More immutability and locking tests.

io_buffer.c

@@ -417,7 +417,6 @@ rb_io_buffer_to_s(VALUE self)
     }
 
     return rb_str_cat2(result, ">");
-
 }
 
 static VALUE
@@ -701,6 +700,13 @@ size_t rb_io_buffer_copy(VALUE self, VALUE source, size_t offset)
     const void *source_base = NULL;
     size_t source_size = 0;
 
+    struct rb_io_buffer *data = NULL;
+    TypedData_Get_Struct(self, struct rb_io_buffer, &rb_io_buffer_type, data);
+
+    if (data->flags & RB_IO_BUFFER_IMMUTABLE) {
+        rb_raise(rb_eRuntimeError, "Buffer is immutable!");
+    }
+
     if (RB_TYPE_P(source, T_STRING)) {
         RSTRING_GETMEM(source, source_base, source_size);
     }
@@ -708,9 +714,6 @@ size_t rb_io_buffer_copy(VALUE self, VALUE source, size_t offset)
         rb_io_buffer_get_immutable(source, &source_base, &source_size);
     }
 
-    struct rb_io_buffer *data = NULL;
-    TypedData_Get_Struct(self, struct rb_io_buffer, &rb_io_buffer_type, data);
-
     rb_io_buffer_validate(data, offset, source_size);
 
     memcpy((char*)data->base + offset, source_base, source_size);

test/ruby/test_io_buffer.rb

@@ -44,6 +44,19 @@ class TestIOBuffer < Test::Unit::TestCase
     assert buffer.mapped?
   end
 
+  def test_new_immutable
+    buffer = IO::Buffer.new(128, IO::Buffer::INTERNAL|IO::Buffer::IMMUTABLE)
+    assert buffer.immutable?
+
+    assert_raise RuntimeError do
+      buffer.copy("", 0)
+    end
+
+    assert_raise RuntimeError do
+      buffer.copy("!", 1)
+    end
+  end
+
   def test_file_mapped
     buffer = File.open(__FILE__) {|file| IO::Buffer.map(file)}
     assert_include buffer.to_str, "Hello World"
@@ -103,6 +116,22 @@ class TestIOBuffer < Test::Unit::TestCase
     # end
   end
 
+  def test_locked
+    buffer = IO::Buffer.new(128, IO::Buffer::INTERNAL|IO::Buffer::LOCKED)
+
+    assert_raise RuntimeError do
+      buffer.resize(256, 0)
+    end
+
+    assert_equal 128, buffer.size
+
+    assert_raise RuntimeError do
+      buffer.free
+    end
+
+    assert_equal 128, buffer.size
+  end
+
   def test_invalidation
     input, output = IO.pipe