github.com/primecitizens/pcz/std@v0.2.1/text/unicode/utf8/utf8.go (about)

     1  // SPDX-License-Identifier: Apache-2.0
     2  // Copyright 2023 The Prime Citizens
     3  //
     4  // Copyright 2009 The Go Authors. All rights reserved.
     5  // Use of this source code is governed by a BSD-style
     6  // license that can be found in the LICENSE file.
     7  
     8  package utf8
     9  
    10  import (
    11  	"unsafe"
    12  )
    13  
    14  func AsString(s []byte) String {
    15  	return String(unsafe.String(unsafe.SliceData(s), len(s)))
    16  }
    17  
    18  type String string
    19  
    20  func (s String) Slice() []byte {
    21  	return unsafe.Slice(unsafe.StringData(string(s)), len(s))
    22  }
    23  
    24  const (
    25  	RuneSelf     = 0x80 // characters below RuneSelf are represented as themselves in a single byte.
    26  	RuneErrorLen = 3    // encoded UTF-8 length of a unicodeconst.RuneError
    27  	MaxRuneLen   = 4    // maximum number of bytes of a UTF-8 encoded Unicode character.
    28  )
    29  
    30  const (
    31  	t1 = 0x00 // 0000 0000
    32  	tx = 0x80 // 1000 0000
    33  	t2 = 0xC0 // 1100 0000
    34  	t3 = 0xE0 // 1110 0000
    35  	t4 = 0xF0 // 1111 0000
    36  	t5 = 0xF8 // 1111 1000
    37  
    38  	maskx = 0x3F // 0011 1111
    39  	mask2 = 0x1F // 0001 1111
    40  	mask3 = 0x0F // 0000 1111
    41  	mask4 = 0x07 // 0000 0111
    42  
    43  	Rune1Max = 1<<7 - 1
    44  	Rune2Max = 1<<11 - 1
    45  	Rune3Max = 1<<16 - 1
    46  
    47  	// The default lowest and highest continuation byte.
    48  	locb = 0x80 // 1000 0000
    49  	hicb = 0xBF // 1011 1111
    50  
    51  	// These names of these constants are chosen to give nice alignment in the
    52  	// table below. The first nibble is an index into acceptRanges or F for
    53  	// special one-byte cases. The second nibble is the Rune length or the
    54  	// Status for the special one-byte case.
    55  	xx = 0xF1 // invalid: size 1
    56  	as = 0xF0 // ASCII: size 1
    57  	s1 = 0x02 // accept 0, size 2
    58  	s2 = 0x13 // accept 1, size 3
    59  	s3 = 0x03 // accept 0, size 3
    60  	s4 = 0x23 // accept 2, size 3
    61  	s5 = 0x34 // accept 3, size 4
    62  	s6 = 0x04 // accept 0, size 4
    63  	s7 = 0x44 // accept 4, size 4
    64  )
    65  
    66  // first is information about the first byte in a UTF-8 sequence.
    67  var first = [256]uint8{
    68  	//   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
    69  	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x00-0x0F
    70  	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x10-0x1F
    71  	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x20-0x2F
    72  	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x30-0x3F
    73  	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x40-0x4F
    74  	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x50-0x5F
    75  	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x60-0x6F
    76  	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x70-0x7F
    77  	//   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
    78  	xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x80-0x8F
    79  	xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x90-0x9F
    80  	xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xA0-0xAF
    81  	xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xB0-0xBF
    82  	xx, xx, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xC0-0xCF
    83  	s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xD0-0xDF
    84  	s2, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s4, s3, s3, // 0xE0-0xEF
    85  	s5, s6, s6, s6, s7, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xF0-0xFF
    86  }
    87  
    88  // acceptRange gives the range of valid values for the second byte in a UTF-8
    89  // sequence.
    90  type acceptRange struct {
    91  	lo uint8 // lowest value for second byte.
    92  	hi uint8 // highest value for second byte.
    93  }
    94  
    95  // acceptRanges has size 16 to avoid bounds checks in the code that uses it.
    96  var acceptRanges = [16]acceptRange{
    97  	0: {lo: locb, hi: hicb},
    98  	1: {lo: 0xA0, hi: hicb},
    99  	2: {lo: locb, hi: 0x9F},
   100  	3: {lo: 0x90, hi: hicb},
   101  	4: {lo: locb, hi: 0x8F},
   102  }