From: Marcel van Lohuizen Date: Mon, 16 Nov 2015 13:00:31 +0000 (+0100) Subject: unicode/utf8: table-based algorithm for decoding X-Git-Tag: go1.6beta1~430 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=bf5b4e71be59d90f35a571a644e5731c581e9f6c;p=gostls13.git 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 --- diff --git a/src/unicode/utf8/utf8.go b/src/unicode/utf8/utf8.go index 5d29ec080e..bcb0de402e 100644 --- a/src/unicode/utf8/utf8.go +++ b/src/unicode/utf8/utf8.go @@ -40,175 +40,106 @@ const ( rune1Max = 1<<7 - 1 rune2Max = 1<<11 - 1 rune3Max = 1<<16 - 1 -) - -func decodeRuneInternal(p []byte) (r rune, size int, short bool) { - n := len(p) - if n < 1 { - return RuneError, 0, true - } - c0 := p[0] - - // 1-byte, 7-bit sequence? - if c0 < tx { - return rune(c0), 1, false - } - - // unexpected continuation byte? - if c0 < t2 { - return RuneError, 1, false - } - - // need first continuation byte - if n < 2 { - return RuneError, 1, true - } - c1 := p[1] - if c1 < tx || t2 <= c1 { - return RuneError, 1, false - } - - // 2-byte, 11-bit sequence? - if c0 < t3 { - r = rune(c0&mask2)<<6 | rune(c1&maskx) - if r <= rune1Max { - return RuneError, 1, false - } - return r, 2, false - } - - // need second continuation byte - if n < 3 { - return RuneError, 1, true - } - c2 := p[2] - if c2 < tx || t2 <= c2 { - return RuneError, 1, false - } - - // 3-byte, 16-bit sequence? - if c0 < t4 { - r = rune(c0&mask3)<<12 | rune(c1&maskx)<<6 | rune(c2&maskx) - if r <= rune2Max { - return RuneError, 1, false - } - if surrogateMin <= r && r <= surrogateMax { - return RuneError, 1, false - } - return r, 3, false - } - - // need third continuation byte - if n < 4 { - return RuneError, 1, true - } - c3 := p[3] - if c3 < tx || t2 <= c3 { - return RuneError, 1, false - } - // 4-byte, 21-bit sequence? - if c0 < t5 { - r = rune(c0&mask4)<<18 | rune(c1&maskx)<<12 | rune(c2&maskx)<<6 | rune(c3&maskx) - if r <= rune3Max || MaxRune < r { - return RuneError, 1, false - } - return r, 4, false - } + // The default lowest and highest continuation byte. + locb = 0x80 // 1000 0000 + hicb = 0xBF // 1011 1111 + + // These names of these constants are chosen to give nice alignment in the + // table below. The first nibble is an index into acceptRanges or F for + // special one-byte cases. The second nibble is the Rune length or the + // Status for the special one-byte case. + xx = 0xF1 // invalid: size 1 + as = 0xF0 // ASCII: size 1 + s1 = 0x02 // accept 0, size 2 + s2 = 0x13 // accept 1, size 3 + s3 = 0x03 // accept 0, size 3 + s4 = 0x23 // accept 2, size 3 + s5 = 0x34 // accept 3, size 4 + s6 = 0x04 // accept 0, size 4 + s7 = 0x44 // accept 4, size 4 +) - // error - return RuneError, 1, false +// first is information about the first byte in a UTF-8 sequence. +var first = [256]uint8{ + // 1 2 3 4 5 6 7 8 9 A B C D E F + as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x00-0x0F + as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x10-0x1F + as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x20-0x2F + as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x30-0x3F + as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x40-0x4F + as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x50-0x5F + as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x60-0x6F + as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x70-0x7F + // 1 2 3 4 5 6 7 8 9 A B C D E F + xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x80-0x8F + xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x90-0x9F + xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xA0-0xAF + xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xB0-0xBF + xx, xx, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xC0-0xCF + s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xD0-0xDF + s2, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s4, s3, s3, // 0xE0-0xEF + s5, s6, s6, s6, s7, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xF0-0xFF } -func decodeRuneInStringInternal(s string) (r rune, size int, short bool) { - n := len(s) - if n < 1 { - return RuneError, 0, true - } - c0 := s[0] - - // 1-byte, 7-bit sequence? - if c0 < tx { - return rune(c0), 1, false - } - - // unexpected continuation byte? - if c0 < t2 { - return RuneError, 1, false - } - - // need first continuation byte - if n < 2 { - return RuneError, 1, true - } - c1 := s[1] - if c1 < tx || t2 <= c1 { - return RuneError, 1, false - } - - // 2-byte, 11-bit sequence? - if c0 < t3 { - r = rune(c0&mask2)<<6 | rune(c1&maskx) - if r <= rune1Max { - return RuneError, 1, false - } - return r, 2, false - } - - // need second continuation byte - if n < 3 { - return RuneError, 1, true - } - c2 := s[2] - if c2 < tx || t2 <= c2 { - return RuneError, 1, false - } - - // 3-byte, 16-bit sequence? - if c0 < t4 { - r = rune(c0&mask3)<<12 | rune(c1&maskx)<<6 | rune(c2&maskx) - if r <= rune2Max { - return RuneError, 1, false - } - if surrogateMin <= r && r <= surrogateMax { - return RuneError, 1, false - } - return r, 3, false - } - - // need third continuation byte - if n < 4 { - return RuneError, 1, true - } - c3 := s[3] - if c3 < tx || t2 <= c3 { - return RuneError, 1, false - } - - // 4-byte, 21-bit sequence? - if c0 < t5 { - r = rune(c0&mask4)<<18 | rune(c1&maskx)<<12 | rune(c2&maskx)<<6 | rune(c3&maskx) - if r <= rune3Max || MaxRune < r { - return RuneError, 1, false - } - return r, 4, false - } +// acceptRange gives the range of valid values for the second byte in a UTF-8 +// sequence. +type acceptRange struct { + lo uint8 // lowest value for second byte. + hi uint8 // highest value for second byte. +} - // error - return RuneError, 1, false +var acceptRanges = [...]acceptRange{ + 0: {locb, hicb}, + 1: {0xA0, hicb}, + 2: {locb, 0x9F}, + 3: {0x90, hicb}, + 4: {locb, 0x8F}, } // FullRune reports whether the bytes in p begin with a full UTF-8 encoding of a rune. // An invalid encoding is considered a full Rune since it will convert as a width-1 error rune. func FullRune(p []byte) bool { - _, _, short := decodeRuneInternal(p) - return !short + n := len(p) + if n == 0 { + return false + } + x := first[p[0]] + if n >= int(x&7) { + return true // ASCII, invalid or valid. + } + // Must be short or invalid. + accept := acceptRanges[x>>4] + if n > 1 { + if c := p[1]; c < accept.lo || accept.hi < c { + return true + } else if n > 2 && (p[2] < locb || hicb < p[2]) { + return true + } + } + return false } // FullRuneInString is like FullRune but its input is a string. func FullRuneInString(s string) bool { - _, _, short := decodeRuneInStringInternal(s) - return !short + n := len(s) + if n == 0 { + return false + } + x := first[s[0]] + if n >= int(x&7) { + return true // ASCII, invalid, or valid. + } + // Must be short or invalid. + accept := acceptRanges[x>>4] + if n > 1 { + if c := s[1]; c < accept.lo || accept.hi < c { + return true + } else if n > 2 && (s[2] < locb || hicb < s[2]) { + return true + } + } + return false } // DecodeRune unpacks the first UTF-8 encoding in p and returns the rune and @@ -220,8 +151,43 @@ func FullRuneInString(s string) bool { // out of range, or is not the shortest possible UTF-8 encoding for the // value. No other validation is performed. func DecodeRune(p []byte) (r rune, size int) { - r, size, _ = decodeRuneInternal(p) - return + n := len(p) + if n < 1 { + return RuneError, 0 + } + p0 := p[0] + x := first[p0] + if x >= as { + // The following code simulates an additional check for x == xx and + // handling the ASCII and invalid cases accordingly. This mask-and-or + // approach prevents an additional branch. + mask := rune(x) << 31 >> 31 // Create 0x0000 or 0xFFFF. + return rune(p[0])&^mask | RuneError&mask, 1 + } + sz := x & 7 + accept := acceptRanges[x>>4] + if n < int(sz) { + return RuneError, 1 + } + b1 := p[1] + if b1 < accept.lo || accept.hi < b1 { + return RuneError, 1 + } + if sz == 2 { + return rune(p0&mask2)<<6 | rune(b1&maskx), 2 + } + b2 := p[2] + if b2 < locb || hicb < b2 { + return RuneError, 1 + } + if sz == 3 { + return rune(p0&mask3)<<12 | rune(b1&maskx)<<6 | rune(b2&maskx), 3 + } + b3 := p[3] + if b3 < locb || hicb < b3 { + return RuneError, 1 + } + return rune(p0&mask4)<<18 | rune(b1&maskx)<<12 | rune(b2&maskx)<<6 | rune(b3&maskx), 4 } // DecodeRuneInString is like DecodeRune but its input is a string. If s is @@ -232,8 +198,43 @@ func DecodeRune(p []byte) (r rune, size int) { // out of range, or is not the shortest possible UTF-8 encoding for the // value. No other validation is performed. func DecodeRuneInString(s string) (r rune, size int) { - r, size, _ = decodeRuneInStringInternal(s) - return + n := len(s) + if n < 1 { + return RuneError, 0 + } + s0 := s[0] + x := first[s0] + if x >= as { + // The following code simulates an additional check for x == xx and + // handling the ASCII and invalid cases accordingly. This mask-and-or + // approach prevents an additional branch. + mask := rune(x) << 31 >> 31 // Create 0x0000 or 0xFFFF. + return rune(s[0])&^mask | RuneError&mask, 1 + } + sz := x & 7 + accept := acceptRanges[x>>4] + if n < int(sz) { + return RuneError, 1 + } + s1 := s[1] + if s1 < accept.lo || accept.hi < s1 { + return RuneError, 1 + } + if sz == 2 { + return rune(s0&mask2)<<6 | rune(s1&maskx), 2 + } + s2 := s[2] + if s2 < locb || hicb < s2 { + return RuneError, 1 + } + if sz == 3 { + 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 @@ -367,73 +368,141 @@ func EncodeRune(p []byte, r rune) int { // RuneCount returns the number of runes in p. Erroneous and short // encodings are treated as single runes of width 1 byte. func RuneCount(p []byte) int { - i := 0 + np := len(p) var n int - for n = 0; i < len(p); n++ { - if p[i] < RuneSelf { + for i := 0; i < np; { + n++ + c := p[i] + if c < RuneSelf { + // ASCII fast path i++ - } else { - _, size := DecodeRune(p[i:]) - i += size + continue + } + 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 } // RuneCountInString is like RuneCount but its input is a string. func RuneCountInString(s string) (n int) { - for i := 0; i < len(s); { - n++ - if s[i] < RuneSelf { + ns := len(s) + for i := 0; i < ns; n++ { + c := s[i] + if c < RuneSelf { + // ASCII fast path i++ - } else { - _, size := DecodeRuneInString(s[i:]) - i += size + continue + } + 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 } -// RuneStart reports whether the byte could be the first byte of -// an encoded rune. Second and subsequent bytes always have the top -// two bits set to 10. +// RuneStart reports whether the byte could be the first byte of an encoded, +// possibly invalid rune. Second and subsequent bytes always have the top two +// bits set to 10. func RuneStart(b byte) bool { return b&0xC0 != 0x80 } // Valid reports whether p consists entirely of valid UTF-8-encoded runes. func Valid(p []byte) bool { - i := 0 - for i < len(p) { - if p[i] < RuneSelf { + n := len(p) + for i := 0; i < n; { + pi := p[i] + if pi < RuneSelf { i++ - } else { - _, size := DecodeRune(p[i:]) - if size == 1 { - // All valid runes of size 1 (those - // below RuneSelf) were handled above. - // This must be a RuneError. - return false - } - i += size + continue + } + x := first[pi] + if x == xx { + return false // Illegal starter byte. } + 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 + } + i += size } return true } // ValidString reports whether s consists entirely of valid UTF-8-encoded runes. func ValidString(s string) bool { - for i := 0; i < len(s); { - if s[i] < RuneSelf { + n := len(s) + for i := 0; i < n; { + si := s[i] + if si < RuneSelf { i++ - } else { - _, size := DecodeRuneInString(s[i:]) - if size == 1 { - // All valid runes of size 1 (those - // below RuneSelf) were handled above. - // This must be a RuneError. - return false - } - i += size + continue + } + x := first[si] + if x == xx { + return false // Illegal starter byte. + } + 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 } + i += size } return true } diff --git a/src/unicode/utf8/utf8_test.go b/src/unicode/utf8/utf8_test.go index 36d3959eee..60ce362f09 100644 --- a/src/unicode/utf8/utf8_test.go +++ b/src/unicode/utf8/utf8_test.go @@ -300,6 +300,8 @@ var runecounttests = []RuneCountTest{ {"☺☻☹", 3}, {"1,2,3,4", 7}, {"\xe2\x00", 2}, + {"\xe2\x80", 2}, + {"a\xe2\x80", 3}, } func TestRuneCount(t *testing.T) { @@ -352,6 +354,7 @@ var validTests = []ValidTest{ {"ЖЖ", true}, {"брэд-ЛГТМ", true}, {"☺☻☹", true}, + {"aa\xe2", false}, {string([]byte{66, 250}), false}, {string([]byte{66, 250, 67}), false}, {"a\uFFFDb", true},