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https://github.com/autc04/Retro68.git
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526 lines
14 KiB
Go
526 lines
14 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package utf8 implements functions and constants to support text encoded in
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// UTF-8. It includes functions to translate between runes and UTF-8 byte sequences.
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package utf8
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// The conditions RuneError==unicode.ReplacementChar and
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// MaxRune==unicode.MaxRune are verified in the tests.
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// Defining them locally avoids this package depending on package unicode.
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// Numbers fundamental to the encoding.
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const (
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RuneError = '\uFFFD' // the "error" Rune or "Unicode replacement character"
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RuneSelf = 0x80 // characters below Runeself are represented as themselves in a single byte.
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MaxRune = '\U0010FFFF' // Maximum valid Unicode code point.
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UTFMax = 4 // maximum number of bytes of a UTF-8 encoded Unicode character.
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)
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// Code points in the surrogate range are not valid for UTF-8.
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const (
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surrogateMin = 0xD800
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surrogateMax = 0xDFFF
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)
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const (
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t1 = 0x00 // 0000 0000
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tx = 0x80 // 1000 0000
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t2 = 0xC0 // 1100 0000
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t3 = 0xE0 // 1110 0000
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t4 = 0xF0 // 1111 0000
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t5 = 0xF8 // 1111 1000
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maskx = 0x3F // 0011 1111
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mask2 = 0x1F // 0001 1111
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mask3 = 0x0F // 0000 1111
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mask4 = 0x07 // 0000 0111
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rune1Max = 1<<7 - 1
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rune2Max = 1<<11 - 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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// first is information about the first byte in a UTF-8 sequence.
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var first = [256]uint8{
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// 1 2 3 4 5 6 7 8 9 A B C D E F
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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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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x10-0x1F
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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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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x40-0x4F
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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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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x60-0x6F
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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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xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x80-0x8F
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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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xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xA0-0xAF
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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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s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xD0-0xDF
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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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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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// acceptRange gives the range of valid values for the second byte in a UTF-8
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// sequence.
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type acceptRange struct {
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lo uint8 // lowest value for second byte.
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hi uint8 // highest value for second byte.
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}
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var acceptRanges = [...]acceptRange{
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0: {locb, hicb},
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1: {0xA0, hicb},
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2: {locb, 0x9F},
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3: {0x90, hicb},
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4: {locb, 0x8F},
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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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// 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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n := len(p)
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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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// FullRuneInString is like FullRune but its input is a string.
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func FullRuneInString(s string) bool {
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n := len(s)
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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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// DecodeRune unpacks the first UTF-8 encoding in p and returns the rune and
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// its width in bytes. If p is empty it returns (RuneError, 0). Otherwise, if
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// the encoding is invalid, it returns (RuneError, 1). Both are impossible
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// results for correct, non-empty UTF-8.
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//
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// An encoding is invalid if it is incorrect UTF-8, encodes a rune that is
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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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func DecodeRune(p []byte) (r rune, size int) {
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n := len(p)
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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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// DecodeRuneInString is like DecodeRune but its input is a string. If s is
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// empty it returns (RuneError, 0). Otherwise, if the encoding is invalid, it
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// returns (RuneError, 1). Both are impossible results for correct, non-empty
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// UTF-8.
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//
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// An encoding is invalid if it is incorrect UTF-8, encodes a rune that is
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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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func DecodeRuneInString(s string) (r rune, size int) {
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n := len(s)
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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
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}
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s3 := s[3]
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if s3 < locb || hicb < s3 {
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return RuneError, 1
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}
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return rune(s0&mask4)<<18 | rune(s1&maskx)<<12 | rune(s2&maskx)<<6 | rune(s3&maskx), 4
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}
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// DecodeLastRune unpacks the last UTF-8 encoding in p and returns the rune and
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// its width in bytes. If p is empty it returns (RuneError, 0). Otherwise, if
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// the encoding is invalid, it returns (RuneError, 1). Both are impossible
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// results for correct, non-empty UTF-8.
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//
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// An encoding is invalid if it is incorrect UTF-8, encodes a rune that is
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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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func DecodeLastRune(p []byte) (r rune, size int) {
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end := len(p)
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if end == 0 {
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return RuneError, 0
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}
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start := end - 1
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r = rune(p[start])
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if r < RuneSelf {
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return r, 1
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}
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// guard against O(n^2) behavior when traversing
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// backwards through strings with long sequences of
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// invalid UTF-8.
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lim := end - UTFMax
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if lim < 0 {
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lim = 0
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}
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for start--; start >= lim; start-- {
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if RuneStart(p[start]) {
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break
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}
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}
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if start < 0 {
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start = 0
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}
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r, size = DecodeRune(p[start:end])
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if start+size != end {
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return RuneError, 1
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}
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return r, size
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}
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// DecodeLastRuneInString is like DecodeLastRune but its input is a string. If
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// s is empty it returns (RuneError, 0). Otherwise, if the encoding is invalid,
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// it returns (RuneError, 1). Both are impossible results for correct,
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// non-empty UTF-8.
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//
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// An encoding is invalid if it is incorrect UTF-8, encodes a rune that is
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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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func DecodeLastRuneInString(s string) (r rune, size int) {
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end := len(s)
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if end == 0 {
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return RuneError, 0
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}
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start := end - 1
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r = rune(s[start])
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if r < RuneSelf {
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return r, 1
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}
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// guard against O(n^2) behavior when traversing
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// backwards through strings with long sequences of
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// invalid UTF-8.
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lim := end - UTFMax
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if lim < 0 {
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lim = 0
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}
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for start--; start >= lim; start-- {
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if RuneStart(s[start]) {
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break
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}
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}
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if start < 0 {
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start = 0
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}
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r, size = DecodeRuneInString(s[start:end])
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if start+size != end {
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return RuneError, 1
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}
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return r, size
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}
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// RuneLen returns the number of bytes required to encode the rune.
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// It returns -1 if the rune is not a valid value to encode in UTF-8.
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func RuneLen(r rune) int {
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switch {
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case r < 0:
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return -1
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case r <= rune1Max:
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return 1
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case r <= rune2Max:
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return 2
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case surrogateMin <= r && r <= surrogateMax:
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return -1
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case r <= rune3Max:
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return 3
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case r <= MaxRune:
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return 4
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}
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return -1
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}
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// EncodeRune writes into p (which must be large enough) the UTF-8 encoding of the rune.
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// It returns the number of bytes written.
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func EncodeRune(p []byte, r rune) int {
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// Negative values are erroneous. Making it unsigned addresses the problem.
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switch i := uint32(r); {
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case i <= rune1Max:
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p[0] = byte(r)
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return 1
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case i <= rune2Max:
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_ = p[1] // eliminate bounds checks
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p[0] = t2 | byte(r>>6)
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p[1] = tx | byte(r)&maskx
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return 2
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case i > MaxRune, surrogateMin <= i && i <= surrogateMax:
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r = RuneError
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fallthrough
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case i <= rune3Max:
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_ = p[2] // eliminate bounds checks
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p[0] = t3 | byte(r>>12)
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p[1] = tx | byte(r>>6)&maskx
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p[2] = tx | byte(r)&maskx
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return 3
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default:
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_ = p[3] // eliminate bounds checks
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p[0] = t4 | byte(r>>18)
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p[1] = tx | byte(r>>12)&maskx
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p[2] = tx | byte(r>>6)&maskx
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p[3] = tx | byte(r)&maskx
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return 4
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}
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}
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// RuneCount returns the number of runes in p. Erroneous and short
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// encodings are treated as single runes of width 1 byte.
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func RuneCount(p []byte) int {
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np := len(p)
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var n int
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for i := 0; i < np; {
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n++
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c := p[i]
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if c < RuneSelf {
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// ASCII fast path
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i++
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continue
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}
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x := first[c]
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if x == xx {
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i++ // invalid.
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continue
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}
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size := int(x & 7)
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if i+size > np {
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i++ // Short or invalid.
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continue
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}
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accept := acceptRanges[x>>4]
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if c := p[i+1]; c < accept.lo || accept.hi < c {
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size = 1
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} else if size == 2 {
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} else if c := p[i+2]; c < locb || hicb < c {
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size = 1
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} else if size == 3 {
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} else if c := p[i+3]; c < locb || hicb < c {
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size = 1
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}
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i += size
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}
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return n
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}
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// RuneCountInString is like RuneCount but its input is a string.
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func RuneCountInString(s string) (n int) {
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ns := len(s)
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for i := 0; i < ns; n++ {
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c := s[i]
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if c < RuneSelf {
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// ASCII fast path
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i++
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continue
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}
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x := first[c]
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if x == xx {
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i++ // invalid.
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continue
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}
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size := int(x & 7)
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if i+size > ns {
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i++ // Short or invalid.
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continue
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}
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accept := acceptRanges[x>>4]
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if c := s[i+1]; c < accept.lo || accept.hi < c {
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size = 1
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} else if size == 2 {
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} else if c := s[i+2]; c < locb || hicb < c {
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size = 1
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} else if size == 3 {
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} else if c := s[i+3]; c < locb || hicb < c {
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size = 1
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}
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i += size
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}
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return n
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}
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// RuneStart reports whether the byte could be the first byte of an encoded,
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// possibly invalid rune. Second and subsequent bytes always have the top two
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// bits set to 10.
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func RuneStart(b byte) bool { return b&0xC0 != 0x80 }
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// Valid reports whether p consists entirely of valid UTF-8-encoded runes.
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func Valid(p []byte) bool {
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n := len(p)
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for i := 0; i < n; {
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pi := p[i]
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if pi < RuneSelf {
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i++
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continue
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}
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x := first[pi]
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if x == xx {
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return false // Illegal starter byte.
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}
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size := int(x & 7)
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if i+size > n {
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return false // Short or invalid.
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}
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accept := acceptRanges[x>>4]
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if c := p[i+1]; c < accept.lo || accept.hi < c {
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return false
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} else if size == 2 {
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} else if c := p[i+2]; c < locb || hicb < c {
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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 {
|
|
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
|
|
}
|