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|
// Copyright 2013 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 language
import (
"bytes"
"errors"
"fmt"
"sort"
"strconv"
"strings"
"golang.org/x/text/internal/tag"
)
// isAlpha returns true if the byte is not a digit.
// b must be an ASCII letter or digit.
func isAlpha(b byte) bool {
return b > '9'
}
// isAlphaNum returns true if the string contains only ASCII letters or digits.
func isAlphaNum(s []byte) bool {
for _, c := range s {
if !('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9') {
return false
}
}
return true
}
// errSyntax is returned by any of the parsing functions when the
// input is not well-formed, according to BCP 47.
// TODO: return the position at which the syntax error occurred?
var errSyntax = errors.New("language: tag is not well-formed")
// ValueError is returned by any of the parsing functions when the
// input is well-formed but the respective subtag is not recognized
// as a valid value.
type ValueError struct {
v [8]byte
}
func mkErrInvalid(s []byte) error {
var e ValueError
copy(e.v[:], s)
return e
}
func (e ValueError) tag() []byte {
n := bytes.IndexByte(e.v[:], 0)
if n == -1 {
n = 8
}
return e.v[:n]
}
// Error implements the error interface.
func (e ValueError) Error() string {
return fmt.Sprintf("language: subtag %q is well-formed but unknown", e.tag())
}
// Subtag returns the subtag for which the error occurred.
func (e ValueError) Subtag() string {
return string(e.tag())
}
// scanner is used to scan BCP 47 tokens, which are separated by _ or -.
type scanner struct {
b []byte
bytes [max99thPercentileSize]byte
token []byte
start int // start position of the current token
end int // end position of the current token
next int // next point for scan
err error
done bool
}
func makeScannerString(s string) scanner {
scan := scanner{}
if len(s) <= len(scan.bytes) {
scan.b = scan.bytes[:copy(scan.bytes[:], s)]
} else {
scan.b = []byte(s)
}
scan.init()
return scan
}
// makeScanner returns a scanner using b as the input buffer.
// b is not copied and may be modified by the scanner routines.
func makeScanner(b []byte) scanner {
scan := scanner{b: b}
scan.init()
return scan
}
func (s *scanner) init() {
for i, c := range s.b {
if c == '_' {
s.b[i] = '-'
}
}
s.scan()
}
// restToLower converts the string between start and end to lower case.
func (s *scanner) toLower(start, end int) {
for i := start; i < end; i++ {
c := s.b[i]
if 'A' <= c && c <= 'Z' {
s.b[i] += 'a' - 'A'
}
}
}
func (s *scanner) setError(e error) {
if s.err == nil || (e == errSyntax && s.err != errSyntax) {
s.err = e
}
}
// resizeRange shrinks or grows the array at position oldStart such that
// a new string of size newSize can fit between oldStart and oldEnd.
// Sets the scan point to after the resized range.
func (s *scanner) resizeRange(oldStart, oldEnd, newSize int) {
s.start = oldStart
if end := oldStart + newSize; end != oldEnd {
diff := end - oldEnd
if end < cap(s.b) {
b := make([]byte, len(s.b)+diff)
copy(b, s.b[:oldStart])
copy(b[end:], s.b[oldEnd:])
s.b = b
} else {
s.b = append(s.b[end:], s.b[oldEnd:]...)
}
s.next = end + (s.next - s.end)
s.end = end
}
}
// replace replaces the current token with repl.
func (s *scanner) replace(repl string) {
s.resizeRange(s.start, s.end, len(repl))
copy(s.b[s.start:], repl)
}
// gobble removes the current token from the input.
// Caller must call scan after calling gobble.
func (s *scanner) gobble(e error) {
s.setError(e)
if s.start == 0 {
s.b = s.b[:+copy(s.b, s.b[s.next:])]
s.end = 0
} else {
s.b = s.b[:s.start-1+copy(s.b[s.start-1:], s.b[s.end:])]
s.end = s.start - 1
}
s.next = s.start
}
// deleteRange removes the given range from s.b before the current token.
func (s *scanner) deleteRange(start, end int) {
s.setError(errSyntax)
s.b = s.b[:start+copy(s.b[start:], s.b[end:])]
diff := end - start
s.next -= diff
s.start -= diff
s.end -= diff
}
// scan parses the next token of a BCP 47 string. Tokens that are larger
// than 8 characters or include non-alphanumeric characters result in an error
// and are gobbled and removed from the output.
// It returns the end position of the last token consumed.
func (s *scanner) scan() (end int) {
end = s.end
s.token = nil
for s.start = s.next; s.next < len(s.b); {
i := bytes.IndexByte(s.b[s.next:], '-')
if i == -1 {
s.end = len(s.b)
s.next = len(s.b)
i = s.end - s.start
} else {
s.end = s.next + i
s.next = s.end + 1
}
token := s.b[s.start:s.end]
if i < 1 || i > 8 || !isAlphaNum(token) {
s.gobble(errSyntax)
continue
}
s.token = token
return end
}
if n := len(s.b); n > 0 && s.b[n-1] == '-' {
s.setError(errSyntax)
s.b = s.b[:len(s.b)-1]
}
s.done = true
return end
}
// acceptMinSize parses multiple tokens of the given size or greater.
// It returns the end position of the last token consumed.
func (s *scanner) acceptMinSize(min int) (end int) {
end = s.end
s.scan()
for ; len(s.token) >= min; s.scan() {
end = s.end
}
return end
}
// Parse parses the given BCP 47 string and returns a valid Tag. If parsing
// failed it returns an error and any part of the tag that could be parsed.
// If parsing succeeded but an unknown value was found, it returns
// ValueError. The Tag returned in this case is just stripped of the unknown
// value. All other values are preserved. It accepts tags in the BCP 47 format
// and extensions to this standard defined in
// http://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
// The resulting tag is canonicalized using the default canonicalization type.
func Parse(s string) (t Tag, err error) {
return Default.Parse(s)
}
// Parse parses the given BCP 47 string and returns a valid Tag. If parsing
// failed it returns an error and any part of the tag that could be parsed.
// If parsing succeeded but an unknown value was found, it returns
// ValueError. The Tag returned in this case is just stripped of the unknown
// value. All other values are preserved. It accepts tags in the BCP 47 format
// and extensions to this standard defined in
// http://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
// The resulting tag is canonicalized using the the canonicalization type c.
func (c CanonType) Parse(s string) (t Tag, err error) {
// TODO: consider supporting old-style locale key-value pairs.
if s == "" {
return und, errSyntax
}
if len(s) <= maxAltTaglen {
b := [maxAltTaglen]byte{}
for i, c := range s {
// Generating invalid UTF-8 is okay as it won't match.
if 'A' <= c && c <= 'Z' {
c += 'a' - 'A'
} else if c == '_' {
c = '-'
}
b[i] = byte(c)
}
if t, ok := grandfathered(b); ok {
return t, nil
}
}
scan := makeScannerString(s)
t, err = parse(&scan, s)
t, changed := t.canonicalize(c)
if changed {
t.remakeString()
}
return t, err
}
func parse(scan *scanner, s string) (t Tag, err error) {
t = und
var end int
if n := len(scan.token); n <= 1 {
scan.toLower(0, len(scan.b))
if n == 0 || scan.token[0] != 'x' {
return t, errSyntax
}
end = parseExtensions(scan)
} else if n >= 4 {
return und, errSyntax
} else { // the usual case
t, end = parseTag(scan)
if n := len(scan.token); n == 1 {
t.pExt = uint16(end)
end = parseExtensions(scan)
} else if end < len(scan.b) {
scan.setError(errSyntax)
scan.b = scan.b[:end]
}
}
if int(t.pVariant) < len(scan.b) {
if end < len(s) {
s = s[:end]
}
if len(s) > 0 && tag.Compare(s, scan.b) == 0 {
t.str = s
} else {
t.str = string(scan.b)
}
} else {
t.pVariant, t.pExt = 0, 0
}
return t, scan.err
}
// parseTag parses language, script, region and variants.
// It returns a Tag and the end position in the input that was parsed.
func parseTag(scan *scanner) (t Tag, end int) {
var e error
// TODO: set an error if an unknown lang, script or region is encountered.
t.lang, e = getLangID(scan.token)
scan.setError(e)
scan.replace(t.lang.String())
langStart := scan.start
end = scan.scan()
for len(scan.token) == 3 && isAlpha(scan.token[0]) {
// From http://tools.ietf.org/html/bcp47, <lang>-<extlang> tags are equivalent
// to a tag of the form <extlang>.
lang, e := getLangID(scan.token)
if lang != 0 {
t.lang = lang
copy(scan.b[langStart:], lang.String())
scan.b[langStart+3] = '-'
scan.start = langStart + 4
}
scan.gobble(e)
end = scan.scan()
}
if len(scan.token) == 4 && isAlpha(scan.token[0]) {
t.script, e = getScriptID(script, scan.token)
if t.script == 0 {
scan.gobble(e)
}
end = scan.scan()
}
if n := len(scan.token); n >= 2 && n <= 3 {
t.region, e = getRegionID(scan.token)
if t.region == 0 {
scan.gobble(e)
} else {
scan.replace(t.region.String())
}
end = scan.scan()
}
scan.toLower(scan.start, len(scan.b))
t.pVariant = byte(end)
end = parseVariants(scan, end, t)
t.pExt = uint16(end)
return t, end
}
var separator = []byte{'-'}
// parseVariants scans tokens as long as each token is a valid variant string.
// Duplicate variants are removed.
func parseVariants(scan *scanner, end int, t Tag) int {
start := scan.start
varIDBuf := [4]uint8{}
variantBuf := [4][]byte{}
varID := varIDBuf[:0]
variant := variantBuf[:0]
last := -1
needSort := false
for ; len(scan.token) >= 4; scan.scan() {
// TODO: measure the impact of needing this conversion and redesign
// the data structure if there is an issue.
v, ok := variantIndex[string(scan.token)]
if !ok {
// unknown variant
// TODO: allow user-defined variants?
scan.gobble(mkErrInvalid(scan.token))
continue
}
varID = append(varID, v)
variant = append(variant, scan.token)
if !needSort {
if last < int(v) {
last = int(v)
} else {
needSort = true
// There is no legal combinations of more than 7 variants
// (and this is by no means a useful sequence).
const maxVariants = 8
if len(varID) > maxVariants {
break
}
}
}
end = scan.end
}
if needSort {
sort.Sort(variantsSort{varID, variant})
k, l := 0, -1
for i, v := range varID {
w := int(v)
if l == w {
// Remove duplicates.
continue
}
varID[k] = varID[i]
variant[k] = variant[i]
k++
l = w
}
if str := bytes.Join(variant[:k], separator); len(str) == 0 {
end = start - 1
} else {
scan.resizeRange(start, end, len(str))
copy(scan.b[scan.start:], str)
end = scan.end
}
}
return end
}
type variantsSort struct {
i []uint8
v [][]byte
}
func (s variantsSort) Len() int {
return len(s.i)
}
func (s variantsSort) Swap(i, j int) {
s.i[i], s.i[j] = s.i[j], s.i[i]
s.v[i], s.v[j] = s.v[j], s.v[i]
}
func (s variantsSort) Less(i, j int) bool {
return s.i[i] < s.i[j]
}
type bytesSort [][]byte
func (b bytesSort) Len() int {
return len(b)
}
func (b bytesSort) Swap(i, j int) {
b[i], b[j] = b[j], b[i]
}
func (b bytesSort) Less(i, j int) bool {
return bytes.Compare(b[i], b[j]) == -1
}
// parseExtensions parses and normalizes the extensions in the buffer.
// It returns the last position of scan.b that is part of any extension.
// It also trims scan.b to remove excess parts accordingly.
func parseExtensions(scan *scanner) int {
start := scan.start
exts := [][]byte{}
private := []byte{}
end := scan.end
for len(scan.token) == 1 {
extStart := scan.start
ext := scan.token[0]
end = parseExtension(scan)
extension := scan.b[extStart:end]
if len(extension) < 3 || (ext != 'x' && len(extension) < 4) {
scan.setError(errSyntax)
end = extStart
continue
} else if start == extStart && (ext == 'x' || scan.start == len(scan.b)) {
scan.b = scan.b[:end]
return end
} else if ext == 'x' {
private = extension
break
}
exts = append(exts, extension)
}
sort.Sort(bytesSort(exts))
if len(private) > 0 {
exts = append(exts, private)
}
scan.b = scan.b[:start]
if len(exts) > 0 {
scan.b = append(scan.b, bytes.Join(exts, separator)...)
} else if start > 0 {
// Strip trailing '-'.
scan.b = scan.b[:start-1]
}
return end
}
// parseExtension parses a single extension and returns the position of
// the extension end.
func parseExtension(scan *scanner) int {
start, end := scan.start, scan.end
switch scan.token[0] {
case 'u':
attrStart := end
scan.scan()
for last := []byte{}; len(scan.token) > 2; scan.scan() {
if bytes.Compare(scan.token, last) != -1 {
// Attributes are unsorted. Start over from scratch.
p := attrStart + 1
scan.next = p
attrs := [][]byte{}
for scan.scan(); len(scan.token) > 2; scan.scan() {
attrs = append(attrs, scan.token)
end = scan.end
}
sort.Sort(bytesSort(attrs))
copy(scan.b[p:], bytes.Join(attrs, separator))
break
}
last = scan.token
end = scan.end
}
var last, key []byte
for attrEnd := end; len(scan.token) == 2; last = key {
key = scan.token
keyEnd := scan.end
end = scan.acceptMinSize(3)
// TODO: check key value validity
if keyEnd == end || bytes.Compare(key, last) != 1 {
// We have an invalid key or the keys are not sorted.
// Start scanning keys from scratch and reorder.
p := attrEnd + 1
scan.next = p
keys := [][]byte{}
for scan.scan(); len(scan.token) == 2; {
keyStart, keyEnd := scan.start, scan.end
end = scan.acceptMinSize(3)
if keyEnd != end {
keys = append(keys, scan.b[keyStart:end])
} else {
scan.setError(errSyntax)
end = keyStart
}
}
sort.Sort(bytesSort(keys))
reordered := bytes.Join(keys, separator)
if e := p + len(reordered); e < end {
scan.deleteRange(e, end)
end = e
}
copy(scan.b[p:], bytes.Join(keys, separator))
break
}
}
case 't':
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
}
// Compose creates a Tag from individual parts, which may be of type Tag, Base,
// Script, Region, Variant, []Variant, Extension, []Extension or error. If a
// Base, Script or Region or slice of type Variant or Extension is passed more
// than once, the latter will overwrite the former. Variants and Extensions are
// accumulated, but if two extensions of the same type are passed, the latter
// will replace the former. A Tag overwrites all former values and typically
// only makes sense as the first argument. The resulting tag is returned after
// canonicalizing using the Default CanonType. If one or more errors are
// encountered, one of the errors is returned.
func Compose(part ...interface{}) (t Tag, err error) {
return Default.Compose(part...)
}
// Compose creates a Tag from individual parts, which may be of type Tag, Base,
// Script, Region, Variant, []Variant, Extension, []Extension or error. If a
// Base, Script or Region or slice of type Variant or Extension is passed more
// than once, the latter will overwrite the former. Variants and Extensions are
// accumulated, but if two extensions of the same type are passed, the latter
// will replace the former. A Tag overwrites all former values and typically
// only makes sense as the first argument. The resulting tag is returned after
// canonicalizing using CanonType c. If one or more errors are encountered,
// one of the errors is returned.
func (c CanonType) Compose(part ...interface{}) (t Tag, err error) {
var b builder
if err = b.update(part...); err != nil {
return und, err
}
t, _ = b.tag.canonicalize(c)
if len(b.ext) > 0 || len(b.variant) > 0 {
sort.Sort(sortVariant(b.variant))
sort.Strings(b.ext)
if b.private != "" {
b.ext = append(b.ext, b.private)
}
n := maxCoreSize + tokenLen(b.variant...) + tokenLen(b.ext...)
buf := make([]byte, n)
p := t.genCoreBytes(buf)
t.pVariant = byte(p)
p += appendTokens(buf[p:], b.variant...)
t.pExt = uint16(p)
p += appendTokens(buf[p:], b.ext...)
t.str = string(buf[:p])
} else if b.private != "" {
t.str = b.private
t.remakeString()
}
return
}
type builder struct {
tag Tag
private string // the x extension
ext []string
variant []string
err error
}
func (b *builder) addExt(e string) {
if e == "" {
} else if e[0] == 'x' {
b.private = e
} else {
b.ext = append(b.ext, e)
}
}
var errInvalidArgument = errors.New("invalid Extension or Variant")
func (b *builder) update(part ...interface{}) (err error) {
replace := func(l *[]string, s string, eq func(a, b string) bool) bool {
if s == "" {
b.err = errInvalidArgument
return true
}
for i, v := range *l {
if eq(v, s) {
(*l)[i] = s
return true
}
}
return false
}
for _, x := range part {
switch v := x.(type) {
case Tag:
b.tag.lang = v.lang
b.tag.region = v.region
b.tag.script = v.script
if v.str != "" {
b.variant = nil
for x, s := "", v.str[v.pVariant:v.pExt]; s != ""; {
x, s = nextToken(s)
b.variant = append(b.variant, x)
}
b.ext, b.private = nil, ""
for i, e := int(v.pExt), ""; i < len(v.str); {
i, e = getExtension(v.str, i)
b.addExt(e)
}
}
case Base:
b.tag.lang = v.langID
case Script:
b.tag.script = v.scriptID
case Region:
b.tag.region = v.regionID
case Variant:
if !replace(&b.variant, v.variant, func(a, b string) bool { return a == b }) {
b.variant = append(b.variant, v.variant)
}
case Extension:
if !replace(&b.ext, v.s, func(a, b string) bool { return a[0] == b[0] }) {
b.addExt(v.s)
}
case []Variant:
b.variant = nil
for _, x := range v {
b.update(x)
}
case []Extension:
b.ext, b.private = nil, ""
for _, e := range v {
b.update(e)
}
// TODO: support parsing of raw strings based on morphology or just extensions?
case error:
err = v
}
}
return
}
func tokenLen(token ...string) (n int) {
for _, t := range token {
n += len(t) + 1
}
return
}
func appendTokens(b []byte, token ...string) int {
p := 0
for _, t := range token {
b[p] = '-'
copy(b[p+1:], t)
p += 1 + len(t)
}
return p
}
type sortVariant []string
func (s sortVariant) Len() int {
return len(s)
}
func (s sortVariant) Swap(i, j int) {
s[j], s[i] = s[i], s[j]
}
func (s sortVariant) Less(i, j int) bool {
return variantIndex[s[i]] < variantIndex[s[j]]
}
func findExt(list []string, x byte) int {
for i, e := range list {
if e[0] == x {
return i
}
}
return -1
}
// 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)
}
var errInvalidWeight = errors.New("ParseAcceptLanguage: invalid weight")
// ParseAcceptLanguage parses the contents of an Accept-Language header as
// defined in http://www.ietf.org/rfc/rfc2616.txt and returns a list of Tags and
// a list of corresponding quality weights. It is more permissive than RFC 2616
// and may return non-nil slices even if the input is not valid.
// The Tags will be sorted by highest weight first and then by first occurrence.
// Tags with a weight of zero will be dropped. An error will be returned if the
// input could not be parsed.
func ParseAcceptLanguage(s string) (tag []Tag, q []float32, err error) {
var entry string
for s != "" {
if entry, s = split(s, ','); entry == "" {
continue
}
entry, weight := split(entry, ';')
// Scan the language.
t, err := Parse(entry)
if err != nil {
id, ok := acceptFallback[entry]
if !ok {
return nil, nil, err
}
t = Tag{lang: id}
}
// Scan the optional weight.
w := 1.0
if weight != "" {
weight = consume(weight, 'q')
weight = consume(weight, '=')
// consume returns the empty string when a token could not be
// consumed, resulting in an error for ParseFloat.
if w, err = strconv.ParseFloat(weight, 32); err != nil {
return nil, nil, errInvalidWeight
}
// Drop tags with a quality weight of 0.
if w <= 0 {
continue
}
}
tag = append(tag, t)
q = append(q, float32(w))
}
sortStable(&tagSort{tag, q})
return tag, q, nil
}
// consume removes a leading token c from s and returns the result or the empty
// string if there is no such token.
func consume(s string, c byte) string {
if s == "" || s[0] != c {
return ""
}
return strings.TrimSpace(s[1:])
}
func split(s string, c byte) (head, tail string) {
if i := strings.IndexByte(s, c); i >= 0 {
return strings.TrimSpace(s[:i]), strings.TrimSpace(s[i+1:])
}
return strings.TrimSpace(s), ""
}
// Add hack mapping to deal with a small number of cases that that occur
// in Accept-Language (with reasonable frequency).
var acceptFallback = map[string]langID{
"english": _en,
"deutsch": _de,
"italian": _it,
"french": _fr,
"*": _mul, // defined in the spec to match all languages.
}
type tagSort struct {
tag []Tag
q []float32
}
func (s *tagSort) Len() int {
return len(s.q)
}
func (s *tagSort) Less(i, j int) bool {
return s.q[i] > s.q[j]
}
func (s *tagSort) Swap(i, j int) {
s.tag[i], s.tag[j] = s.tag[j], s.tag[i]
s.q[i], s.q[j] = s.q[j], s.q[i]
}
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