312 lines
7.9 KiB
C
312 lines
7.9 KiB
C
/* cache .c - a LRU cache
|
|
*
|
|
* Copyright (C) 2004-2010 Gerhard Häring <gh@ghaering.de>
|
|
*
|
|
* This file is part of pysqlite.
|
|
*
|
|
* This software is provided 'as-is', without any express or implied
|
|
* warranty. In no event will the authors be held liable for any damages
|
|
* arising from the use of this software.
|
|
*
|
|
* Permission is granted to anyone to use this software for any purpose,
|
|
* including commercial applications, and to alter it and redistribute it
|
|
* freely, subject to the following restrictions:
|
|
*
|
|
* 1. The origin of this software must not be misrepresented; you must not
|
|
* claim that you wrote the original software. If you use this software
|
|
* in a product, an acknowledgment in the product documentation would be
|
|
* appreciated but is not required.
|
|
* 2. Altered source versions must be plainly marked as such, and must not be
|
|
* misrepresented as being the original software.
|
|
* 3. This notice may not be removed or altered from any source distribution.
|
|
*/
|
|
|
|
#include "cache.h"
|
|
#include <limits.h>
|
|
|
|
/* only used internally */
|
|
pysqlite_Node* pysqlite_new_node(PyObject* key, PyObject* data)
|
|
{
|
|
pysqlite_Node* node;
|
|
|
|
node = (pysqlite_Node*) (pysqlite_NodeType->tp_alloc(pysqlite_NodeType, 0));
|
|
if (!node) {
|
|
return NULL;
|
|
}
|
|
|
|
Py_INCREF(key);
|
|
node->key = key;
|
|
|
|
Py_INCREF(data);
|
|
node->data = data;
|
|
|
|
node->prev = NULL;
|
|
node->next = NULL;
|
|
|
|
return node;
|
|
}
|
|
|
|
void pysqlite_node_dealloc(pysqlite_Node* self)
|
|
{
|
|
PyTypeObject *tp = Py_TYPE(self);
|
|
|
|
Py_DECREF(self->key);
|
|
Py_DECREF(self->data);
|
|
|
|
tp->tp_free(self);
|
|
Py_DECREF(tp);
|
|
}
|
|
|
|
int pysqlite_cache_init(pysqlite_Cache* self, PyObject* args, PyObject* kwargs)
|
|
{
|
|
PyObject* factory;
|
|
int size = 10;
|
|
|
|
self->factory = NULL;
|
|
|
|
if (!PyArg_ParseTuple(args, "O|i", &factory, &size)) {
|
|
return -1;
|
|
}
|
|
|
|
/* minimum cache size is 5 entries */
|
|
if (size < 5) {
|
|
size = 5;
|
|
}
|
|
self->size = size;
|
|
self->first = NULL;
|
|
self->last = NULL;
|
|
|
|
self->mapping = PyDict_New();
|
|
if (!self->mapping) {
|
|
return -1;
|
|
}
|
|
|
|
Py_INCREF(factory);
|
|
self->factory = factory;
|
|
|
|
self->decref_factory = 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
void pysqlite_cache_dealloc(pysqlite_Cache* self)
|
|
{
|
|
PyTypeObject *tp = Py_TYPE(self);
|
|
pysqlite_Node* node;
|
|
pysqlite_Node* delete_node;
|
|
|
|
if (!self->factory) {
|
|
/* constructor failed, just get out of here */
|
|
return;
|
|
}
|
|
|
|
/* iterate over all nodes and deallocate them */
|
|
node = self->first;
|
|
while (node) {
|
|
delete_node = node;
|
|
node = node->next;
|
|
Py_DECREF(delete_node);
|
|
}
|
|
|
|
if (self->decref_factory) {
|
|
Py_DECREF(self->factory);
|
|
}
|
|
Py_DECREF(self->mapping);
|
|
|
|
tp->tp_free(self);
|
|
Py_DECREF(tp);
|
|
}
|
|
|
|
PyObject* pysqlite_cache_get(pysqlite_Cache* self, PyObject* key)
|
|
{
|
|
pysqlite_Node* node;
|
|
pysqlite_Node* ptr;
|
|
PyObject* data;
|
|
|
|
node = (pysqlite_Node*)PyDict_GetItemWithError(self->mapping, key);
|
|
if (node) {
|
|
/* an entry for this key already exists in the cache */
|
|
|
|
/* increase usage counter of the node found */
|
|
if (node->count < LONG_MAX) {
|
|
node->count++;
|
|
}
|
|
|
|
/* if necessary, reorder entries in the cache by swapping positions */
|
|
if (node->prev && node->count > node->prev->count) {
|
|
ptr = node->prev;
|
|
|
|
while (ptr->prev && node->count > ptr->prev->count) {
|
|
ptr = ptr->prev;
|
|
}
|
|
|
|
if (node->next) {
|
|
node->next->prev = node->prev;
|
|
} else {
|
|
self->last = node->prev;
|
|
}
|
|
if (node->prev) {
|
|
node->prev->next = node->next;
|
|
}
|
|
if (ptr->prev) {
|
|
ptr->prev->next = node;
|
|
} else {
|
|
self->first = node;
|
|
}
|
|
|
|
node->next = ptr;
|
|
node->prev = ptr->prev;
|
|
if (!node->prev) {
|
|
self->first = node;
|
|
}
|
|
ptr->prev = node;
|
|
}
|
|
}
|
|
else if (PyErr_Occurred()) {
|
|
return NULL;
|
|
}
|
|
else {
|
|
/* There is no entry for this key in the cache, yet. We'll insert a new
|
|
* entry in the cache, and make space if necessary by throwing the
|
|
* least used item out of the cache. */
|
|
|
|
if (PyDict_GET_SIZE(self->mapping) == self->size) {
|
|
if (self->last) {
|
|
node = self->last;
|
|
|
|
if (PyDict_DelItem(self->mapping, self->last->key) != 0) {
|
|
return NULL;
|
|
}
|
|
|
|
if (node->prev) {
|
|
node->prev->next = NULL;
|
|
}
|
|
self->last = node->prev;
|
|
node->prev = NULL;
|
|
|
|
Py_DECREF(node);
|
|
}
|
|
}
|
|
|
|
/* We cannot replace this by PyObject_CallOneArg() since
|
|
* PyObject_CallFunction() has a special case when using a
|
|
* single tuple as argument. */
|
|
data = PyObject_CallFunction(self->factory, "O", key);
|
|
|
|
if (!data) {
|
|
return NULL;
|
|
}
|
|
|
|
node = pysqlite_new_node(key, data);
|
|
if (!node) {
|
|
return NULL;
|
|
}
|
|
node->prev = self->last;
|
|
|
|
Py_DECREF(data);
|
|
|
|
if (PyDict_SetItem(self->mapping, key, (PyObject*)node) != 0) {
|
|
Py_DECREF(node);
|
|
return NULL;
|
|
}
|
|
|
|
if (self->last) {
|
|
self->last->next = node;
|
|
} else {
|
|
self->first = node;
|
|
}
|
|
self->last = node;
|
|
}
|
|
|
|
Py_INCREF(node->data);
|
|
return node->data;
|
|
}
|
|
|
|
PyObject* pysqlite_cache_display(pysqlite_Cache* self, PyObject* args)
|
|
{
|
|
pysqlite_Node* ptr;
|
|
PyObject* prevkey;
|
|
PyObject* nextkey;
|
|
PyObject* display_str;
|
|
|
|
ptr = self->first;
|
|
|
|
while (ptr) {
|
|
if (ptr->prev) {
|
|
prevkey = ptr->prev->key;
|
|
} else {
|
|
prevkey = Py_None;
|
|
}
|
|
|
|
if (ptr->next) {
|
|
nextkey = ptr->next->key;
|
|
} else {
|
|
nextkey = Py_None;
|
|
}
|
|
|
|
display_str = PyUnicode_FromFormat("%S <- %S -> %S\n",
|
|
prevkey, ptr->key, nextkey);
|
|
if (!display_str) {
|
|
return NULL;
|
|
}
|
|
PyObject_Print(display_str, stdout, Py_PRINT_RAW);
|
|
Py_DECREF(display_str);
|
|
|
|
ptr = ptr->next;
|
|
}
|
|
|
|
Py_RETURN_NONE;
|
|
}
|
|
|
|
static PyType_Slot pysqlite_NodeType_slots[] = {
|
|
{Py_tp_dealloc, pysqlite_node_dealloc},
|
|
{Py_tp_new, PyType_GenericNew},
|
|
{0, NULL},
|
|
};
|
|
|
|
static PyType_Spec pysqlite_NodeType_spec = {
|
|
.name = MODULE_NAME ".Node",
|
|
.basicsize = sizeof(pysqlite_Node),
|
|
.flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
|
|
.slots = pysqlite_NodeType_slots,
|
|
};
|
|
PyTypeObject *pysqlite_NodeType = NULL;
|
|
|
|
static PyMethodDef cache_methods[] = {
|
|
{"get", (PyCFunction)pysqlite_cache_get, METH_O,
|
|
PyDoc_STR("Gets an entry from the cache or calls the factory function to produce one.")},
|
|
{"display", (PyCFunction)pysqlite_cache_display, METH_NOARGS,
|
|
PyDoc_STR("For debugging only.")},
|
|
{NULL, NULL}
|
|
};
|
|
|
|
static PyType_Slot pysqlite_CacheType_slots[] = {
|
|
{Py_tp_dealloc, pysqlite_cache_dealloc},
|
|
{Py_tp_methods, cache_methods},
|
|
{Py_tp_new, PyType_GenericNew},
|
|
{Py_tp_init, pysqlite_cache_init},
|
|
{0, NULL},
|
|
};
|
|
|
|
static PyType_Spec pysqlite_CacheType_spec = {
|
|
.name = MODULE_NAME ".Cache",
|
|
.basicsize = sizeof(pysqlite_Cache),
|
|
.flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
|
|
.slots = pysqlite_CacheType_slots,
|
|
};
|
|
PyTypeObject *pysqlite_CacheType = NULL;
|
|
|
|
extern int pysqlite_cache_setup_types(PyObject *mod)
|
|
{
|
|
pysqlite_NodeType = (PyTypeObject *)PyType_FromModuleAndSpec(mod, &pysqlite_NodeType_spec, NULL);
|
|
if (pysqlite_NodeType == NULL) {
|
|
return -1;
|
|
}
|
|
|
|
pysqlite_CacheType = (PyTypeObject *)PyType_FromModuleAndSpec(mod, &pysqlite_CacheType_spec, NULL);
|
|
if (pysqlite_CacheType == NULL) {
|
|
return -1;
|
|
}
|
|
return 0;
|
|
}
|