io.c: io_set_read_length

* io.c (io_set_read_length): if the read length equals to the buffer
  string size then nothing to do.  or ensure the string modifiable
  before setting the length only when the former is shorter.  based on
  the patch in [ruby-core:47541] by Hiroshi Shirosaki.
  [ruby-core:46586] [Bug #6764]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36980 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,11 @@
+Sun Sep 16 11:39:12 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* io.c (io_set_read_length): if the read length equals to the buffer
+	  string size then nothing to do.  or ensure the string modifiable
+	  before setting the length only when the former is shorter.  based on
+	  the patch in [ruby-core:47541] by Hiroshi Shirosaki.
+	  [ruby-core:46586] [Bug #6764]
+
 Sun Sep 16 08:57:52 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* configure.in (strict_warnflags): separate strict flags from

io.c

@@ -2158,6 +2158,15 @@ io_setstrbuf(VALUE *str, long len)
     rb_str_modify_expand(*str, len);
 }
 
+static void
+io_set_read_length(VALUE str, long n)
+{
+    if (RSTRING_LEN(str) != n) {
+	rb_str_modify(str);
+	rb_str_set_len(str, n);
+    }
+}
+
 static VALUE
 read_all(rb_io_t *fptr, long siz, VALUE str)
 {
@@ -2281,7 +2290,7 @@ io_getpartial(int argc, VALUE *argv, VALUE io, int nonblock)
             rb_sys_fail_path(fptr->pathv);
         }
     }
-    rb_str_set_len(str, n);
+    io_set_read_length(str, n);
 
     if (n == 0)
         return Qnil;
@@ -2602,7 +2611,7 @@ io_read(int argc, VALUE *argv, VALUE io)
     previous_mode = set_binary_mode_with_seek_cur(fptr);
 #endif
     n = io_fread(str, 0, len, fptr);
-    rb_str_set_len(str, n);
+    io_set_read_length(str, n);
 #if defined(RUBY_TEST_CRLF_ENVIRONMENT) || defined(_WIN32)
     if (previous_mode == O_TEXT) {
 	setmode(fptr->fd, O_TEXT);
@@ -4390,7 +4399,7 @@ rb_io_sysread(int argc, VALUE *argv, VALUE io)
     if (n == -1) {
 	rb_sys_fail_path(fptr->pathv);
     }
-    rb_str_set_len(str, n);
+    io_set_read_length(str, n);
     if (n == 0 && ilen > 0) {
 	rb_eof_error();
     }

test/ruby/test_io.rb

@@ -2446,5 +2446,54 @@ End
       assert_raise(Errno::ESPIPE, Errno::EINVAL) { w.advise(:willneed) }
     end
   end
+
+  def assert_buffer_not_raise_shared_string_error
+    bug6764 = '[ruby-core:46586]'
+    size = 28
+    data = [*"a".."z", *"A".."Z"].shuffle.join("")
+    t = Tempfile.new("test_io")
+    t.write(data)
+    t.close
+    w = Tempfile.new("test_io")
+    assert_nothing_raised(RuntimeError, bug6764) do
+      File.open(t.path, "r") do |r|
+        buf = ''
+        while yield(r, size, buf)
+          w << buf
+        end
+      end
+    end
+    w.close
+    assert_equal(data, w.open.read, bug6764)
+  ensure
+    t.close!
+    w.close!
+  end
+
+  def test_read_buffer_not_raise_shared_string_error
+    assert_buffer_not_raise_shared_string_error do |r, size, buf|
+      r.read(size, buf)
+    end
+  end
+
+  def test_sysread_buffer_not_raise_shared_string_error
+    assert_buffer_not_raise_shared_string_error do |r, size, buf|
+      begin
+        r.sysread(size, buf)
+      rescue EOFError
+        nil
+      end
+    end
+  end
+
+  def test_readpartial_buffer_not_raise_shared_string_error
+    assert_buffer_not_raise_shared_string_error do |r, size, buf|
+      begin
+        r.readpartial(size, buf)
+      rescue EOFError
+        nil
+      end
+    end
+  end
 end