mirror of https://github.com/hslam/msg.git
122 lines
3.3 KiB
Go
122 lines
3.3 KiB
Go
// Copyright (c) 2020 Meng Huang (mhboy@outlook.com)
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// This package is licensed under a MIT license that can be found in the LICENSE file.
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package msg
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import (
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"errors"
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"syscall"
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"unsafe"
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)
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const (
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// IPC_CREAT creates if key is nonexistent
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IPC_CREAT = 01000
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// IPC_EXCL fails if key exists.
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IPC_EXCL = 02000
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// IPC_NOWAIT returns error no wait.
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IPC_NOWAIT = 04000
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// IPC_PRIVATE is private key
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IPC_PRIVATE = 00000
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// SEM_UNDO sets up adjust on exit entry
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SEM_UNDO = 010000
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// IPC_RMID removes identifier
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IPC_RMID = 0
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// IPC_SET sets ipc_perm options.
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IPC_SET = 1
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// IPC_STAT gets ipc_perm options.
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IPC_STAT = 2
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maxText = 8192
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)
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// ErrTooLong is returned when the Text length is bigger than maxText.
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var ErrTooLong = errors.New("Text length is too long")
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type message struct {
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Type uint
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Text [maxText]byte
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}
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// Get calls the msgget system call.
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func Get(key int, msgflg int) (int, error) {
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r1, _, err := syscall.Syscall(syscall.SYS_MSGGET, uintptr(key), uintptr(msgflg), 0)
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msgid := int(r1)
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if msgid < 0 {
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return msgid, syscall.Errno(err)
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}
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return msgid, nil
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}
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// Snd calls the msgsnd system call.
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//
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// The msgsnd() and msgrcv() system calls are used to send messages to,
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// and receive messages from, a System V message queue. The calling
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// process must have write permission on the message queue in order to
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// send a message, and read permission to receive a message.
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// The msgp argument is a pointer to a caller-defined structure of the
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// following general form:
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//
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// struct msgbuf {
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// long mtype; /* message type, must be > 0 */
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// char mtext[1]; /* message data */
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// };
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// The mtext field is an array (or other structure) whose size is speci‐
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// fied by msgsz, a nonnegative integer value. Messages of zero length
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// (i.e., no mtext field) are permitted. The mtype field must have a
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// strictly positive integer value. This value can be used by the re‐
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// ceiving process for message selection (see the description of ms‐
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// grcv() below).
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//
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func Snd(msgid int, msgp uintptr, msgsz int, msgflg int) error {
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_, _, err := syscall.Syscall6(syscall.SYS_MSGSND, uintptr(msgid), uintptr(msgp), uintptr(msgsz), uintptr(msgflg), 0, 0)
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if err != 0 {
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return err
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}
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return nil
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}
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// Rcv calls the msgrcv system call.
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func Rcv(msgid int, msgp uintptr, msgsz int, msgtyp uint, msgflg int) (int, error) {
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r1, _, err := syscall.Syscall6(syscall.SYS_MSGRCV, uintptr(msgid), msgp, uintptr(msgsz), uintptr(msgtyp), uintptr(msgflg), 0)
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length := int(r1)
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if err != 0 {
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return length, err
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}
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return length, nil
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}
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// Send calls the msgsnd system call.
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func Send(msgid int, msgType uint, msgText []byte, flags int) error {
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if len(msgText) > maxText {
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return ErrTooLong
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}
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m := message{Type: msgType}
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copy(m.Text[:], msgText)
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return Snd(msgid, uintptr(unsafe.Pointer(&m)), len(msgText), flags)
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}
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// Receive calls the msgrcv system call.
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func Receive(msgid int, msgType uint, flags int) ([]byte, error) {
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m := message{Type: msgType}
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length, err := Rcv(msgid, uintptr(unsafe.Pointer(&m)), maxText, msgType, flags)
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if err != nil {
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return nil, err
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}
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return m.Text[:length], nil
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}
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// Remove removes the message queue with the given id.
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func Remove(msgid int) error {
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r1, _, errno := syscall.Syscall(syscall.SYS_MSGCTL, uintptr(msgid), IPC_RMID, 0)
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if int(r1) < 0 {
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return syscall.Errno(errno)
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}
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return nil
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}
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