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// 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.
//go:build unix || (js && wasm) || wasip1
// Read system port mappings from /etc/services
package net
import (
"internal/bytealg"
"sync"
)
var onceReadServices sync.Once
func readServices() {
file, err := open("/etc/services")
if err != nil {
return
}
defer file.close()
for line, ok := file.readLine(); ok; line, ok = file.readLine() {
// "http 80/tcp www www-http # World Wide Web HTTP"
if i := bytealg.IndexByteString(line, '#'); i >= 0 {
line = line[:i]
}
f := getFields(line)
if len(f) < 2 {
continue
}
portnet := f[1] // "80/tcp"
port, j, ok := dtoi(portnet)
if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {
continue
}
netw := portnet[j+1:] // "tcp"
m, ok1 := services[netw]
if !ok1 {
m = make(map[string]int)
services[netw] = m
}
for i := 0; i < len(f); i++ {
if i != 1 { // f[1] was port/net
m[f[i]] = port
}
}
}
}
// goLookupPort is the native Go implementation of LookupPort.
func goLookupPort(network, service string) (port int, err error) {
onceReadServices.Do(readServices)
return lookupPortMap(network, service)
}
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