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/*
* The authors of this software are Rob Pike and Ken Thompson.
* Copyright (c) 2002 by Lucent Technologies.
* Portions Copyright 2009 The Go Authors. All rights reserved.
* Permission to use, copy, modify, and distribute this software for any
* purpose without fee is hereby granted, provided that this entire notice
* is included in all copies of any software which is or includes a copy
* or modification of this software and in all copies of the supporting
* documentation for such software.
* THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE ANY
* REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
* OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
*/
/*
* This code is copied, with slight editing due to type differences,
* from a subset of ../lib9/utf/rune.c
*/
package runtime
const (
bit1 = 7
bitx = 6
bit2 = 5
bit3 = 4
bit4 = 3
bit5 = 2
t1 = ((1 << (bit1 + 1)) - 1) ^ 0xFF /* 0000 0000 */
tx = ((1 << (bitx + 1)) - 1) ^ 0xFF /* 1000 0000 */
t2 = ((1 << (bit2 + 1)) - 1) ^ 0xFF /* 1100 0000 */
t3 = ((1 << (bit3 + 1)) - 1) ^ 0xFF /* 1110 0000 */
t4 = ((1 << (bit4 + 1)) - 1) ^ 0xFF /* 1111 0000 */
t5 = ((1 << (bit5 + 1)) - 1) ^ 0xFF /* 1111 1000 */
rune1 = (1 << (bit1 + 0*bitx)) - 1 /* 0000 0000 0111 1111 */
rune2 = (1 << (bit2 + 1*bitx)) - 1 /* 0000 0111 1111 1111 */
rune3 = (1 << (bit3 + 2*bitx)) - 1 /* 1111 1111 1111 1111 */
rune4 = (1 << (bit4 + 3*bitx)) - 1 /* 0001 1111 1111 1111 1111 1111 */
maskx = (1 << bitx) - 1 /* 0011 1111 */
testx = maskx ^ 0xFF /* 1100 0000 */
runeerror = 0xFFFD
runeself = 0x80
surrogateMin = 0xD800
surrogateMax = 0xDFFF
bad = runeerror
runemax = 0x10FFFF /* maximum rune value */
)
/*
* Modified by Wei-Hwa Huang, Google Inc., on 2004-09-24
* This is a slower but "safe" version of the old chartorune
* that works on strings that are not necessarily null-terminated.
*
* If you know for sure that your string is null-terminated,
* chartorune will be a bit faster.
*
* It is guaranteed not to attempt to access "length"
* past the incoming pointer. This is to avoid
* possible access violations. If the string appears to be
* well-formed but incomplete (i.e., to get the whole Rune
* we'd need to read past str+length) then we'll set the Rune
* to Bad and return 0.
*
* Note that if we have decoding problems for other
* reasons, we return 1 instead of 0.
*/
func charntorune(s string) (rune, int) {
/* When we're not allowed to read anything */
if len(s) <= 0 {
return bad, 1
}
/*
* one character sequence (7-bit value)
* 00000-0007F => T1
*/
c := s[0]
if c < tx {
return rune(c), 1
}
// If we can't read more than one character we must stop
if len(s) <= 1 {
return bad, 1
}
/*
* two character sequence (11-bit value)
* 0080-07FF => t2 tx
*/
c1 := s[1] ^ tx
if (c1 & testx) != 0 {
return bad, 1
}
if c < t3 {
if c < t2 {
return bad, 1
}
l := ((rune(c) << bitx) | rune(c1)) & rune2
if l <= rune1 {
return bad, 1
}
return l, 2
}
// If we can't read more than two characters we must stop
if len(s) <= 2 {
return bad, 1
}
/*
* three character sequence (16-bit value)
* 0800-FFFF => t3 tx tx
*/
c2 := s[2] ^ tx
if (c2 & testx) != 0 {
return bad, 1
}
if c < t4 {
l := ((((rune(c) << bitx) | rune(c1)) << bitx) | rune(c2)) & rune3
if l <= rune2 {
return bad, 1
}
if surrogateMin <= l && l <= surrogateMax {
return bad, 1
}
return l, 3
}
if len(s) <= 3 {
return bad, 1
}
/*
* four character sequence (21-bit value)
* 10000-1FFFFF => t4 tx tx tx
*/
c3 := s[3] ^ tx
if (c3 & testx) != 0 {
return bad, 1
}
if c < t5 {
l := ((((((rune(c) << bitx) | rune(c1)) << bitx) | rune(c2)) << bitx) | rune(c3)) & rune4
if l <= rune3 || l > runemax {
return bad, 1
}
return l, 4
}
// Support for 5-byte or longer UTF-8 would go here, but
// since we don't have that, we'll just return bad.
return bad, 1
}
// runetochar converts r to bytes and writes the result to str.
// returns the number of bytes generated.
func runetochar(str []byte, r rune) int {
/* runes are signed, so convert to unsigned for range check. */
c := uint32(r)
/*
* one character sequence
* 00000-0007F => 00-7F
*/
if c <= rune1 {
str[0] = byte(c)
return 1
}
/*
* two character sequence
* 0080-07FF => t2 tx
*/
if c <= rune2 {
str[0] = byte(t2 | (c >> (1 * bitx)))
str[1] = byte(tx | (c & maskx))
return 2
}
/*
* If the rune is out of range or a surrogate half, convert it to the error rune.
* Do this test here because the error rune encodes to three bytes.
* Doing it earlier would duplicate work, since an out of range
* rune wouldn't have fit in one or two bytes.
*/
if c > runemax {
c = runeerror
}
if surrogateMin <= c && c <= surrogateMax {
c = runeerror
}
/*
* three character sequence
* 0800-FFFF => t3 tx tx
*/
if c <= rune3 {
str[0] = byte(t3 | (c >> (2 * bitx)))
str[1] = byte(tx | ((c >> (1 * bitx)) & maskx))
str[2] = byte(tx | (c & maskx))
return 3
}
/*
* four character sequence (21-bit value)
* 10000-1FFFFF => t4 tx tx tx
*/
str[0] = byte(t4 | (c >> (3 * bitx)))
str[1] = byte(tx | ((c >> (2 * bitx)) & maskx))
str[2] = byte(tx | ((c >> (1 * bitx)) & maskx))
str[3] = byte(tx | (c & maskx))
return 4
}
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