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utf8.go
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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.
// This contains a copy of utf.ValidString() which also considers NULL bytes
// invalid.
package zvalidate
const (
runeSelf = 0x80 // characters below Runeself are represented as themselves in a single byte.
)
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},
}
// 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 == 0 {
return false
}
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
}