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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}
}