[pypy-commit] pypy default: Try to fix rounding in datetime.fromtimestamp(). Mostly done

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: 
Changeset: r44888:c5617952be56
Date: 2011-06-11 21:37 +0200
http://bitbucket.org/pypy/pypy/changeset/c5617952be56/

Log:	Try to fix rounding in datetime.fromtimestamp(). Mostly done by
	trying out reasonable-looking alternatives until found one that
	matches CPython's behavior. I *think* that the new test covers all
	cases, so it should work.

diff --git a/lib_pypy/datetime.py b/lib_pypy/datetime.py
--- a/lib_pypy/datetime.py
+++ b/lib_pypy/datetime.py
@@ -1422,12 +1422,17 @@
             converter = _time.localtime
         else:
             converter = _time.gmtime
-        if 1 - (t % 1.0) < 0.000001:
-            t = float(int(t)) + 1
-        if t < 0:
-            t -= 1
+        if t < 0.0:
+            us = int(round(((-t) % 1.0) * 1000000))
+            if us > 0:
+                us = 1000000 - us
+                t -= 1.0
+        else:
+            us = int(round((t % 1.0) * 1000000))
+            if us == 1000000:
+                us = 0
+                t += 1.0
         y, m, d, hh, mm, ss, weekday, jday, dst = converter(t)
-        us = int((t % 1.0) * 1000000)
         ss = min(ss, 59)    # clamp out leap seconds if the platform has them
         result = cls(y, m, d, hh, mm, ss, us, tz)
         if tz is not None:
diff --git a/lib_pypy/pypy_test/test_datetime.py b/lib_pypy/pypy_test/test_datetime.py
--- a/lib_pypy/pypy_test/test_datetime.py
+++ b/lib_pypy/pypy_test/test_datetime.py
@@ -32,4 +32,28 @@
     assert datetime.datetime.utcfromtimestamp(a).microsecond == 0
     assert datetime.datetime.utcfromtimestamp(a).second == 1
 
-    
+def test_more_datetime_rounding():
+    # this test verified on top of CPython 2.7 (using a plain
+    # "import datetime" above)
+    expected_results = {
+        -1000.0: 'datetime.datetime(1970, 1, 1, 0, 43, 20)',
+        -999.9999996: 'datetime.datetime(1970, 1, 1, 0, 43, 20)',
+        -999.4: 'datetime.datetime(1970, 1, 1, 0, 43, 20, 600000)',
+        -999.0000004: 'datetime.datetime(1970, 1, 1, 0, 43, 21)',
+        -1.0: 'datetime.datetime(1970, 1, 1, 0, 59, 59)',
+        -0.9999996: 'datetime.datetime(1970, 1, 1, 0, 59, 59)',
+        -0.4: 'datetime.datetime(1970, 1, 1, 0, 59, 59, 600000)',
+        -0.0000004: 'datetime.datetime(1970, 1, 1, 1, 0)',
+        0.0: 'datetime.datetime(1970, 1, 1, 1, 0)',
+        0.0000004: 'datetime.datetime(1970, 1, 1, 1, 0)',
+        0.4: 'datetime.datetime(1970, 1, 1, 1, 0, 0, 400000)',
+        0.9999996: 'datetime.datetime(1970, 1, 1, 1, 0, 1)',
+        1000.0: 'datetime.datetime(1970, 1, 1, 1, 16, 40)',
+        1000.0000004: 'datetime.datetime(1970, 1, 1, 1, 16, 40)',
+        1000.4: 'datetime.datetime(1970, 1, 1, 1, 16, 40, 400000)',
+        1000.9999996: 'datetime.datetime(1970, 1, 1, 1, 16, 41)',
+        1293843661.191: 'datetime.datetime(2011, 1, 1, 2, 1, 1, 191000)',
+        }
+    for t in sorted(expected_results):
+        dt = datetime.datetime.fromtimestamp(t)
+        assert repr(dt) == expected_results[t]