Android NDK基础8:C_文件IO

文件IO

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#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");
}
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//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'
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//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");
}
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//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

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//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");
}
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//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();
}

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