消息队列msg_queue API

[TOC]

• 数据结构

  struct msg_queue {
  	struct kern_ipc_perm q_perm;
  	time64_t q_stime;		/* last msgsnd time */
  	time64_t q_rtime;		/* last msgrcv time */
  	time64_t q_ctime;		/* last change time */
  	unsigned long q_cbytes;		/* current number of bytes on queue */
  	unsigned long q_qnum;		/* number of messages in queue */
  	unsigned long q_qbytes;		/* max number of bytes on queue */
  	struct pid *q_lspid;		/* pid of last msgsnd */
  	struct pid *q_lrpid;		/* last receive pid */
  
  	struct list_head q_messages;
  	struct list_head q_receivers;
  	struct list_head q_senders;
  } __randomize_layout;
  

  常用的消息队列的封装格式如下。

  struct msgbuf {
      long mtype;       /* message type, must be > 0 */
      char mtext[1];    /* message data */
  };
  

• 创建

  #include <sys/types.h>
  #include <sys/ipc.h>
  #include <sys/msg.h>
  
  int msgget(key_t key, int msgflg);
  

• 收发

  #include <sys/types.h>
  #include <sys/ipc.h>
  #include <sys/msg.h>
  
  int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg);
  
  ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp,
                 int msgflg);
  

• 控制

  #include <sys/types.h>
  #include <sys/ipc.h>
  #include <sys/msg.h>
  
  int msgctl(int msqid, int cmd, struct msqid_ds *buf);