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         if file, servicesError = open("/etc/services"); servicesError != nil {
  22                 return
  23         }
  24         for line, ok := file.readLine(); ok; line, ok = file.readLine() {
  25                 // "http 80/tcp www www-http # World Wide Web HTTP"
  26                 if i := byteIndex(line, '#'); i >= 0 {
  27                         line = line[0:i]
  28                 }
  29                 f := getFields(line)
  30                 if len(f) < 2 {
  31                         continue
  32                 }
  33                 portnet := f[1] // "tcp/80"
  34                 port, j, ok := dtoi(portnet, 0)
  35                 if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {
  36                         continue
  37                 }
  38                 netw := portnet[j+1:] // "tcp"
  39                 m, ok1 := services[netw]
  40                 if !ok1 {
  41                         m = make(map[string]int)
  42                         services[netw] = m
  43                 }
  44                 for i := 0; i < len(f); i++ {
  45                         if i != 1 { // f[1] was port/net
  46                                 m[f[i]] = port
  47                         }
  48                 }
  49         }
  50         file.close()
  51 }
  52
  53 // LookupPort looks up the port for the given network and service.
  54 func LookupPort(network, service string) (port int, err os.Error) {
  55         onceReadServices.Do(readServices)
  56
  57         switch network {
  58         case "tcp4", "tcp6":
  59                 network = "tcp"
  60         case "udp4", "udp6":
  61                 network = "udp"
  62         }
  63
  64         if m, ok := services[network]; ok {
  65                 if port, ok = m[service]; ok {
  66                         return
  67                 }
  68         }
  69         return 0, &AddrError{"unknown port", network + "/" + service}
  70 }