gh-111765: Move old PyFloat_* tests to Lib/test/test_capi/test_float.py (GH-111766)

1 files changed, 65 insertions, 0 deletions

diff --git a/Lib/test/test_capi/test_float.py b/Lib/test/test_capi/test_float.py
index 95635e8..cb94d56 100644
--- a/Lib/test/test_capi/test_float.py
+++ b/Lib/test/test_capi/test_float.py
@@ -12,6 +12,19 @@ _testcapi = import_helper.import_module('_testcapi')
 
 NULL = None
 
+# For PyFloat_Pack/Unpack*
+BIG_ENDIAN = 0
+LITTLE_ENDIAN = 1
+EPSILON = {
+    2: 2.0 ** -11,  # binary16
+    4: 2.0 ** -24,  # binary32
+    8: 2.0 ** -53,  # binary64
+}
+
+HAVE_IEEE_754 = float.__getformat__("double").startswith("IEEE")
+INF = float("inf")
+NAN = float("nan")
+
 
 class CAPIFloatTest(unittest.TestCase):
     def test_check(self):
@@ -112,6 +125,58 @@ class CAPIFloatTest(unittest.TestCase):
 
         self.assertEqual(getmin(), sys.float_info.min)
 
+    def test_pack(self):
+        # Test PyFloat_Pack2(), PyFloat_Pack4() and PyFloat_Pack8()
+        pack = _testcapi.float_pack
+
+        self.assertEqual(pack(2, 1.5, BIG_ENDIAN), b'>\x00')
+        self.assertEqual(pack(4, 1.5, BIG_ENDIAN), b'?\xc0\x00\x00')
+        self.assertEqual(pack(8, 1.5, BIG_ENDIAN),
+                         b'?\xf8\x00\x00\x00\x00\x00\x00')
+        self.assertEqual(pack(2, 1.5, LITTLE_ENDIAN), b'\x00>')
+        self.assertEqual(pack(4, 1.5, LITTLE_ENDIAN), b'\x00\x00\xc0?')
+        self.assertEqual(pack(8, 1.5, LITTLE_ENDIAN),
+                         b'\x00\x00\x00\x00\x00\x00\xf8?')
+
+    def test_unpack(self):
+        # Test PyFloat_Unpack2(), PyFloat_Unpack4() and PyFloat_Unpack8()
+        unpack = _testcapi.float_unpack
+
+        self.assertEqual(unpack(b'>\x00', BIG_ENDIAN), 1.5)
+        self.assertEqual(unpack(b'?\xc0\x00\x00', BIG_ENDIAN), 1.5)
+        self.assertEqual(unpack(b'?\xf8\x00\x00\x00\x00\x00\x00', BIG_ENDIAN),
+                         1.5)
+        self.assertEqual(unpack(b'\x00>', LITTLE_ENDIAN), 1.5)
+        self.assertEqual(unpack(b'\x00\x00\xc0?', LITTLE_ENDIAN), 1.5)
+        self.assertEqual(unpack(b'\x00\x00\x00\x00\x00\x00\xf8?', LITTLE_ENDIAN),
+                         1.5)
+
+    def test_pack_unpack_roundtrip(self):
+        pack = _testcapi.float_pack
+        unpack = _testcapi.float_unpack
+
+        large = 2.0 ** 100
+        values = [1.0, 1.5, large, 1.0/7, math.pi]
+        if HAVE_IEEE_754:
+            values.extend((INF, NAN))
+        for value in values:
+            for size in (2, 4, 8,):
+                if size == 2 and value == large:
+                    # too large for 16-bit float
+                    continue
+                rel_tol = EPSILON[size]
+                for endian in (BIG_ENDIAN, LITTLE_ENDIAN):
+                    with self.subTest(value=value, size=size, endian=endian):
+                        data = pack(size, value, endian)
+                        value2 = unpack(data, endian)
+                        if math.isnan(value):
+                            self.assertTrue(math.isnan(value2), (value, value2))
+                        elif size < 8:
+                            self.assertTrue(math.isclose(value2, value, rel_tol=rel_tol),
+                                            (value, value2))
+                        else:
+                            self.assertEqual(value2, value)
+
 
 if __name__ == "__main__":
     unittest.main()