utils.go

// Copyright 2015 sip authors. All rights reserved.
// Use of this source code is governed by a MIT-style license that can be
// found in the LICENSE file.

package sip

import (
	"bytes"
	"fmt"
	"math/rand"
	"os"
	"time"
)

func init() {
	rand.Seed(time.Now().UnixNano())
}

const branchMagicCookie = "z9hG4bK"

// generateRandom generates random strings for tags/call-ids/branches
func generateRandom(charsToDouble int) string {
	var buf bytes.Buffer
	for i := 0; i < charsToDouble; i++ {
		buf.WriteByte(byte(randInt(65, 90)))
		buf.WriteByte(byte(randInt(97, 122)))
	}

	return string(buf.Bytes())
}

// Helper for generating random number between two given numbers
func randInt(min int, max int) int {
	return min + rand.Intn(max-min)
}

// GenerateBranch generates branch for via header
func GenerateBranch() string {
	randomPart := generateRandom(4)
	return branchMagicCookie + randomPart
}

// GenerateTag generates tags for To/From headers
func GenerateTag() string {
	return generateRandom(4)
}

// GenerateCallID generates call-id
func GenerateCallID() string {
	return generateRandom(7)
}

// CheckConnError is used to check for errors encountered during connection establishment
func CheckConnError(err error) {
	if err != nil {
		fmt.Println(err.Error())
		os.Exit(1)
	}
}