mirror of
https://github.com/genuinetools/reg.git
synced 2024-08-22 22:40:24 -04:00
337 lines
9.3 KiB
Go
337 lines
9.3 KiB
Go
// Copyright 2016 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 bidirule implements the Bidi Rule defined by RFC 5893.
|
|
//
|
|
// This package is under development. The API may change without notice and
|
|
// without preserving backward compatibility.
|
|
package bidirule
|
|
|
|
import (
|
|
"errors"
|
|
"unicode/utf8"
|
|
|
|
"golang.org/x/text/transform"
|
|
"golang.org/x/text/unicode/bidi"
|
|
)
|
|
|
|
// This file contains an implementation of RFC 5893: Right-to-Left Scripts for
|
|
// Internationalized Domain Names for Applications (IDNA)
|
|
//
|
|
// A label is an individual component of a domain name. Labels are usually
|
|
// shown separated by dots; for example, the domain name "www.example.com" is
|
|
// composed of three labels: "www", "example", and "com".
|
|
//
|
|
// An RTL label is a label that contains at least one character of class R, AL,
|
|
// or AN. An LTR label is any label that is not an RTL label.
|
|
//
|
|
// A "Bidi domain name" is a domain name that contains at least one RTL label.
|
|
//
|
|
// The following guarantees can be made based on the above:
|
|
//
|
|
// o In a domain name consisting of only labels that satisfy the rule,
|
|
// the requirements of Section 3 are satisfied. Note that even LTR
|
|
// labels and pure ASCII labels have to be tested.
|
|
//
|
|
// o In a domain name consisting of only LDH labels (as defined in the
|
|
// Definitions document [RFC5890]) and labels that satisfy the rule,
|
|
// the requirements of Section 3 are satisfied as long as a label
|
|
// that starts with an ASCII digit does not come after a
|
|
// right-to-left label.
|
|
//
|
|
// No guarantee is given for other combinations.
|
|
|
|
// ErrInvalid indicates a label is invalid according to the Bidi Rule.
|
|
var ErrInvalid = errors.New("bidirule: failed Bidi Rule")
|
|
|
|
type ruleState uint8
|
|
|
|
const (
|
|
ruleInitial ruleState = iota
|
|
ruleLTR
|
|
ruleLTRFinal
|
|
ruleRTL
|
|
ruleRTLFinal
|
|
ruleInvalid
|
|
)
|
|
|
|
type ruleTransition struct {
|
|
next ruleState
|
|
mask uint16
|
|
}
|
|
|
|
var transitions = [...][2]ruleTransition{
|
|
// [2.1] The first character must be a character with Bidi property L, R, or
|
|
// AL. If it has the R or AL property, it is an RTL label; if it has the L
|
|
// property, it is an LTR label.
|
|
ruleInitial: {
|
|
{ruleLTRFinal, 1 << bidi.L},
|
|
{ruleRTLFinal, 1<<bidi.R | 1<<bidi.AL},
|
|
},
|
|
ruleRTL: {
|
|
// [2.3] In an RTL label, the end of the label must be a character with
|
|
// Bidi property R, AL, EN, or AN, followed by zero or more characters
|
|
// with Bidi property NSM.
|
|
{ruleRTLFinal, 1<<bidi.R | 1<<bidi.AL | 1<<bidi.EN | 1<<bidi.AN},
|
|
|
|
// [2.2] In an RTL label, only characters with the Bidi properties R,
|
|
// AL, AN, EN, ES, CS, ET, ON, BN, or NSM are allowed.
|
|
// We exclude the entries from [2.3]
|
|
{ruleRTL, 1<<bidi.ES | 1<<bidi.CS | 1<<bidi.ET | 1<<bidi.ON | 1<<bidi.BN | 1<<bidi.NSM},
|
|
},
|
|
ruleRTLFinal: {
|
|
// [2.3] In an RTL label, the end of the label must be a character with
|
|
// Bidi property R, AL, EN, or AN, followed by zero or more characters
|
|
// with Bidi property NSM.
|
|
{ruleRTLFinal, 1<<bidi.R | 1<<bidi.AL | 1<<bidi.EN | 1<<bidi.AN | 1<<bidi.NSM},
|
|
|
|
// [2.2] In an RTL label, only characters with the Bidi properties R,
|
|
// AL, AN, EN, ES, CS, ET, ON, BN, or NSM are allowed.
|
|
// We exclude the entries from [2.3] and NSM.
|
|
{ruleRTL, 1<<bidi.ES | 1<<bidi.CS | 1<<bidi.ET | 1<<bidi.ON | 1<<bidi.BN},
|
|
},
|
|
ruleLTR: {
|
|
// [2.6] In an LTR label, the end of the label must be a character with
|
|
// Bidi property L or EN, followed by zero or more characters with Bidi
|
|
// property NSM.
|
|
{ruleLTRFinal, 1<<bidi.L | 1<<bidi.EN},
|
|
|
|
// [2.5] In an LTR label, only characters with the Bidi properties L,
|
|
// EN, ES, CS, ET, ON, BN, or NSM are allowed.
|
|
// We exclude the entries from [2.6].
|
|
{ruleLTR, 1<<bidi.ES | 1<<bidi.CS | 1<<bidi.ET | 1<<bidi.ON | 1<<bidi.BN | 1<<bidi.NSM},
|
|
},
|
|
ruleLTRFinal: {
|
|
// [2.6] In an LTR label, the end of the label must be a character with
|
|
// Bidi property L or EN, followed by zero or more characters with Bidi
|
|
// property NSM.
|
|
{ruleLTRFinal, 1<<bidi.L | 1<<bidi.EN | 1<<bidi.NSM},
|
|
|
|
// [2.5] In an LTR label, only characters with the Bidi properties L,
|
|
// EN, ES, CS, ET, ON, BN, or NSM are allowed.
|
|
// We exclude the entries from [2.6].
|
|
{ruleLTR, 1<<bidi.ES | 1<<bidi.CS | 1<<bidi.ET | 1<<bidi.ON | 1<<bidi.BN},
|
|
},
|
|
ruleInvalid: {
|
|
{ruleInvalid, 0},
|
|
{ruleInvalid, 0},
|
|
},
|
|
}
|
|
|
|
// [2.4] In an RTL label, if an EN is present, no AN may be present, and
|
|
// vice versa.
|
|
const exclusiveRTL = uint16(1<<bidi.EN | 1<<bidi.AN)
|
|
|
|
// From RFC 5893
|
|
// An RTL label is a label that contains at least one character of type
|
|
// R, AL, or AN.
|
|
//
|
|
// An LTR label is any label that is not an RTL label.
|
|
|
|
// Direction reports the direction of the given label as defined by RFC 5893.
|
|
// The Bidi Rule does not have to be applied to labels of the category
|
|
// LeftToRight.
|
|
func Direction(b []byte) bidi.Direction {
|
|
for i := 0; i < len(b); {
|
|
e, sz := bidi.Lookup(b[i:])
|
|
if sz == 0 {
|
|
i++
|
|
}
|
|
c := e.Class()
|
|
if c == bidi.R || c == bidi.AL || c == bidi.AN {
|
|
return bidi.RightToLeft
|
|
}
|
|
i += sz
|
|
}
|
|
return bidi.LeftToRight
|
|
}
|
|
|
|
// DirectionString reports the direction of the given label as defined by RFC
|
|
// 5893. The Bidi Rule does not have to be applied to labels of the category
|
|
// LeftToRight.
|
|
func DirectionString(s string) bidi.Direction {
|
|
for i := 0; i < len(s); {
|
|
e, sz := bidi.LookupString(s[i:])
|
|
if sz == 0 {
|
|
i++
|
|
continue
|
|
}
|
|
c := e.Class()
|
|
if c == bidi.R || c == bidi.AL || c == bidi.AN {
|
|
return bidi.RightToLeft
|
|
}
|
|
i += sz
|
|
}
|
|
return bidi.LeftToRight
|
|
}
|
|
|
|
// Valid reports whether b conforms to the BiDi rule.
|
|
func Valid(b []byte) bool {
|
|
var t Transformer
|
|
if n, ok := t.advance(b); !ok || n < len(b) {
|
|
return false
|
|
}
|
|
return t.isFinal()
|
|
}
|
|
|
|
// ValidString reports whether s conforms to the BiDi rule.
|
|
func ValidString(s string) bool {
|
|
var t Transformer
|
|
if n, ok := t.advanceString(s); !ok || n < len(s) {
|
|
return false
|
|
}
|
|
return t.isFinal()
|
|
}
|
|
|
|
// New returns a Transformer that verifies that input adheres to the Bidi Rule.
|
|
func New() *Transformer {
|
|
return &Transformer{}
|
|
}
|
|
|
|
// Transformer implements transform.Transform.
|
|
type Transformer struct {
|
|
state ruleState
|
|
hasRTL bool
|
|
seen uint16
|
|
}
|
|
|
|
// A rule can only be violated for "Bidi Domain names", meaning if one of the
|
|
// following categories has been observed.
|
|
func (t *Transformer) isRTL() bool {
|
|
const isRTL = 1<<bidi.R | 1<<bidi.AL | 1<<bidi.AN
|
|
return t.seen&isRTL != 0
|
|
}
|
|
|
|
// Reset implements transform.Transformer.
|
|
func (t *Transformer) Reset() { *t = Transformer{} }
|
|
|
|
// Transform implements transform.Transformer. This Transformer has state and
|
|
// needs to be reset between uses.
|
|
func (t *Transformer) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
|
|
if len(dst) < len(src) {
|
|
src = src[:len(dst)]
|
|
atEOF = false
|
|
err = transform.ErrShortDst
|
|
}
|
|
n, err1 := t.Span(src, atEOF)
|
|
copy(dst, src[:n])
|
|
if err == nil || err1 != nil && err1 != transform.ErrShortSrc {
|
|
err = err1
|
|
}
|
|
return n, n, err
|
|
}
|
|
|
|
// Span returns the first n bytes of src that conform to the Bidi rule.
|
|
func (t *Transformer) Span(src []byte, atEOF bool) (n int, err error) {
|
|
if t.state == ruleInvalid && t.isRTL() {
|
|
return 0, ErrInvalid
|
|
}
|
|
n, ok := t.advance(src)
|
|
switch {
|
|
case !ok:
|
|
err = ErrInvalid
|
|
case n < len(src):
|
|
if !atEOF {
|
|
err = transform.ErrShortSrc
|
|
break
|
|
}
|
|
err = ErrInvalid
|
|
case !t.isFinal():
|
|
err = ErrInvalid
|
|
}
|
|
return n, err
|
|
}
|
|
|
|
// Precomputing the ASCII values decreases running time for the ASCII fast path
|
|
// by about 30%.
|
|
var asciiTable [128]bidi.Properties
|
|
|
|
func init() {
|
|
for i := range asciiTable {
|
|
p, _ := bidi.LookupRune(rune(i))
|
|
asciiTable[i] = p
|
|
}
|
|
}
|
|
|
|
func (t *Transformer) advance(s []byte) (n int, ok bool) {
|
|
var e bidi.Properties
|
|
var sz int
|
|
for n < len(s) {
|
|
if s[n] < utf8.RuneSelf {
|
|
e, sz = asciiTable[s[n]], 1
|
|
} else {
|
|
e, sz = bidi.Lookup(s[n:])
|
|
if sz <= 1 {
|
|
if sz == 1 {
|
|
// We always consider invalid UTF-8 to be invalid, even if
|
|
// the string has not yet been determined to be RTL.
|
|
// TODO: is this correct?
|
|
return n, false
|
|
}
|
|
return n, true // incomplete UTF-8 encoding
|
|
}
|
|
}
|
|
// TODO: using CompactClass would result in noticeable speedup.
|
|
// See unicode/bidi/prop.go:Properties.CompactClass.
|
|
c := uint16(1 << e.Class())
|
|
t.seen |= c
|
|
if t.seen&exclusiveRTL == exclusiveRTL {
|
|
t.state = ruleInvalid
|
|
return n, false
|
|
}
|
|
switch tr := transitions[t.state]; {
|
|
case tr[0].mask&c != 0:
|
|
t.state = tr[0].next
|
|
case tr[1].mask&c != 0:
|
|
t.state = tr[1].next
|
|
default:
|
|
t.state = ruleInvalid
|
|
if t.isRTL() {
|
|
return n, false
|
|
}
|
|
}
|
|
n += sz
|
|
}
|
|
return n, true
|
|
}
|
|
|
|
func (t *Transformer) advanceString(s string) (n int, ok bool) {
|
|
var e bidi.Properties
|
|
var sz int
|
|
for n < len(s) {
|
|
if s[n] < utf8.RuneSelf {
|
|
e, sz = asciiTable[s[n]], 1
|
|
} else {
|
|
e, sz = bidi.LookupString(s[n:])
|
|
if sz <= 1 {
|
|
if sz == 1 {
|
|
return n, false // invalid UTF-8
|
|
}
|
|
return n, true // incomplete UTF-8 encoding
|
|
}
|
|
}
|
|
// TODO: using CompactClass results in noticeable speedup.
|
|
// See unicode/bidi/prop.go:Properties.CompactClass.
|
|
c := uint16(1 << e.Class())
|
|
t.seen |= c
|
|
if t.seen&exclusiveRTL == exclusiveRTL {
|
|
t.state = ruleInvalid
|
|
return n, false
|
|
}
|
|
switch tr := transitions[t.state]; {
|
|
case tr[0].mask&c != 0:
|
|
t.state = tr[0].next
|
|
case tr[1].mask&c != 0:
|
|
t.state = tr[1].next
|
|
default:
|
|
t.state = ruleInvalid
|
|
if t.isRTL() {
|
|
return n, false
|
|
}
|
|
}
|
|
n += sz
|
|
}
|
|
return n, true
|
|
}
|