From 517a1245ac8e89d0cd18684eee9266f4975aadcb Mon Sep 17 00:00:00 2001
From: Chris Hanson <org/chris-hanson/cph>
Date: Wed, 22 Feb 2017 02:05:16 -0800
Subject: [PATCH] Move reverse-string into ustring.

---
 src/runtime/runtime.pkg |  3 +--
 src/runtime/string.scm  | 26 +++++---------------------
 src/runtime/ustring.scm | 10 +++++++++-
 3 files changed, 15 insertions(+), 24 deletions(-)

diff --git a/src/runtime/runtime.pkg b/src/runtime/runtime.pkg
index 547d9dfd8..934888ded 100644
--- a/src/runtime/runtime.pkg
+++ b/src/runtime/runtime.pkg
@@ -1036,8 +1036,6 @@ USA.
 	  guarantee-substring
 	  guarantee-substring-end-index
 	  guarantee-substring-start-index
-	  reverse-string
-	  reverse-substring
 	  string-pad-left
 	  string-pad-right
 	  string-search-all
@@ -1092,6 +1090,7 @@ USA.
 	  (substring string-copy)
 	  list->string
 	  make-string
+	  reverse-string
 	  string
 	  string*
 	  string->list
diff --git a/src/runtime/string.scm b/src/runtime/string.scm
index b2a6bac1a..cde00ab1b 100644
--- a/src/runtime/string.scm
+++ b/src/runtime/string.scm
@@ -55,7 +55,7 @@ USA.
   vector-8b-find-previous-char-ci
   (vector-8b-ref 2)
   (vector-8b-set! 3))
-
+
 ;;;; Basic Operations
 
 (define (make-legacy-string k #!optional char)
@@ -71,23 +71,6 @@ USA.
 		      (if (default-object? ascii)
 			  ascii
 			  (integer->char ascii))))
-
-(define (reverse-string string)
-  (guarantee-string string 'REVERSE-STRING)
-  (%reverse-substring string 0 (string-length string)))
-
-(define (reverse-substring string start end)
-  (guarantee-substring string start end 'REVERSE-SUBSTRING)
-  (%reverse-substring string start end))
-
-(define (%reverse-substring string start end)
-  (let ((n (fix:- end start)))
-    (let ((result (make-legacy-string n)))
-      (do ((i start (fix:+ i 1))
-	   (j (fix:- n 1) (fix:- j 1)))
-	  ((fix:= i end))
-	(string-set! result j (string-ref string i)))
-      result)))
 
 ;;;; Trim
 
@@ -313,7 +296,7 @@ USA.
 (define (%bm-substring-search-backward text tstart tend pattern pstart pend)
   (let ((m (fix:- pend pstart))
 	(pend-1 (fix:- pend 1))
-	(rpattern (reverse-substring pattern pstart pend)))
+	(rpattern (reverse-string (string-slice pattern pstart pend))))
     (let ((tstart+m (fix:+ tstart m))
 	  (lambda* (compute-last-occurrence-function rpattern 0 m))
 	  (gamma
@@ -369,8 +352,9 @@ USA.
 (define (compute-good-suffix-function pattern pstart pend gamma0)
   (let ((m (fix:- pend pstart)))
     (let ((pi
-	   (compute-prefix-function (reverse-substring pattern pstart pend)
-				    0 m))
+	   (compute-prefix-function
+	    (reverse-string (string-slice pattern pstart pend))
+	    0 m))
 	  (gamma (make-vector m gamma0))
 	  (m-1 (fix:- m 1)))
       (do ((l 0 (fix:+ l 1)))
diff --git a/src/runtime/ustring.scm b/src/runtime/ustring.scm
index 1f34cc266..b8c2590e3 100644
--- a/src/runtime/ustring.scm
+++ b/src/runtime/ustring.scm
@@ -830,13 +830,21 @@ USA.
 
 (define (burst-string string delimiter allow-runs?)
   ((string-splitter delimiter allow-runs?) string))
-
+
 (define (string-replace string char1 char2)
   (guarantee bitless-char? char1 'string-replace)
   (guarantee bitless-char? char2 'string-replace)
   (string-map (lambda (char)
 		(if (char=? char char1) char2 char))
 	      string))
+
+(define (reverse-string string)
+  (let ((builder (string-builder)))
+    (do ((i (fix:- (string-length string) 1)
+	    (fix:- i 1)))
+	((not (fix:>= i 0)))
+      (builder (string-ref string i)))
+    (builder)))
 
 (define (string-8-bit? string)
   (receive (string start end) (translate-slice string 0 (string-length string))
-- 
2.25.1