Commit f6a898f9 authored by Tim Peters's avatar Tim Peters

Fix for http://collector.zope.org/Zope/419,

"BTreeItems slice contains 1 too many elements"
This also fixes many related glitches, such as that giving an
out-of-bound slice index raised IndexError instead of clipping.

BTreeItems_slice():  Emulate Python slicing semantics in all cases.

testBTrees.py:  new testSlicing() tests in MappingBase and NormalSetTests
to ensure that slicing of .keys()/.items()/.values() works exactly the
same way as slicing of Python lists, in all one-sided, two-sided and
whole-structure ([:]) cases, with both negative and positive slice indices,
and mixtures of + and -, and whether in bounds or out of bounds.
parent 918da832
......@@ -12,7 +12,7 @@
****************************************************************************/
#define BTREEITEMSTEMPLATE_C "$Id: BTreeItemsTemplate.c,v 1.10 2002/06/09 17:19:05 tim_one Exp $\n"
#define BTREEITEMSTEMPLATE_C "$Id: BTreeItemsTemplate.c,v 1.11 2002/06/09 19:27:48 tim_one Exp $\n"
typedef struct {
PyObject_HEAD
......@@ -20,7 +20,7 @@ typedef struct {
Bucket *currentbucket; /* Current bucket position */
Bucket *lastbucket; /* Last bucket position */
int currentoffset; /* Start count of current bucket*/
int pseudoindex; /* Its an indicator */
int pseudoindex; /* It's an indicator */
int first, last;
char kind;
} BTreeItems;
......@@ -348,10 +348,62 @@ BTreeItems_slice(BTreeItems *self, int ilow, int ihigh)
Bucket *highbucket;
int lowoffset;
int highoffset;
int length = -1; /* len(self), but computed only if needed */
/* Complications:
* A Python slice never raises IndexError, but BTreeItems_seek does.
* Python did only part of index normalization before calling this:
* ilow may be < 0 now, and ihigh may be arbitrarily large. It's
* our responsibility to clip them.
* A Python slice is exclusive of the high index, but a BTreeItems
* struct is inclusive on both ends.
*/
/* First adjust ilow and ihigh to be legit endpoints in the Python
* sense (ilow inclusive, ihigh exclusive). This block duplicates the
* logic from Python's list_slice function (slicing for builtin lists).
*/
if (ilow < 0)
ilow = 0;
else {
if (length < 0)
length = BTreeItems_length(self);
if (ilow > length)
ilow = length;
}
if (ihigh < ilow)
ihigh = ilow;
else {
if (length < 0)
length = BTreeItems_length(self);
if (ihigh > length)
ihigh = length;
}
assert(0 <= ilow && ilow <= ihigh);
assert(length < 0 || ihigh <= length);
/* Now adjust for that our struct is inclusive on both ends. This is
* easy *except* when the slice is empty: there's no good way to spell
* that in an inclusive-on-both-ends scheme. For example, if the
* slice is btree.items([:0]), ilow == ihigh == 0 at this point, and if
* we were to subtract 1 from ihigh that would get interpreted by
* BTreeItems_seek as meaning the *entire* set of items. Setting ilow==1
* and ihigh==0 doesn't work either, as BTreeItems_seek raises IndexError
* if we attempt to seek to ilow==1 when the underlying sequence is empty.
* It seems simplest to deal with empty slices as a special case here.
*/
if (ilow == ihigh) {
/* empty slice */
lowbucket = highbucket = self->currentbucket;
lowoffset = 1;
highoffset = 0;
}
else {
assert(ilow < ihigh);
--ihigh; /* exclusive -> inclusive */
if (BTreeItems_seek(self, ilow) < 0) return NULL;
lowbucket = self->currentbucket;
lowoffset = self->currentoffset;
......@@ -359,7 +411,7 @@ BTreeItems_slice(BTreeItems *self, int ilow, int ihigh)
highbucket = self->currentbucket;
highoffset = self->currentoffset;
}
return newBTreeItems(self->kind,
lowbucket, lowoffset, highbucket, highoffset);
}
......
......@@ -250,6 +250,82 @@ class MappingBase(Base):
self.assertEqual(list(t.keys(6,8)),[], list(t.keys(6,8)))
self.assertEqual(list(t.keys(10,12)),[], list(t.keys(10,12)))
def testSlicing(self):
# Test that slicing of .keys()/.values()/.items() works exactly the
# same way as slicing a Python list with the same contents.
# This tests fixes to several bugs in this area, starting with
# http://collector.zope.org/Zope/419,
# "BTreeItems slice contains 1 too many elements".
t = self.t
for n in range(10):
t.clear()
self.assertEqual(len(t), 0)
keys = []
values = []
items = []
for key in range(n):
value = -2 * key
t[key] = value
keys.append(key)
values.append(value)
items.append((key, value))
self.assertEqual(len(t), n)
kslice = t.keys()
vslice = t.values()
islice = t.items()
self.assertEqual(len(kslice), n)
self.assertEqual(len(vslice), n)
self.assertEqual(len(islice), n)
# Test whole-structure slices.
x = kslice[:]
self.assertEqual(list(x), keys[:])
x = vslice[:]
self.assertEqual(list(x), values[:])
x = islice[:]
self.assertEqual(list(x), items[:])
for lo in range(-2*n, 2*n+1):
# Test one-sided slices.
x = kslice[:lo]
self.assertEqual(list(x), keys[:lo])
x = kslice[lo:]
self.assertEqual(list(x), keys[lo:])
x = vslice[:lo]
self.assertEqual(list(x), values[:lo])
x = vslice[lo:]
self.assertEqual(list(x), values[lo:])
x = islice[:lo]
self.assertEqual(list(x), items[:lo])
x = islice[lo:]
self.assertEqual(list(x), items[lo:])
for hi in range(-2*n, 2*n+1):
# Test two-sided slices.
x = kslice[lo:hi]
self.assertEqual(list(x), keys[lo:hi])
x = vslice[lo:hi]
self.assertEqual(list(x), values[lo:hi])
x = islice[lo:hi]
self.assertEqual(list(x), items[lo:hi])
# The specific test case from Zope collector 419.
t.clear()
for i in xrange(100):
t[i] = 1
tslice = t.items()[20:80]
self.assertEqual(len(tslice), 60)
self.assertEqual(list(tslice), zip(range(20, 80), [1]*60))
class NormalSetTests(Base):
""" Test common to all set types """
......@@ -352,6 +428,39 @@ class NormalSetTests(Base):
self.assertEqual(list(t.keys(6,8)),[], list(t.keys(6,8)))
self.assertEqual(list(t.keys(10,12)),[], list(t.keys(10,12)))
def testSlicing(self):
# Test that slicing of .keys() works exactly the same way as slicing
# a Python list with the same contents.
t = self.t
for n in range(10):
t.clear()
self.assertEqual(len(t), 0)
keys = range(10*n, 11*n)
t.update(keys)
self.assertEqual(len(t), n)
kslice = t.keys()
self.assertEqual(len(kslice), n)
# Test whole-structure slices.
x = kslice[:]
self.assertEqual(list(x), keys[:])
for lo in range(-2*n, 2*n+1):
# Test one-sided slices.
x = kslice[:lo]
self.assertEqual(list(x), keys[:lo])
x = kslice[lo:]
self.assertEqual(list(x), keys[lo:])
for hi in range(-2*n, 2*n+1):
# Test two-sided slices.
x = kslice[lo:hi]
self.assertEqual(list(x), keys[lo:hi])
class ExtendedSetTests(NormalSetTests):
def testLen(self):
t = self.t
......
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