|
|
/* cache .c - a LRU cache
* * Copyright (C) 2004-2010 Gerhard H�ring <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 "sqlitecompat.h"
#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* fmt_args; PyObject* template; PyObject* display_str;
ptr = self->first;
while (ptr) { if (ptr->prev) { prevkey = ptr->prev->key; } else { prevkey = Py_None; } Py_INCREF(prevkey);
if (ptr->next) { nextkey = ptr->next->key; } else { nextkey = Py_None; } Py_INCREF(nextkey);
fmt_args = Py_BuildValue("OOO", prevkey, ptr->key, nextkey); if (!fmt_args) { return NULL; } template = PyString_FromString("%s <- %s ->%s\n"); if (!template) { Py_DECREF(fmt_args); return NULL; } display_str = PyString_Format(template, fmt_args); Py_DECREF(template); Py_DECREF(fmt_args); if (!display_str) { return NULL; } PyObject_Print(display_str, stdout, Py_PRINT_RAW); Py_DECREF(display_str);
Py_DECREF(prevkey); Py_DECREF(nextkey);
ptr = ptr->next; }
Py_INCREF(Py_None); return Py_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_compare */ 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_compare */ 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;}
|
