1 files changed, 87 insertions, 0 deletions
diff --git a/generic/tkTextIndex.c b/generic/tkTextIndex.c
index 70c94db..25b4666 100644
--- a/generic/tkTextIndex.c
+++ b/generic/tkTextIndex.c
@@ -40,6 +40,9 @@ static CONST char *	StartEnd(TkText *textPtr, CONST char *string,
 static int		GetIndex(Tcl_Interp *interp, TkSharedText *sharedPtr,
 			    TkText *textPtr, CONST char *string,
 			    TkTextIndex *indexPtr, int *canCachePtr);
+static int              IndexCountBytesOrdered(CONST TkText *textPtr,
+                            CONST TkTextIndex *indexPtr1,
+                            CONST TkTextIndex *indexPtr2);
 
 /*
  * The "textindex" Tcl_Obj definition:
@@ -1628,6 +1631,90 @@ TkTextIndexForwChars(
 /*
  *---------------------------------------------------------------------------
  *
+ * TkTextIndexCountBytes --
+ *
+ *	Given a pair of indices in a text widget, this function counts how
+ *	many bytes are between the two indices. The two indices do not need
+ *	to be ordered.
+ *
+ * Results:
+ *	The number of bytes in the given range.
+ *
+ * Side effects:
+ *	None.
+ *
+ *---------------------------------------------------------------------------
+ */
+
+int
+TkTextIndexCountBytes(
+    CONST TkText *textPtr,
+    CONST TkTextIndex *indexPtr1, /* Index describing one location. */
+    CONST TkTextIndex *indexPtr2) /* Index describing second location. */
+{
+    int compare = TkTextIndexCmp(indexPtr1, indexPtr2);
+
+    if (compare == 0) {
+	return 0;
+    } else if (compare > 0) {
+	return IndexCountBytesOrdered(textPtr, indexPtr2, indexPtr1);
+    } else {
+	return IndexCountBytesOrdered(textPtr, indexPtr1, indexPtr2);
+    }
+}
+
+static int
+IndexCountBytesOrdered(
+    CONST TkText *textPtr,
+    CONST TkTextIndex *indexPtr1,
+				/* Index describing location of character from
+				 * which to count. */
+    CONST TkTextIndex *indexPtr2)
+				/* Index describing location of last character
+				 * at which to stop the count. */
+{
+    int byteCount, offset;
+    TkTextSegment *segPtr, *segPtr1;
+    TkTextLine *linePtr;
+
+    if (indexPtr1->linePtr == indexPtr2->linePtr) {
+        return indexPtr2->byteIndex - indexPtr1->byteIndex;
+    }
+
+    /*
+     * indexPtr2 is on a line strictly after the line containing indexPtr1.
+     * Add up:
+     *   bytes between indexPtr1 and end of its line
+     *   bytes in lines strictly between indexPtr1 and indexPtr2
+     *   bytes between start of the indexPtr2 line and indexPtr2
+     */
+
+    segPtr1 = TkTextIndexToSeg(indexPtr1, &offset);
+    byteCount = -offset;
+    for (segPtr = segPtr1; segPtr != NULL; segPtr = segPtr->nextPtr) {
+        byteCount += segPtr->size;
+    }
+
+    linePtr = indexPtr1->linePtr->nextPtr;
+    while (linePtr != indexPtr2->linePtr) {
+	for (segPtr = linePtr->segPtr; segPtr != NULL;
+                segPtr = segPtr->nextPtr) {
+            byteCount += segPtr->size;
+        }
+        linePtr = TkBTreeNextLine(textPtr, linePtr);
+        if (linePtr == NULL) {
+            Tcl_Panic("TextIndexCountBytesOrdered ran out of lines");
+        }
+    }
+
+    byteCount += indexPtr2->byteIndex;
+
+    return byteCount;
+}
+
+/*
+ *---------------------------------------------------------------------------
+ *
  * TkTextIndexCount --
  *
  *	Given an ordered pair of indices in a text widget, this function