[pypy-svn] pypy default: Implement io.StringIO.truncate.

[alex_gaynor]

Author: Alex Gaynor <alex.gaynor at gmail.com>
Branch: 
Changeset: r41463:3f1f650b2424
Date: 2011-01-29 14:01 -0500
http://bitbucket.org/pypy/pypy/changeset/3f1f650b2424/

Log:	Implement io.StringIO.truncate.

diff --git a/pypy/module/_io/test/test_stringio.py b/pypy/module/_io/test/test_stringio.py
--- a/pypy/module/_io/test/test_stringio.py
+++ b/pypy/module/_io/test/test_stringio.py
@@ -73,6 +73,36 @@
         sio.close()
         raises(ValueError, sio.tell)
 
+    def test_truncate(self):
+        import io
+
+        s = u"1234567890"
+        sio = io.StringIO(s)
+
+        raises(ValueError, sio.truncate, -1)
+        sio.seek(6)
+        res = sio.truncate()
+        assert res == 6
+        assert sio.getvalue() == s[:6]
+        res = sio.truncate(4)
+        assert res == 4
+        assert sio.getvalue() == s[:4]
+        # truncate() accepts long objects
+        res = sio.truncate(4L)
+        assert res == 4
+        assert sio.getvalue() == s[:4]
+        assert sio.tell() == 6
+        sio.seek(0, 2)
+        sio.write(s)
+        assert sio.getvalue() == s[:4] + s
+        pos = sio.tell()
+        res = sio.truncate(None)
+        assert res == pos
+        assert sio.tell() == pos
+        raises(TypeError, sio.truncate, '0')
+        sio.close()
+        raises(ValueError, sio.truncate, 0)
+
     def test_write_error(self):
         import io
 

diff --git a/pypy/module/_io/interp_stringio.py b/pypy/module/_io/interp_stringio.py
--- a/pypy/module/_io/interp_stringio.py
+++ b/pypy/module/_io/interp_stringio.py
@@ -100,6 +100,24 @@
         self.pos = pos
         return space.wrap(pos)
 
+    @unwrap_spec('self', ObjSpace, W_Root)
+    def truncate_w(self, space, w_size=None):
+        self._check_closed(space)
+        if space.is_w(w_size, space.w_None):
+            size = self.pos
+        else:
+            size = space.int_w(w_size)
+
+        if size < 0:
+            raise operationerrfmt(space.w_ValueError,
+                "Negative size value %d", size
+            )
+
+        if size < len(self.buf):
+            self.resize_buffer(size)
+
+        return space.wrap(size)
+
     @unwrap_spec('self', ObjSpace)
     def getvalue_w(self, space):
         self._check_closed(space)
@@ -131,6 +149,7 @@
     write = interp2app(W_StringIO.write_w),
     read = interp2app(W_StringIO.read_w),
     seek = interp2app(W_StringIO.seek_w),
+    truncate = interp2app(W_StringIO.truncate_w),
     getvalue = interp2app(W_StringIO.getvalue_w),
     readable = interp2app(W_StringIO.readable_w),
     writable = interp2app(W_StringIO.writable_w),