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// Copyright 2015 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 pkcs12
import (
"errors"
"unicode/utf16"
)
// bmpString returns s encoded in UCS-2 with a zero terminator.
func bmpString(s string) ([]byte, error) {
// References:
// https://tools.ietf.org/html/rfc7292#appendix-B.1
// https://en.wikipedia.org/wiki/Plane_(Unicode)#Basic_Multilingual_Plane
// - non-BMP characters are encoded in UTF 16 by using a surrogate pair of 16-bit codes
// EncodeRune returns 0xfffd if the rune does not need special encoding
// - the above RFC provides the info that BMPStrings are NULL terminated.
ret := make([]byte, 0, 2*len(s)+2)
for _, r := range s {
if t, _ := utf16.EncodeRune(r); t != 0xfffd {
return nil, errors.New("pkcs12: string contains characters that cannot be encoded in UCS-2")
}
ret = append(ret, byte(r/256), byte(r%256))
}
return append(ret, 0, 0), nil
}
func decodeBMPString(bmpString []byte) (string, error) {
if len(bmpString)%2 != 0 {
return "", errors.New("pkcs12: odd-length BMP string")
}
// strip terminator if present
if l := len(bmpString); l >= 2 && bmpString[l-1] == 0 && bmpString[l-2] == 0 {
bmpString = bmpString[:l-2]
}
s := make([]uint16, 0, len(bmpString)/2)
for len(bmpString) > 0 {
s = append(s, uint16(bmpString[0])<<8+uint16(bmpString[1]))
bmpString = bmpString[2:]
}
return string(utf16.Decode(s)), nil
}
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