->elemCount;
            return (numElems == 0);
        }
        if (stricmp(objPtr->typePtr->name, "string") != 0)
            return 0;
     }
++++++<<<<<<<<
     Tcl_GetStringFromObj(objPtr, &length);
     return (length == 0);
} 

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