C实现文件内部操作

main.c

#include "file_op.h"

void show_menu()
{
    printf("F : 显示前一行\n");
    printf("B : 显示后一行\n");
    printf("S : 保存\n");
    printf("Q : 退出程序\n");
}
void init(char *file_name)
{
    char cmd[20] = {'\0'};

    FILE *fd = open_file(file_name);
    init_list(fd);
    fclose(fd);

    while (1)
    {
        show_menu();
        printf("请输入你的选择: ");
        fgets(cmd, sizeof(cmd), stdin);
        if (strlen(cmd) != 2)
        { 
            printf("您的输入有误\n");
            continue;
        }
        if (cmd[0] == 'Q')
            break;

        switch (cmd[0])
        {
        case 'F':
            show_pre_content();
            break;
        case 'B':
            show_next_content();
            break;
        case 'S':
        {
            char file_name[100] = { '0' };
            printf("请输入要保存的文件名: ");
            scanf("%s", file_name);
            save_contents(file_name);
        }
            break;
        default:
            break;
        }
    }
    delete_list();
}
int main(int argc, char *argv[])
{
    assert(argc == 2);

    init(argv[1]);

    return 0;
}

file_op.c

#include "file_op.h"

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

file_data *head = NULL;
file_data *current = NULL;

#define BUFFSIZE 1024

FILE * open_file(char *file_name)
{
    FILE *fd = fopen(file_name, "r");
    assert(fd != NULL);

    return fd;
}

void init_list(FILE * fd)
{

    file_data *printData;

    char buf[BUFFSIZE] = {'\0'};
    int len = 0;
    while (!feof(fd))
    {
        memset(buf, sizeof(buf), 0);
        if (fgets(buf, sizeof(buf), fd))
        {
            file_data *data;
            assert(buf != NULL);
            data = (file_data *)malloc(sizeof(file_data));
            assert(data != NULL);
            insert_node(data, buf);
        }   
    }

    printData = head;
    while (1)
    {
        printf("%s\n", printData->content);
        printData = printData->next;
        if (printData == head)
            break;
    }
}

void insert_node(file_data *data, char *buf)
{
    int len = strlen(buf);  //这里+1,是为了忽略了末尾的\n
    data->content = (char *)malloc(len);
    memset(data->content, sizeof(data->content), 0);
    memcpy(data->content, buf, len);
    if (data->content[len - 1] == '\n')
        data->content[len - 1] = '\0';

    if (head == NULL)
    {
        head = data;
        head->pre = head;
        head->next = head;
        current = head;
    }
    else
    {
        data->next = head;
        data->pre = head->pre;
        head->pre->next = data;
        head->pre = data;
    }
}

void delete_list()
{
    file_data *last_data = head->pre;
    file_data *node = head;
    file_data *tmp;
    while (1)
    {
        if (node == last_data)
        {
            free(last_data);
            last_data = NULL;
            break;
        }
        tmp = node;

        node = node->next;
        tmp->pre->next = node;
        node->pre = tmp->pre;
        free(tmp);
        tmp = NULL;
    }
}

void show_pre_content()
{
    if (current != head)
    {
        current = current->pre;
        printf("%s\n", current->content);
    }
    else
    {
        printf("已经是第一行数据\n");
    }
}

void show_next_content()
{
    if (current->next != head)
    { 
        current = current->next;
        printf("%s\n", current->content);
    }
    else
    {
        printf("已经是最后一行数据\n");
    }
}

void save_contents(char *save_fila_name)
{
    FILE *fd;
    file_data * data;
    int len = 0;
    int flag = 0;   //是否保存完的标志

    assert(save_fila_name != NULL);
    fd = fopen(save_fila_name, "w");

    data = head->pre;

    while (1)
    {
        char *content;
        if (data == head)
            flag = 1;   //

        len = strlen(data->content);
        content = (char *)malloc(len * sizeof(char) + 1);
        desc_content(content, data->content, len);
        printf("%s\n", content);
        fprintf(fd, "%s\n", content);
        free(content);
        content = NULL;
        data = data->pre;

        if (flag == 1)  //保存完退出保存
            break;
    }
    fclose(fd);

    printf("文件保存成功\n");
}

char * desc_content(char *dest, char *src, int len)
{
    int i = 0;
    assert(src != NULL && dest != NULL);

    while (i < len)
    {
        dest[i] = src[len - i - 1];
        i++;
    }
    dest[i] = '\0';

    return dest;
}

file_op.h

#ifndef __FILE_OP_H__
#define __FILE_OP_H__
#define _CRT_SECURE_NO_WARNINGS
#include <assert.h>
#include <stdio.h>

typedef struct file_data_struct file_data;

struct file_data_struct
{
    char *content;      //存储每一行内容
    file_data * pre;
    file_data * next;
};

//加载文件到链表系列函数
FILE * open_file(char *file_name);
void init_list(FILE * fd);
void insert_node(file_data *data, char *buf);
//释放链表内存
void delete_list();

//显示上一行下一行系列函数
void show_pre_content();
void show_next_content();

//保存文件系列函数
void save_contents(char *save_fila_name);
char * desc_content(char *dest, char *src, int len);
#endif // __FILE_OP__