! sysv.f90
!
! Fortran 2003 ISO C binding interfaces to SysV message queues.
!
! Author:   Philipp Engel
! Date:     2020-03-30
! Licence:  ISC
module sysv
    use, intrinsic :: iso_c_binding, only: c_char, c_int, c_long, c_ptr, c_size_t
    implicit none
    private

    public :: c_msgctl
    public :: c_msgget
    public :: c_msgrcv
    public :: c_msgsnd

    integer(kind=c_int),    parameter, public :: IPC_CREAT   = 0010000
    integer(kind=c_int),    parameter, public :: IPC_EXCL    = 0020000
    integer(kind=c_int),    parameter, public :: IPC_NOWAIT  = 0040000
    integer(kind=c_long),   parameter, public :: IPC_PRIVATE = int(0, kind=c_long)

    integer(kind=c_int),    parameter, public :: IPC_RMID    = 0
    integer(kind=c_int),    parameter, public :: IPC_SET     = 1
    integer(kind=c_int),    parameter, public :: IPC_STAT    = 2

    integer(kind=c_size_t), parameter, public :: MESSAGE_LEN = 256

    ! Message type for SysV message queues.
    type, bind(c), public :: message_type
        integer(kind=c_long)   :: type
        character(kind=c_char) :: text(MESSAGE_LEN)
    end type message_type

    interface
        ! int msgctl(int msqid, int cmd, struct msqid_ds *buf)
        function c_msgctl(msqid, cmd, buf) bind(c, name='msgctl')
            import :: c_int, c_ptr
            integer(kind=c_int), intent(in), value :: msqid
            integer(kind=c_int), intent(in), value :: cmd
            type(c_ptr),         intent(in), value :: buf
            integer(kind=c_int)                    :: c_msgctl
        end function c_msgctl

        ! int msgget(key_t key, int msgflg)
        function c_msgget(key, msgflg) bind(c, name='msgget')
            import :: c_int, c_long
            integer(kind=c_long), intent(in), value :: key
            integer(kind=c_int),  intent(in), value :: msgflg
            integer(kind=c_int)                     :: c_msgget
        end function c_msgget

        ! ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg)
        function c_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg) bind(c, name='msgrcv')
            import :: c_int, c_long, c_ptr, c_size_t
            integer(kind=c_int),    intent(in), value :: msqid
            type(c_ptr),            intent(in), value :: msgp
            integer(kind=c_size_t), intent(in), value :: msgsz
            integer(kind=c_long)  , intent(in), value :: msgtyp
            integer(kind=c_int),    intent(in), value :: msgflg
            integer(kind=c_size_t)                    :: c_msgrcv
        end function c_msgrcv

        ! int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg)
        function c_msgsnd(msqid, msgp, msgsz, msgflg) bind(c, name='msgsnd')
            import :: c_int, c_ptr, c_size_t
            integer(kind=c_int),    intent(in), value :: msqid
            type(c_ptr),            intent(in), value :: msgp
            integer(kind=c_size_t), intent(in), value :: msgsz
            integer(kind=c_int),    intent(in), value :: msgflg
            integer(kind=c_int)                       :: c_msgsnd
        end function c_msgsnd
    end interface
end module sysv