Apply performance improvement to short byte array search.

* re.c (rb_memsearch_ss): Apply performance improvement to short
  byte array search for platforms without memmem(3).
  [Feature #6311] [ruby-dev:45530]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37793 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Thu Nov 22 14:14:36 2012  Akinori MUSHA  <knu@iDaemons.org>
+
+	* re.c (rb_memsearch_ss): Apply performance improvement to short
+	  byte array search for platforms without memmem(3).
+	  [Feature #6311] [ruby-dev:45530]
+
 Thu Nov 22 12:52:19 2012  Akinori MUSHA  <knu@iDaemons.org>
 
 	* test/ruby/test_string.rb (TestString#test_index): Add some

re.c

@@ -126,6 +126,9 @@ rb_memsearch_ss(const unsigned char *xs, long m, const unsigned char *ys, long n
     if (m > SIZEOF_VALUE)
 	rb_bug("!!too long pattern string!!");
 
+    if (!(y = memchr(y, *x, n - m + 1)))
+	return -1;
+
     /* Prepare hash value */
     for (hx = *x++, hy = *y++; x < xe; ++x, ++y) {
 	hx <<= CHAR_BIT;

test/ruby/test_string.rb

@@ -837,6 +837,13 @@ class TestString < Test::Unit::TestCase
     assert_equal(0, S("hello").index(S("")))
     assert_equal(0, S("hello").index(//))
 
+    s = S("long") * 1000 << "x"
+    assert_nil(s.index(S("y")))
+    assert_equal(4 * 1000, s.index(S("x")))
+    s << "yx"
+    assert_equal(4 * 1000, s.index(S("x")))
+    assert_equal(4 * 1000, s.index(S("xyx")))
+
     o = Object.new
     def o.to_str; "bar"; end
     assert_equal(3, "foobarbarbaz".index(o))