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C语言-简单实现单片机中的malloc示例

news 2025/8/5 9:53:02

概述

在实际项目中，有些单片机资源紧缺，需要mallloc内存，库又没有自带malloc函数时，此时，就需要手动编写，在此做个笔录。（已在项目上使用），还可进入对齐管理机制。

直接上源码 ^_^

一、示例1：

1、mem_malloc.h文件

#ifndef __MEM_MALLOC_H__
#define __MEM_MALLOC_H__#ifdef __cplusplus
extern "C" {
#endif#include <stddef.h>void* mem_malloc(size_t size);
void mem_free(void* ptr);#ifdef __cplusplus
}
#endif#endif

2、mem_malloc.c文件

#include "mem_malloc.h"
#include "stdint.h"// 定义内存块结构
typedef struct MemoryBlock {size_t size;struct MemoryBlock* next;
} MemoryBlock;// 定义内存池起始地址
#define MEMORY_POOL_SIZE 1024
static uint8_t memoryPool[MEMORY_POOL_SIZE];// 全局指针，指向内存池起始位置
static MemoryBlock* memoryPoolPtr = NULL;// 初始化内存池
void memoryPoolInit(void)
{memoryPoolPtr = (MemoryBlock*)memoryPool;memoryPoolPtr->size = MEMORY_POOL_SIZE - sizeof(MemoryBlock);memoryPoolPtr->next = NULL;
}// 分配内存
void* mem_malloc(size_t size)
{//memoryPoolInit();if (size == 0)return NULL;MemoryBlock* currentBlock = memoryPoolPtr;//MemoryBlock* prevBlock = NULL;// 遍历内存池中的内存块，找到合适大小的内存块while (currentBlock != NULL) {if (currentBlock->size >= size + sizeof(MemoryBlock)) {// 如果当前内存块大于所需内存，分配内存if (currentBlock->size >= size + sizeof(MemoryBlock) + sizeof(size_t)) {MemoryBlock* newBlock = (MemoryBlock*)((uint8_t*)currentBlock + sizeof(MemoryBlock) + size);newBlock->size = currentBlock->size - sizeof(MemoryBlock) - size;newBlock->next = currentBlock->next;currentBlock->next = newBlock;currentBlock->size = size;}// 返回分配的内存块的地址return (uint8_t*)currentBlock + sizeof(MemoryBlock);}//prevBlock = currentBlock;currentBlock = currentBlock->next;}// 没有足够的内存块可供分配return NULL;
}// 释放内存
void mem_free(void* ptr)
{if (ptr == NULL)return;MemoryBlock* block = (MemoryBlock*)((uint8_t*)ptr - sizeof(MemoryBlock));block->next = memoryPoolPtr;memoryPoolPtr = block;
}// 示例代码
int main(void) 
{// 初始化内存池memoryPoolInit();// 分配内存int* intPtr = (int*)mem_malloc(sizeof(int));if (intPtr != NULL) {*intPtr = 42;free(intPtr);}return 0;
}

二、示例2：

#include <stdio.h>#define MEMORY_POOL_SIZE (1024 * 2)unsigned char memoryBuff[MEMORY_POOL_SIZE];typedef struct {unsigned char* start;size_t size;
} MemoryBlock;static MemoryBlock memoryBlocks[MEMORY_POOL_SIZE] = { 0 };
static int numBlocks = 0;// 从内存池中分配内存
void* mem_malloc(size_t size)
{// 寻找空闲块for (int i = 0; i < numBlocks; i++) {if (memoryBlocks[i].size == 0 && size <= MEMORY_POOL_SIZE) {// 找到合适大小的内存块，返回内存块地址memoryBlocks[i].start = memoryBuff;memoryBlocks[i].size = size;return memoryBlocks[i].start;}}// 分配新的块if (numBlocks < MEMORY_POOL_SIZE) {memoryBlocks[numBlocks].start = memoryBuff + numBlocks;memoryBlocks[numBlocks].size = size;numBlocks++;return memoryBlocks[numBlocks - 1].start;}// 分配失败return NULL;
}void mem_free(void* ptr)
{// 查找要释放的块for (int i = 0; i < numBlocks; i++) {if (memoryBlocks[i].start == ptr) {memoryBlocks[i].size = 0;break;}}
}int main(void)
{// 使用mem_malloc和mem_free进行内存管理unsigned char* ptr1 = (unsigned char*)mem_malloc(50);unsigned char* ptr2 = (unsigned char*)mem_malloc(100);if (ptr1 != NULL && ptr2 != NULL) {// 使用分配的内存for (int i = 0; i < 50; i++) {ptr1[i] = i;}for (int i = 0; i < 100; i++) {ptr2[i] = i + 50;}// 打印分配的内存printf("ptr1: ");for (int i = 0; i < 50; i++) {printf("%d ", ptr1[i]);}printf("\n");printf("ptr2: ");for (int i = 0; i < 100; i++) {printf("%d ", ptr2[i]);}printf("\n");}mem_free(ptr1);mem_free(ptr2);return 0;
}