c - 将二进制文件的内容读取为 unsigned long，更新并保存在另一个二进制文件中

Question

我想读取一个二进制文件，操作64位加密逻辑并将返回的文件保存在二进制文件中。由于加密对 2 个 4 字节整数 block 进行操作，因此我读取了该文件两次并转换为 long int。但是当我尝试使用相同的过程解密时，我发现从加密输出中保存的内容是错误的。到目前为止，这是我的代码。

     while (fread(buffer, 1, 4, src) == 4) {
    //convert char to long
    message_left = buffer[3] | (unsigned long) (buffer[2] << 8) | (unsigned long) (buffer[1] << 16) | (unsigned long)(buffer[0] << 24);
    fread(buffer, 1, 4, src);
    //convert char to long
    message_right = buffer[3] | (unsigned long) (buffer[2] << 8) | (unsigned long) (buffer[1] << 16) | (unsigned long)(buffer[0] << 24);
    //encrypt
    Encrypt(ctx,&message_left,&message_right);
    //convert back to char and save
    buffer[3] = (unsigned char)message_left;
    buffer[2] = (unsigned char)(message_left >>  8);
    buffer[1] = (unsigned char)(message_left >> 16);
    buffer[0] = (unsigned char)(message_left >> 24);
    fwrite(buffer,4,1,dest);
    buffer[3] = message_rigt;
    buffer[2] = (unsigned char)(message_right >>  8);
    buffer[1] = (unsigned char)(message_right >> 16);
    buffer[0] = (unsigned char)(message_right >> 24);
    fwrite(buffer,4,1,dest);
    }

Answer 1

这样的东西有用吗？

unsigned long n[2];
while (fread(n, sizeof(n), 1, src) == 1) {
    Encrypt(ctx, &n[0], &n[1]);
    fwrite(n, sizeof(n), 1, dest);
}