patch [ 1105730 ] Faster commonprefix in macpath, ntpath, etc.
diff --git a/Lib/plat-riscos/riscospath.py b/Lib/plat-riscos/riscospath.py
index 97b4f65..ea39e60 100644
--- a/Lib/plat-riscos/riscospath.py
+++ b/Lib/plat-riscos/riscospath.py
@@ -168,23 +168,16 @@
return split(p)[0]
-def commonprefix(ps):
- """
- Return the longest prefix of all list elements. Purely string-based; does not
- separate any path parts. Why am I in os.path?
- """
- if len(ps)==0:
- return ''
- prefix= ps[0]
- for p in ps[1:]:
- prefix= prefix[:len(p)]
- for i in range(len(prefix)):
- if prefix[i] <> p[i]:
- prefix= prefix[:i]
- if i==0:
- return ''
- break
- return prefix
+def commonprefix(m):
+ "Given a list of pathnames, returns the longest common leading component"
+ if not m: return ''
+ s1 = min(m)
+ s2 = max(m)
+ n = min(len(s1), len(s2))
+ for i in xrange(n):
+ if s1[i] != s2[i]:
+ return s1[:i]
+ return s1[:n]
## File access functions. Why are we in os.path?