84 lines
3.0 KiB
C++
84 lines
3.0 KiB
C++
#pragma once
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#include <cstddef>
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#include <type_traits>
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class Object_Pool {
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#if defined(_DEBUG)
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typedef struct free_link_node {
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free_link_node* next;
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}* free_link;
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#endif
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typedef struct chunk_link_node {
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union {
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chunk_link_node* next;
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char padding[sizeof(std::max_align_t)];
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};
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char data[0];
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}* chunk_link;
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public:
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Object_Pool(const Object_Pool&) = delete;
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void operator=(const Object_Pool&) = delete;
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Object_Pool(size_t element_size, size_t element_count) : first_(nullptr), chunk_(nullptr),
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element_size_(element_size),
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element_count_(element_count) {
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release(allocate_from_process_heap()); // preallocate 1 chunk
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}
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Object_Pool(size_t element_size, size_t element_count, std::false_type /*preallocate?*/) : first_(nullptr),
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chunk_(nullptr), element_size_(element_size), element_count_(element_count) {}
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virtual ~Object_Pool() { this->purge(); }
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void purge() {
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if (this->chunk_ == nullptr) return;
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chunk_link_node *p, **q = &this->chunk_;
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while ((p = *q) != nullptr) {
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*q = p->next;
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delete[] (uint8_t*)(p);
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}
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first_ = nullptr;
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}
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void cleanup() {
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if (this->chunk_ == nullptr) return;
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chunk_link_node* chunk = this->chunk_;
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void* last = this->tidy_chunk(chunk);
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while ((chunk = chunk->next) != nullptr) {
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nextof(last) = firstof(chunk);
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last = this->tidy_chunk(chunk);
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}
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nextof(last) = nullptr;
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first_ = firstof(this->chunk_);
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}
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void* get() { return (first_ != nullptr) ? allocate_from_chunk(first_) : allocate_from_process_heap(); }
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void release(void* Ptr) {
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nextof(Ptr) = first_;
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first_ = Ptr;
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}
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private:
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void* allocate_from_chunk(void* current) {
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first_ = nextof(current);
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return current;
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}
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static void* firstof(chunk_link chunk) { return chunk->data; }
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static void*& nextof(void* const ptr) { return *(static_cast<void**>(ptr)); }
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void* allocate_from_process_heap() {
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auto new_chunk = (chunk_link)new uint8_t[sizeof(chunk_link_node) + element_size_ * element_count_];
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#ifdef _DEBUG
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::memset(new_chunk, 0x00, sizeof(chunk_link_node));
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#endif
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nextof(tidy_chunk(new_chunk)) = nullptr;
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// link the new_chunk
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new_chunk->next = this->chunk_;
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this->chunk_ = new_chunk;
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// allocate 1 object
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return allocate_from_chunk(firstof(new_chunk));
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}
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void* tidy_chunk(chunk_link chunk) const {
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char* last = chunk->data + (element_count_ - 1) * element_size_;
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for (char* ptr = chunk->data; ptr < last; ptr += element_size_) nextof(ptr) = (ptr + element_size_);
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return last;
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}
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private:
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void* first_; // link to free head
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chunk_link chunk_; // chunk link
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const size_t element_size_;
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const size_t element_count_;
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};
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