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-rw-r--r--src/unicode/utf8/utf8.go552
1 files changed, 552 insertions, 0 deletions
diff --git a/src/unicode/utf8/utf8.go b/src/unicode/utf8/utf8.go
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+// Copyright 2009 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 utf8 implements functions and constants to support text encoded in
+// UTF-8. It includes functions to translate between runes and UTF-8 byte sequences.
+// See https://en.wikipedia.org/wiki/UTF-8
+package utf8
+
+// The conditions RuneError==unicode.ReplacementChar and
+// MaxRune==unicode.MaxRune are verified in the tests.
+// Defining them locally avoids this package depending on package unicode.
+
+// Numbers fundamental to the encoding.
+const (
+ RuneError = '\uFFFD' // the "error" Rune or "Unicode replacement character"
+ RuneSelf = 0x80 // characters below RuneSelf are represented as themselves in a single byte.
+ MaxRune = '\U0010FFFF' // Maximum valid Unicode code point.
+ UTFMax = 4 // maximum number of bytes of a UTF-8 encoded Unicode character.
+)
+
+// Code points in the surrogate range are not valid for UTF-8.
+const (
+ surrogateMin = 0xD800
+ surrogateMax = 0xDFFF
+)
+
+const (
+ t1 = 0b00000000
+ tx = 0b10000000
+ t2 = 0b11000000
+ t3 = 0b11100000
+ t4 = 0b11110000
+ t5 = 0b11111000
+
+ maskx = 0b00111111
+ mask2 = 0b00011111
+ mask3 = 0b00001111
+ mask4 = 0b00000111
+
+ rune1Max = 1<<7 - 1
+ rune2Max = 1<<11 - 1
+ rune3Max = 1<<16 - 1
+
+ // The default lowest and highest continuation byte.
+ locb = 0b10000000
+ hicb = 0b10111111
+
+ // 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
+)
+
+// 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
+}
+
+// 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.
+}
+
+// acceptRanges has size 16 to avoid bounds checks in the code that uses it.
+var acceptRanges = [16]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 {
+ 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 && (p[1] < accept.lo || accept.hi < p[1]) {
+ 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 {
+ 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 && (s[1] < accept.lo || accept.hi < s[1]) {
+ 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
+// its width in bytes. If p is empty it returns (RuneError, 0). Otherwise, if
+// the encoding is invalid, it returns (RuneError, 1). Both are impossible
+// results for correct, non-empty UTF-8.
+//
+// An encoding is invalid if it is incorrect UTF-8, encodes a rune that is
+// 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) {
+ 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 := int(x & 7)
+ accept := acceptRanges[x>>4]
+ if n < sz {
+ return RuneError, 1
+ }
+ b1 := p[1]
+ if b1 < accept.lo || accept.hi < b1 {
+ return RuneError, 1
+ }
+ if sz <= 2 { // <= instead of == to help the compiler eliminate some bounds checks
+ 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
+// empty it returns (RuneError, 0). Otherwise, if the encoding is invalid, it
+// returns (RuneError, 1). Both are impossible results for correct, non-empty
+// UTF-8.
+//
+// An encoding is invalid if it is incorrect UTF-8, encodes a rune that 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) {
+ 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 := int(x & 7)
+ accept := acceptRanges[x>>4]
+ if n < sz {
+ return RuneError, 1
+ }
+ s1 := s[1]
+ if s1 < accept.lo || accept.hi < s1 {
+ return RuneError, 1
+ }
+ if sz <= 2 { // <= instead of == to help the compiler eliminate some bounds checks
+ 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
+// its width in bytes. If p is empty it returns (RuneError, 0). Otherwise, if
+// the encoding is invalid, it returns (RuneError, 1). Both are impossible
+// results for correct, non-empty UTF-8.
+//
+// An encoding is invalid if it is incorrect UTF-8, encodes a rune that is
+// out of range, or is not the shortest possible UTF-8 encoding for the
+// value. No other validation is performed.
+func DecodeLastRune(p []byte) (r rune, size int) {
+ end := len(p)
+ if end == 0 {
+ return RuneError, 0
+ }
+ start := end - 1
+ r = rune(p[start])
+ if r < RuneSelf {
+ return r, 1
+ }
+ // guard against O(n^2) behavior when traversing
+ // backwards through strings with long sequences of
+ // invalid UTF-8.
+ lim := end - UTFMax
+ if lim < 0 {
+ lim = 0
+ }
+ for start--; start >= lim; start-- {
+ if RuneStart(p[start]) {
+ break
+ }
+ }
+ if start < 0 {
+ start = 0
+ }
+ r, size = DecodeRune(p[start:end])
+ if start+size != end {
+ return RuneError, 1
+ }
+ return r, size
+}
+
+// DecodeLastRuneInString is like DecodeLastRune but its input is a string. If
+// s is empty it returns (RuneError, 0). Otherwise, if the encoding is invalid,
+// it returns (RuneError, 1). Both are impossible results for correct,
+// non-empty UTF-8.
+//
+// An encoding is invalid if it is incorrect UTF-8, encodes a rune that is
+// out of range, or is not the shortest possible UTF-8 encoding for the
+// value. No other validation is performed.
+func DecodeLastRuneInString(s string) (r rune, size int) {
+ end := len(s)
+ if end == 0 {
+ return RuneError, 0
+ }
+ start := end - 1
+ r = rune(s[start])
+ if r < RuneSelf {
+ return r, 1
+ }
+ // guard against O(n^2) behavior when traversing
+ // backwards through strings with long sequences of
+ // invalid UTF-8.
+ lim := end - UTFMax
+ if lim < 0 {
+ lim = 0
+ }
+ for start--; start >= lim; start-- {
+ if RuneStart(s[start]) {
+ break
+ }
+ }
+ if start < 0 {
+ start = 0
+ }
+ r, size = DecodeRuneInString(s[start:end])
+ if start+size != end {
+ return RuneError, 1
+ }
+ return r, size
+}
+
+// RuneLen returns the number of bytes required to encode the rune.
+// It returns -1 if the rune is not a valid value to encode in UTF-8.
+func RuneLen(r rune) int {
+ switch {
+ case r < 0:
+ return -1
+ case r <= rune1Max:
+ return 1
+ case r <= rune2Max:
+ return 2
+ case surrogateMin <= r && r <= surrogateMax:
+ return -1
+ case r <= rune3Max:
+ return 3
+ case r <= MaxRune:
+ return 4
+ }
+ return -1
+}
+
+// EncodeRune writes into p (which must be large enough) the UTF-8 encoding of the rune.
+// If the rune is out of range, it writes the encoding of RuneError.
+// It returns the number of bytes written.
+func EncodeRune(p []byte, r rune) int {
+ // Negative values are erroneous. Making it unsigned addresses the problem.
+ switch i := uint32(r); {
+ case i <= rune1Max:
+ p[0] = byte(r)
+ return 1
+ case i <= rune2Max:
+ _ = p[1] // eliminate bounds checks
+ p[0] = t2 | byte(r>>6)
+ p[1] = tx | byte(r)&maskx
+ return 2
+ case i > MaxRune, surrogateMin <= i && i <= surrogateMax:
+ r = RuneError
+ fallthrough
+ case i <= rune3Max:
+ _ = p[2] // eliminate bounds checks
+ p[0] = t3 | byte(r>>12)
+ p[1] = tx | byte(r>>6)&maskx
+ p[2] = tx | byte(r)&maskx
+ return 3
+ default:
+ _ = p[3] // eliminate bounds checks
+ p[0] = t4 | byte(r>>18)
+ p[1] = tx | byte(r>>12)&maskx
+ p[2] = tx | byte(r>>6)&maskx
+ p[3] = tx | byte(r)&maskx
+ return 4
+ }
+}
+
+// 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 {
+ np := len(p)
+ var n int
+ for i := 0; i < np; {
+ n++
+ c := p[i]
+ if c < RuneSelf {
+ // ASCII fast path
+ i++
+ 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) {
+ ns := len(s)
+ for i := 0; i < ns; n++ {
+ c := s[i]
+ if c < RuneSelf {
+ // ASCII fast path
+ i++
+ 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,
+// 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 {
+ // Fast path. Check for and skip 8 bytes of ASCII characters per iteration.
+ for len(p) >= 8 {
+ // Combining two 32 bit loads allows the same code to be used
+ // for 32 and 64 bit platforms.
+ // The compiler can generate a 32bit load for first32 and second32
+ // on many platforms. See test/codegen/memcombine.go.
+ first32 := uint32(p[0]) | uint32(p[1])<<8 | uint32(p[2])<<16 | uint32(p[3])<<24
+ second32 := uint32(p[4]) | uint32(p[5])<<8 | uint32(p[6])<<16 | uint32(p[7])<<24
+ if (first32|second32)&0x80808080 != 0 {
+ // Found a non ASCII byte (>= RuneSelf).
+ break
+ }
+ p = p[8:]
+ }
+ n := len(p)
+ for i := 0; i < n; {
+ pi := p[i]
+ if pi < RuneSelf {
+ i++
+ 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 {
+ // Fast path. Check for and skip 8 bytes of ASCII characters per iteration.
+ for len(s) >= 8 {
+ // Combining two 32 bit loads allows the same code to be used
+ // for 32 and 64 bit platforms.
+ // The compiler can generate a 32bit load for first32 and second32
+ // on many platforms. See test/codegen/memcombine.go.
+ first32 := uint32(s[0]) | uint32(s[1])<<8 | uint32(s[2])<<16 | uint32(s[3])<<24
+ second32 := uint32(s[4]) | uint32(s[5])<<8 | uint32(s[6])<<16 | uint32(s[7])<<24
+ if (first32|second32)&0x80808080 != 0 {
+ // Found a non ASCII byte (>= RuneSelf).
+ break
+ }
+ s = s[8:]
+ }
+ n := len(s)
+ for i := 0; i < n; {
+ si := s[i]
+ if si < RuneSelf {
+ i++
+ 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
+}
+
+// ValidRune reports whether r can be legally encoded as UTF-8.
+// Code points that are out of range or a surrogate half are illegal.
+func ValidRune(r rune) bool {
+ switch {
+ case 0 <= r && r < surrogateMin:
+ return true
+ case surrogateMax < r && r <= MaxRune:
+ return true
+ }
+ return false
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-15 01:25:05 +0000