mirror of https://github.com/goccy/go-json.git
Merge pull request #311 from goccy/feature/optimize-encode-path
Optimize encoding path for escaped string
This commit is contained in:
Masaaki Goshima
GitHub
commit
2d98d47d0f
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@ -0,0 +1,127 @@
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package encoder
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import "unicode/utf8"
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const (
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// The default lowest and highest continuation byte.
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locb = 128 //0b10000000
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hicb = 191 //0b10111111
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// These names of these constants are chosen to give nice alignment in the
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// table below. The first nibble is an index into acceptRanges or F for
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// special one-byte cases. The second nibble is the Rune length or the
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// Status for the special one-byte case.
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xx = 0xF1 // invalid: size 1
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as = 0xF0 // ASCII: size 1
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s1 = 0x02 // accept 0, size 2
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s2 = 0x13 // accept 1, size 3
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s3 = 0x03 // accept 0, size 3
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s4 = 0x23 // accept 2, size 3
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s5 = 0x34 // accept 3, size 4
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s6 = 0x04 // accept 0, size 4
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s7 = 0x44 // accept 4, size 4
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)
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// first is information about the first byte in a UTF-8 sequence.
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var first = [256]uint8{
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// 1 2 3 4 5 6 7 8 9 A B C D E F
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x00-0x0F
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x10-0x1F
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x20-0x2F
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x30-0x3F
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x40-0x4F
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x50-0x5F
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x60-0x6F
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as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x70-0x7F
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// 1 2 3 4 5 6 7 8 9 A B C D E F
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xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x80-0x8F
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xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x90-0x9F
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xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xA0-0xAF
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xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xB0-0xBF
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xx, xx, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xC0-0xCF
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s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xD0-0xDF
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s2, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s4, s3, s3, // 0xE0-0xEF
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s5, s6, s6, s6, s7, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xF0-0xFF
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}
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// acceptRange gives the range of valid values for the second byte in a UTF-8
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// sequence.
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type acceptRange struct {
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lo uint8 // lowest value for second byte.
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hi uint8 // highest value for second byte.
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}
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const (
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lineSep = byte(168) //'\u2028'
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paragraphSep = byte(169) //'\u2029'
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)
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type decodeRuneState int
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const (
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validUTF8State decodeRuneState = iota
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runeErrorState
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lineSepState
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paragraphSepState
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)
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func decodeRuneInString(s string) (decodeRuneState, int) {
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n := len(s)
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s0 := s[0]
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x := first[s0]
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if x >= as {
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// The following code simulates an additional check for x == xx and
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// handling the ASCII and invalid cases accordingly. This mask-and-or
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// approach prevents an additional branch.
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mask := rune(x) << 31 >> 31 // Create 0x0000 or 0xFFFF.
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if rune(s[0])&^mask|utf8.RuneError&mask == utf8.RuneError {
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return runeErrorState, 1
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}
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return validUTF8State, 1
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}
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sz := int(x & 7)
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var accept acceptRange
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switch x >> 4 {
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case 0:
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accept = acceptRange{locb, hicb}
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case 1:
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accept = acceptRange{0xA0, hicb}
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case 2:
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accept = acceptRange{locb, 0x9F}
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case 3:
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accept = acceptRange{0x90, hicb}
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case 4:
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accept = acceptRange{locb, 0x8F}
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}
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if n < sz {
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return runeErrorState, 1
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}
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s1 := s[1]
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if s1 < accept.lo || accept.hi < s1 {
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return runeErrorState, 1
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}
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if sz <= 2 {
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return validUTF8State, 2
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}
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s2 := s[2]
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if s2 < locb || hicb < s2 {
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return runeErrorState, 1
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}
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if sz <= 3 {
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// separator character prefixes: [2]byte{226, 128}
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if s0 == 226 && s1 == 128 {
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switch s2 {
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case lineSep:
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return lineSepState, 3
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case paragraphSep:
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return paragraphSepState, 3
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}
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}
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return validUTF8State, 3
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}
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s3 := s[3]
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if s3 < locb || hicb < s3 {
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return runeErrorState, 1
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}
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return validUTF8State, 4
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}
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@ -3,7 +3,6 @@ package encoder
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import (
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"math/bits"
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"reflect"
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"unicode/utf8"
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"unsafe"
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)
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@ -349,53 +348,6 @@ var needEscape = [256]bool{
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var hex = "0123456789abcdef"
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// escapeIndex finds the index of the first char in `s` that requires escaping.
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// A char requires escaping if it's outside of the range of [0x20, 0x7F] or if
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// it includes a double quote or backslash.
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// If no chars in `s` require escaping, the return value is -1.
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func escapeIndex(s string) int {
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chunks := stringToUint64Slice(s)
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for _, n := range chunks {
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// combine masks before checking for the MSB of each byte. We include
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// `n` in the mask to check whether any of the *input* byte MSBs were
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// set (i.e. the byte was outside the ASCII range).
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mask := n | below(n, 0x20) | contains(n, '"') | contains(n, '\\')
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if (mask & msb) != 0 {
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return bits.TrailingZeros64(mask&msb) / 8
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}
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}
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valLen := len(s)
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for i := len(chunks) * 8; i < valLen; i++ {
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if needEscape[s[i]] {
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return i
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}
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}
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return -1
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}
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// below return a mask that can be used to determine if any of the bytes
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// in `n` are below `b`. If a byte's MSB is set in the mask then that byte was
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// below `b`. The result is only valid if `b`, and each byte in `n`, is below
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// 0x80.
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func below(n uint64, b byte) uint64 {
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return n - expand(b)
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}
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// contains returns a mask that can be used to determine if any of the
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// bytes in `n` are equal to `b`. If a byte's MSB is set in the mask then
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// that byte is equal to `b`. The result is only valid if `b`, and each
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// byte in `n`, is below 0x80.
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func contains(n uint64, b byte) uint64 {
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return (n ^ expand(b)) - lsb
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}
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// expand puts the specified byte into each of the 8 bytes of a uint64.
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func expand(b byte) uint64 {
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return lsb * uint64(b)
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}
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//nolint:govet
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func stringToUint64Slice(s string) []uint64 {
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return *(*[]uint64)(unsafe.Pointer(&reflect.SliceHeader{
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@ -489,10 +441,9 @@ ESCAPE_END:
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i = j + 1
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j = j + 1
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continue
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}
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// This encodes bytes < 0x20 except for \t, \n and \r.
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if c < 0x20 {
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case 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x0B, 0x0C, 0x0E, 0x0F, // 0x00-0x0F
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0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F: // 0x10-0x1F
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buf = append(buf, s[i:j]...)
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buf = append(buf, `\u00`...)
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buf = append(buf, hex[c>>4], hex[c&0xF])
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@ -501,18 +452,14 @@ ESCAPE_END:
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continue
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}
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r, size := utf8.DecodeRuneInString(s[j:])
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if r == utf8.RuneError && size == 1 {
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state, size := decodeRuneInString(s[j:])
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switch state {
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case runeErrorState:
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buf = append(buf, s[i:j]...)
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buf = append(buf, `\ufffd`...)
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i = j + size
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j = j + size
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i = j + 1
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j = j + 1
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continue
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}
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switch r {
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case '\u2028', '\u2029':
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// U+2028 is LINE SEPARATOR.
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// U+2029 is PARAGRAPH SEPARATOR.
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// They are both technically valid characters in JSON strings,
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@ -520,14 +467,19 @@ ESCAPE_END:
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// and can lead to security holes there. It is valid JSON to
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// escape them, so we do so unconditionally.
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// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
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case lineSepState:
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buf = append(buf, s[i:j]...)
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buf = append(buf, `\u202`...)
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buf = append(buf, hex[r&0xF])
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i = j + size
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j = j + size
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buf = append(buf, `\u2028`...)
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i = j + 3
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j = j + 3
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continue
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case paragraphSepState:
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buf = append(buf, s[i:j]...)
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buf = append(buf, `\u2029`...)
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i = j + 3
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j = j + 3
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continue
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}
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j += size
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}
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@ -540,19 +492,37 @@ func appendString(buf []byte, s string) []byte {
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return append(buf, `""`...)
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}
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buf = append(buf, '"')
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var escapeIdx int
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var (
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i, j int
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)
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if valLen >= 8 {
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if escapeIdx = escapeIndex(s); escapeIdx < 0 {
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return append(append(buf, s...), '"')
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chunks := stringToUint64Slice(s)
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for _, n := range chunks {
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// combine masks before checking for the MSB of each byte. We include
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// `n` in the mask to check whether any of the *input* byte MSBs were
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// set (i.e. the byte was outside the ASCII range).
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mask := n | (n - (lsb * 0x20)) |
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((n ^ (lsb * '"')) - lsb) |
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((n ^ (lsb * '\\')) - lsb)
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if (mask & msb) != 0 {
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j = bits.TrailingZeros64(mask&msb) / 8
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goto ESCAPE_END
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}
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}
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valLen := len(s)
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for i := len(chunks) * 8; i < valLen; i++ {
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if needEscape[s[i]] {
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j = i
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goto ESCAPE_END
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}
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}
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return append(append(buf, s...), '"')
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}
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i := 0
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j := escapeIdx
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ESCAPE_END:
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for j < valLen {
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c := s[j]
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if c >= 0x20 && c <= 0x7f && c != '\\' && c != '"' {
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if !needEscape[c] {
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// fast path: most of the time, printable ascii characters are used
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j++
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continue
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@ -594,10 +564,9 @@ func appendString(buf []byte, s string) []byte {
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i = j + 1
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j = j + 1
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continue
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}
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// This encodes bytes < 0x20 except for \t, \n and \r.
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if c < 0x20 {
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case 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x0B, 0x0C, 0x0E, 0x0F, // 0x00-0x0F
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0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F: // 0x10-0x1F
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buf = append(buf, s[i:j]...)
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buf = append(buf, `\u00`...)
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buf = append(buf, hex[c>>4], hex[c&0xF])
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@ -606,18 +575,14 @@ func appendString(buf []byte, s string) []byte {
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continue
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}
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r, size := utf8.DecodeRuneInString(s[j:])
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if r == utf8.RuneError && size == 1 {
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state, size := decodeRuneInString(s[j:])
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switch state {
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case runeErrorState:
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buf = append(buf, s[i:j]...)
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buf = append(buf, `\ufffd`...)
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i = j + size
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j = j + size
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i = j + 1
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j = j + 1
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continue
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}
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switch r {
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case '\u2028', '\u2029':
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// U+2028 is LINE SEPARATOR.
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// U+2029 is PARAGRAPH SEPARATOR.
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// They are both technically valid characters in JSON strings,
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@ -625,14 +590,19 @@ func appendString(buf []byte, s string) []byte {
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// and can lead to security holes there. It is valid JSON to
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// escape them, so we do so unconditionally.
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// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
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case lineSepState:
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buf = append(buf, s[i:j]...)
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buf = append(buf, `\u202`...)
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buf = append(buf, hex[r&0xF])
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i = j + size
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j = j + size
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buf = append(buf, `\u2028`...)
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i = j + 3
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j = j + 3
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continue
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case paragraphSepState:
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buf = append(buf, s[i:j]...)
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buf = append(buf, `\u2029`...)
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i = j + 3
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j = j + 3
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continue
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}
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j += size
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}
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