[Python-checkins] cpython: Hoist the deque->maxlen lookup out of the inner-loop.

[raymond.hettinger]

https://hg.python.org/cpython/rev/0c8a9cafb24c
changeset:   98690:0c8a9cafb24c
user:        Raymond Hettinger <python at rcn.com>
date:        Sun Oct 11 09:43:50 2015 -0700
summary:
  Hoist the deque->maxlen lookup out of the inner-loop.

files:
  Modules/_collectionsmodule.c |  16 ++++++++++------
  1 files changed, 10 insertions(+), 6 deletions(-)


diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -385,7 +385,7 @@
 {
     PyObject *it, *item;
     PyObject *(*iternext)(PyObject *);
-    int trim = (deque->maxlen >= 0);
+    Py_ssize_t maxlen = deque->maxlen;
 
     /* Handle case where id(deque) == id(iterable) */
     if ((PyObject *)deque == iterable) {
@@ -433,8 +433,10 @@
         Py_SIZE(deque)++;
         deque->rightindex++;
         deque->rightblock->data[deque->rightindex] = item;
-        if (trim)
-            deque_trim_left(deque);
+        if (maxlen >= 0 && Py_SIZE(deque) > maxlen) {
+            PyObject *rv = deque_popleft(deque, NULL);
+            Py_DECREF(rv);
+        }
     }
     return finalize_iterator(it);
 }
@@ -447,7 +449,7 @@
 {
     PyObject *it, *item;
     PyObject *(*iternext)(PyObject *);
-    int trim = (deque->maxlen >= 0);
+    Py_ssize_t maxlen = deque->maxlen;
 
     /* Handle case where id(deque) == id(iterable) */
     if ((PyObject *)deque == iterable) {
@@ -495,8 +497,10 @@
         Py_SIZE(deque)++;
         deque->leftindex--;
         deque->leftblock->data[deque->leftindex] = item;
-        if (trim)
-            deque_trim_right(deque);
+        if (maxlen >= 0 && Py_SIZE(deque) > maxlen) {
+            PyObject *rv = deque_pop(deque, NULL);
+            Py_DECREF(rv);
+        }
     }
     return finalize_iterator(it);
 }

-- 
Repository URL: https://hg.python.org/cpython