Subversion Repositories openrisc

// 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 static host/IP entries from /etc/hosts.

package net

import (

        "sync"

        "time"

)

const cacheMaxAge = 5 * time.Minute

// hostsPath points to the file with static IP/address entries.

var hostsPath = "/etc/hosts"

// Simple cache.

var hosts struct {

        sync.Mutex

        byName map[string][]string

        byAddr map[string][]string

        expire time.Time

        path   string

}

func readHosts() {

        now := time.Now()

        hp := hostsPath

        if len(hosts.byName) == 0 || now.After(hosts.expire) || hosts.path != hp {

                hs := make(map[string][]string)

                is := make(map[string][]string)

                var file *file

                if file, _ = open(hp); file == nil {

                        return

                }

                for line, ok := file.readLine(); ok; line, ok = file.readLine() {

                        if i := byteIndex(line, '#'); i >= 0 {

                                // Discard comments.

                                line = line[0:i]

                        }

                        f := getFields(line)

                        if len(f) < 2 || ParseIP(f[0]) == nil {

                                continue

                        }

                        for i := 1; i < len(f); i++ {

                                h := f[i]

                                hs[h] = append(hs[h], f[0])

                                is[f[0]] = append(is[f[0]], h)

                        }

                }

                // Update the data cache.

                hosts.expire = time.Now().Add(cacheMaxAge)

                hosts.path = hp

                hosts.byName = hs

                hosts.byAddr = is

                file.close()

        }

}

// lookupStaticHost looks up the addresses for the given host from /etc/hosts.

func lookupStaticHost(host string) []string {

        hosts.Lock()

        defer hosts.Unlock()

        readHosts()

        if len(hosts.byName) != 0 {

                if ips, ok := hosts.byName[host]; ok {

                        return ips

                }

        }

        return nil

}

// lookupStaticAddr looks up the hosts for the given address from /etc/hosts.

func lookupStaticAddr(addr string) []string {

        hosts.Lock()

        defer hosts.Unlock()

        readHosts()

        if len(hosts.byAddr) != 0 {

                if hosts, ok := hosts.byAddr[addr]; ok {

                        return hosts

                }

        }

        return nil

}