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 // +build darwin freebsd linux openbsd
   6
   7 // Read system port mappings from /etc/services
   8
   9 package net
  10
  11 import (
  12         "os"
  13         "sync"
  14 )
  15
  16 var services map[string]map[string]int
  17 var servicesError os.Error
  18 var onceReadServices sync.Once
  19
  20 func readServices() {
  21         services = make(map[string]map[string]int)
  22         var file *file
  23         if file, servicesError = open("/etc/services"); servicesError != nil {
  24                 return
  25         }
  26         for line, ok := file.readLine(); ok; line, ok = file.readLine() {
  27                 // "http 80/tcp www www-http # World Wide Web HTTP"
  28                 if i := byteIndex(line, '#'); i >= 0 {
  29                         line = line[0:i]
  30                 }
  31                 f := getFields(line)
  32                 if len(f) < 2 {
  33                         continue
  34                 }
  35                 portnet := f[1] // "tcp/80"
  36                 port, j, ok := dtoi(portnet, 0)
  37                 if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {
  38                         continue
  39                 }
  40                 netw := portnet[j+1:] // "tcp"
  41                 m, ok1 := services[netw]
  42                 if !ok1 {
  43                         m = make(map[string]int)
  44                         services[netw] = m
  45                 }
  46                 for i := 0; i < len(f); i++ {
  47                         if i != 1 { // f[1] was port/net
  48                                 m[f[i]] = port
  49                         }
  50                 }
  51         }
  52         file.close()
  53 }
  54
  55 // goLookupPort is the native Go implementation of LookupPort.
  56 func goLookupPort(network, service string) (port int, err os.Error) {
  57         onceReadServices.Do(readServices)
  58
  59         switch network {
  60         case "tcp4", "tcp6":
  61                 network = "tcp"
  62         case "udp4", "udp6":
  63                 network = "udp"
  64         }
  65
  66         if m, ok := services[network]; ok {
  67                 if port, ok = m[service]; ok {
  68                         return
  69                 }
  70         }
  71         return 0, &AddrError{"unknown port", network + "/" + service}
  72 }