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Diffstat (limited to 'vendor/golang.org/x/text/secure/bidirule/bidirule.go')
| -rw-r--r-- | vendor/golang.org/x/text/secure/bidirule/bidirule.go | 336 |
1 files changed, 336 insertions, 0 deletions
diff --git a/vendor/golang.org/x/text/secure/bidirule/bidirule.go b/vendor/golang.org/x/text/secure/bidirule/bidirule.go new file mode 100644 index 0000000..e2b70f7 --- /dev/null +++ b/vendor/golang.org/x/text/secure/bidirule/bidirule.go @@ -0,0 +1,336 @@ +// 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 +} |