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66
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1 package syntax
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2
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3 import (
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4 "bytes"
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5 "strconv"
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6 "strings"
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7 "unicode"
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8 )
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9
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10 func Escape(input string) string {
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11 b := &bytes.Buffer{}
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12 for _, r := range input {
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13 escape(b, r, false)
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14 }
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15 return b.String()
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16 }
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17
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18 const meta = `\.+*?()|[]{}^$# `
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19
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20 func escape(b *bytes.Buffer, r rune, force bool) {
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21 if unicode.IsPrint(r) {
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22 if strings.IndexRune(meta, r) >= 0 || force {
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23 b.WriteRune('\\')
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24 }
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25 b.WriteRune(r)
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26 return
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27 }
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28
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29 switch r {
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30 case '\a':
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31 b.WriteString(`\a`)
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32 case '\f':
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33 b.WriteString(`\f`)
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34 case '\n':
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35 b.WriteString(`\n`)
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36 case '\r':
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37 b.WriteString(`\r`)
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38 case '\t':
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39 b.WriteString(`\t`)
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40 case '\v':
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41 b.WriteString(`\v`)
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42 default:
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43 if r < 0x100 {
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44 b.WriteString(`\x`)
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45 s := strconv.FormatInt(int64(r), 16)
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46 if len(s) == 1 {
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47 b.WriteRune('0')
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48 }
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49 b.WriteString(s)
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50 break
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51 }
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52 b.WriteString(`\u`)
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53 b.WriteString(strconv.FormatInt(int64(r), 16))
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54 }
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55 }
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56
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57 func Unescape(input string) (string, error) {
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58 idx := strings.IndexRune(input, '\\')
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59 // no slashes means no unescape needed
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60 if idx == -1 {
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61 return input, nil
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62 }
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63
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64 buf := bytes.NewBufferString(input[:idx])
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65 // get the runes for the rest of the string -- we're going full parser scan on this
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66
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67 p := parser{}
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68 p.setPattern(input[idx+1:])
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69 for {
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70 if p.rightMost() {
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71 return "", p.getErr(ErrIllegalEndEscape)
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72 }
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73 r, err := p.scanCharEscape()
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74 if err != nil {
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75 return "", err
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76 }
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77 buf.WriteRune(r)
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78 // are we done?
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79 if p.rightMost() {
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80 return buf.String(), nil
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81 }
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82
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83 r = p.moveRightGetChar()
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84 for r != '\\' {
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85 buf.WriteRune(r)
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86 if p.rightMost() {
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87 // we're done, no more slashes
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88 return buf.String(), nil
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89 }
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90 // keep scanning until we get another slash
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91 r = p.moveRightGetChar()
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92 }
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93 }
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94 }
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