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// Copyright 2009 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

// +build darwin freebsd linux netbsd openbsd

// Read system port mappings from /etc/services

package net

import "sync"

var services map[string]map[string]int

var servicesError error

var onceReadServices sync.Once

func readServices() {

        services = make(map[string]map[string]int)

        var file *file

        if file, servicesError = open("/etc/services"); servicesError != nil {

                return

        }

        for line, ok := file.readLine(); ok; line, ok = file.readLine() {

                // "http 80/tcp www www-http # World Wide Web HTTP"

                if i := byteIndex(line, '#'); i >= 0 {

                        line = line[0:i]

                }

                f := getFields(line)

                if len(f) < 2 {

                        continue

                }

                portnet := f[1] // "tcp/80"

                port, j, ok := dtoi(portnet, 0)

                if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {

                        continue

                }

                netw := portnet[j+1:] // "tcp"

                m, ok1 := services[netw]

                if !ok1 {

                        m = make(map[string]int)

                        services[netw] = m

                }

                for i := 0; i < len(f); i++ {

                        if i != 1 { // f[1] was port/net

                                m[f[i]] = port

                        }

                }

        }

        file.close()

}

// goLookupPort is the native Go implementation of LookupPort.

func goLookupPort(network, service string) (port int, err error) {

        onceReadServices.Do(readServices)

        switch network {

        case "tcp4", "tcp6":

                network = "tcp"

        case "udp4", "udp6":

                network = "udp"

        }

        if m, ok := services[network]; ok {

                if port, ok = m[service]; ok {

                        return

                }

        }

        return 0, &AddrError{"unknown port", network + "/" + service}

}