[diffoscope] 01/02: Remove some quadratic string concatenations in HTML presenter

[Jérémy Bobbio]

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lunar pushed a commit to branch master
in repository diffoscope.

commit 61429da5d2511ad588163a5190121acf0e4f4b0f
Author: Jérémy Bobbio <lunar at debian.org>
Date:   Wed Dec 16 10:05:12 2015 +0000

    Remove some quadratic string concatenations in HTML presenter
---
 diffoscope/presenters/html.py | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/diffoscope/presenters/html.py b/diffoscope/presenters/html.py
index cbf092d..957b48f 100644
--- a/diffoscope/presenters/html.py
+++ b/diffoscope/presenters/html.py
@@ -32,6 +32,7 @@
 #
 
 import cgi
+from io import StringIO
 import re
 import sys
 import os
@@ -213,9 +214,9 @@ def linediff(s, t):
     Original line diff algorithm of diff2html. It's character based.
     '''
     if len(s):
-        s = str(reduce(lambda x, y:x+y, [ sane(c) for c in s ]))
+        s = ''.join([ sane(c) for c in s ])
     if len(t):
-        t = str(reduce(lambda x, y:x+y, [ sane(c) for c in t ]))
+        t = ''.join([ sane(c) for c in t ])
 
     m, n = len(s), len(t)
     d = [[(0, 0) for i in range(n+1)] for i in range(m+1)]
@@ -270,46 +271,45 @@ def linediff(s, t):
             l1.append(s[fx])
             l2.append(t[fy])
 
-    r1, r2 = (reduce(lambda x, y:x+y, l1), reduce(lambda x, y:x+y, l2))
-    return r1, r2
+    return ''.join(l1), ''.join(l2)
 
 
 def convert(s, ponct=0):
     i = 0
-    t = u""
+    t = StringIO()
     for c in s:
         # used by diffs
         if c == DIFFON:
-            t += u'<span class="diffchanged2">'
+            t.write('<span class="diffchanged2">')
         elif c == DIFFOFF:
-            t += u"</span>"
+            t.write('</span>')
 
         # special highlighted chars
         elif c == "\t" and ponct == 1:
             n = TABSIZE-(i%TABSIZE)
             if n == 0:
                 n = TABSIZE
-            t += (u'<span class="diffponct">»</span>'+' '*(n-1))
+            t.write('<span class="diffponct">»</span>'+' '*(n-1))
         elif c == " " and ponct == 1:
-            t += u'<span class="diffponct">·</span>'
+            t.write('<span class="diffponct">·</span>')
         elif c == "\n" and ponct == 1:
-            t += u'<br/><span class="diffponct">\</span>'
+            t.write('<br/><span class="diffponct">\</span>')
         elif ord(c) < 32:
             conv = u"\\x%x" % ord(c)
-            t += u"<em>%s</em>" % conv
+            t.write('<em>%s</em>' % conv)
             i += len(conv)
         else:
-            t += cgi.escape(c)
+            t.write(cgi.escape(c))
             i += 1
 
         if WORDBREAK.count(c) == 1:
-            t += u'​'
+            t.write('​')
             i = 0
         if i > LINESIZE:
             i = 0
-            t += u"​"
+            t.write("​")
 
-    return t
+    return t.getvalue()
 
 
 def output_hunk(print_func):

-- 
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