Issue #25155: Fix _PyTime_Divide() rounding

vstinner · vstinner · commit ec26f83f2ea1 · 2015-09-18T14:21:14.000+02:00
_PyTime_Divide() rounding was wrong: copy code from Python default which has
now much better unit tests.
diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py
@@ -946,14 +946,14 @@ def test_milliseconds(self):
             # nanoseconds
             (1, 0, FLOOR),
             (1, 1, CEILING),
-            (-1, 0, FLOOR),
-            (-1, -1, CEILING),
+            (-1, -1, FLOOR),
+            (-1, 0, CEILING),
 
             # seconds + nanoseconds
             (1234 * MS_TO_NS + 1, 1234, FLOOR),
             (1234 * MS_TO_NS + 1, 1235, CEILING),
-            (-1234 * MS_TO_NS - 1, -1234, FLOOR),
-            (-1234 * MS_TO_NS - 1, -1235, CEILING),
+            (-1234 * MS_TO_NS - 1, -1235, FLOOR),
+            (-1234 * MS_TO_NS - 1, -1234, CEILING),
         ):
             with self.subTest(nanoseconds=ns, milliseconds=ms, round=rnd):
                 self.assertEqual(PyTime_AsMilliseconds(ns, rnd), ms)
@@ -983,14 +983,14 @@ def test_microseconds(self):
             # nanoseconds
             (1, 0, FLOOR),
             (1, 1, CEILING),
-            (-1, 0, FLOOR),
-            (-1, -1, CEILING),
+            (-1, -1, FLOOR),
+            (-1, 0, CEILING),
 
             # seconds + nanoseconds
             (1234 * US_TO_NS + 1, 1234, FLOOR),
             (1234 * US_TO_NS + 1, 1235, CEILING),
-            (-1234 * US_TO_NS - 1, -1234, FLOOR),
-            (-1234 * US_TO_NS - 1, -1235, CEILING),
+            (-1234 * US_TO_NS - 1, -1235, FLOOR),
+            (-1234 * US_TO_NS - 1, -1234, CEILING),
         ):
             with self.subTest(nanoseconds=ns, milliseconds=ms, round=rnd):
                 self.assertEqual(PyTime_AsMicroseconds(ns, rnd), ms)
diff --git a/Python/pytime.c b/Python/pytime.c
@@ -305,17 +305,22 @@ _PyTime_AsNanosecondsObject(_PyTime_t t)
 }
 
 static _PyTime_t
-_PyTime_Divide(_PyTime_t t, _PyTime_t k, _PyTime_round_t round)
+_PyTime_Divide(const _PyTime_t t, const _PyTime_t k,
+               const _PyTime_round_t round)
 {
     assert(k > 1);
     if (round == _PyTime_ROUND_CEILING) {
         if (t >= 0)
             return (t + k - 1) / k;
+        else
+            return t / k;
+    }
+    else {
+        if (t >= 0)
+            return t / k;
         else
             return (t - (k - 1)) / k;
     }
-    else
-        return t / k;
 }
 
 _PyTime_t

Original file line number	Diff line number	Diff line change
`@@ -305,17 +305,22 @@ _PyTime_AsNanosecondsObject(_PyTime_t t)`
`305`	`305`	`}`
`306`	`306`
`307`	`307`	`static _PyTime_t`
`308`		`-_PyTime_Divide(_PyTime_t t, _PyTime_t k, _PyTime_round_t round)`
	`308`	`+_PyTime_Divide(const _PyTime_t t, const _PyTime_t k,`
	`309`	`+ const _PyTime_round_t round)`
`309`	`310`	`{`
`310`	`311`	`assert(k > 1);`
`311`	`312`	`if (round == _PyTime_ROUND_CEILING) {`
`312`	`313`	`if (t >= 0)`
`313`	`314`	`return (t + k - 1) / k;`
	`315`	`+ else`
	`316`	`+ return t / k;`
	`317`	`+ }`
	`318`	`+ else {`
	`319`	`+ if (t >= 0)`
	`320`	`+ return t / k;`
`314`	`321`	`else`
`315`	`322`	`return (t - (k - 1)) / k;`
`316`	`323`	`}`
`317`		`- else`
`318`		`- return t / k;`
`319`	`324`	`}`
`320`	`325`
`321`	`326`	`_PyTime_t`