[Python-checkins] cpython: Refactor the deque trim logic to eliminate the two separate trim functions.

[raymond.hettinger]

https://hg.python.org/cpython/rev/4c9c0eb6e75c
changeset:   98705:4c9c0eb6e75c
user:        Raymond Hettinger <python at rcn.com>
date:        Sun Oct 11 22:34:48 2015 -0700
summary:
  Refactor the deque trim logic to eliminate the two separate trim functions.

files:
  Modules/_collectionsmodule.c |  39 ++++++++---------------
  1 files changed, 14 insertions(+), 25 deletions(-)


diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -276,29 +276,12 @@
  * the limit. If it has, we get the size back down to the limit by popping an
  * item off of the opposite end.  The methods that can trigger this are append(),
  * appendleft(), extend(), and extendleft().
+ *
+ * The macro to check whether a deque needs to be trimmed uses a single
+ * unsigned test that returns true whenever 0 <= maxlen < Py_SIZE(deque).
  */
 
-static void
-deque_trim_right(dequeobject *deque)
-{
-    if (deque->maxlen >= 0 && Py_SIZE(deque) > deque->maxlen) {
-        PyObject *rv = deque_pop(deque, NULL);
-        assert(rv != NULL);
-        assert(Py_SIZE(deque) <= deque->maxlen);
-        Py_DECREF(rv);
-    }
-}
-
-static void
-deque_trim_left(dequeobject *deque)
-{
-    if (deque->maxlen >= 0 && Py_SIZE(deque) > deque->maxlen) {
-        PyObject *rv = deque_popleft(deque, NULL);
-        assert(rv != NULL);
-        assert(Py_SIZE(deque) <= deque->maxlen);
-        Py_DECREF(rv);
-    }
-}
+#define NEEDS_TRIM(deque, maxlen) ((size_t)(maxlen) < (size_t)(Py_SIZE(deque)))
 
 static PyObject *
 deque_append(dequeobject *deque, PyObject *item)
@@ -319,7 +302,10 @@
     Py_INCREF(item);
     deque->rightindex++;
     deque->rightblock->data[deque->rightindex] = item;
-    deque_trim_left(deque);
+    if (NEEDS_TRIM(deque, deque->maxlen)) {
+        PyObject *rv = deque_popleft(deque, NULL);
+        Py_DECREF(rv);
+    }
     Py_RETURN_NONE;
 }
 
@@ -344,7 +330,10 @@
     Py_INCREF(item);
     deque->leftindex--;
     deque->leftblock->data[deque->leftindex] = item;
-    deque_trim_right(deque);
+    if (NEEDS_TRIM(deque, deque->maxlen)) {
+        PyObject *rv = deque_pop(deque, NULL);
+        Py_DECREF(rv);
+    }
     Py_RETURN_NONE;
 }
 
@@ -433,7 +422,7 @@
         Py_SIZE(deque)++;
         deque->rightindex++;
         deque->rightblock->data[deque->rightindex] = item;
-        if (maxlen >= 0 && Py_SIZE(deque) > maxlen) {
+        if (NEEDS_TRIM(deque, maxlen)) {
             PyObject *rv = deque_popleft(deque, NULL);
             Py_DECREF(rv);
         }
@@ -497,7 +486,7 @@
         Py_SIZE(deque)++;
         deque->leftindex--;
         deque->leftblock->data[deque->leftindex] = item;
-        if (maxlen >= 0 && Py_SIZE(deque) > maxlen) {
+        if (NEEDS_TRIM(deque, maxlen)) {
             PyObject *rv = deque_pop(deque, NULL);
             Py_DECREF(rv);
         }

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