Add from_buffer and from_buffer_copy class methods to ctypes types.

Lib/ctypes/test/test_frombuffer.py

@@ -0,0 +1,81 @@
+from ctypes import *
+import array
+import gc
+import unittest
+
+class X(Structure):
+    _fields_ = [("c_int", c_int)]
+    init_called = False
+    def __init__(self):
+        self._init_called = True
+
+class Test(unittest.TestCase):
+    def test_fom_buffer(self):
+        a = array.array("i", range(16))
+        x = (c_int * 16).from_buffer(a)
+
+        y = X.from_buffer(a)
+        self.assertEqual(y.c_int, a[0])
+        self.failIf(y.init_called)
+
+        self.assertEqual(x[:], a.tolist())
+
+        a[0], a[-1] = 200, -200
+        self.assertEqual(x[:], a.tolist())
+
+        self.assert_(a in x._objects.values())
+
+        self.assertRaises(ValueError,
+                          c_int.from_buffer, a, -1)
+
+        expected = x[:]
+        del a; gc.collect(); gc.collect(); gc.collect()
+        self.assertEqual(x[:], expected)
+
+        self.assertRaises(TypeError,
+                          (c_char * 16).from_buffer, "a" * 16)
+
+    def test_fom_buffer_with_offset(self):
+        a = array.array("i", range(16))
+        x = (c_int * 15).from_buffer(a, sizeof(c_int))
+
+        self.assertEqual(x[:], a.tolist()[1:])
+        self.assertRaises(ValueError, lambda: (c_int * 16).from_buffer(a, sizeof(c_int)))
+        self.assertRaises(ValueError, lambda: (c_int * 1).from_buffer(a, 16 * sizeof(c_int)))
+
+    def test_from_buffer_copy(self):
+        a = array.array("i", range(16))
+        x = (c_int * 16).from_buffer_copy(a)
+
+        y = X.from_buffer_copy(a)
+        self.assertEqual(y.c_int, a[0])
+        self.failIf(y.init_called)
+
+        self.assertEqual(x[:], range(16))
+
+        a[0], a[-1] = 200, -200
+        self.assertEqual(x[:], range(16))
+
+        self.assertEqual(x._objects, None)
+
+        self.assertRaises(ValueError,
+                          c_int.from_buffer, a, -1)
+
+        del a; gc.collect(); gc.collect(); gc.collect()
+        self.assertEqual(x[:], range(16))
+
+        x = (c_char * 16).from_buffer_copy("a" * 16)
+        self.assertEqual(x[:], "a" * 16)
+
+    def test_fom_buffer_copy_with_offset(self):
+        a = array.array("i", range(16))
+        x = (c_int * 15).from_buffer_copy(a, sizeof(c_int))
+
+        self.assertEqual(x[:], a.tolist()[1:])
+        self.assertRaises(ValueError,
+                          (c_int * 16).from_buffer_copy, a, sizeof(c_int))
+        self.assertRaises(ValueError,
+                          (c_int * 1).from_buffer_copy, a, 16 * sizeof(c_int))
+
+if __name__ == '__main__':
+    unittest.main()