Revise empty string tests so that we avoid potentially expensive string rep

generations, especially for dicts.

2 files changed, 16 insertions, 61 deletions

diff --git a/ChangeLog b/ChangeLog
index a26e005..74d5613 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2011-05-09  Don Porter  <dgp@users.sourceforge.net>
+
+	* generic/tclListObj.c:	Revise empty string tests so that we avoid
+	potentially expensive string rep generations, especially for dicts.
+
 2011-05-07  Miguel Sofer  <msofer@users.sf.net>
 
 	* generic/tclInt.h: fix USE_TCLALLOC so that it can be enabled
diff --git a/generic/tclListObj.c b/generic/tclListObj.c
index c4061b3..c2e9c78 100644
--- a/generic/tclListObj.c
+++ b/generic/tclListObj.c
@@ -460,24 +460,13 @@ Tcl_ListObjGetElements(
     register List *listRepPtr;
 
     if (listPtr->typePtr != &tclListType) {
-	int result, length;
+	int result;
 
-	/*
-	 * Don't get the string version of a dictionary; that transformation
-	 * is not lossy, but is expensive.
-	 */
-
-	if (listPtr->typePtr == &tclDictType) {
-	    (void) Tcl_DictObjSize(NULL, listPtr, &length);
-	} else {
-	    (void) TclGetStringFromObj(listPtr, &length);
-	}
-	if (!length) {
+	if (listPtr->bytes == tclEmptyStringRep) {
 	    *objcPtr = 0;
 	    *objvPtr = NULL;
 	    return TCL_OK;
 	}
-
 	result = SetListFromAny(interp, listPtr);
 	if (result != TCL_OK) {
 	    return result;
@@ -587,18 +576,12 @@ Tcl_ListObjAppendElement(
 	Tcl_Panic("%s called with shared object", "Tcl_ListObjAppendElement");
     }
     if (listPtr->typePtr != &tclListType) {
-	int result, length;
+	int result;
 
-	if (listPtr->typePtr == &tclDictType) {
-	    (void) Tcl_DictObjSize(NULL, listPtr, &length);
-	} else {
-	    (void) TclGetStringFromObj(listPtr, &length);
-	}
-	if (!length) {
+	if (listPtr->bytes == tclEmptyStringRep) {
 	    Tcl_SetListObj(listPtr, 1, &objPtr);
 	    return TCL_OK;
 	}
-
 	result = SetListFromAny(interp, listPtr);
 	if (result != TCL_OK) {
 	    return result;
@@ -702,18 +685,12 @@ Tcl_ListObjIndex(
     register List *listRepPtr;
 
     if (listPtr->typePtr != &tclListType) {
-	int result, length;
+	int result;
 
-	if (listPtr->typePtr == &tclDictType) {
-	    (void) Tcl_DictObjSize(NULL, listPtr, &length);
-	} else {
-	    (void) TclGetStringFromObj(listPtr, &length);
-	}
-	if (!length) {
+	if (listPtr->bytes == tclEmptyStringRep) {
 	    *objPtrPtr = NULL;
 	    return TCL_OK;
 	}
-
 	result = SetListFromAny(interp, listPtr);
 	if (result != TCL_OK) {
 	    return result;
@@ -761,27 +738,12 @@ Tcl_ListObjLength(
     register List *listRepPtr;
 
     if (listPtr->typePtr != &tclListType) {
-	int result, length;
+	int result;
 
-	if (listPtr->typePtr == &tclDictType) {
-	    (void) Tcl_DictObjSize(NULL, listPtr, &length);
-	    /*
-	     * It's tempting to just report 2*length as the list length
-	     * of this dict, but arguably that's false since the max sizes
-	     * for dicts and lists are not the same, so some dicts don't
-	     * actually convert to lists, and it's good to get that error
-	     * back from the SetListFromAny() call below instead of a false
-	     * indication we can treat the value as a list.  ([llength $val]
-	     * often used as a "listiness" test)
-	     */
-	} else {
-	    (void) TclGetStringFromObj(listPtr, &length);
-	}
-	if (!length) {
+	if (listPtr->bytes == tclEmptyStringRep) {
 	    *intPtr = 0;
 	    return TCL_OK;
 	}
-
 	result = SetListFromAny(interp, listPtr);
 	if (result != TCL_OK) {
 	    return result;
@@ -849,14 +811,7 @@ Tcl_ListObjReplace(
 	Tcl_Panic("%s called with shared object", "Tcl_ListObjReplace");
     }
     if (listPtr->typePtr != &tclListType) {
-	int length;
-
-	if (listPtr->typePtr == &tclDictType) {
-	    (void) Tcl_DictObjSize(NULL, listPtr, &length);
-	} else {
-	    (void) TclGetStringFromObj(listPtr, &length);
-	}
-	if (!length) {
+	if (listPtr->bytes == tclEmptyStringRep) {
 	    if (objc) {
 		Tcl_SetListObj(listPtr, objc, NULL);
 	    } else {
@@ -1551,14 +1506,9 @@ TclListObjSetElement(
 	Tcl_Panic("%s called with shared object", "TclListObjSetElement");
     }
     if (listPtr->typePtr != &tclListType) {
-	int length, result;
+	int result;
 
-	if (listPtr->typePtr == &tclDictType) {
-	    (void) Tcl_DictObjSize(NULL, listPtr, &length);
-	} else {
-	    (void) TclGetStringFromObj(listPtr, &length);
-	}
-	if (!length) {
+	if (listPtr->bytes == tclEmptyStringRep) {
 	    if (interp != NULL) {
 		Tcl_SetObjResult(interp,
 			Tcl_NewStringObj("list index out of range", -1));