88 lines
3.5 KiB
Go
88 lines
3.5 KiB
Go
// Copyright 2015 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 utf8internal contains low-level utf8-related constants, tables, etc.
|
|
// that are used internally by the text package.
|
|
package utf8internal
|
|
|
|
// The default lowest and highest continuation byte.
|
|
const (
|
|
LoCB = 0x80 // 1000 0000
|
|
HiCB = 0xBF // 1011 1111
|
|
)
|
|
|
|
// Constants related to getting information of first bytes of UTF-8 sequences.
|
|
const (
|
|
// ASCII identifies a UTF-8 byte as ASCII.
|
|
ASCII = as
|
|
|
|
// FirstInvalid indicates a byte is invalid as a first byte of a UTF-8
|
|
// sequence.
|
|
FirstInvalid = xx
|
|
|
|
// SizeMask is a mask for the size bits. Use use x&SizeMask to get the size.
|
|
SizeMask = 7
|
|
|
|
// AcceptShift is the right-shift count for the first byte info byte to get
|
|
// the index into the AcceptRanges table. See AcceptRanges.
|
|
AcceptShift = 4
|
|
|
|
// The 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 for any value for First that is not ASCII or FirstInvalid.
|
|
type AcceptRange struct {
|
|
Lo uint8 // lowest value for second byte.
|
|
Hi uint8 // highest value for second byte.
|
|
}
|
|
|
|
// AcceptRanges is a slice of AcceptRange values. For a given byte sequence b
|
|
//
|
|
// AcceptRanges[First[b[0]]>>AcceptShift]
|
|
//
|
|
// will give the value of AcceptRange for the multi-byte UTF-8 sequence starting
|
|
// at b[0].
|
|
var AcceptRanges = [...]AcceptRange{
|
|
0: {LoCB, HiCB},
|
|
1: {0xA0, HiCB},
|
|
2: {LoCB, 0x9F},
|
|
3: {0x90, HiCB},
|
|
4: {LoCB, 0x8F},
|
|
}
|