Minor edits: Tighten-up the halflen logic and touch-up the assertions and comments.
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index d0a47b8..a8938ab 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -3,13 +3,13 @@
/* collections module implementation of a deque() datatype
Written and maintained by Raymond D. Hettinger <python@rcn.com>
- Copyright (c) 2004 Python Software Foundation.
+ Copyright (c) 2004-2013 Python Software Foundation.
All rights reserved.
*/
/* The block length may be set to any number over 1. Larger numbers
* reduce the number of calls to the memory allocator but take more
- * memory. Ideally, BLOCKLEN should be set with an eye to the
+ * memory. Ideally, BLOCKLEN should be set to a multiple of the
* length of a cache line.
*/
@@ -413,7 +413,7 @@
static int
_deque_rotate(dequeobject *deque, Py_ssize_t n)
{
- Py_ssize_t i, m, len=deque->len, halflen=(len+1)>>1;
+ Py_ssize_t i, m, len=deque->len, halflen=len>>1;
block *prevblock;
if (len <= 1)
@@ -426,7 +426,7 @@
n += len;
}
assert(deque->len > 1);
- assert((n < len / 2) || (n > len / -2));
+ assert(-halflen <= n && n <= halflen);
deque->state++;
for (i=0 ; i<n ; ) {
@@ -446,9 +446,7 @@
m = deque->rightindex + 1;
if (m > deque->leftindex)
m = deque->leftindex;
- assert (m > 0);
- assert (deque->leftblock != deque->rightblock ||
- deque->leftindex < deque->rightindex - m + 1);
+ assert (m > 0 && m <= deque->len);
memcpy(&deque->leftblock->data[deque->leftindex - m],
&deque->rightblock->data[deque->rightindex - m + 1],
m * sizeof(PyObject *));
@@ -483,9 +481,7 @@
m = BLOCKLEN - deque->leftindex;
if (m > BLOCKLEN - 1 - deque->rightindex)
m = BLOCKLEN - 1 - deque->rightindex;
- assert (m > 0);
- assert (deque->leftblock != deque->rightblock ||
- deque->leftindex + m < deque->rightindex + 1);
+ assert (m > 0 && m <= deque->len);
memcpy(&deque->rightblock->data[deque->rightindex + 1],
&deque->leftblock->data[deque->leftindex],
m * sizeof(PyObject *));