More immutability and locking tests.

1 files changed, 7 insertions, 4 deletions

diff --git a/io_buffer.c b/io_buffer.c
index af05388036..1acc942987 100644
--- a/io_buffer.c
+++ b/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);