【001】文件加密

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#define KEY 0xFA
char *filename = "data.dat";
int main(int argc, char *argv[]) {
    FILE *fpr, *fpw;
    char ch, k = (char) KEY;
    //命令行参数有误
    if (argc != 3 || *argv[2] != '+' && *argv[2] != '-') {
        printf("Useage: execute_file filename+/-\n");
        exit(0);
    }
    fpr = fopen(argv[1], "rb");
    if (fpr == NULL) {
        printf("can not open file: %s", argv[1]);
        exit(0);
    }
    fpw = fopen(argv[1], "rb+");
    if (fpw == NULL) {
        printf("can not open file: %s", argv[1]);
    }
    while ((ch = fgetc(fpr)) != EOF) {
        //0xFA
        fputc(ch ^ k, fpw);
        k = (*argv[2] == '+') ? ch : ch ^ k;
    }
    fclose(fpr);
    fclose(fpw);
    return 0;
}