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bpo-36482: let struct module's internal cache use FIFO policy #12624

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bpo-36482: let struct module's internal cache use FIFO policy #12624

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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2019-03-30-10-44-19.bpo-36482.Fl5Ok8.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Let struct module's internal cache use FIFO policy. Patch by Ma Lin.
16 changes: 12 additions & 4 deletions Modules/_struct.c
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Expand Up @@ -2068,13 +2068,15 @@ PyTypeObject PyStructType = {

/* ---- Standalone functions ---- */

#define MAXCACHE 100
#define MAXCACHE 512
static PyObject *cache = NULL;

static int
cache_struct_converter(PyObject *fmt, PyStructObject **ptr)
{
PyObject * s_object;
PyObject *s_object;
PyObject *key, *value;
Py_ssize_t pos;

if (fmt == NULL) {
Py_DECREF(*ptr);
Expand All @@ -2100,8 +2102,14 @@ cache_struct_converter(PyObject *fmt, PyStructObject **ptr)

s_object = PyObject_CallFunctionObjArgs((PyObject *)(&PyStructType), fmt, NULL);
if (s_object != NULL) {
if (PyDict_GET_SIZE(cache) >= MAXCACHE)
PyDict_Clear(cache);
if (PyDict_GET_SIZE(cache) >= MAXCACHE) {
/* Drop the oldest item */
pos = 0;
if (PyDict_Next(cache, &pos, &key, &value)) {
if (PyDict_DelItem(cache, key) == -1)
PyErr_Clear();
}
}
/* Attempt to cache the result */
if (PyDict_SetItem(cache, fmt, s_object) == -1)
PyErr_Clear();
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