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package syntax
import (
"bytes"
"strconv"
"strings"
"unicode"
)
func Escape(input string) string {
b := &bytes.Buffer{}
for _, r := range input {
escape(b, r, false)
}
return b.String()
}
const meta = `\.+*?()|[]{}^$# `
func escape(b *bytes.Buffer, r rune, force bool) {
if unicode.IsPrint(r) {
if strings.IndexRune(meta, r) >= 0 || force {
b.WriteRune('\\')
}
b.WriteRune(r)
return
}
switch r {
case '\a':
b.WriteString(`\a`)
case '\f':
b.WriteString(`\f`)
case '\n':
b.WriteString(`\n`)
case '\r':
b.WriteString(`\r`)
case '\t':
b.WriteString(`\t`)
case '\v':
b.WriteString(`\v`)
default:
if r < 0x100 {
b.WriteString(`\x`)
s := strconv.FormatInt(int64(r), 16)
if len(s) == 1 {
b.WriteRune('0')
}
b.WriteString(s)
break
}
b.WriteString(`\u`)
b.WriteString(strconv.FormatInt(int64(r), 16))
}
}
func Unescape(input string) (string, error) {
idx := strings.IndexRune(input, '\\')
// no slashes means no unescape needed
if idx == -1 {
return input, nil
}
buf := bytes.NewBufferString(input[:idx])
// get the runes for the rest of the string -- we're going full parser scan on this
p := parser{}
p.setPattern(input[idx+1:])
for {
if p.rightMost() {
return "", p.getErr(ErrIllegalEndEscape)
}
r, err := p.scanCharEscape()
if err != nil {
return "", err
}
buf.WriteRune(r)
// are we done?
if p.rightMost() {
return buf.String(), nil
}
r = p.moveRightGetChar()
for r != '\\' {
buf.WriteRune(r)
if p.rightMost() {
// we're done, no more slashes
return buf.String(), nil
}
// keep scanning until we get another slash
r = p.moveRightGetChar()
}
}
}
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