cpython/Modules/_sqlite/cache.c at v3.6.15 · python/cpython · GitHub

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/* cache .c - a LRU cache

* 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)

{

Py_DECREF(self->key);

Py_DECREF(self->data);

Py_TYPE(self)->tp_free((PyObject*)self);

}

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)

{

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);

Py_TYPE(self)->tp_free((PyObject*)self);

}

PyObject* pysqlite_cache_get(pysqlite_Cache* self, PyObject* args)

{

PyObject* key = args;

pysqlite_Node* node;

pysqlite_Node* ptr;

PyObject* data;

node = (pysqlite_Node*)PyDict_GetItem(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 {

/* 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_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);

}

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 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}

};

PyTypeObject pysqlite_NodeType = {

PyVarObject_HEAD_INIT(NULL, 0)

MODULE_NAME "Node", /* tp_name */

sizeof(pysqlite_Node), /* tp_basicsize */

0, /* tp_itemsize */

(destructor)pysqlite_node_dealloc, /* tp_dealloc */

0, /* tp_print */

0, /* tp_getattr */

0, /* tp_setattr */

0, /* tp_reserved */

0, /* tp_repr */

0, /* tp_as_number */

0, /* tp_as_sequence */

0, /* tp_as_mapping */

0, /* tp_hash */

0, /* tp_call */

0, /* tp_str */

0, /* tp_getattro */

0, /* tp_setattro */

0, /* tp_as_buffer */

Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE, /* tp_flags */

0, /* tp_doc */

0, /* tp_traverse */

0, /* tp_clear */

0, /* tp_richcompare */

0, /* tp_weaklistoffset */

0, /* tp_iter */

0, /* tp_iternext */

0, /* tp_methods */

0, /* tp_members */

0, /* tp_getset */

0, /* tp_base */

0, /* tp_dict */

0, /* tp_descr_get */

0, /* tp_descr_set */

0, /* tp_dictoffset */

(initproc)0, /* tp_init */

0, /* tp_alloc */

0, /* tp_new */

0 /* tp_free */

};

PyTypeObject pysqlite_CacheType = {

PyVarObject_HEAD_INIT(NULL, 0)

MODULE_NAME ".Cache", /* tp_name */

sizeof(pysqlite_Cache), /* tp_basicsize */

0, /* tp_itemsize */

(destructor)pysqlite_cache_dealloc, /* tp_dealloc */

0, /* tp_print */

0, /* tp_getattr */

0, /* tp_setattr */

0, /* tp_reserved */

0, /* tp_repr */

0, /* tp_as_number */

0, /* tp_as_sequence */

0, /* tp_as_mapping */

0, /* tp_hash */

0, /* tp_call */

0, /* tp_str */

0, /* tp_getattro */

0, /* tp_setattro */

0, /* tp_as_buffer */

Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE, /* tp_flags */

0, /* tp_doc */

0, /* tp_traverse */

0, /* tp_clear */

0, /* tp_richcompare */

0, /* tp_weaklistoffset */

0, /* tp_iter */

0, /* tp_iternext */

cache_methods, /* tp_methods */

0, /* tp_members */

0, /* tp_getset */

0, /* tp_base */

0, /* tp_dict */

0, /* tp_descr_get */

0, /* tp_descr_set */

0, /* tp_dictoffset */

(initproc)pysqlite_cache_init, /* tp_init */

0, /* tp_alloc */

0, /* tp_new */

0 /* tp_free */

};

extern int pysqlite_cache_setup_types(void)

{

int rc;

pysqlite_NodeType.tp_new = PyType_GenericNew;

pysqlite_CacheType.tp_new = PyType_GenericNew;

rc = PyType_Ready(&pysqlite_NodeType);

if (rc < 0) {

return rc;

}

rc = PyType_Ready(&pysqlite_CacheType);

return rc;

}

cpython/Modules/_sqlite/cache.c at v3.6.15 · python/cpython · GitHub

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