325 lines
7.3 KiB
C++
325 lines
7.3 KiB
C++
/*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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/** \file
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* \ingroup memutil
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*/
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#ifndef __MEM_CACHELIMITER_H__
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#define __MEM_CACHELIMITER_H__
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/**
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* \section MEM_CacheLimiter
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* This class defines a generic memory cache management system
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* to limit memory usage to a fixed global maximum.
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*
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* \note Please use the C-API in MEM_CacheLimiterC-Api.h for code written in C.
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*
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* Usage example:
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*
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* \code{.cpp}
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* class BigFatImage {
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* public:
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* ~BigFatImage() { tell_everyone_we_are_gone(this); }
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* };
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*
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* void doit()
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* {
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* MEM_Cache<BigFatImage> BigFatImages;
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*
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* MEM_Cache_Handle<BigFatImage>* h = BigFatImages.insert(new BigFatImage);
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*
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* BigFatImages.enforce_limits();
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* h->ref();
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*
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* // work with image...
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*
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* h->unref();
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*
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* // leave image in cache.
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* \endcode
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*/
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#include "MEM_Allocator.h"
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#include <list>
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#include <queue>
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#include <vector>
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template<class T> class MEM_CacheLimiter;
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#ifndef __MEM_CACHELIMITERC_API_H__
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extern "C" {
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void MEM_CacheLimiter_set_maximum(size_t m);
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size_t MEM_CacheLimiter_get_maximum();
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void MEM_CacheLimiter_set_disabled(bool disabled);
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bool MEM_CacheLimiter_is_disabled(void);
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};
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#endif
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template<class T> class MEM_CacheLimiterHandle {
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public:
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explicit MEM_CacheLimiterHandle(T *data_, MEM_CacheLimiter<T> *parent_)
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: data(data_), refcount(0), parent(parent_)
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{
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}
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void ref()
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{
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refcount++;
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}
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void unref()
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{
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refcount--;
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}
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T *get()
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{
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return data;
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}
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const T *get() const
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{
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return data;
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}
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int get_refcount() const
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{
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return refcount;
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}
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bool can_destroy() const
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{
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return !data || !refcount;
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}
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bool destroy_if_possible()
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{
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if (can_destroy()) {
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delete data;
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data = NULL;
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unmanage();
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return true;
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}
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return false;
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}
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void unmanage()
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{
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parent->unmanage(this);
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}
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void touch()
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{
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parent->touch(this);
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}
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private:
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friend class MEM_CacheLimiter<T>;
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T *data;
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int refcount;
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int pos;
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MEM_CacheLimiter<T> *parent;
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};
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template<class T> class MEM_CacheLimiter {
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public:
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typedef size_t (*MEM_CacheLimiter_DataSize_Func)(void *data);
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typedef int (*MEM_CacheLimiter_ItemPriority_Func)(void *item, int default_priority);
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typedef bool (*MEM_CacheLimiter_ItemDestroyable_Func)(void *item);
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MEM_CacheLimiter(MEM_CacheLimiter_DataSize_Func data_size_func) : data_size_func(data_size_func)
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{
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}
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~MEM_CacheLimiter()
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{
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int i;
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for (i = 0; i < queue.size(); i++) {
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delete queue[i];
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}
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}
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MEM_CacheLimiterHandle<T> *insert(T *elem)
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{
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queue.push_back(new MEM_CacheLimiterHandle<T>(elem, this));
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queue.back()->pos = queue.size() - 1;
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return queue.back();
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}
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void unmanage(MEM_CacheLimiterHandle<T> *handle)
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{
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int pos = handle->pos;
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queue[pos] = queue.back();
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queue[pos]->pos = pos;
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queue.pop_back();
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delete handle;
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}
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size_t get_memory_in_use()
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{
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size_t size = 0;
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if (data_size_func) {
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int i;
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for (i = 0; i < queue.size(); i++) {
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size += data_size_func(queue[i]->get()->get_data());
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}
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}
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else {
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size = MEM_get_memory_in_use();
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}
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return size;
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}
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void enforce_limits()
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{
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size_t max = MEM_CacheLimiter_get_maximum();
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bool is_disabled = MEM_CacheLimiter_is_disabled();
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size_t mem_in_use, cur_size;
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if (is_disabled) {
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return;
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}
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if (max == 0) {
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return;
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}
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mem_in_use = get_memory_in_use();
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if (mem_in_use <= max) {
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return;
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}
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while (!queue.empty() && mem_in_use > max) {
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MEM_CacheElementPtr elem = get_least_priority_destroyable_element();
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if (!elem)
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break;
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if (data_size_func) {
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cur_size = data_size_func(elem->get()->get_data());
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}
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else {
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cur_size = mem_in_use;
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}
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if (elem->destroy_if_possible()) {
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if (data_size_func) {
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mem_in_use -= cur_size;
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}
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else {
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mem_in_use -= cur_size - MEM_get_memory_in_use();
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}
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}
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}
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}
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void touch(MEM_CacheLimiterHandle<T> *handle)
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{
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/* If we're using custom priority callback re-arranging the queue
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* doesn't make much sense because we'll iterate it all to get
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* least priority element anyway.
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*/
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if (item_priority_func == NULL) {
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queue[handle->pos] = queue.back();
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queue[handle->pos]->pos = handle->pos;
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queue.pop_back();
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queue.push_back(handle);
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handle->pos = queue.size() - 1;
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}
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}
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void set_item_priority_func(MEM_CacheLimiter_ItemPriority_Func item_priority_func)
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{
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this->item_priority_func = item_priority_func;
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}
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void set_item_destroyable_func(MEM_CacheLimiter_ItemDestroyable_Func item_destroyable_func)
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{
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this->item_destroyable_func = item_destroyable_func;
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}
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private:
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typedef MEM_CacheLimiterHandle<T> *MEM_CacheElementPtr;
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typedef std::vector<MEM_CacheElementPtr, MEM_Allocator<MEM_CacheElementPtr>> MEM_CacheQueue;
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typedef typename MEM_CacheQueue::iterator iterator;
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/* Check whether element can be destroyed when enforcing cache limits */
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bool can_destroy_element(MEM_CacheElementPtr &elem)
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{
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if (!elem->can_destroy()) {
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/* Element is referenced */
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return false;
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}
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if (item_destroyable_func) {
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if (!item_destroyable_func(elem->get()->get_data()))
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return false;
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}
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return true;
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}
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MEM_CacheElementPtr get_least_priority_destroyable_element(void)
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{
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if (queue.empty())
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return NULL;
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MEM_CacheElementPtr best_match_elem = NULL;
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if (!item_priority_func) {
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for (iterator it = queue.begin(); it != queue.end(); it++) {
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MEM_CacheElementPtr elem = *it;
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if (!can_destroy_element(elem))
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continue;
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best_match_elem = elem;
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break;
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}
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}
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else {
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int best_match_priority = 0;
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int i;
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for (i = 0; i < queue.size(); i++) {
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MEM_CacheElementPtr elem = queue[i];
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if (!can_destroy_element(elem))
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continue;
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/* by default 0 means highest priority element */
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/* casting a size type to int is questionable,
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but unlikely to cause problems */
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int priority = -((int)(queue.size()) - i - 1);
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priority = item_priority_func(elem->get()->get_data(), priority);
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if (priority < best_match_priority || best_match_elem == NULL) {
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best_match_priority = priority;
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best_match_elem = elem;
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}
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}
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}
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return best_match_elem;
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}
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MEM_CacheQueue queue;
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MEM_CacheLimiter_DataSize_Func data_size_func;
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MEM_CacheLimiter_ItemPriority_Func item_priority_func;
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MEM_CacheLimiter_ItemDestroyable_Func item_destroyable_func;
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};
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#endif // __MEM_CACHELIMITER_H__
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