util.go

package main

import (
	"bufio"
	"fmt"
	"net"
	"os"
	"sort"

	"golang.org/x/crypto/bcrypt"
)

func FileExists(name string) bool {
	fi, err := os.Stat(name)
	if err != nil {
		return false
	}
	return fi.Mode().IsRegular()
}

func ReadLines(name string) ([]string, error) {
	f, err := os.Open(name)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	var lines []string
	sc := bufio.NewScanner(f)
	for sc.Scan() {
		lines = append(lines, sc.Text())
	}
	return lines, sc.Err()
}

// This function does not make any actual connections
func GetOutboundIP() (net.IP, error) {
	conn, err := net.Dial("udp", "8.8.8.8:53")
	if err != nil {
		return nil, err
	}
	defer conn.Close()

	addr, ok := conn.LocalAddr().(*net.UDPAddr)
	if !ok {
		return nil, fmt.Errorf("Could not get outbound IP")
	}
	return addr.IP, nil
}

func Prefix(s string, n int) string {
	if len(s) > n {
		return s[:n]
	} else {
		return s
	}
}

type Set map[string]struct{}

func (s Set) Array() []string {
	var a []string
	for k := range s {
		a = append(a, k)
	}
	sort.Strings(a)
	return a
}

func (s Set) Insert(k string) {
	s[k] = struct{}{}
}

func (s Set) Union(a Set) Set {
	u := make(Set)
	for k := range s {
		u[k] = struct{}{}
	}
	for k := range a {
		u[k] = struct{}{}
	}
	return u
}

func HashPassword(password string) (string, error) {
	bytes, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	return string(bytes), err
}