某移动通信系统中，要求给每个呼叫中用户分配一个呼叫标识（callid），其中CallID为无符号整形数值。有一个callid的类，实现callid池的功能。初始化时给出最大标识，要求呼叫开始时可以申请一个callid，呼叫结束时可以释放，可以分别打印正在使用或callid列表，针对跟定calid可以判断是否有效（0~max callid）、是否在忙。-A mobile communication system, the requirements call for each user is assigned a call ID (callid), one of CallID plastic for unsigned values. There is a class callid, callid pool implementation functions. Initialization give the largest logo, call the beginning of the requirements can apply for a callid, can call the end of the release, you can print is being used separately or callid list, set for with calid can determine the validity of (0 ~ max callid), whether at busy.