文件加密解密小程序

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

int process(char *filename, char *opration);
int read_file(char *filename, char **buf);
int write_file(char *buf, long file_size);
int decode(char *buf, int file_size, int key);
int encrypt(char *buf, int file_size, int key);

int main(int argc, char **argv)
{
char flag;

if (argc != 3)
{
printf("error!the type is :%s <filename> <opration>\n", argv[0]);
exit(-1);
}

if ((*argv[2] == 'e') || (*argv[2] == 'd'))
process(argv[1], argv[2]);
else
{
printf("error:opration only be e(encrypt) or d(decode)\n");
exit(-1);
}

return 0;
}

int process(char *filename, char *opration)
{
FILE *myfile_dst;
char *buf;
int key = 123;
long file_size;

file_size = read_file(filename, &buf);

if (*opration == 'e')
encrypt(buf, file_size, key);
else if(*opration == 'd')
decode(buf, file_size, key);

write_file(buf, file_size);

return 0;
}

int read_file(char *filename, char **buf)
{
FILE *myfile_src;
long file_size;

if (!(myfile_src = fopen(filename, "r")))
{
perror("fopen");
}

fseek(myfile_src, 0, SEEK_END);
file_size = ftell(myfile_src);
fseek(myfile_src, 0, SEEK_SET);

*buf = (char *)malloc(file_size);
fread(*buf, 1, file_size, myfile_src);
fclose(myfile_src);

return file_size;
}

int write_file(char *buf, long file_size)
{
FILE *myfile_dst;
char filename[20];

printf("please input the file name that you want to save:\n");
scanf("%s", filename);
if (!(myfile_dst = fopen(filename, "wb")))
{
perror("fopen");
}
fwrite(buf, 1, file_size, myfile_dst);
printf(">>>>>>>>>>>>>>%s is save<<<<<<<<<<<<<<<\n", filename);
fclose(myfile_dst);

return 0;
}

int encrypt(char buf[], int file_size, int key)
{
int i;

for(i = 0; i < file_size; i ++)
buf[i] = buf[i] + key;

return 0;
}

int decode(char *buf, int file_size, int key)
{
int i;

for(i = 0; i < file_size; i ++)
buf[i] = buf[i] - key;

return 0;
}