forked from mirrors/gotosocial
604 lines
15 KiB
Go
604 lines
15 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package language
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import (
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"bytes"
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"errors"
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"fmt"
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"sort"
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"golang.org/x/text/internal/tag"
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)
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// isAlpha returns true if the byte is not a digit.
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// b must be an ASCII letter or digit.
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func isAlpha(b byte) bool {
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return b > '9'
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}
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// isAlphaNum returns true if the string contains only ASCII letters or digits.
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func isAlphaNum(s []byte) bool {
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for _, c := range s {
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if !('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9') {
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return false
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}
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}
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return true
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}
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// ErrSyntax is returned by any of the parsing functions when the
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// input is not well-formed, according to BCP 47.
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// TODO: return the position at which the syntax error occurred?
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var ErrSyntax = errors.New("language: tag is not well-formed")
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// ErrDuplicateKey is returned when a tag contains the same key twice with
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// different values in the -u section.
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var ErrDuplicateKey = errors.New("language: different values for same key in -u extension")
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// ValueError is returned by any of the parsing functions when the
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// input is well-formed but the respective subtag is not recognized
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// as a valid value.
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type ValueError struct {
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v [8]byte
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}
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// NewValueError creates a new ValueError.
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func NewValueError(tag []byte) ValueError {
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var e ValueError
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copy(e.v[:], tag)
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return e
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}
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func (e ValueError) tag() []byte {
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n := bytes.IndexByte(e.v[:], 0)
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if n == -1 {
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n = 8
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}
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return e.v[:n]
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}
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// Error implements the error interface.
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func (e ValueError) Error() string {
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return fmt.Sprintf("language: subtag %q is well-formed but unknown", e.tag())
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}
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// Subtag returns the subtag for which the error occurred.
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func (e ValueError) Subtag() string {
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return string(e.tag())
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}
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// scanner is used to scan BCP 47 tokens, which are separated by _ or -.
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type scanner struct {
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b []byte
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bytes [max99thPercentileSize]byte
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token []byte
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start int // start position of the current token
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end int // end position of the current token
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next int // next point for scan
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err error
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done bool
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}
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func makeScannerString(s string) scanner {
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scan := scanner{}
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if len(s) <= len(scan.bytes) {
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scan.b = scan.bytes[:copy(scan.bytes[:], s)]
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} else {
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scan.b = []byte(s)
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}
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scan.init()
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return scan
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}
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// makeScanner returns a scanner using b as the input buffer.
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// b is not copied and may be modified by the scanner routines.
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func makeScanner(b []byte) scanner {
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scan := scanner{b: b}
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scan.init()
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return scan
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}
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func (s *scanner) init() {
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for i, c := range s.b {
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if c == '_' {
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s.b[i] = '-'
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}
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}
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s.scan()
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}
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// restToLower converts the string between start and end to lower case.
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func (s *scanner) toLower(start, end int) {
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for i := start; i < end; i++ {
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c := s.b[i]
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if 'A' <= c && c <= 'Z' {
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s.b[i] += 'a' - 'A'
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}
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}
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}
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func (s *scanner) setError(e error) {
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if s.err == nil || (e == ErrSyntax && s.err != ErrSyntax) {
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s.err = e
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}
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}
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// resizeRange shrinks or grows the array at position oldStart such that
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// a new string of size newSize can fit between oldStart and oldEnd.
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// Sets the scan point to after the resized range.
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func (s *scanner) resizeRange(oldStart, oldEnd, newSize int) {
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s.start = oldStart
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if end := oldStart + newSize; end != oldEnd {
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diff := end - oldEnd
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var b []byte
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if n := len(s.b) + diff; n > cap(s.b) {
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b = make([]byte, n)
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copy(b, s.b[:oldStart])
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} else {
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b = s.b[:n]
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}
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copy(b[end:], s.b[oldEnd:])
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s.b = b
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s.next = end + (s.next - s.end)
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s.end = end
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}
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}
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// replace replaces the current token with repl.
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func (s *scanner) replace(repl string) {
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s.resizeRange(s.start, s.end, len(repl))
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copy(s.b[s.start:], repl)
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}
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// gobble removes the current token from the input.
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// Caller must call scan after calling gobble.
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func (s *scanner) gobble(e error) {
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s.setError(e)
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if s.start == 0 {
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s.b = s.b[:+copy(s.b, s.b[s.next:])]
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s.end = 0
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} else {
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s.b = s.b[:s.start-1+copy(s.b[s.start-1:], s.b[s.end:])]
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s.end = s.start - 1
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}
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s.next = s.start
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}
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// deleteRange removes the given range from s.b before the current token.
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func (s *scanner) deleteRange(start, end int) {
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s.b = s.b[:start+copy(s.b[start:], s.b[end:])]
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diff := end - start
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s.next -= diff
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s.start -= diff
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s.end -= diff
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}
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// scan parses the next token of a BCP 47 string. Tokens that are larger
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// than 8 characters or include non-alphanumeric characters result in an error
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// and are gobbled and removed from the output.
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// It returns the end position of the last token consumed.
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func (s *scanner) scan() (end int) {
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end = s.end
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s.token = nil
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for s.start = s.next; s.next < len(s.b); {
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i := bytes.IndexByte(s.b[s.next:], '-')
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if i == -1 {
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s.end = len(s.b)
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s.next = len(s.b)
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i = s.end - s.start
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} else {
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s.end = s.next + i
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s.next = s.end + 1
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}
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token := s.b[s.start:s.end]
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if i < 1 || i > 8 || !isAlphaNum(token) {
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s.gobble(ErrSyntax)
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continue
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}
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s.token = token
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return end
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}
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if n := len(s.b); n > 0 && s.b[n-1] == '-' {
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s.setError(ErrSyntax)
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s.b = s.b[:len(s.b)-1]
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}
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s.done = true
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return end
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}
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// acceptMinSize parses multiple tokens of the given size or greater.
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// It returns the end position of the last token consumed.
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func (s *scanner) acceptMinSize(min int) (end int) {
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end = s.end
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s.scan()
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for ; len(s.token) >= min; s.scan() {
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end = s.end
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}
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return end
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}
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// Parse parses the given BCP 47 string and returns a valid Tag. If parsing
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// failed it returns an error and any part of the tag that could be parsed.
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// If parsing succeeded but an unknown value was found, it returns
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// ValueError. The Tag returned in this case is just stripped of the unknown
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// value. All other values are preserved. It accepts tags in the BCP 47 format
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// and extensions to this standard defined in
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// https://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
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func Parse(s string) (t Tag, err error) {
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// TODO: consider supporting old-style locale key-value pairs.
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if s == "" {
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return Und, ErrSyntax
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}
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defer func() {
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if recover() != nil {
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t = Und
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err = ErrSyntax
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return
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}
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}()
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if len(s) <= maxAltTaglen {
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b := [maxAltTaglen]byte{}
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for i, c := range s {
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// Generating invalid UTF-8 is okay as it won't match.
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if 'A' <= c && c <= 'Z' {
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c += 'a' - 'A'
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} else if c == '_' {
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c = '-'
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}
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b[i] = byte(c)
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}
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if t, ok := grandfathered(b); ok {
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return t, nil
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}
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}
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scan := makeScannerString(s)
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return parse(&scan, s)
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}
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func parse(scan *scanner, s string) (t Tag, err error) {
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t = Und
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var end int
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if n := len(scan.token); n <= 1 {
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scan.toLower(0, len(scan.b))
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if n == 0 || scan.token[0] != 'x' {
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return t, ErrSyntax
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}
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end = parseExtensions(scan)
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} else if n >= 4 {
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return Und, ErrSyntax
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} else { // the usual case
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t, end = parseTag(scan)
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if n := len(scan.token); n == 1 {
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t.pExt = uint16(end)
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end = parseExtensions(scan)
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} else if end < len(scan.b) {
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scan.setError(ErrSyntax)
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scan.b = scan.b[:end]
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}
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}
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if int(t.pVariant) < len(scan.b) {
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if end < len(s) {
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s = s[:end]
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}
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if len(s) > 0 && tag.Compare(s, scan.b) == 0 {
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t.str = s
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} else {
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t.str = string(scan.b)
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}
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} else {
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t.pVariant, t.pExt = 0, 0
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}
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return t, scan.err
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}
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// parseTag parses language, script, region and variants.
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// It returns a Tag and the end position in the input that was parsed.
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func parseTag(scan *scanner) (t Tag, end int) {
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var e error
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// TODO: set an error if an unknown lang, script or region is encountered.
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t.LangID, e = getLangID(scan.token)
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scan.setError(e)
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scan.replace(t.LangID.String())
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langStart := scan.start
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end = scan.scan()
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for len(scan.token) == 3 && isAlpha(scan.token[0]) {
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// From http://tools.ietf.org/html/bcp47, <lang>-<extlang> tags are equivalent
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// to a tag of the form <extlang>.
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lang, e := getLangID(scan.token)
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if lang != 0 {
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t.LangID = lang
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copy(scan.b[langStart:], lang.String())
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scan.b[langStart+3] = '-'
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scan.start = langStart + 4
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}
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scan.gobble(e)
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end = scan.scan()
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}
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if len(scan.token) == 4 && isAlpha(scan.token[0]) {
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t.ScriptID, e = getScriptID(script, scan.token)
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if t.ScriptID == 0 {
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scan.gobble(e)
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}
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end = scan.scan()
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}
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if n := len(scan.token); n >= 2 && n <= 3 {
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t.RegionID, e = getRegionID(scan.token)
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if t.RegionID == 0 {
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scan.gobble(e)
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} else {
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scan.replace(t.RegionID.String())
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}
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end = scan.scan()
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}
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scan.toLower(scan.start, len(scan.b))
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t.pVariant = byte(end)
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end = parseVariants(scan, end, t)
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t.pExt = uint16(end)
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return t, end
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}
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var separator = []byte{'-'}
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// parseVariants scans tokens as long as each token is a valid variant string.
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// Duplicate variants are removed.
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func parseVariants(scan *scanner, end int, t Tag) int {
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start := scan.start
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varIDBuf := [4]uint8{}
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variantBuf := [4][]byte{}
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varID := varIDBuf[:0]
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variant := variantBuf[:0]
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last := -1
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needSort := false
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for ; len(scan.token) >= 4; scan.scan() {
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// TODO: measure the impact of needing this conversion and redesign
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// the data structure if there is an issue.
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v, ok := variantIndex[string(scan.token)]
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if !ok {
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// unknown variant
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// TODO: allow user-defined variants?
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scan.gobble(NewValueError(scan.token))
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continue
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}
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varID = append(varID, v)
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variant = append(variant, scan.token)
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if !needSort {
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if last < int(v) {
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last = int(v)
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} else {
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needSort = true
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// There is no legal combinations of more than 7 variants
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// (and this is by no means a useful sequence).
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const maxVariants = 8
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if len(varID) > maxVariants {
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break
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}
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}
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}
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end = scan.end
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}
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if needSort {
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sort.Sort(variantsSort{varID, variant})
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k, l := 0, -1
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for i, v := range varID {
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w := int(v)
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if l == w {
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// Remove duplicates.
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continue
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}
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varID[k] = varID[i]
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variant[k] = variant[i]
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k++
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l = w
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}
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if str := bytes.Join(variant[:k], separator); len(str) == 0 {
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end = start - 1
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} else {
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scan.resizeRange(start, end, len(str))
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copy(scan.b[scan.start:], str)
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end = scan.end
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}
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}
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return end
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}
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type variantsSort struct {
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i []uint8
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v [][]byte
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}
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func (s variantsSort) Len() int {
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return len(s.i)
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}
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func (s variantsSort) Swap(i, j int) {
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s.i[i], s.i[j] = s.i[j], s.i[i]
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s.v[i], s.v[j] = s.v[j], s.v[i]
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}
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func (s variantsSort) Less(i, j int) bool {
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return s.i[i] < s.i[j]
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}
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type bytesSort struct {
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b [][]byte
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n int // first n bytes to compare
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}
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func (b bytesSort) Len() int {
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return len(b.b)
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}
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func (b bytesSort) Swap(i, j int) {
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b.b[i], b.b[j] = b.b[j], b.b[i]
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}
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func (b bytesSort) Less(i, j int) bool {
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for k := 0; k < b.n; k++ {
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if b.b[i][k] == b.b[j][k] {
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continue
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}
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return b.b[i][k] < b.b[j][k]
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}
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return false
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}
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// parseExtensions parses and normalizes the extensions in the buffer.
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// It returns the last position of scan.b that is part of any extension.
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// It also trims scan.b to remove excess parts accordingly.
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func parseExtensions(scan *scanner) int {
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start := scan.start
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exts := [][]byte{}
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private := []byte{}
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end := scan.end
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for len(scan.token) == 1 {
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extStart := scan.start
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ext := scan.token[0]
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end = parseExtension(scan)
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extension := scan.b[extStart:end]
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if len(extension) < 3 || (ext != 'x' && len(extension) < 4) {
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scan.setError(ErrSyntax)
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end = extStart
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continue
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} else if start == extStart && (ext == 'x' || scan.start == len(scan.b)) {
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scan.b = scan.b[:end]
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return end
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} else if ext == 'x' {
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private = extension
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break
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}
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exts = append(exts, extension)
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}
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sort.Sort(bytesSort{exts, 1})
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if len(private) > 0 {
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exts = append(exts, private)
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}
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scan.b = scan.b[:start]
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if len(exts) > 0 {
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scan.b = append(scan.b, bytes.Join(exts, separator)...)
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} else if start > 0 {
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// Strip trailing '-'.
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scan.b = scan.b[:start-1]
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}
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return end
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}
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// parseExtension parses a single extension and returns the position of
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// the extension end.
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func parseExtension(scan *scanner) int {
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start, end := scan.start, scan.end
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switch scan.token[0] {
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case 'u': // https://www.ietf.org/rfc/rfc6067.txt
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attrStart := end
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scan.scan()
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for last := []byte{}; len(scan.token) > 2; scan.scan() {
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if bytes.Compare(scan.token, last) != -1 {
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// Attributes are unsorted. Start over from scratch.
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p := attrStart + 1
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scan.next = p
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attrs := [][]byte{}
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for scan.scan(); len(scan.token) > 2; scan.scan() {
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attrs = append(attrs, scan.token)
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end = scan.end
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}
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sort.Sort(bytesSort{attrs, 3})
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copy(scan.b[p:], bytes.Join(attrs, separator))
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break
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}
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last = scan.token
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end = scan.end
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}
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// Scan key-type sequences. A key is of length 2 and may be followed
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// by 0 or more "type" subtags from 3 to the maximum of 8 letters.
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var last, key []byte
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for attrEnd := end; len(scan.token) == 2; last = key {
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key = scan.token
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end = scan.end
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for scan.scan(); end < scan.end && len(scan.token) > 2; scan.scan() {
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end = scan.end
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}
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// TODO: check key value validity
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if bytes.Compare(key, last) != 1 || scan.err != nil {
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// We have an invalid key or the keys are not sorted.
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// Start scanning keys from scratch and reorder.
|
|
p := attrEnd + 1
|
|
scan.next = p
|
|
keys := [][]byte{}
|
|
for scan.scan(); len(scan.token) == 2; {
|
|
keyStart := scan.start
|
|
end = scan.end
|
|
for scan.scan(); end < scan.end && len(scan.token) > 2; scan.scan() {
|
|
end = scan.end
|
|
}
|
|
keys = append(keys, scan.b[keyStart:end])
|
|
}
|
|
sort.Stable(bytesSort{keys, 2})
|
|
if n := len(keys); n > 0 {
|
|
k := 0
|
|
for i := 1; i < n; i++ {
|
|
if !bytes.Equal(keys[k][:2], keys[i][:2]) {
|
|
k++
|
|
keys[k] = keys[i]
|
|
} else if !bytes.Equal(keys[k], keys[i]) {
|
|
scan.setError(ErrDuplicateKey)
|
|
}
|
|
}
|
|
keys = keys[:k+1]
|
|
}
|
|
reordered := bytes.Join(keys, separator)
|
|
if e := p + len(reordered); e < end {
|
|
scan.deleteRange(e, end)
|
|
end = e
|
|
}
|
|
copy(scan.b[p:], reordered)
|
|
break
|
|
}
|
|
}
|
|
case 't': // https://www.ietf.org/rfc/rfc6497.txt
|
|
scan.scan()
|
|
if n := len(scan.token); n >= 2 && n <= 3 && isAlpha(scan.token[1]) {
|
|
_, end = parseTag(scan)
|
|
scan.toLower(start, end)
|
|
}
|
|
for len(scan.token) == 2 && !isAlpha(scan.token[1]) {
|
|
end = scan.acceptMinSize(3)
|
|
}
|
|
case 'x':
|
|
end = scan.acceptMinSize(1)
|
|
default:
|
|
end = scan.acceptMinSize(2)
|
|
}
|
|
return end
|
|
}
|
|
|
|
// getExtension returns the name, body and end position of the extension.
|
|
func getExtension(s string, p int) (end int, ext string) {
|
|
if s[p] == '-' {
|
|
p++
|
|
}
|
|
if s[p] == 'x' {
|
|
return len(s), s[p:]
|
|
}
|
|
end = nextExtension(s, p)
|
|
return end, s[p:end]
|
|
}
|
|
|
|
// nextExtension finds the next extension within the string, searching
|
|
// for the -<char>- pattern from position p.
|
|
// In the fast majority of cases, language tags will have at most
|
|
// one extension and extensions tend to be small.
|
|
func nextExtension(s string, p int) int {
|
|
for n := len(s) - 3; p < n; {
|
|
if s[p] == '-' {
|
|
if s[p+2] == '-' {
|
|
return p
|
|
}
|
|
p += 3
|
|
} else {
|
|
p++
|
|
}
|
|
}
|
|
return len(s)
|
|
}
|