From: Heesob Park <redmine@...>
Date: 2011-01-22T22:11:09+09:00
Subject: [ruby-core:34787] [Ruby 1.9-Bug#4298] Duration of calling String#[] with the same index is strangely related to string length.

Issue #4298 has been updated by Heesob Park.


This bug(or feature) is due to the repetitive calling of str_strlen() function.

Here is a sentry patch for rb_str_substr() function of string.c

--- string.c	2011-01-22 21:25:38.000000000 +0900
+++ string.c.new	2011-01-22 21:28:05.000000000 +0900
@@ -1603,7 +1603,7 @@
 	    if (beg < 0) return Qnil;
 	}
     }
-    else if (beg > 0 && beg > str_strlen(str, enc)) {
+    else if (beg > 0 && beg > RSTRING_LEN(str) && beg > str_strlen(str, enc)) {
 	return Qnil;
     }
     if (len == 0) {


Before patch:
phasis:~ phasis$ /usr/local/bin/ruby t1.rb
  0.000000   0.000000   0.000000 (  0.000398)
  1.690000   0.010000   1.700000 (  1.731168)

After patch:
phasis:~ phasis$ /usr/local/bin/ruby t1.rb
  0.000000   0.000000   0.000000 (  0.000355)
  0.000000   0.000000   0.000000 (  0.000356)


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http://redmine.ruby-lang.org/issues/show/4298

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