Add ensure_open_and_* methods to StringIO.

kernel/common/io19.rb

@@ -280,7 +280,14 @@ def run
         saved_pos = 0
       end
 
-      @from.seek @offset, IO::SEEK_CUR if @offset
+      if @offset
+        if @from.respond_to?(:descriptor) && @from.descriptor != -1
+          @from.seek @offset, IO::SEEK_CUR
+        else
+          raise ArgumentError, "cannot specify src_offset for non-IO"
+        end
+      end
+
 
       size = @length ? @length : 16384
       bytes = 0
@@ -296,7 +303,9 @@ def run
         # done reading
       end
 
-      @to.flush
+      # Should only flush if @from and @to are both descended from IO
+      # in other words, MRI does not flush copy_stream from/to a StringIO
+      @to.flush if @from.kind_of?(IO) && @to.kind_of?(IO)
       return bytes
     ensure
       if @from_io
@@ -305,7 +314,7 @@ def run
         @from.close
       end
 
-      @to.close unless @to_io
+      @to.close unless @to_io || @to.closed?
     end
   end
 

lib/19/stringio.rb

@@ -66,13 +66,15 @@ def check_readable
     raise IOError, "not opened for reading" unless @readable
   end
 
+  alias_method :ensure_open_and_readable, :check_readable
   private :check_readable
 
   def check_writable
     raise IOError, "not opened for writing" unless @writable
     raise IOError, "unable to modify data" if @__data__.string.frozen?
   end
 
+  alias_method :ensure_open_and_writable, :check_writable
   private :check_writable
 
   def set_encoding(external, internal=nil, options=nil)

spec/ruby/core/io/copy_stream_spec.rb

@@ -1,5 +1,6 @@
 require File.expand_path('../../../spec_helper', __FILE__)
 require File.expand_path('../fixtures/classes', __FILE__)
+require 'stringio'
 
 ruby_version_is "1.9" do
   describe :io_copy_stream_to_file, :shared => true do
@@ -46,6 +47,7 @@
   describe :io_copy_stream_to_io, :shared => true do
     it "copies the entire IO contents to the IO" do
       IO.copy_stream(@object.from, @to_io)
+      @to_io.flush if @object.flush?
       @to_name.should have_data(@content)
       IO.copy_stream(@from_bigfile, @to_io)
       @to_name.should have_data(@content + @content_bigfile)
@@ -59,6 +61,7 @@
     it "starts writing at the destination IO's current position" do
       @to_io.write("prelude ")
       IO.copy_stream(@object.from, @to_io)
+      @to_io.flush if @object.flush?
       @to_name.should have_data("prelude " + @content)
     end
 
@@ -80,6 +83,7 @@
 
     it "copies only length bytes when specified" do
       IO.copy_stream(@object.from, @to_io, 8).should == 8
+      @to_io.flush if @object.flush?
       @to_name.should have_data("Line one")
     end
   end
@@ -235,5 +239,37 @@
         it_behaves_like :io_copy_stream_to_io, nil, IOSpecs::CopyStream
       end
     end
+
+    describe "from a string IO" do
+      before :each do
+        @from_io = StringIO.new(@content)
+        IOSpecs::CopyStream.from = @from_io
+        IOSpecs::CopyStream.flush = true
+      end
+
+      describe "to a file name" do
+        it_behaves_like :io_copy_stream_to_file, nil, IOSpecs::CopyStream
+
+        it "raises an error when an offset is specified" do
+          lambda { IO.copy_stream(@from_io, @to_name, 8, 4) }.should raise_error(ArgumentError)
+        end
+      end
+
+      describe "to an IO" do
+        before :each do
+          @to_io = new_io @to_name, "w:utf-8"
+        end
+
+        after :each do
+          @to_io.close
+        end
+
+        it_behaves_like :io_copy_stream_to_io, nil, IOSpecs::CopyStream
+
+        it "raises an error when an offset is specified" do
+          lambda { IO.copy_stream(@from_io, @to_io, 8, 4) }.should raise_error(ArgumentError)
+        end
+      end
+    end
   end
 end

spec/ruby/core/io/fixtures/classes.rb

@@ -121,7 +121,7 @@ def self.closed_io
     io.close
     io
   end
-  
+
   # Creates a pipe-based IO fixture containing the specified
   # contents
   def self.pipe_fixture(content)
@@ -146,5 +146,13 @@ def self.from=(from)
     def self.from
       @from
     end
+
+    def self.flush=(flush)
+      @flush = flush
+    end
+
+    def self.flush?
+      @flush
+    end
   end
 end