1 files changed, 30 insertions, 0 deletions
diff --git a/lisp/subr.el b/lisp/subr.el
index b1537fd27a6..b8331760e34 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -4411,6 +4411,36 @@ Unless optional argument INPLACE is non-nil, return a new string."
 	  (aset newstr i tochar)))
     newstr))
 
+(defun replace-in-string (fromstring tostring instring)
+  "Replace FROMSTRING with TOSTRING in INSTRING each time it occurs.
+This function returns a freshly created string."
+  (declare (side-effect-free t))
+  (let ((i 0)
+        (start 0)
+        (result nil))
+    (while (< i (length instring))
+      (if (eq (aref instring i)
+              (aref fromstring 0))
+          ;; See if we're in a match.
+          (let ((ii i)
+                (if 0))
+            (while (and (< ii (length instring))
+                        (< if (length fromstring))
+                        (eq (aref instring ii)
+                            (aref fromstring if)))
+              (setq ii (1+ ii)
+                    if (1+ if)))
+            (when (= if (length fromstring))
+              (when (not (= start i))
+                (push (substring instring start i) result))
+              (push tostring result)
+              (setq i ii
+                    start ii)))
+        (setq i (1+ i))))
+    (when (not (= start i))
+      (push (substring instring start i) result))
+    (apply #'concat (nreverse result))))
+
 (defun replace-regexp-in-string (regexp rep string &optional
 					fixedcase literal subexp start)
   "Replace all matches for REGEXP with REP in STRING.