first commit

msg.go

@@ -0,0 +1,5 @@
+// Copyright (c) 2020 Meng Huang (mhboy@outlook.com)
+// This package is licensed under a MIT license that can be found in the LICENSE file.
+
+// Package msg provides a way to use message queue.
+package msg

msg_unix.go

@@ -0,0 +1,92 @@
+// Copyright (c) 2020 Meng Huang (mhboy@outlook.com)
+// This package is licensed under a MIT license that can be found in the LICENSE file.
+
+package msg
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+const (
+	// IPC_CREAT creates if key is nonexistent
+	IPC_CREAT = 00001000
+
+	// IPC_RMID removes identifier
+	IPC_RMID = 0
+
+	maxText = 512
+)
+
+type message struct {
+	Type uint
+	flag uint8
+	Text [maxText]byte
+}
+
+// Msg represents a message.
+type Msg struct {
+	Type uint
+	Text []byte
+}
+
+// Get calls the msgget system call.
+func Get(key int, msgflg int) (uintptr, error) {
+	msgid, _, err := syscall.Syscall(syscall.SYS_MSGGET, uintptr(key), uintptr(msgflg), 0)
+	if int(msgid) < 0 {
+		return 0, syscall.Errno(err)
+	}
+	return msgid, nil
+}
+
+// Snd calls the msgsnd system call.
+func Snd(msgid uintptr, msg *Msg, flags uint) error {
+	offset := 0
+	m := message{Type: msg.Type}
+	for len(msg.Text)-offset > 0 {
+		if len(msg.Text)-offset > maxText {
+			m.flag = 1
+			copy(m.Text[:], msg.Text[offset:offset+maxText])
+			_, _, err := syscall.Syscall6(syscall.SYS_MSGSND, msgid, uintptr(unsafe.Pointer(&m)), 1+maxText, uintptr(flags), 0, 0)
+			if err != 0 {
+				return err
+			}
+			offset += maxText
+		} else {
+			m.flag = 0
+			copy(m.Text[:], msg.Text[offset:len(msg.Text)])
+			_, _, err := syscall.Syscall6(syscall.SYS_MSGSND, msgid, uintptr(unsafe.Pointer(&m)), 1+uintptr(len(msg.Text)-offset), uintptr(flags), 0, 0)
+			if err != 0 {
+				return err
+			}
+			offset += len(msg.Text) - offset
+		}
+	}
+	return nil
+}
+
+// Rcv calls the msgrcv system call.
+func Rcv(msgid uintptr, msg *Msg, flags uint) error {
+	m := message{Type: msg.Type}
+	for {
+		length, _, err := syscall.Syscall6(syscall.SYS_MSGRCV, msgid, uintptr(unsafe.Pointer(&m)), 1+maxText, uintptr(msg.Type), uintptr(flags), 0)
+		if err != 0 {
+			return err
+		}
+		msg.Type = m.Type
+		msg.Text = append(msg.Text, m.Text[:length-1]...)
+		if m.flag == 0 {
+			break
+		}
+	}
+	return nil
+}
+
+// Remove removes the message queue with the given id.
+func Remove(msgid uintptr) error {
+	r1, _, errno := syscall.Syscall(syscall.SYS_MSGCTL, msgid, IPC_RMID, 0)
+	if int(r1) < 0 {
+		return syscall.Errno(errno)
+	}
+	return nil
+}