Enrico Fraccaroli (Galfurian)
149 lines
5.7 KiB
C
149 lines
5.7 KiB
C
/// @file msg.h
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/// @brief Definition of structure for managing message queues.
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/// @copyright (c) 2014-2024 This file is distributed under the MIT License.
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/// See LICENSE.md for details.
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#pragma once
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#include "sys/ipc.h"
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#include "stddef.h"
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#include "sys/types.h"
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#include "time.h"
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/// The maximum size for a message text.
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#define MSGMAX 8192
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/// The default maximum size in bytes of a message queue.
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#define MSGMNB 16384
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/// Specify that we should not treat as an error if the message we are trying to
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/// return to the user, is too big. That message will be truncated to fit the
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/// user-defined reading buffer. If not specified, the message is kept in the
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/// queue, and an error is returned.
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#define MSG_NOERROR 010000
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/// @brief Buffer to use with the message queue IPC.
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struct msgbuf {
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/// Type of the message.
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long mtype;
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/// Text of the message.
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char mtext[1];
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};
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/// Keeps track of a stored message.
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struct msg {
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/// Pointer to the next message on queue.
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struct msg *msg_next;
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/// The type of message.
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long msg_type;
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/// Pointer to the beginning of the message.
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char *msg_ptr;
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/// The length of the message.
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size_t msg_size;
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};
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/// @brief Message queue data structure.
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struct msqid_ds {
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/// Ownership and permissions.
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struct ipc_perm msg_perm;
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/// Time of last msgsnd(2).
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time_t msg_stime;
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/// Time of last msgrcv(2).
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time_t msg_rtime;
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/// Time of creation or last modification by msgctl().
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time_t msg_ctime;
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/// Number of bytes in queue.
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unsigned short msg_cbytes;
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/// Number of messages in queue.
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unsigned short msg_qnum;
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/// Maximum number of bytes in queue.
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unsigned short msg_qbytes;
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/// PID of last msgsnd(2).
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pid_t msg_lspid;
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/// PID of last msgrcv(2).
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pid_t msg_lrpid;
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};
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#ifdef __KERNEL__
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/// @brief Initializes the message queue system.
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/// @return 0 on success, 1 on failure.
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int msq_init(void);
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/// @brief Get a System V message queue identifier.
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/// @param key can be used either to obtain the identifier of a previously
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/// created message queue, or to create a new set.
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/// @param msgflg controls the behaviour of the function.
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/// @return the message queue identifier, -1 on failure, and errno is set to
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/// indicate the error.
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int sys_msgget(key_t key, int msgflg);
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/// @brief Used to send messages.
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/// @param msqid the message queue identifier.
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/// @param msgp points to a used-defined msgbuf.
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/// @param msgsz specifies the size in bytes of mtext.
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/// @param msgflg specifies the action to be taken in case of specific events.
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/// @return 0 on success, -1 on failure and errno is set to indicate the error.
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int sys_msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg);
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/// @brief Used to receive messages.
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/// @param msqid the message queue identifier.
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/// @param msgp points to a used-defined msgbuf.
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/// @param msgsz specifies the size in bytes of mtext.
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/// @param msgtyp specifies the type of message requested, as follows:
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/// - msgtyp == 0: the first message on the queue is received.
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/// - msgtyp > 0: the first message of type, msgtyp, is received.
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/// - msgtyp < 0: the first message of the lowest type that is less than or
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/// equal to the absolute value of msgtyp is received.
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/// @param msgflg specifies the action to be taken in case of specific events.
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/// @return the number of bytes actually copied on success, -1 on failure and
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/// errno is set to indicate the error.
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ssize_t sys_msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg);
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/// @brief Message queue control operations.
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/// @param msqid the message queue identifier.
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/// @param cmd The command to perform.
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/// @param buf used with IPC_STAT and IPC_SET.
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/// @return 0 on success, -1 on failure and errno is set to indicate the error.
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int sys_msgctl(int msqid, int cmd, struct msqid_ds *buf);
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#else
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/// @brief Get a System V message queue identifier.
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/// @param key can be used either to obtain the identifier of a previously
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/// created message queue, or to create a new set.
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/// @param msgflg controls the behaviour of the function.
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/// @return the message queue identifier, -1 on failure, and errno is set to
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/// indicate the error.
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int msgget(key_t key, int msgflg);
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/// @brief Used to send messages.
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/// @param msqid the message queue identifier.
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/// @param msgp points to a used-defined msgbuf.
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/// @param msgsz specifies the size in bytes of mtext.
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/// @param msgflg specifies the action to be taken in case of specific events.
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/// @return 0 on success, -1 on failure and errno is set to indicate the error.
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int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg);
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/// @brief Used to receive messages.
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/// @param msqid the message queue identifier.
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/// @param msgp points to a used-defined msgbuf.
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/// @param msgsz specifies the size in bytes of mtext.
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/// @param msgtyp specifies the type of message requested, as follows:
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/// - msgtyp == 0: the first message on the queue is received.
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/// - msgtyp > 0: the first message of type, msgtyp, is received.
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/// - msgtyp < 0: the first message of the lowest type that is less than or
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/// equal to the absolute value of msgtyp is received.
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/// @param msgflg specifies the action to be taken in case of specific events.
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/// @return the number of bytes actually copied on success, -1 on failure and
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/// errno is set to indicate the error.
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ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg);
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/// @brief Message queue control operations.
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/// @param msqid the message queue identifier.
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/// @param cmd The command to perform.
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/// @param buf used with IPC_STAT and IPC_SET.
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/// @return 0 on success, -1 on failure and errno is set to indicate the error.
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int msgctl(int msqid, int cmd, struct msqid_ds *buf);
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#endif
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