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Optimize encoding path for escaped string

This commit is contained in:
Masaaki Goshima 2021-12-27 21:48:21 +09:00
parent 5686ae09f7
commit 0d18c6d7ce
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GPG Key ID: 6A53785055537153
2 changed files with 176 additions and 35 deletions
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142
internal/encoder/decode_rune.go Normal file
View File

@ -0,0 +1,142 @@
package encoder
import "unicode/utf8"
// Code points in the surrogate range are not valid for UTF-8.
const (
surrogateMin = 0xD800
surrogateMax = 0xDFFF
)
const (
maskx = 63 //0b00111111
mask2 = 31 //0b00011111
mask3 = 15 //0b00001111
mask4 = 7 //0b00000111
rune1Max = 1<<7 - 1
rune2Max = 1<<11 - 1
rune3Max = 1<<16 - 1
// The default lowest and highest continuation byte.
locb = 128 //0b10000000
hicb = 191 //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.
}
var (
sep = [2]byte{226, 128}
lineSep = byte(168) //'\u2028'
paragraphSep = byte(169) //'\u2029'
)
type decodeRuneState int
const (
validUTF8State decodeRuneState = iota
runeErrorState
lineSepState
paragraphSepState
)
func decodeRuneInString(s string) (decodeRuneState, int) {
n := len(s)
s0 := s[0]
x := first[s0]
if x >= as {
// The following code simulates an additional check for x == xx and
// handling the ASCII and invalid cases accordingly. This mask-and-or
// approach prevents an additional branch.
mask := rune(x) << 31 >> 31 // Create 0x0000 or 0xFFFF.
if rune(s[0])&^mask|utf8.RuneError&mask == utf8.RuneError {
return runeErrorState, 1
}
return validUTF8State, 1
}
sz := int(x & 7)
var accept acceptRange
switch x >> 4 {
case 0:
accept = acceptRange{locb, hicb}
case 1:
accept = acceptRange{0xA0, hicb}
case 2:
accept = acceptRange{locb, 0x9F}
case 3:
accept = acceptRange{0x90, hicb}
case 4:
accept = acceptRange{locb, 0x8F}
}
if n < sz {
return runeErrorState, 1
}
s1 := s[1]
if s1 < accept.lo || accept.hi < s1 {
return runeErrorState, 1
}
if sz <= 2 {
return validUTF8State, 2
}
s2 := s[2]
if s2 < locb || hicb < s2 {
return runeErrorState, 1
}
if sz <= 3 {
if s[0] == sep[0] && s[1] == sep[1] {
switch s[2] {
case lineSep:
return lineSepState, 3
case paragraphSep:
return paragraphSepState, 3
}
}
return validUTF8State, 3
}
s3 := s[3]
if s3 < locb || hicb < s3 {
return runeErrorState, 1
}
return validUTF8State, 4
}

69
internal/encoder/string.go
View File

@ -3,7 +3,6 @@ package encoder
import (
"math/bits"
"reflect"
"unicode/utf8"
"unsafe"
)
@ -489,10 +488,9 @@ ESCAPE_END:
i = j + 1
j = j + 1
continue
}
// This encodes bytes < 0x20 except for \t, \n and \r.
if c < 0x20 {
case 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x0B, 0x0C, 0x0E, 0x0F, // 0x00-0x0F
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F: // 0x10-0x1F
buf = append(buf, s[i:j]...)
buf = append(buf, `\u00`...)
buf = append(buf, hex[c>>4], hex[c&0xF])
@ -501,18 +499,14 @@ ESCAPE_END:
continue
}
r, size := utf8.DecodeRuneInString(s[j:])
if r == utf8.RuneError && size == 1 {
state, size := decodeRuneInString(s[j:])
switch state {
case runeErrorState:
buf = append(buf, s[i:j]...)
buf = append(buf, `\ufffd`...)
i = j + size
j = j + size
i = j + 1
j = j + 1
continue
}
switch r {
case '\u2028', '\u2029':
// U+2028 is LINE SEPARATOR.
// U+2029 is PARAGRAPH SEPARATOR.
// They are both technically valid characters in JSON strings,
@ -520,14 +514,19 @@ ESCAPE_END:
// and can lead to security holes there. It is valid JSON to
// escape them, so we do so unconditionally.
// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
case lineSepState:
buf = append(buf, s[i:j]...)
buf = append(buf, `\u202`...)
buf = append(buf, hex[r&0xF])
i = j + size
j = j + size
buf = append(buf, `\u2028`...)
i = j + 3
j = j + 3
continue
case paragraphSepState:
buf = append(buf, s[i:j]...)
buf = append(buf, `\u2029`...)
i = j + 3
j = j + 3
continue
}
j += size
}
@ -594,10 +593,9 @@ func appendString(buf []byte, s string) []byte {
i = j + 1
j = j + 1
continue
}
// This encodes bytes < 0x20 except for \t, \n and \r.
if c < 0x20 {
case 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x0B, 0x0C, 0x0E, 0x0F, // 0x00-0x0F
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F: // 0x10-0x1F
buf = append(buf, s[i:j]...)
buf = append(buf, `\u00`...)
buf = append(buf, hex[c>>4], hex[c&0xF])
@ -606,18 +604,14 @@ func appendString(buf []byte, s string) []byte {
continue
}
r, size := utf8.DecodeRuneInString(s[j:])
if r == utf8.RuneError && size == 1 {
state, size := decodeRuneInString(s[j:])
switch state {
case runeErrorState:
buf = append(buf, s[i:j]...)
buf = append(buf, `\ufffd`...)
i = j + size
j = j + size
i = j + 1
j = j + 1
continue
}
switch r {
case '\u2028', '\u2029':
// U+2028 is LINE SEPARATOR.
// U+2029 is PARAGRAPH SEPARATOR.
// They are both technically valid characters in JSON strings,
@ -625,14 +619,19 @@ func appendString(buf []byte, s string) []byte {
// and can lead to security holes there. It is valid JSON to
// escape them, so we do so unconditionally.
// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
case lineSepState:
buf = append(buf, s[i:j]...)
buf = append(buf, `\u202`...)
buf = append(buf, hex[r&0xF])
i = j + size
j = j + size
buf = append(buf, `\u2028`...)
i = j + 3
j = j + 3
continue
case paragraphSepState:
buf = append(buf, s[i:j]...)
buf = append(buf, `\u2029`...)
i = j + 3
j = j + 3
continue
}
j += size
}