crypto/openpgp/packet: add UserId packet type

This was split from CL 4124054

R=bradfitzgo
CC=golang-dev
https://golang.org/cl/4126057

src/pkg/crypto/openpgp/packet/userid.go

+// Copyright 2011 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.
+
+package packet
+
+import (
+	"io"
+	"io/ioutil"
+	"os"
+	"strings"
+)
+
+// UserId contains text that is intended to represent the name and email
+// address of the key holder. See RFC 4880, section 5.11. By convention, this
+// takes the form "Full Name (Comment) <email@example.com>"
+type UserId struct {
+	Id string // By convention, this takes the form "Full Name (Comment) <email@example.com>" which is split out in the fields below.
+
+	Name, Comment, Email string
+}
+
+func (uid *UserId) parse(r io.Reader) (err os.Error) {
+	// RFC 4880, section 5.11
+	b, err := ioutil.ReadAll(r)
+	if err != nil {
+		return
+	}
+	uid.Id = string(b)
+	uid.Name, uid.Comment, uid.Email = parseUserId(uid.Id)
+	return
+}
+
+// parseUserId extracts the name, comment and email from a user id string that
+// is formatted as "Full Name (Comment) <email@example.com>".
+func parseUserId(id string) (name, comment, email string) {
+	var n, c, e struct {
+		start, end int
+	}
+	var state int
+
+	for offset, rune := range id {
+		switch state {
+		case 0:
+			// Entering name
+			n.start = offset
+			state = 1
+			fallthrough
+		case 1:
+			// In name
+			if rune == '(' {
+				state = 2
+				n.end = offset
+			} else if rune == '<' {
+				state = 5
+				n.end = offset
+			}
+		case 2:
+			// Entering comment
+			c.start = offset
+			state = 3
+			fallthrough
+		case 3:
+			// In comment
+			if rune == ')' {
+				state = 4
+				c.end = offset
+			}
+		case 4:
+			// Between comment and email
+			if rune == '<' {
+				state = 5
+			}
+		case 5:
+			// Entering email
+			e.start = offset
+			state = 6
+			fallthrough
+		case 6:
+			// In email
+			if rune == '>' {
+				state = 7
+				e.end = offset
+			}
+		default:
+			// After email
+		}
+	}
+	switch state {
+	case 1:
+		// ended in the name
+		n.end = len(id)
+	case 3:
+		// ended in comment
+		c.end = len(id)
+	case 6:
+		// ended in email
+		e.end = len(id)
+	}
+
+	name = strings.TrimSpace(id[n.start:n.end])
+	comment = strings.TrimSpace(id[c.start:c.end])
+	email = strings.TrimSpace(id[e.start:e.end])
+	return
+}

src/pkg/crypto/openpgp/packet/userid_test.go

+// Copyright 2011 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.
+
+package packet
+
+import (
+	"testing"
+)
+
+var userIdTests = []struct {
+	id                   string
+	name, comment, email string
+}{
+	{"", "", "", ""},
+	{"John Smith", "John Smith", "", ""},
+	{"John Smith ()", "John Smith", "", ""},
+	{"John Smith () <>", "John Smith", "", ""},
+	{"(comment", "", "comment", ""},
+	{"(comment)", "", "comment", ""},
+	{"<email", "", "", "email"},
+	{"<email>   sdfk", "", "", "email"},
+	{"  John Smith  (  Comment ) asdkflj < email > lksdfj", "John Smith", "Comment", "email"},
+	{"  John Smith  < email > lksdfj", "John Smith", "", "email"},
+	{"(<foo", "", "<foo", ""},
+	{"René Descartes (العربي)", "René Descartes", "العربي", ""},
+}
+
+func TestParseUserId(t *testing.T) {
+	for i, test := range userIdTests {
+		name, comment, email := parseUserId(test.id)
+		if name != test.name {
+			t.Errorf("%d: name mismatch got:%s want:%s", i, name, test.name)
+		}
+		if comment != test.comment {
+			t.Errorf("%d: comment mismatch got:%s want:%s", i, comment, test.comment)
+		}
+		if email != test.email {
+			t.Errorf("%d: email mismatch got:%s want:%s", i, email, test.email)
+		}
+	}
+}