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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 (
"io";
"net";
"once";
"os";
"strconv";
)
// The error returned by LookupPort when a network service
// is not listed in the database.
var ErrNoService = &Error{"unknown network service"};
var services map[string] map[string] int
var servicesError os.Error
func readServices() {
services = make(map[string] map[string] int);
var file *file;
file, servicesError = open("/etc/services");
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:len(portnet)]; // "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) {
once.Do(readServices);
switch network {
case "tcp4", "tcp6":
network = "tcp";
case "udp4", "udp6":
network = "udp";
}
m, ok := services[network];
if !ok {
return 0, ErrNoService;
}
port, ok = m[service];
if !ok {
return 0, ErrNoService;
}
return port, nil;
}
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