simplify port range parsing

common/net/port.go

@@ -1,15 +1,38 @@
 package net
 
 import (
+	"errors"
+	"strconv"
+
 	"github.com/v2ray/v2ray-core/common/serial"
 )
 
+var (
+	// ErrorInvalidPortRage indicates an error during port range parsing.
+	ErrorInvalidPortRange = errors.New("Invalid port range.")
+)
+
 type Port serial.Uint16Literal
 
 func PortFromBytes(port []byte) Port {
 	return Port(serial.BytesLiteral(port).Uint16Value())
 }
 
+func PortFromInt(v int) (Port, error) {
+	if v <= 0 || v > 65535 {
+		return Port(0), ErrorInvalidPortRange
+	}
+	return Port(v), nil
+}
+
+func PortFromString(s string) (Port, error) {
+	v, err := strconv.Atoi(s)
+	if err != nil {
+		return Port(0), ErrorInvalidPortRange
+	}
+	return PortFromInt(v)
+}
+
 func (this Port) Value() uint16 {
 	return uint16(this)
 }