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
}