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encodejson.go
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encodejson.go
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package compiler
import (
"math/bits"
)
// From https://github.com/goccy/go-json/blob/master/internal/encoder/string.go
// Modified to avoid use of unsafe (perhaps at some small cost in performance).
var needEscape = [256]bool{
'"': true,
'\\': true,
0x00: true,
0x01: true,
0x02: true,
0x03: true,
0x04: true,
0x05: true,
0x06: true,
0x07: true,
0x08: true,
0x09: true,
0x0a: true,
0x0b: true,
0x0c: true,
0x0d: true,
0x0e: true,
0x0f: true,
0x10: true,
0x11: true,
0x12: true,
0x13: true,
0x14: true,
0x15: true,
0x16: true,
0x17: true,
0x18: true,
0x19: true,
0x1a: true,
0x1b: true,
0x1c: true,
0x1d: true,
0x1e: true,
0x1f: true,
/* 0x20 - 0xff */
}
var hex = "0123456789abcdef"
const (
lsb = 0x0101010101010101
msb = 0x8080808080808080
)
func appendJsonString(buf []byte, s string) []byte {
valLen := len(s)
if valLen == 0 {
return append(buf, `""`...)
}
buf = append(buf, '"')
var (
i, j int
)
if valLen >= 8 {
// Original code used this unsafe func, which we replace with some nasty string indexing.
//chunks := stringToUint64Slice(s)
nChunks := 0
for i := 0; i < len(s); {
nChunks++
var n uint64 = uint64(s[i])
i++
n |= uint64(s[i]) << 8
i++
n |= uint64(s[i]) << 16
i++
n |= uint64(s[i]) << 24
i++
n |= uint64(s[i]) << 32
i++
n |= uint64(s[i]) << 48
i++
// combine masks before checking for the MSB of each byte. We include
// `n` in the mask to check whether any of the *input* byte MSBs were
// set (i.e. the byte was outside the ASCII range).
mask := n | (n - (lsb * 0x20)) |
((n ^ (lsb * '"')) - lsb) |
((n ^ (lsb * '\\')) - lsb)
if (mask & msb) != 0 {
j = bits.TrailingZeros64(mask&msb) / 8
goto ESCAPE_END
}
}
valLen := len(s)
for i := nChunks * 8; i < valLen; i++ {
if needEscape[s[i]] {
j = i
goto ESCAPE_END
}
}
return append(append(buf, s...), '"')
}
ESCAPE_END:
for j < valLen {
c := s[j]
if !needEscape[c] {
// fast path: most of the time, printable ascii characters are used
j++
continue
}
switch c {
case '\\', '"':
buf = append(buf, s[i:j]...)
buf = append(buf, '\\', c)
i = j + 1
j = j + 1
continue
case '\n':
buf = append(buf, s[i:j]...)
buf = append(buf, '\\', 'n')
i = j + 1
j = j + 1
continue
case '\r':
buf = append(buf, s[i:j]...)
buf = append(buf, '\\', 'r')
i = j + 1
j = j + 1
continue
case '\t':
buf = append(buf, s[i:j]...)
buf = append(buf, '\\', 't')
i = j + 1
j = j + 1
continue
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])
i = j + 1
j = j + 1
continue
}
j++
}
return append(append(buf, s[i:]...), '"')
}
func appendJsonPosInt(buf []byte, v int) []byte {
start := len(buf)
nd := 0
for {
buf = append(buf, byte(v%10)+'0')
nd++
v /= 10
if v == 0 {
break
}
}
for i := 0; i < nd/2; i++ {
pos1 := start + i
pos2 := start + nd - i - 1
tmp := buf[pos1]
buf[pos1] = buf[pos2]
buf[pos2] = tmp
}
return buf
}