From 5cb2f3eb58a48c22bd4e56bdfd89e0591232295e Mon Sep 17 00:00:00 2001
From: Danny Yoo <dyoo@hashcollision.org>
Date: Wed, 7 Nov 2012 16:03:04 -0700
Subject: [PATCH] Avoid regexp-replace* unless the string really contains
 escapable characters.

---
 collects/xml/private/writer.rkt | 8 ++++++++
 collects/xml/private/xexpr.rkt  | 4 ++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/collects/xml/private/writer.rkt b/collects/xml/private/writer.rkt
index 7443ccf236..4b06e7611f 100644
--- a/collects/xml/private/writer.rkt
+++ b/collects/xml/private/writer.rkt
@@ -168,7 +168,15 @@
 (define (escape x table)
   (regexp-replace* table x replace-escaped))
 
+(define (display/escape x table out)
+  (cond [(regexp-match table x)
+         (display (escape x table) out)]
+        [else
+         (display x out)]))
+
+
 (provide escape
+         display/escape
          escape-table
          escape-attribute-table
          lowercase-symbol
diff --git a/collects/xml/private/xexpr.rkt b/collects/xml/private/xexpr.rkt
index 67112dbaa2..349a1a60df 100644
--- a/collects/xml/private/xexpr.rkt
+++ b/collects/xml/private/xexpr.rkt
@@ -141,7 +141,7 @@
          (display (car att) out)
          (display "=" out)
          (display "\"" out)
-         (display (escape (cadr att) escape-attribute-table) out)
+         (display/escape (cadr att) escape-attribute-table out)
          (display "\"" out))
        ; Write end of opening tag
        (if (and (null? content)
@@ -161,7 +161,7 @@
              (display ">" out)))]
       ; PCData
       [(string? x)
-       (display (escape x escape-table) out)]
+       (display/escape x escape-table out)]
       ; Entities
       [(symbol? x)
        (display "&" out)