Bucket_rangeSearch(): If the min key passed in was larger than the max key

passed in, it was quite possible for this to return *low > *high, and the
caller could crash due to trying to create a list with "negative length".
Changed the routine to consider a range empty if min>max on input, and added
test cases that fail before this patch.

src/BTrees/BucketTemplate.c

@@ -12,7 +12,7 @@
 
  ****************************************************************************/
 
-#define BUCKETTEMPLATE_C "$Id: BucketTemplate.c,v 1.40 2002/06/12 20:19:58 tim_one Exp $\n"
+#define BUCKETTEMPLATE_C "$Id: BucketTemplate.c,v 1.41 2002/06/13 19:19:41 tim_one Exp $\n"
 
 /* Use BUCKET_SEARCH to find the index at which a key belongs.
  * INDEX    An int lvalue to hold the index i such that KEY belongs at
@@ -624,13 +624,15 @@ Bucket_rangeSearch(Bucket *self, PyObject *args, int *low, int *high)
           goto empty;
         }
     }
-  else *high=self->len - 1;
+  else *high = self->len - 1;
 
-  return 0;
+  /* If f < l to begin with, it's quite possible that low > high now. */
+  if (*low <= *high)
+    return 0;
 
  empty:
-  *low=0;
-  *high=-1;
+  *low = 0;
+  *high = -1;
   return 0;
 }
 

src/BTrees/tests/testBTrees.py

@@ -243,12 +243,13 @@ class MappingBase(Base):
         self.assertEqual(list(self.t.items()) , items)
 
     def testEmptyRangeSearches(self):
-        t=self.t
-        t.update([(1,1),(5,5),(9,9)])
-        self.assertEqual(list(t.keys(-6,-4)),[], list(t.keys(-6,-4)))
-        self.assertEqual(list(t.keys(2,4)),[], list(t.keys(2,4)))
-        self.assertEqual(list(t.keys(6,8)),[], list(t.keys(6,8)))
-        self.assertEqual(list(t.keys(10,12)),[], list(t.keys(10,12)))
+        t = self.t
+        t.update([(1,1), (5,5), (9,9)])
+        self.assertEqual(list(t.keys(-6,-4)), [], list(t.keys(-6,-4)))
+        self.assertEqual(list(t.keys(2,4)), [], list(t.keys(2,4)))
+        self.assertEqual(list(t.keys(6,8)), [], list(t.keys(6,8)))
+        self.assertEqual(list(t.keys(10,12)), [], list(t.keys(10,12)))
+        self.assertEqual(list(t.keys(9, 1)), [], list(t.keys(9, 1)))
 
     def testSlicing(self):
         # Test that slicing of .keys()/.values()/.items() works exactly the
@@ -421,12 +422,13 @@ class NormalSetTests(Base):
         self.assertEqual(list(self.t.keys()) , items)
 
     def testEmptyRangeSearches(self):
-        t=self.t
-        t.update([1,5,9])
-        self.assertEqual(list(t.keys(-6,-4)),[], list(t.keys(-6,-4)))
-        self.assertEqual(list(t.keys(2,4)),[], list(t.keys(2,4)))
-        self.assertEqual(list(t.keys(6,8)),[], list(t.keys(6,8)))
-        self.assertEqual(list(t.keys(10,12)),[], list(t.keys(10,12)))
+        t = self.t
+        t.update([1, 5, 9])
+        self.assertEqual(list(t.keys(-6,-4)), [], list(t.keys(-6,-4)))
+        self.assertEqual(list(t.keys(2,4)), [], list(t.keys(2,4)))
+        self.assertEqual(list(t.keys(6,8)), [], list(t.keys(6,8)))
+        self.assertEqual(list(t.keys(10,12)), [], list(t.keys(10,12)))
+        self.assertEqual(list(t.keys(9,1)), [], list(t.keys(9,1)))
 
     def testSlicing(self):
         # Test that slicing of .keys() works exactly the same way as slicing