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
// 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
// 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
// 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
}