C++解压库内存碎片处理

在C++中，处理内存碎片的方法有很多种。这里，我将向您介绍一种使用自定义内存分配器的方法来减少内存碎片。自定义内存分配器可以根据程序的需求来管理内存，从而降低内存碎片的产生。

以下是一个简单的自定义内存分配器的示例：

#include <iostream>
#include <vector>
#include <cstdlib>
#include <mutex>

class MemoryAllocator {
public:
    MemoryAllocator(size_t totalSize) {
        this->totalSize = totalSize;
        this->memory = new char[totalSize];
        this->freeList = new FreeListNode(totalSize - 1, totalSize - 1);
    }

    ~MemoryAllocator() {
        delete[] this->memory;
        delete this->freeList;
    }

    void* allocate(size_t size) {
        std::lock_guard<std::mutex> lock(mutex);
        FreeListNode* current = freeList;
        FreeListNode* prev = nullptr;

        while (current != nullptr) {
            if (current->size >= size) {
                if (current->size > size + sizeof(FreeListNode)) {
                    FreeListNode* newBlock = new FreeListNode(current->start, current->start + size);
                    newBlock->next = current->next;
                    if (prev != nullptr) {
                        prev->next = newBlock;
                    } else {
                        freeList = newBlock;
                    }
                    current->start += size;
                    current->size -= size;
                } else {
                    current->size = 0;
                }
                return this->memory + current->start;
            }
            prev = current;
            current = current->next;
        }

        return nullptr;
    }

    void deallocate(void* ptr, size_t size) {
        std::lock_guard<std::mutex> lock(mutex);
        FreeListNode* current = freeList;
        FreeListNode* prev = nullptr;

        while (current != nullptr) {
            if (this->memory + current->start == ptr) {
                if (current->size >= size + sizeof(FreeListNode)) {
                    FreeListNode* newBlock = new FreeListNode(current->start + size, current->end);
                    newBlock->next = current->next;
                    if (prev != nullptr) {
                        prev->next = newBlock;
                    } else {
                        freeList = newBlock;
                    }
                    current->size -= size;
                } else {
                    current->size = 0;
                }
                return;
            }
            prev = current;
            current = current->next;
        }
    }

private:
    struct FreeListNode {
        size_t start;
        size_t end;
        size_t size;
        FreeListNode* next;

        FreeListNode(size_t start, size_t end) : start(start), end(end), size(end - start + 1), next(nullptr) {}
    };

    char* memory;
    FreeListNode* freeList;
    std::mutex mutex;
    size_t totalSize;
};

int main() {
    MemoryAllocator allocator(1024);

    void* ptr1 = allocator.allocate(100);
    void* ptr2 = allocator.allocate(200);
    void* ptr3 = allocator.allocate(50);

    allocator.deallocate(ptr2, 200);

    void* ptr4 = allocator.allocate(150);

    return 0;
}

这个示例中，我们创建了一个名为MemoryAllocator的类，它使用一个自定义的内存分配策略来减少内存碎片。MemoryAllocator类包含一个FreeListNode结构体，用于表示内存中的空闲块。allocate方法根据请求的大小查找合适的空闲块，并将其分配给请求者。deallocate方法将释放的内存块添加到空闲列表中。

请注意，这个示例仅用于演示目的，实际应用中可能需要根据具体需求进行调整。在实际项目中，您可能需要考虑使用更高级的内存管理技术，例如内存池、对象池等，以进一步优化内存使用。