Initial Commit

Author: freakmaxi

client.go

@@ -0,0 +1,174 @@
+package client
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"net"
+	"time"
+)
+
+type LockingCenter interface {
+	Lock(key string)
+	Unlock(key string)
+	Wait(key string)
+	Reset(key string)
+}
+
+type lockingCenter struct {
+	address *net.TCPAddr
+}
+
+func NewLockingCenter(address string) (LockingCenter, error) {
+	addr, err := net.ResolveTCPAddr("tcp", address)
+	if err != nil {
+		return nil, err
+	}
+
+	lc := &lockingCenter{
+		address: addr,
+	}
+	if err := lc.ping(); err != nil {
+		return nil, err
+	}
+	return lc, nil
+}
+
+func (l *lockingCenter) connect() (*net.TCPConn, error) {
+	conn, err := net.DialTCP("tcp", nil, l.address)
+	if err != nil {
+		return nil, err
+	}
+	return conn, nil
+}
+
+func (l *lockingCenter) ping() error {
+	conn, err := l.connect()
+	if err != nil {
+		return err
+	}
+	return conn.Close()
+}
+
+func (l *lockingCenter) preparePackage(key string, action byte) ([]byte, error) {
+	if len(key) == 0 || len(key) > 128 {
+		return nil, fmt.Errorf("key can not be empty or more than 128 characters")
+	}
+
+	data := make([]byte, 0)
+	buffer := bytes.NewBuffer(data)
+
+	keySize := int8(len(key))
+	if err := binary.Write(buffer, binary.LittleEndian, keySize); err != nil {
+		return nil, err
+	}
+
+	if err := binary.Write(buffer, binary.LittleEndian, []byte(key)); err != nil {
+		return nil, err
+	}
+
+	if err := binary.Write(buffer, binary.LittleEndian, action); err != nil {
+		return nil, err
+	}
+
+	return buffer.Bytes(), nil
+}
+
+func (l *lockingCenter) result(conn *net.TCPConn) bool {
+	r := make([]byte, 1)
+
+	if _, err := io.ReadAtLeast(conn, r, len(r)); err != nil {
+		return false
+	}
+
+	return string(r) == "+"
+}
+
+func (l *lockingCenter) Lock(key string) {
+	query := func() bool {
+		conn, err := l.connect()
+		if err != nil {
+			fmt.Printf("ERROR: connection failure: %s\n", err)
+			return false
+		}
+		defer conn.Close()
+
+		if err := l.query(conn, key, 1); err != nil {
+			fmt.Printf("ERROR: locking error: %s\n", err)
+			return false
+		}
+
+		return true
+	}
+
+	for !query() {
+		time.Sleep(time.Second)
+	}
+}
+
+func (l *lockingCenter) Unlock(key string) {
+	query := func() bool {
+		conn, err := l.connect()
+		if err != nil {
+			fmt.Printf("ERROR: connection failure: %s\n", err)
+			return false
+		}
+		defer conn.Close()
+
+		if err := l.query(conn, key, 2); err != nil {
+			fmt.Printf("ERROR: unlocking error: %s\n", err)
+			return false
+		}
+
+		return true
+	}
+
+	for !query() {
+		time.Sleep(time.Second)
+	}
+}
+
+func (l *lockingCenter) Wait(key string) {
+	l.Lock(key)
+	defer l.Unlock(key)
+}
+
+func (l *lockingCenter) Reset(key string) {
+	query := func() bool {
+		conn, err := l.connect()
+		if err != nil {
+			fmt.Printf("ERROR: connection failure: %s\n", err)
+			return false
+		}
+		defer conn.Close()
+
+		if err := l.query(conn, key, 3); err != nil {
+			fmt.Printf("ERROR: reseting error: %s\n", err)
+			return false
+		}
+
+		return true
+	}
+
+	for !query() {
+		time.Sleep(time.Second)
+	}
+}
+
+func (l *lockingCenter) query(conn *net.TCPConn, key string, action byte) error {
+	payload, err := l.preparePackage(key, action)
+	if err != nil {
+		return err
+	}
+
+	if _, err := conn.Write(payload); err != nil {
+		return err
+	}
+
+	if !l.result(conn) {
+		return fmt.Errorf("remote server execution error")
+	}
+
+	return nil
+}

go.mod

@@ -0,0 +1,3 @@
+module github.com/freakmaxi/locking-center
+
+go 1.14