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https://github.com/golang/go
synced 2024-09-30 08:18:40 -06:00
unicode/utf8: table-based algorithm for decoding
This simplifies covering all cases, reducing the number of branches and making unrolling for simpler functions manageable. This significantly improves performance of non-ASCII input. This change will also allow addressing Issue #11733 in an efficient manner. RuneCountTenASCIIChars-8 13.7ns ± 4% 13.5ns ± 2% ~ (p=0.116 n=7+8) RuneCountTenJapaneseChars-8 153ns ± 3% 74ns ± 2% -51.42% (p=0.000 n=8+8) RuneCountInStringTenASCIIChars-8 13.5ns ± 2% 12.5ns ± 3% -7.13% (p=0.000 n=8+7) RuneCountInStringTenJapaneseChars-8 145ns ± 2% 68ns ± 2% -53.21% (p=0.000 n=8+8) ValidTenASCIIChars-8 14.1ns ± 3% 12.5ns ± 5% -11.38% (p=0.000 n=8+8) ValidTenJapaneseChars-8 147ns ± 3% 71ns ± 4% -51.72% (p=0.000 n=8+8) ValidStringTenASCIIChars-8 12.5ns ± 3% 12.3ns ± 3% ~ (p=0.095 n=8+8) ValidStringTenJapaneseChars-8 146ns ± 4% 70ns ± 2% -51.62% (p=0.000 n=8+7) DecodeASCIIRune-8 5.91ns ± 2% 4.83ns ± 3% -18.28% (p=0.001 n=7+7) DecodeJapaneseRune-8 12.2ns ± 7% 8.5ns ± 3% -29.79% (p=0.000 n=8+7) FullASCIIRune-8 5.95ns ± 3% 4.27ns ± 1% -28.23% (p=0.000 n=8+7) FullJapaneseRune-8 12.0ns ± 6% 4.3ns ± 3% -64.39% (p=0.000 n=8+8) Change-Id: Iea1d6b0180cbbee1739659a0a38038126beecaca Reviewed-on: https://go-review.googlesource.com/16940 Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
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@ -40,175 +40,106 @@ const (
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rune1Max = 1<<7 - 1
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rune1Max = 1<<7 - 1
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rune2Max = 1<<11 - 1
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rune2Max = 1<<11 - 1
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rune3Max = 1<<16 - 1
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rune3Max = 1<<16 - 1
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// The default lowest and highest continuation byte.
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locb = 0x80 // 1000 0000
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hicb = 0xBF // 1011 1111
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// These names of these constants are chosen to give nice alignment in the
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// table below. The first nibble is an index into acceptRanges or F for
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// special one-byte cases. The second nibble is the Rune length or the
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// Status for the special one-byte case.
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xx = 0xF1 // invalid: size 1
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as = 0xF0 // ASCII: size 1
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s1 = 0x02 // accept 0, size 2
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s2 = 0x13 // accept 1, size 3
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s3 = 0x03 // accept 0, size 3
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s4 = 0x23 // accept 2, size 3
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s5 = 0x34 // accept 3, size 4
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s6 = 0x04 // accept 0, size 4
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s7 = 0x44 // accept 4, size 4
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)
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)
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func decodeRuneInternal(p []byte) (r rune, size int, short bool) {
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// first is information about the first byte in a UTF-8 sequence.
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n := len(p)
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var first = [256]uint8{
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if n < 1 {
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// 1 2 3 4 5 6 7 8 9 A B C D E F
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return RuneError, 0, true
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x00-0x0F
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}
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x10-0x1F
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c0 := p[0]
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x20-0x2F
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x30-0x3F
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// 1-byte, 7-bit sequence?
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x40-0x4F
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if c0 < tx {
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x50-0x5F
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return rune(c0), 1, false
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x60-0x6F
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}
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x70-0x7F
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// 1 2 3 4 5 6 7 8 9 A B C D E F
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// unexpected continuation byte?
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xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x80-0x8F
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if c0 < t2 {
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xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x90-0x9F
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return RuneError, 1, false
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xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xA0-0xAF
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}
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xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xB0-0xBF
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xx, xx, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xC0-0xCF
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// need first continuation byte
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s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xD0-0xDF
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if n < 2 {
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s2, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s4, s3, s3, // 0xE0-0xEF
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return RuneError, 1, true
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s5, s6, s6, s6, s7, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xF0-0xFF
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}
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c1 := p[1]
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if c1 < tx || t2 <= c1 {
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return RuneError, 1, false
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}
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// 2-byte, 11-bit sequence?
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if c0 < t3 {
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r = rune(c0&mask2)<<6 | rune(c1&maskx)
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if r <= rune1Max {
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return RuneError, 1, false
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}
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return r, 2, false
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}
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// need second continuation byte
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if n < 3 {
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return RuneError, 1, true
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}
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c2 := p[2]
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if c2 < tx || t2 <= c2 {
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return RuneError, 1, false
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}
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// 3-byte, 16-bit sequence?
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if c0 < t4 {
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r = rune(c0&mask3)<<12 | rune(c1&maskx)<<6 | rune(c2&maskx)
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if r <= rune2Max {
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return RuneError, 1, false
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}
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if surrogateMin <= r && r <= surrogateMax {
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return RuneError, 1, false
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}
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return r, 3, false
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}
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// need third continuation byte
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if n < 4 {
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return RuneError, 1, true
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}
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c3 := p[3]
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if c3 < tx || t2 <= c3 {
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return RuneError, 1, false
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}
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// 4-byte, 21-bit sequence?
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if c0 < t5 {
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r = rune(c0&mask4)<<18 | rune(c1&maskx)<<12 | rune(c2&maskx)<<6 | rune(c3&maskx)
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if r <= rune3Max || MaxRune < r {
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return RuneError, 1, false
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}
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return r, 4, false
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}
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// error
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return RuneError, 1, false
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}
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}
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func decodeRuneInStringInternal(s string) (r rune, size int, short bool) {
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// acceptRange gives the range of valid values for the second byte in a UTF-8
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n := len(s)
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// sequence.
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if n < 1 {
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type acceptRange struct {
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return RuneError, 0, true
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lo uint8 // lowest value for second byte.
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}
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hi uint8 // highest value for second byte.
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c0 := s[0]
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}
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// 1-byte, 7-bit sequence?
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var acceptRanges = [...]acceptRange{
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if c0 < tx {
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0: {locb, hicb},
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return rune(c0), 1, false
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1: {0xA0, hicb},
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}
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2: {locb, 0x9F},
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3: {0x90, hicb},
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// unexpected continuation byte?
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4: {locb, 0x8F},
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if c0 < t2 {
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return RuneError, 1, false
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}
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// need first continuation byte
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if n < 2 {
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return RuneError, 1, true
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}
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c1 := s[1]
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if c1 < tx || t2 <= c1 {
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return RuneError, 1, false
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}
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// 2-byte, 11-bit sequence?
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if c0 < t3 {
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r = rune(c0&mask2)<<6 | rune(c1&maskx)
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if r <= rune1Max {
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return RuneError, 1, false
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}
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return r, 2, false
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}
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// need second continuation byte
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if n < 3 {
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return RuneError, 1, true
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}
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c2 := s[2]
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if c2 < tx || t2 <= c2 {
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return RuneError, 1, false
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}
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// 3-byte, 16-bit sequence?
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if c0 < t4 {
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r = rune(c0&mask3)<<12 | rune(c1&maskx)<<6 | rune(c2&maskx)
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if r <= rune2Max {
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return RuneError, 1, false
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}
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if surrogateMin <= r && r <= surrogateMax {
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return RuneError, 1, false
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}
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return r, 3, false
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}
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// need third continuation byte
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if n < 4 {
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return RuneError, 1, true
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}
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c3 := s[3]
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if c3 < tx || t2 <= c3 {
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return RuneError, 1, false
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}
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// 4-byte, 21-bit sequence?
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if c0 < t5 {
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r = rune(c0&mask4)<<18 | rune(c1&maskx)<<12 | rune(c2&maskx)<<6 | rune(c3&maskx)
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if r <= rune3Max || MaxRune < r {
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return RuneError, 1, false
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}
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return r, 4, false
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}
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// error
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return RuneError, 1, false
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}
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}
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// FullRune reports whether the bytes in p begin with a full UTF-8 encoding of a rune.
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// FullRune reports whether the bytes in p begin with a full UTF-8 encoding of a rune.
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// An invalid encoding is considered a full Rune since it will convert as a width-1 error rune.
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// An invalid encoding is considered a full Rune since it will convert as a width-1 error rune.
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func FullRune(p []byte) bool {
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func FullRune(p []byte) bool {
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_, _, short := decodeRuneInternal(p)
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n := len(p)
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return !short
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if n == 0 {
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return false
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}
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x := first[p[0]]
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if n >= int(x&7) {
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return true // ASCII, invalid or valid.
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}
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// Must be short or invalid.
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accept := acceptRanges[x>>4]
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if n > 1 {
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if c := p[1]; c < accept.lo || accept.hi < c {
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return true
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} else if n > 2 && (p[2] < locb || hicb < p[2]) {
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return true
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}
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}
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return false
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}
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}
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// FullRuneInString is like FullRune but its input is a string.
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// FullRuneInString is like FullRune but its input is a string.
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func FullRuneInString(s string) bool {
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func FullRuneInString(s string) bool {
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_, _, short := decodeRuneInStringInternal(s)
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n := len(s)
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return !short
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if n == 0 {
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return false
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}
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x := first[s[0]]
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if n >= int(x&7) {
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return true // ASCII, invalid, or valid.
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}
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// Must be short or invalid.
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accept := acceptRanges[x>>4]
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if n > 1 {
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if c := s[1]; c < accept.lo || accept.hi < c {
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return true
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} else if n > 2 && (s[2] < locb || hicb < s[2]) {
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return true
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}
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}
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return false
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}
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}
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// DecodeRune unpacks the first UTF-8 encoding in p and returns the rune and
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// DecodeRune unpacks the first UTF-8 encoding in p and returns the rune and
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@ -220,8 +151,43 @@ func FullRuneInString(s string) bool {
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// out of range, or is not the shortest possible UTF-8 encoding for the
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// out of range, or is not the shortest possible UTF-8 encoding for the
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// value. No other validation is performed.
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// value. No other validation is performed.
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func DecodeRune(p []byte) (r rune, size int) {
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func DecodeRune(p []byte) (r rune, size int) {
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r, size, _ = decodeRuneInternal(p)
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n := len(p)
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return
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if n < 1 {
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return RuneError, 0
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}
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p0 := p[0]
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x := first[p0]
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if x >= as {
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// The following code simulates an additional check for x == xx and
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// handling the ASCII and invalid cases accordingly. This mask-and-or
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// approach prevents an additional branch.
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mask := rune(x) << 31 >> 31 // Create 0x0000 or 0xFFFF.
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return rune(p[0])&^mask | RuneError&mask, 1
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}
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sz := x & 7
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accept := acceptRanges[x>>4]
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if n < int(sz) {
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return RuneError, 1
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}
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b1 := p[1]
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if b1 < accept.lo || accept.hi < b1 {
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return RuneError, 1
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}
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if sz == 2 {
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return rune(p0&mask2)<<6 | rune(b1&maskx), 2
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}
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b2 := p[2]
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if b2 < locb || hicb < b2 {
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return RuneError, 1
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}
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if sz == 3 {
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return rune(p0&mask3)<<12 | rune(b1&maskx)<<6 | rune(b2&maskx), 3
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}
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b3 := p[3]
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if b3 < locb || hicb < b3 {
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return RuneError, 1
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}
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return rune(p0&mask4)<<18 | rune(b1&maskx)<<12 | rune(b2&maskx)<<6 | rune(b3&maskx), 4
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}
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}
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// DecodeRuneInString is like DecodeRune but its input is a string. If s is
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// DecodeRuneInString is like DecodeRune but its input is a string. If s is
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@ -232,8 +198,43 @@ func DecodeRune(p []byte) (r rune, size int) {
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// out of range, or is not the shortest possible UTF-8 encoding for the
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// out of range, or is not the shortest possible UTF-8 encoding for the
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// value. No other validation is performed.
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// value. No other validation is performed.
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func DecodeRuneInString(s string) (r rune, size int) {
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func DecodeRuneInString(s string) (r rune, size int) {
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r, size, _ = decodeRuneInStringInternal(s)
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n := len(s)
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return
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if n < 1 {
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return RuneError, 0
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}
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s0 := s[0]
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x := first[s0]
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if x >= as {
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// The following code simulates an additional check for x == xx and
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// handling the ASCII and invalid cases accordingly. This mask-and-or
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// approach prevents an additional branch.
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mask := rune(x) << 31 >> 31 // Create 0x0000 or 0xFFFF.
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return rune(s[0])&^mask | RuneError&mask, 1
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}
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sz := x & 7
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accept := acceptRanges[x>>4]
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if n < int(sz) {
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return RuneError, 1
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}
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s1 := s[1]
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if s1 < accept.lo || accept.hi < s1 {
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return RuneError, 1
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}
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if sz == 2 {
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return rune(s0&mask2)<<6 | rune(s1&maskx), 2
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}
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s2 := s[2]
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if s2 < locb || hicb < s2 {
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return RuneError, 1
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}
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if sz == 3 {
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||||||
|
return rune(s0&mask3)<<12 | rune(s1&maskx)<<6 | rune(s2&maskx), 3
|
||||||
|
}
|
||||||
|
s3 := s[3]
|
||||||
|
if s3 < locb || hicb < s3 {
|
||||||
|
return RuneError, 1
|
||||||
|
}
|
||||||
|
return rune(s0&mask4)<<18 | rune(s1&maskx)<<12 | rune(s2&maskx)<<6 | rune(s3&maskx), 4
|
||||||
}
|
}
|
||||||
|
|
||||||
// DecodeLastRune unpacks the last UTF-8 encoding in p and returns the rune and
|
// DecodeLastRune unpacks the last UTF-8 encoding in p and returns the rune and
|
||||||
@ -367,74 +368,142 @@ func EncodeRune(p []byte, r rune) int {
|
|||||||
// RuneCount returns the number of runes in p. Erroneous and short
|
// RuneCount returns the number of runes in p. Erroneous and short
|
||||||
// encodings are treated as single runes of width 1 byte.
|
// encodings are treated as single runes of width 1 byte.
|
||||||
func RuneCount(p []byte) int {
|
func RuneCount(p []byte) int {
|
||||||
i := 0
|
np := len(p)
|
||||||
var n int
|
var n int
|
||||||
for n = 0; i < len(p); n++ {
|
for i := 0; i < np; {
|
||||||
if p[i] < RuneSelf {
|
n++
|
||||||
|
c := p[i]
|
||||||
|
if c < RuneSelf {
|
||||||
|
// ASCII fast path
|
||||||
i++
|
i++
|
||||||
} else {
|
continue
|
||||||
_, size := DecodeRune(p[i:])
|
|
||||||
i += size
|
|
||||||
}
|
}
|
||||||
|
x := first[c]
|
||||||
|
if x == xx {
|
||||||
|
i++ // invalid.
|
||||||
|
continue
|
||||||
|
}
|
||||||
|
size := int(x & 7)
|
||||||
|
if i+size > np {
|
||||||
|
i++ // Short or invalid.
|
||||||
|
continue
|
||||||
|
}
|
||||||
|
accept := acceptRanges[x>>4]
|
||||||
|
if c := p[i+1]; c < accept.lo || accept.hi < c {
|
||||||
|
size = 1
|
||||||
|
} else if size == 2 {
|
||||||
|
} else if c := p[i+2]; c < locb || hicb < c {
|
||||||
|
size = 1
|
||||||
|
} else if size == 3 {
|
||||||
|
} else if c := p[i+3]; c < locb || hicb < c {
|
||||||
|
size = 1
|
||||||
|
}
|
||||||
|
i += size
|
||||||
}
|
}
|
||||||
return n
|
return n
|
||||||
}
|
}
|
||||||
|
|
||||||
// RuneCountInString is like RuneCount but its input is a string.
|
// RuneCountInString is like RuneCount but its input is a string.
|
||||||
func RuneCountInString(s string) (n int) {
|
func RuneCountInString(s string) (n int) {
|
||||||
for i := 0; i < len(s); {
|
ns := len(s)
|
||||||
n++
|
for i := 0; i < ns; n++ {
|
||||||
if s[i] < RuneSelf {
|
c := s[i]
|
||||||
|
if c < RuneSelf {
|
||||||
|
// ASCII fast path
|
||||||
i++
|
i++
|
||||||
} else {
|
continue
|
||||||
_, size := DecodeRuneInString(s[i:])
|
|
||||||
i += size
|
|
||||||
}
|
}
|
||||||
|
x := first[c]
|
||||||
|
if x == xx {
|
||||||
|
i++ // invalid.
|
||||||
|
continue
|
||||||
|
}
|
||||||
|
size := int(x & 7)
|
||||||
|
if i+size > ns {
|
||||||
|
i++ // Short or invalid.
|
||||||
|
continue
|
||||||
|
}
|
||||||
|
accept := acceptRanges[x>>4]
|
||||||
|
if c := s[i+1]; c < accept.lo || accept.hi < c {
|
||||||
|
size = 1
|
||||||
|
} else if size == 2 {
|
||||||
|
} else if c := s[i+2]; c < locb || hicb < c {
|
||||||
|
size = 1
|
||||||
|
} else if size == 3 {
|
||||||
|
} else if c := s[i+3]; c < locb || hicb < c {
|
||||||
|
size = 1
|
||||||
|
}
|
||||||
|
i += size
|
||||||
}
|
}
|
||||||
return n
|
return n
|
||||||
}
|
}
|
||||||
|
|
||||||
// RuneStart reports whether the byte could be the first byte of
|
// RuneStart reports whether the byte could be the first byte of an encoded,
|
||||||
// an encoded rune. Second and subsequent bytes always have the top
|
// possibly invalid rune. Second and subsequent bytes always have the top two
|
||||||
// two bits set to 10.
|
// bits set to 10.
|
||||||
func RuneStart(b byte) bool { return b&0xC0 != 0x80 }
|
func RuneStart(b byte) bool { return b&0xC0 != 0x80 }
|
||||||
|
|
||||||
// Valid reports whether p consists entirely of valid UTF-8-encoded runes.
|
// Valid reports whether p consists entirely of valid UTF-8-encoded runes.
|
||||||
func Valid(p []byte) bool {
|
func Valid(p []byte) bool {
|
||||||
i := 0
|
n := len(p)
|
||||||
for i < len(p) {
|
for i := 0; i < n; {
|
||||||
if p[i] < RuneSelf {
|
pi := p[i]
|
||||||
|
if pi < RuneSelf {
|
||||||
i++
|
i++
|
||||||
} else {
|
continue
|
||||||
_, size := DecodeRune(p[i:])
|
}
|
||||||
if size == 1 {
|
x := first[pi]
|
||||||
// All valid runes of size 1 (those
|
if x == xx {
|
||||||
// below RuneSelf) were handled above.
|
return false // Illegal starter byte.
|
||||||
// This must be a RuneError.
|
}
|
||||||
|
size := int(x & 7)
|
||||||
|
if i+size > n {
|
||||||
|
return false // Short or invalid.
|
||||||
|
}
|
||||||
|
accept := acceptRanges[x>>4]
|
||||||
|
if c := p[i+1]; c < accept.lo || accept.hi < c {
|
||||||
|
return false
|
||||||
|
} else if size == 2 {
|
||||||
|
} else if c := p[i+2]; c < locb || hicb < c {
|
||||||
|
return false
|
||||||
|
} else if size == 3 {
|
||||||
|
} else if c := p[i+3]; c < locb || hicb < c {
|
||||||
return false
|
return false
|
||||||
}
|
}
|
||||||
i += size
|
i += size
|
||||||
}
|
}
|
||||||
}
|
|
||||||
return true
|
return true
|
||||||
}
|
}
|
||||||
|
|
||||||
// ValidString reports whether s consists entirely of valid UTF-8-encoded runes.
|
// ValidString reports whether s consists entirely of valid UTF-8-encoded runes.
|
||||||
func ValidString(s string) bool {
|
func ValidString(s string) bool {
|
||||||
for i := 0; i < len(s); {
|
n := len(s)
|
||||||
if s[i] < RuneSelf {
|
for i := 0; i < n; {
|
||||||
|
si := s[i]
|
||||||
|
if si < RuneSelf {
|
||||||
i++
|
i++
|
||||||
} else {
|
continue
|
||||||
_, size := DecodeRuneInString(s[i:])
|
}
|
||||||
if size == 1 {
|
x := first[si]
|
||||||
// All valid runes of size 1 (those
|
if x == xx {
|
||||||
// below RuneSelf) were handled above.
|
return false // Illegal starter byte.
|
||||||
// This must be a RuneError.
|
}
|
||||||
|
size := int(x & 7)
|
||||||
|
if i+size > n {
|
||||||
|
return false // Short or invalid.
|
||||||
|
}
|
||||||
|
accept := acceptRanges[x>>4]
|
||||||
|
if c := s[i+1]; c < accept.lo || accept.hi < c {
|
||||||
|
return false
|
||||||
|
} else if size == 2 {
|
||||||
|
} else if c := s[i+2]; c < locb || hicb < c {
|
||||||
|
return false
|
||||||
|
} else if size == 3 {
|
||||||
|
} else if c := s[i+3]; c < locb || hicb < c {
|
||||||
return false
|
return false
|
||||||
}
|
}
|
||||||
i += size
|
i += size
|
||||||
}
|
}
|
||||||
}
|
|
||||||
return true
|
return true
|
||||||
}
|
}
|
||||||
|
|
||||||
|
@ -300,6 +300,8 @@ var runecounttests = []RuneCountTest{
|
|||||||
{"☺☻☹", 3},
|
{"☺☻☹", 3},
|
||||||
{"1,2,3,4", 7},
|
{"1,2,3,4", 7},
|
||||||
{"\xe2\x00", 2},
|
{"\xe2\x00", 2},
|
||||||
|
{"\xe2\x80", 2},
|
||||||
|
{"a\xe2\x80", 3},
|
||||||
}
|
}
|
||||||
|
|
||||||
func TestRuneCount(t *testing.T) {
|
func TestRuneCount(t *testing.T) {
|
||||||
@ -352,6 +354,7 @@ var validTests = []ValidTest{
|
|||||||
{"ЖЖ", true},
|
{"ЖЖ", true},
|
||||||
{"брэд-ЛГТМ", true},
|
{"брэд-ЛГТМ", true},
|
||||||
{"☺☻☹", true},
|
{"☺☻☹", true},
|
||||||
|
{"aa\xe2", false},
|
||||||
{string([]byte{66, 250}), false},
|
{string([]byte{66, 250}), false},
|
||||||
{string([]byte{66, 250, 67}), false},
|
{string([]byte{66, 250, 67}), false},
|
||||||
{"a\uFFFDb", true},
|
{"a\uFFFDb", true},
|
||||||
|
Loading…
Reference in New Issue
Block a user