struct image_header {
    unsigned int magic; //魔术字 固定为0x27051956
    unsigned int hcrc; //头部CRC校验码
    unsigned int time; //打包时间
    unsigned int size; //可执行镜像大小
    unsigned int load; //镜像加载位置
    unsigned int ep; //镜像启动位置
    unsigned int dcrc; //镜像CRC校验码
    unsigned char os; //镜像所含系统类型
    unsigned char arch;//镜像目标CPU
    unsigned char type;//镜像类型
    unsigned char comp;//镜像压缩类型
    unsigned char name[IH_NMLEN];//镜像名字
};