1 files changed, 77 insertions, 0 deletions
diff --git a/src/pkg/net/port.go b/src/pkg/net/port.go
new file mode 100644
index 000000000..21e3b48aa
--- /dev/null
+++ b/src/pkg/net/port.go
@@ -0,0 +1,77 @@
+// 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 system port mappings from /etc/services
+
+package net
+
+import (
+	"io";
+	"net";
+	"once";
+	"os";
+	"strconv";
+)
+
+// The error returned by LookupPort when a network service
+// is not listed in the database.
+var ErrNoService = &Error{"unknown network service"};
+
+var services map[string] map[string] int
+var servicesError os.Error
+
+func readServices() {
+	services = make(map[string] map[string] int);
+	var file *file;
+	file, servicesError = open("/etc/services");
+	for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+		// "http 80/tcp www www-http # World Wide Web HTTP"
+		if i := byteIndex(line, '#'); i >= 0 {
+			line = line[0:i];
+		}
+		f := getFields(line);
+		if len(f) < 2 {
+			continue;
+		}
+		portnet := f[1];	// "tcp/80"
+		port, j, ok := dtoi(portnet, 0);
+		if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {
+			continue
+		}
+		netw := portnet[j+1:len(portnet)];	// "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;
+			}
+		}
+	}
+	file.close();
+}
+
+// LookupPort looks up the port for the given network and service.
+func LookupPort(network, service string) (port int, err os.Error) {
+	once.Do(readServices);
+
+	switch network {
+	case "tcp4", "tcp6":
+		network = "tcp";
+	case "udp4", "udp6":
+		network = "udp";
+	}
+
+	m, ok := services[network];
+	if !ok {
+		return 0, ErrNoService;
+	}
+	port, ok = m[service];
+	if !ok {
+		return 0, ErrNoService;
+	}
+	return port, nil;
+}