1 // Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
3 // Copyright 2016 The Go Authors. All rights reserved.
4 // Use of this source code is governed by a BSD-style
5 // license that can be found in the LICENSE file.
9 // This file implements the Punycode algorithm from RFC 3492.
17 // These parameter values are specified in section 5.
19 // All computation is done with int32s, so that overflow behavior is identical
20 // regardless of whether int is 32-bit or 64-bit.
24 initialBias int32 = 72
31 func punyError(s string) error { return &labelError{s, "A3"} }
33 // decode decodes a string as specified in section 6.2.
34 func decode(encoded string) (string, error) {
38 pos := 1 + strings.LastIndex(encoded, "-")
40 return "", punyError(encoded)
42 if pos == len(encoded) {
43 return encoded[:len(encoded)-1], nil
45 output := make([]rune, 0, len(encoded))
47 for _, r := range encoded[:pos-1] {
48 output = append(output, r)
51 i, n, bias := int32(0), initialN, initialBias
52 for pos < len(encoded) {
53 oldI, w := i, int32(1)
54 for k := base; ; k += base {
55 if pos == len(encoded) {
56 return "", punyError(encoded)
58 digit, ok := decodeDigit(encoded[pos])
60 return "", punyError(encoded)
65 return "", punyError(encoded)
77 if w >= math.MaxInt32/base {
78 return "", punyError(encoded)
81 x := int32(len(output) + 1)
82 bias = adapt(i-oldI, x, oldI == 0)
85 if n > utf8.MaxRune || len(output) >= 1024 {
86 return "", punyError(encoded)
88 output = append(output, 0)
89 copy(output[i+1:], output[i:])
93 return string(output), nil
96 // encode encodes a string as specified in section 6.3 and prepends prefix to
99 // The "while h < length(input)" line in the specification becomes "for
100 // remaining != 0" in the Go code, because len(s) in Go is in bytes, not runes.
101 func encode(prefix, s string) (string, error) {
102 output := make([]byte, len(prefix), len(prefix)+1+2*len(s))
104 delta, n, bias := int32(0), initialN, initialBias
105 b, remaining := int32(0), int32(0)
106 for _, r := range s {
109 output = append(output, byte(r))
116 output = append(output, '-')
119 m := int32(0x7fffffff)
120 for _, r := range s {
125 delta += (m - n) * (h + 1)
127 return "", punyError(s)
130 for _, r := range s {
134 return "", punyError(s)
142 for k := base; ; k += base {
152 output = append(output, encodeDigit(t+(q-t)%(base-t)))
153 q = (q - t) / (base - t)
155 output = append(output, encodeDigit(q))
156 bias = adapt(delta, h+1, h == b)
164 return string(output), nil
167 func decodeDigit(x byte) (digit int32, ok bool) {
169 case '0' <= x && x <= '9':
170 return int32(x - ('0' - 26)), true
171 case 'A' <= x && x <= 'Z':
172 return int32(x - 'A'), true
173 case 'a' <= x && x <= 'z':
174 return int32(x - 'a'), true
179 func encodeDigit(digit int32) byte {
181 case 0 <= digit && digit < 26:
182 return byte(digit + 'a')
183 case 26 <= digit && digit < 36:
184 return byte(digit + ('0' - 26))
186 panic("idna: internal error in punycode encoding")
189 // adapt is the bias adaptation function specified in section 6.1.
190 func adapt(delta, numPoints int32, firstTime bool) int32 {
196 delta += delta / numPoints
198 for delta > ((base-tmin)*tmax)/2 {
202 return k + (base-tmin+1)*delta/(delta+skew)