Fix [Bug 2008248] and make dict->list->dict round trip efficient to boot.

FossilOrigin-Name: 256c78f19e7a0c93939f2a7fc1bde0d652d29c51

3 files changed, 64 insertions, 11 deletions

diff --git a/ChangeLog b/ChangeLog
index fb60d1f..b139af2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2008-07-20  Donal K. Fellows  <donal.k.fellows@man.ac.uk>
+
+	* generic/tclDictObj.c (SetDictFromAny): Make the list->dict
+	transformation a bit more efficient; modern dicts are ordered and so
+	we can round-trip through lists without needing the string rep at all.
+	* generic/tclListObj.c (SetListFromAny): Make the dict->list
+	transformation not lossy of internal representations and hence more
+	efficient. [Bug 2008248] (ajpasadyn) but using a more efficient patch.
+
 2008-07-15  Donal K. Fellows  <donal.k.fellows@man.ac.uk>
 
 	* doc/DictObj.3: Fix error in example. [Bug 2016740]
diff --git a/generic/tclDictObj.c b/generic/tclDictObj.c
index a33802d..c74f10f 100644
--- a/generic/tclDictObj.c
+++ b/generic/tclDictObj.c
@@ -9,7 +9,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclDictObj.c,v 1.56 2007/12/13 15:23:16 dgp Exp $
+ * RCS: @(#) $Id: tclDictObj.c,v 1.56.2.1 2008/07/20 22:02:37 dkf Exp $
  */
 
 #include "tclInt.h"
@@ -588,15 +588,6 @@ SetDictFromAny(
 	}
 
 	/*
-	 * If the list is shared its string rep must not be lost so it still
-	 * is the same list.
-	 */
-
-	if (Tcl_IsShared(objPtr)) {
-	    (void) TclGetString(objPtr);
-	}
-
-	/*
 	 * Build the hash of key/value pairs.
 	 */
 
diff --git a/generic/tclListObj.c b/generic/tclListObj.c
index 556a41d..2bbaa22 100644
--- a/generic/tclListObj.c
+++ b/generic/tclListObj.c
@@ -10,7 +10,7 @@
  * See the file "license.terms" for information on usage and redistribution of
  * this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclListObj.c,v 1.49 2007/12/13 15:23:18 dgp Exp $
+ * RCS: @(#) $Id: tclListObj.c,v 1.49.2.1 2008/07/20 22:02:39 dkf Exp $
  */
 
 #include "tclInt.h"
@@ -1658,6 +1658,58 @@ SetListFromAny(
     List *listRepPtr;
 
     /*
+     * Dictionaries are a special case; they have a string representation such
+     * that *all* valid dictionaries are valid lists. Hence we can convert
+     * more directly.
+     */
+
+    if (objPtr->typePtr == &tclDictType) {
+	Tcl_Obj *keyPtr, *valuePtr;
+	Tcl_DictSearch search;
+	int done, size;
+
+	/*
+	 * Create the new list representation. Note that we do not need to do
+	 * anything with the string representation as the transformation (and
+	 * the reverse back to a dictionary) are both order-preserving. Also
+	 * note that since we know we've got a valid dictionary (by
+	 * representation) we also know that fetching the size of the
+	 * dictionary or iterating over it will not fail.
+	 */
+
+	Tcl_DictObjSize(NULL, objPtr, &size);
+	listRepPtr = NewListIntRep(size > 0 ? 2*size : 1, NULL);
+	if (!listRepPtr) {
+	    Tcl_SetResult(interp,
+		    "insufficient memory to allocate list working space",
+		    TCL_STATIC);
+	    return TCL_ERROR;
+	}
+	listRepPtr->elemCount = 2 * size;
+
+	/*
+	 * Populate the list representation.
+	 */
+
+	elemPtrs = &listRepPtr->elements;
+	Tcl_DictObjFirst(NULL, objPtr, &search, &keyPtr, &valuePtr, &done);
+	i = 0;
+	while (!done) {
+	    elemPtrs[i++] = keyPtr;
+	    elemPtrs[i++] = valuePtr;
+	    Tcl_IncrRefCount(keyPtr);
+	    Tcl_IncrRefCount(valuePtr);
+	    Tcl_DictObjNext(&search, &keyPtr, &valuePtr, &done);
+	}
+
+	/*
+	 * Swap the representations.
+	 */
+
+	goto commitRepresentation;
+    }
+
+    /*
      * Get the string representation. Make it up-to-date if necessary.
      */
 
@@ -1742,6 +1794,7 @@ SetListFromAny(
      * Tcl_GetStringFromObj, to use that old internalRep.
      */
 
+  commitRepresentation:
     listRepPtr->refCount++;
     TclFreeIntRep(objPtr);
     objPtr->internalRep.twoPtrValue.ptr1 = (void *) listRepPtr;