c语言实现文件循环存储和查找

下面是一个简单的C语言实现文件循环存储和查找的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define BLOCK_SIZE 1024 // 定义数据块的大小为1024字节
#define MAX_BLOCKS 1000 // 定义最大数据块数量为1000个

typedef struct {
    int id; // 数据块的唯一标识符
    int next; // 指向下一个数据块的指针
    char data[BLOCK_SIZE]; // 存储数据的数组
} DataBlock;

DataBlock blocks[MAX_BLOCKS]; // 数据块数组
int free_head = 0; // 空闲数据块的头指针
int used_head = -1; // 已使用数据块的头指针
int num_blocks = 0; // 当前已使用的数据块数量

// 初始化数据块数组
void init_blocks() {
    int i;
    for (i = 0; i < MAX_BLOCKS; i++) {
        blocks[i].id = i;
        blocks[i].next = i + 1;
    }
    blocks[MAX_BLOCKS - 1].next = 0;
}

// 在空闲数据块链表中分配一个数据块
int allocate_block() {
    if (free_head == 0) {
        return -1; // 空间已满，无法分配
    }
    int new_block = free_head;
    free_head = blocks[free_head].next;
    blocks[new_block].next = -1;
    return new_block;
}

// 释放一个已使用的数据块到空闲链表中
void free_block(int block_id) {
    blocks[block_id].next = free_head;
    free_head = block_id;
}

// 将文件写入数据块链表中
int write_file(char *filename) {
    FILE *fp = fopen(filename, "rb");
    if (fp == NULL) {
        return -1; // 打开文件失败
    }
    int num_blocks = 0;
    int file_size = 0;
    int block_id = allocate_block();
    int prev_block_id = -1;
    while (block_id != -1) {
        blocks[block_id].next = allocate_block();
        num_blocks++;
        if (fread(blocks[block_id].data, BLOCK_SIZE, 1, fp) != 1) {
            break; // 文件读取完成
        }
        file_size += BLOCK_SIZE;
        prev_block_id = block_id;
        block_id = blocks[block_id].next;
    }
    fclose(fp);
    if (prev_block_id != -1) {
        blocks[prev_block_id].next = used_head;
    }
    used_head = allocate_block();
    blocks[used_head].next = used_head;
    blocks[used_head].id = num_blocks;
    return file_size;
}

// 从数据块链表中读取文件
int read_file(char *filename, int file_size) {
    FILE *fp = fopen(filename, "wb");
    if (fp == NULL) {
        return -1; // 创建文件失败
    }
    int block_id = used_head;
    int bytes_read = 0;
    while (bytes_read < file_size && block_id != -1) {
        if (fwrite(blocks[block_id].data, BLOCK_SIZE, 1, fp) != 1) {
            break; // 文件写入失败
        }
        bytes_read += BLOCK_SIZE;
        block_id = blocks[block_id].next;
    }
    fclose(fp);
    return bytes_read;
}

// 释放数据块链表中的文件
int delete_file(int num_blocks) {
    int block_id = used_head;
    int prev_block_id = -1;
    while (block_id != -1 && blocks[block_id].id != num_blocks) {
        prev_block_id = block_id;
        block_id = blocks[block_id].next;
    }
    if (block_id == -1) {
        return -1; // 文件不存在
    }
    if (prev_block_id != -1) {
        blocks[prev_block_id].next = blocks[block_id].next;
    } else {
        used_head = blocks[block_id].next;
    }
    while (block_id != -1) {
        int next_block_id = blocks[block_id].next;
        free_block(block_id);
        block_id = next_block_id;
    }
    return 0;
}

int main() {
    init_blocks(); // 初始化数据块数组
    int file_size = write_file("test.txt"); // 将文件写入数据块链表中
    if (file_size == -1) {
        printf("Failed to open file!\n");
        return -1;
    }
    printf("File saved successfully!\n");
    int bytes_read = read_file("test_copy.txt", file_size); // 从数据块链表中读取文件
    if (bytes_read == -1) {
        printf("Failed to create file!\n");
        return -1;
    }
    printf("File read successfully!\n");
    delete_file(1); // 释放数据块链表中的文件
    printf("File deleted successfully!\n");
    return 0;
}

此代码仅是一个简单的示例，实际应用中需要增加更多的错误处理和异常处理代码。