Android NDK基础8：C_文件IO

文件IO

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

//读取文本文件
void main() {
    char *path = "E:\\ndk\\files\\friends.txt";
    //打开
    FILE *fp = fopen(path, "r");
    if (fp == NULL) {
        printf("文件打开失败...");
        return;
    }
    //读取
    char buff[50]; //缓冲
    while (fgets(buff, 50, fp)) { //文件中读取一字符串
        printf("%s", buff);
    }
    //关闭
    fclose(fp);
    system("pause");
}

//写入文本文件
void main() {
    char *path = "E:\\ndk\\files\\friends_new.txt";
    //打开
    FILE *fp = fopen(path, "w");
    char *text = "yezhpu@androidios.cc, Android & iOS 高级开发社区";
    fputs(text, fp);

    //关闭流
    fclose(fp);
    system("pause");
}

//计算机的文件存储在物理上都是二进制
//文本文件和二进制之分，其实是一个逻辑之分
//C读写文本文件与二进制文件的差别仅仅体现在回车换行符
//写文本时，每遇到一个'\n'，会将其转换成'\r\n'(回车换行)
//读文本时，每遇到一个'\r\n'，会将其转换成'\n'

//文件复制
void main() {
    char *read_path = "E:\\ndk\\files\\liuyan.png";
    char *write_path = "E:\\ndk\\files\\liuyan_new.png";
    //读的文件 b字符表示操作二进制文件binary
    FILE *read_fp = fopen(read_path, "rb");
    //写的文件
    FILE *write_fp = fopen(write_path, "wb");

    //复制
    int buff[50]; //缓冲区域
    int len = 0;  //每次读到的数据长度
    while ((len = fread(buff, sizeof(int), 50, read_fp)) != 0){
        //将读到的内容写入新的文件
        fwrite(buff, sizeof(int), len, write_fp);
    }
    //关闭流
    fclose(read_fp);
    fclose(write_fp);
    system("pause");
}

//获取文件的大小
void main() {
    char *read_path = "E:\\ndk\\files\\liuyan.png";
    FILE *fp = fopen(read_path, "r");
    //重新定位文件指针
    //SEEK_END文件末尾，0偏移量
    fseek(fp, 0, SEEK_END);
    //返回当前的文件指针，相对于文件开头的位移量
    long filesize = ftell(fp);
    printf("%d\n", filesize);

    system("pause");
}

综合案例

//练习：文本文件加解密
//异或
//规则：1^1=0, 0^0=0, 1^0=1, 0^1=1 同为0，不同为1
//加密
void crpypt(char normal_path[], char crypt_path[]) {
    //打开文件
    FILE *normal_fp = fopen(normal_path, "r");
    FILE *crypt_fp = fopen(crypt_path, "w");
    //一次读取一个字符
    int ch;
    while ((ch = fgetc(normal_fp)) != EOF) { //End of File
        //写入（异或运算）
        fputc(ch ^ 9, crypt_fp);
    }
    //关闭
    fclose(crypt_fp);
    fclose(normal_fp);
}

//解密
void decrpypt(char crypt_path[], char decrypt_path[]) {
    //打开文件
    FILE *normal_fp = fopen(crypt_path, "r");
    FILE *crypt_fp = fopen(decrypt_path, "w");
    //一次读取一个字符
    int ch;
    while ((ch = fgetc(normal_fp)) != EOF) { //End of File
        //写入（异或运算）
        fputc(ch ^ 9, crypt_fp);
    }
    //关闭
    fclose(crypt_fp);
    fclose(normal_fp);
}

void main() {
    char *normal_path = "E:\\ndk\\files\\friends.txt";
    char *crypt_path = "E:\\ndk\\files\\friends_crypt.txt";
    char *decrypt_path = "E:\\ndk\\files\\friends_decrypt.txt";

    //加密
    //crpypt(normal_path, crypt_path);
    //解密
    decrpypt(crypt_path, decrypt_path);

    system("pause");
}

//二进制文件加解密
//读取二进制文件中的数据时，一个一个字符读取
//密码：ilovely
void crpypt(char normal_path[], char crypt_path[], char password[]) {
    //打开文件
    FILE *normal_fp = fopen(normal_path, "rb");
    FILE *crypt_fp = fopen(crypt_path, "wb");
    //一次读取一个字符
    int ch;
    int i = 0; //循环使用密码中的字母进行异或运算
    int pwd_len = strlen(password); //密码的长度
    while ((ch = fgetc(normal_fp)) != EOF) { //End of File
        //写入（异或运算）
        fputc(ch ^ password[i % pwd_len], crypt_fp);
        i++;
    }
    //关闭
    fclose(crypt_fp);
    fclose(normal_fp);
}

//解密
void decrpypt(char crypt_path[], char decrypt_path[], char password[]) {
    //打开文件
    FILE *normal_fp = fopen(crypt_path, "rb");
    FILE *crypt_fp = fopen(decrypt_path, "wb");
    //一次读取一个字符
    int ch;
    int i = 0; //循环使用密码中的字母进行异或运算
    int pwd_len = strlen(password); //密码的长度
    while ((ch = fgetc(normal_fp)) != EOF) { //End of File
        //写入（异或运算）
        fputc(ch ^ password[i % pwd_len], crypt_fp);
        i++;
    }
    //关闭
    fclose(crypt_fp);
    fclose(normal_fp);
}

void main() {
    char *normal_path = "E:\\ndk\\files\\liuyan.png";
    char *crypt_path = "E:\\ndk\\files\\liuyan_crypt.png";
    char *decrypt_path = "E:\\ndk\\files\\liuyan_decrypt.png";

    //加密
    //crpypt(normal_path, crypt_path, "appblog.cn");
    //解密
    decrpypt(crypt_path, decrypt_path, "appblog.cn");

    getchar();
}