go-json/encode_string.go

981 lines
18 KiB
Go

package json
import (
"math/bits"
"reflect"
"unicode/utf8"
"unsafe"
)
const (
lsb = 0x0101010101010101
msb = 0x8080808080808080
)
var needEscapeWithHTML = [256]bool{
'"': true,
'&': true,
'<': true,
'>': 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 - 0x7f */
0x80: true,
0x81: true,
0x82: true,
0x83: true,
0x84: true,
0x85: true,
0x86: true,
0x87: true,
0x88: true,
0x89: true,
0x8a: true,
0x8b: true,
0x8c: true,
0x8d: true,
0x8e: true,
0x8f: true,
0x90: true,
0x91: true,
0x92: true,
0x93: true,
0x94: true,
0x95: true,
0x96: true,
0x97: true,
0x98: true,
0x99: true,
0x9a: true,
0x9b: true,
0x9c: true,
0x9d: true,
0x9e: true,
0x9f: true,
0xa0: true,
0xa1: true,
0xa2: true,
0xa3: true,
0xa4: true,
0xa5: true,
0xa6: true,
0xa7: true,
0xa8: true,
0xa9: true,
0xaa: true,
0xab: true,
0xac: true,
0xad: true,
0xae: true,
0xaf: true,
0xb0: true,
0xb1: true,
0xb2: true,
0xb3: true,
0xb4: true,
0xb5: true,
0xb6: true,
0xb7: true,
0xb8: true,
0xb9: true,
0xba: true,
0xbb: true,
0xbc: true,
0xbd: true,
0xbe: true,
0xbf: true,
0xc0: true,
0xc1: true,
0xc2: true,
0xc3: true,
0xc4: true,
0xc5: true,
0xc6: true,
0xc7: true,
0xc8: true,
0xc9: true,
0xca: true,
0xcb: true,
0xcc: true,
0xcd: true,
0xce: true,
0xcf: true,
0xd0: true,
0xd1: true,
0xd2: true,
0xd3: true,
0xd4: true,
0xd5: true,
0xd6: true,
0xd7: true,
0xd8: true,
0xd9: true,
0xda: true,
0xdb: true,
0xdc: true,
0xdd: true,
0xde: true,
0xdf: true,
0xe0: true,
0xe1: true,
0xe2: true,
0xe3: true,
0xe4: true,
0xe5: true,
0xe6: true,
0xe7: true,
0xe8: true,
0xe9: true,
0xea: true,
0xeb: true,
0xec: true,
0xed: true,
0xee: true,
0xef: true,
0xf0: true,
0xf1: true,
0xf2: true,
0xf3: true,
0xf4: true,
0xf5: true,
0xf6: true,
0xf7: true,
0xf8: true,
0xf9: true,
0xfa: true,
0xfb: true,
0xfc: true,
0xfd: true,
0xfe: true,
0xff: true,
}
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 - 0x7f */
0x80: true,
0x81: true,
0x82: true,
0x83: true,
0x84: true,
0x85: true,
0x86: true,
0x87: true,
0x88: true,
0x89: true,
0x8a: true,
0x8b: true,
0x8c: true,
0x8d: true,
0x8e: true,
0x8f: true,
0x90: true,
0x91: true,
0x92: true,
0x93: true,
0x94: true,
0x95: true,
0x96: true,
0x97: true,
0x98: true,
0x99: true,
0x9a: true,
0x9b: true,
0x9c: true,
0x9d: true,
0x9e: true,
0x9f: true,
0xa0: true,
0xa1: true,
0xa2: true,
0xa3: true,
0xa4: true,
0xa5: true,
0xa6: true,
0xa7: true,
0xa8: true,
0xa9: true,
0xaa: true,
0xab: true,
0xac: true,
0xad: true,
0xae: true,
0xaf: true,
0xb0: true,
0xb1: true,
0xb2: true,
0xb3: true,
0xb4: true,
0xb5: true,
0xb6: true,
0xb7: true,
0xb8: true,
0xb9: true,
0xba: true,
0xbb: true,
0xbc: true,
0xbd: true,
0xbe: true,
0xbf: true,
0xc0: true,
0xc1: true,
0xc2: true,
0xc3: true,
0xc4: true,
0xc5: true,
0xc6: true,
0xc7: true,
0xc8: true,
0xc9: true,
0xca: true,
0xcb: true,
0xcc: true,
0xcd: true,
0xce: true,
0xcf: true,
0xd0: true,
0xd1: true,
0xd2: true,
0xd3: true,
0xd4: true,
0xd5: true,
0xd6: true,
0xd7: true,
0xd8: true,
0xd9: true,
0xda: true,
0xdb: true,
0xdc: true,
0xdd: true,
0xde: true,
0xdf: true,
0xe0: true,
0xe1: true,
0xe2: true,
0xe3: true,
0xe4: true,
0xe5: true,
0xe6: true,
0xe7: true,
0xe8: true,
0xe9: true,
0xea: true,
0xeb: true,
0xec: true,
0xed: true,
0xee: true,
0xef: true,
0xf0: true,
0xf1: true,
0xf2: true,
0xf3: true,
0xf4: true,
0xf5: true,
0xf6: true,
0xf7: true,
0xf8: true,
0xf9: true,
0xfa: true,
0xfb: true,
0xfc: true,
0xfd: true,
0xfe: true,
0xff: true,
}
// htmlSafeSet holds the value true if the ASCII character with the given
// array position can be safely represented inside a JSON string, embedded
// inside of HTML <script> tags, without any additional escaping.
//
// All values are true except for the ASCII control characters (0-31), the
// double quote ("), the backslash character ("\"), HTML opening and closing
// tags ("<" and ">"), and the ampersand ("&").
var htmlSafeSet = [256]bool{
' ': true,
'!': true,
'"': false,
'#': true,
'$': true,
'%': true,
'&': false,
'\'': true,
'(': true,
')': true,
'*': true,
'+': true,
',': true,
'-': true,
'.': true,
'/': true,
'0': true,
'1': true,
'2': true,
'3': true,
'4': true,
'5': true,
'6': true,
'7': true,
'8': true,
'9': true,
':': true,
';': true,
'<': false,
'=': true,
'>': false,
'?': true,
'@': true,
'A': true,
'B': true,
'C': true,
'D': true,
'E': true,
'F': true,
'G': true,
'H': true,
'I': true,
'J': true,
'K': true,
'L': true,
'M': true,
'N': true,
'O': true,
'P': true,
'Q': true,
'R': true,
'S': true,
'T': true,
'U': true,
'V': true,
'W': true,
'X': true,
'Y': true,
'Z': true,
'[': true,
'\\': false,
']': true,
'^': true,
'_': true,
'`': true,
'a': true,
'b': true,
'c': true,
'd': true,
'e': true,
'f': true,
'g': true,
'h': true,
'i': true,
'j': true,
'k': true,
'l': true,
'm': true,
'n': true,
'o': true,
'p': true,
'q': true,
'r': true,
's': true,
't': true,
'u': true,
'v': true,
'w': true,
'x': true,
'y': true,
'z': true,
'{': true,
'|': true,
'}': true,
'~': true,
'\u007f': true,
0x80: false,
0x81: false,
0x82: false,
0x83: false,
0x84: false,
0x85: false,
0x86: false,
0x87: false,
0x88: false,
0x89: false,
0x8a: false,
0x8b: false,
0x8c: false,
0x8d: false,
0x8e: false,
0x8f: false,
0x90: false,
0x91: false,
0x92: false,
0x93: false,
0x94: false,
0x95: false,
0x96: false,
0x97: false,
0x98: false,
0x99: false,
0x9a: false,
0x9b: false,
0x9c: false,
0x9d: false,
0x9e: false,
0x9f: false,
0xa0: false,
0xa1: false,
0xa2: false,
0xa3: false,
0xa4: false,
0xa5: false,
0xa6: false,
0xa7: false,
0xa8: false,
0xa9: false,
0xaa: false,
0xab: false,
0xac: false,
0xad: false,
0xae: false,
0xaf: false,
0xb0: false,
0xb1: false,
0xb2: false,
0xb3: false,
0xb4: false,
0xb5: false,
0xb6: false,
0xb7: false,
0xb8: false,
0xb9: false,
0xba: false,
0xbb: false,
0xbc: false,
0xbd: false,
0xbe: false,
0xbf: false,
0xc0: false,
0xc1: false,
0xc2: false,
0xc3: false,
0xc4: false,
0xc5: false,
0xc6: false,
0xc7: false,
0xc8: false,
0xc9: false,
0xca: false,
0xcb: false,
0xcc: false,
0xcd: false,
0xce: false,
0xcf: false,
0xd0: false,
0xd1: false,
0xd2: false,
0xd3: false,
0xd4: false,
0xd5: false,
0xd6: false,
0xd7: false,
0xd8: false,
0xd9: false,
0xda: false,
0xdb: false,
0xdc: false,
0xdd: false,
0xde: false,
0xdf: false,
0xe0: false,
0xe1: false,
0xe2: false,
0xe3: false,
0xe4: false,
0xe5: false,
0xe6: false,
0xe7: false,
0xe8: false,
0xe9: false,
0xea: false,
0xeb: false,
0xec: false,
0xed: false,
0xee: false,
0xef: false,
0xf0: false,
0xf1: false,
0xf2: false,
0xf3: false,
0xf4: false,
0xf5: false,
0xf6: false,
0xf7: false,
0xf8: false,
0xf9: false,
0xfa: false,
0xfb: false,
0xfc: false,
0xfd: false,
0xfe: false,
0xff: false,
}
// safeSet holds the value true if the ASCII character with the given array
// position can be represented inside a JSON string without any further
// escaping.
//
// All values are true except for the ASCII control characters (0-31), the
// double quote ("), and the backslash character ("\").
var safeSet = [utf8.RuneSelf]bool{
' ': true,
'!': true,
'"': false,
'#': true,
'$': true,
'%': true,
'&': true,
'\'': true,
'(': true,
')': true,
'*': true,
'+': true,
',': true,
'-': true,
'.': true,
'/': true,
'0': true,
'1': true,
'2': true,
'3': true,
'4': true,
'5': true,
'6': true,
'7': true,
'8': true,
'9': true,
':': true,
';': true,
'<': true,
'=': true,
'>': true,
'?': true,
'@': true,
'A': true,
'B': true,
'C': true,
'D': true,
'E': true,
'F': true,
'G': true,
'H': true,
'I': true,
'J': true,
'K': true,
'L': true,
'M': true,
'N': true,
'O': true,
'P': true,
'Q': true,
'R': true,
'S': true,
'T': true,
'U': true,
'V': true,
'W': true,
'X': true,
'Y': true,
'Z': true,
'[': true,
'\\': false,
']': true,
'^': true,
'_': true,
'`': true,
'a': true,
'b': true,
'c': true,
'd': true,
'e': true,
'f': true,
'g': true,
'h': true,
'i': true,
'j': true,
'k': true,
'l': true,
'm': true,
'n': true,
'o': true,
'p': true,
'q': true,
'r': true,
's': true,
't': true,
'u': true,
'v': true,
'w': true,
'x': true,
'y': true,
'z': true,
'{': true,
'|': true,
'}': true,
'~': true,
'\u007f': true,
}
var hex = "0123456789abcdef"
// escapeIndex finds the index of the first char in `s` that requires escaping.
// A char requires escaping if it's outside of the range of [0x20, 0x7F] or if
// it includes a double quote or backslash.
// If no chars in `s` require escaping, the return value is -1.
func escapeIndex(s string) int {
chunks := stringToUint64Slice(s)
for _, n := range chunks {
// 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 | below(n, 0x20) | contains(n, '"') | contains(n, '\\')
if (mask & msb) != 0 {
return bits.TrailingZeros64(mask&msb) / 8
}
}
valLen := len(s)
for i := len(chunks) * 8; i < valLen; i++ {
if needEscape[s[i]] {
return i
}
}
return -1
}
// escapeIndex finds the index of the first char in `s` that requires escaping.
// A char requires escaping if it's outside of the range of [0x20, 0x7F] or if
// it includes a double quote or backslash.
// Also, the chars <, > and & require escaping.
// If no chars in `s` require escaping, the return value is -1.
func escapeIndexWithHTMLEscape(s string) int {
chunks := stringToUint64Slice(s)
for _, n := range chunks {
// 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 | below(n, 0x20) | contains(n, '"') | contains(n, '\\') | contains(n, '<') | contains(n, '>') | contains(n, '&')
if (mask & msb) != 0 {
return bits.TrailingZeros64(mask&msb) / 8
}
}
valLen := len(s)
for i := len(chunks) * 8; i < valLen; i++ {
if needEscapeWithHTML[s[i]] {
return i
}
}
return -1
}
// below return a mask that can be used to determine if any of the bytes
// in `n` are below `b`. If a byte's MSB is set in the mask then that byte was
// below `b`. The result is only valid if `b`, and each byte in `n`, is below
// 0x80.
func below(n uint64, b byte) uint64 {
return n - expand(b)
}
// contains returns a mask that can be used to determine if any of the
// bytes in `n` are equal to `b`. If a byte's MSB is set in the mask then
// that byte is equal to `b`. The result is only valid if `b`, and each
// byte in `n`, is below 0x80.
func contains(n uint64, b byte) uint64 {
return (n ^ expand(b)) - lsb
}
// expand puts the specified byte into each of the 8 bytes of a uint64.
func expand(b byte) uint64 {
return lsb * uint64(b)
}
func stringToUint64Slice(s string) []uint64 {
return *(*[]uint64)(unsafe.Pointer(&reflect.SliceHeader{
Data: ((*reflect.StringHeader)(unsafe.Pointer(&s))).Data,
Len: len(s) / 8,
Cap: len(s) / 8,
}))
}
func encodeEscapedString(buf []byte, s string) []byte {
valLen := len(s)
if valLen == 0 {
return append(buf, `""`...)
}
buf = append(buf, '"')
var escapeIdx int
if valLen >= 8 {
if escapeIdx = escapeIndexWithHTMLEscape(s); escapeIdx < 0 {
return append(append(buf, s...), '"')
}
}
i := 0
j := escapeIdx
for j < valLen {
c := s[j]
if c >= 0x20 && c <= 0x7f && c != '\\' && c != '"' && (c != '<' && c != '>' && 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 '<', '>', '&':
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
}
// This encodes bytes < 0x20 except for \t, \n and \r.
if c < 0x20 {
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
}
r, size := utf8.DecodeRuneInString(s[j:])
if r == utf8.RuneError && size == 1 {
buf = append(buf, s[i:j]...)
buf = append(buf, `\ufffd`...)
i = j + size
j = j + size
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,
// but don't work in JSONP, which has to be evaluated as JavaScript,
// 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.
buf = append(buf, s[i:j]...)
buf = append(buf, `\u202`...)
buf = append(buf, hex[r&0xF])
i = j + size
j = j + size
continue
}
j += size
}
return append(append(buf, s[i:]...), '"')
}
func encodeNoEscapedString(buf []byte, s string) []byte {
valLen := len(s)
if valLen == 0 {
return append(buf, `""`...)
}
buf = append(buf, '"')
var escapeIdx int
if valLen >= 8 {
if escapeIdx = escapeIndex(s); escapeIdx < 0 {
return append(append(buf, s...), '"')
}
}
i := 0
j := escapeIdx
for j < valLen {
c := s[j]
if c >= 0x20 && c <= 0x7f && c != '\\' && 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 '<', '>', '&':
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
}
// This encodes bytes < 0x20 except for \t, \n and \r.
if c < 0x20 {
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
}
r, size := utf8.DecodeRuneInString(s[j:])
if r == utf8.RuneError && size == 1 {
buf = append(buf, s[i:j]...)
buf = append(buf, `\ufffd`...)
i = j + size
j = j + size
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,
// but don't work in JSONP, which has to be evaluated as JavaScript,
// 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.
buf = append(buf, s[i:j]...)
buf = append(buf, `\u202`...)
buf = append(buf, hex[r&0xF])
i = j + size
j = j + size
continue
}
j += size
}
return append(append(buf, s[i:]...), '"')
}