libgo/go/net/port.go

   1 // Copyright 2009 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Read system port mappings from /etc/services
   6
   7 package net
   8
   9 import (
  10         "os"
  11         "sync"
  12 )
  13
  14 var services map[string]map[string]int
  15 var servicesError os.Error
  16 var onceReadServices sync.Once
  17
  18 func readServices() {
  19         services = make(map[string]map[string]int)
  20         var file *file
  21         file, servicesError = open("/etc/services")
  22         for line, ok := file.readLine(); ok; line, ok = file.readLine() {
  23                 // "http 80/tcp www www-http # World Wide Web HTTP"
  24                 if i := byteIndex(line, '#'); i >= 0 {
  25                         line = line[0:i]
  26                 }
  27                 f := getFields(line)
  28                 if len(f) < 2 {
  29                         continue
  30                 }
  31                 portnet := f[1] // "tcp/80"
  32                 port, j, ok := dtoi(portnet, 0)
  33                 if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {
  34                         continue
  35                 }
  36                 netw := portnet[j+1:] // "tcp"
  37                 m, ok1 := services[netw]
  38                 if !ok1 {
  39                         m = make(map[string]int)
  40                         services[netw] = m
  41                 }
  42                 for i := 0; i < len(f); i++ {
  43                         if i != 1 { // f[1] was port/net
  44                                 m[f[i]] = port
  45                         }
  46                 }
  47         }
  48         file.close()
  49 }
  50
  51 // LookupPort looks up the port for the given network and service.
  52 func LookupPort(network, service string) (port int, err os.Error) {
  53         onceReadServices.Do(readServices)
  54
  55         switch network {
  56         case "tcp4", "tcp6":
  57                 network = "tcp"
  58         case "udp4", "udp6":
  59                 network = "udp"
  60         }
  61
  62         if m, ok := services[network]; ok {
  63                 if port, ok = m[service]; ok {
  64                         return
  65                 }
  66         }
  67         return 0, &AddrError{"unknown port", network + "/" + service}
  68 }