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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.
// Read system port mappings from /etc/services
package net
import (
"os"
"sync"
)
var services map[string]map[string]int
var servicesError os.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()
}
// LookupPort looks up the port for the given network and service.
func LookupPort(network, service string) (port int, err os.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}
}
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