mirror of https://github.com/python/cpython
Issue #15944: memoryview: Allow arbitrary formats when casting to bytes.
Original patch by Martin Panter.
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@ -3564,7 +3564,7 @@ copying.
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the buffer itself is not copied. Supported casts are 1D -> C-contiguous
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and C-contiguous -> 1D.
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Both formats are restricted to single element native formats in
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The destination format is restricted to a single element native format in
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:mod:`struct` syntax. One of the formats must be a byte format
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('B', 'b' or 'c'). The byte length of the result must be the same
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as the original length.
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@ -3645,6 +3645,9 @@ copying.
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.. versionadded:: 3.3
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.. versionchanged:: 3.5
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The source format is no longer restricted when casting to a byte view.
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There are also several readonly attributes available:
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.. attribute:: obj
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@ -2559,8 +2559,7 @@ class TestBufferProtocol(unittest.TestCase):
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ex = ndarray(sitems, shape=[1], format=sfmt)
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msrc = memoryview(ex)
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for dfmt, _, _ in iter_format(1):
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if (not is_memoryview_format(sfmt) or
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not is_memoryview_format(dfmt)):
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if not is_memoryview_format(dfmt):
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self.assertRaises(ValueError, msrc.cast, dfmt,
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[32//dsize])
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else:
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@ -2773,6 +2772,32 @@ class TestBufferProtocol(unittest.TestCase):
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ndim=ndim, shape=shape, strides=strides,
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lst=lst, cast=True)
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if ctypes:
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# format: "T{>l:x:>d:y:}"
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class BEPoint(ctypes.BigEndianStructure):
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_fields_ = [("x", ctypes.c_long), ("y", ctypes.c_double)]
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point = BEPoint(100, 200.1)
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m1 = memoryview(point)
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m2 = m1.cast('B')
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self.assertEqual(m2.obj, point)
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self.assertEqual(m2.itemsize, 1)
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self.assertEqual(m2.readonly, 0)
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self.assertEqual(m2.ndim, 1)
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self.assertEqual(m2.shape, (m2.nbytes,))
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self.assertEqual(m2.strides, (1,))
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self.assertEqual(m2.suboffsets, ())
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x = ctypes.c_double(1.2)
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m1 = memoryview(x)
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m2 = m1.cast('c')
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self.assertEqual(m2.obj, x)
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self.assertEqual(m2.itemsize, 1)
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self.assertEqual(m2.readonly, 0)
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self.assertEqual(m2.ndim, 1)
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self.assertEqual(m2.shape, (m2.nbytes,))
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self.assertEqual(m2.strides, (1,))
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self.assertEqual(m2.suboffsets, ())
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def test_memoryview_tolist(self):
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# Most tolist() tests are in self.verify() etc.
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@ -492,5 +492,26 @@ class ArrayMemorySliceSliceTest(unittest.TestCase,
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pass
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class OtherTest(unittest.TestCase):
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def test_ctypes_cast(self):
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# Issue 15944: Allow all source formats when casting to bytes.
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ctypes = test.support.import_module("ctypes")
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p6 = bytes(ctypes.c_double(0.6))
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d = ctypes.c_double()
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m = memoryview(d).cast("B")
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m[:2] = p6[:2]
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m[2:] = p6[2:]
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self.assertEqual(d.value, 0.6)
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for format in "Bbc":
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with self.subTest(format):
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d = ctypes.c_double()
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m = memoryview(d).cast(format)
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m[:2] = memoryview(p6).cast(format)[:2]
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m[2:] = memoryview(p6).cast(format)[2:]
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self.assertEqual(d.value, 0.6)
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if __name__ == "__main__":
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unittest.main()
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@ -98,6 +98,9 @@ Core and Builtins
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- Issue #24687: Plug refleak on SyntaxError in function parameters
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annotations.
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- Issue #15944: memoryview: Allow arbitrary formats when casting to bytes.
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Patch by Martin Panter.
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Library
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-------
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@ -1197,13 +1197,6 @@ cast_to_1D(PyMemoryViewObject *mv, PyObject *format)
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assert(view->strides == mv->ob_array + view->ndim);
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assert(view->suboffsets == mv->ob_array + 2*view->ndim);
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if (get_native_fmtchar(&srcchar, view->format) < 0) {
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PyErr_SetString(PyExc_ValueError,
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"memoryview: source format must be a native single character "
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"format prefixed with an optional '@'");
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return ret;
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}
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asciifmt = PyUnicode_AsASCIIString(format);
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if (asciifmt == NULL)
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return ret;
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@ -1216,7 +1209,8 @@ cast_to_1D(PyMemoryViewObject *mv, PyObject *format)
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goto out;
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}
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if (!IS_BYTE_FORMAT(srcchar) && !IS_BYTE_FORMAT(destchar)) {
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if ((get_native_fmtchar(&srcchar, view->format) < 0 ||
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!IS_BYTE_FORMAT(srcchar)) && !IS_BYTE_FORMAT(destchar)) {
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PyErr_SetString(PyExc_TypeError,
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"memoryview: cannot cast between two non-byte formats");
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goto out;
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