| /* 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 "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; | |
| } |