// 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}, }