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1 // Copyright 2018 The Go Authors. All rights reserved. |
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2 // Use of this source code is governed by a BSD-style |
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3 // license that can be found in the LICENSE file. |
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4 |
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5 package text |
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6 |
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7 // parseNumberValue parses a number from the input and returns a Token object. |
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8 func (d *Decoder) parseNumberValue() (Token, bool) { |
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9 in := d.in |
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10 num := parseNumber(in) |
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11 if num.size == 0 { |
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12 return Token{}, false |
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13 } |
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14 numAttrs := num.kind |
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15 if num.neg { |
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16 numAttrs |= isNegative |
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17 } |
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18 strSize := num.size |
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19 last := num.size - 1 |
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20 if num.kind == numFloat && (d.in[last] == 'f' || d.in[last] == 'F') { |
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21 strSize = last |
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22 } |
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23 tok := Token{ |
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24 kind: Scalar, |
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25 attrs: numberValue, |
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26 pos: len(d.orig) - len(d.in), |
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27 raw: d.in[:num.size], |
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28 str: string(d.in[:strSize]), |
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29 numAttrs: numAttrs, |
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30 } |
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31 d.consume(num.size) |
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32 return tok, true |
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33 } |
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34 |
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35 const ( |
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36 numDec uint8 = (1 << iota) / 2 |
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37 numHex |
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38 numOct |
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39 numFloat |
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40 ) |
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41 |
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42 // number is the result of parsing out a valid number from parseNumber. It |
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43 // contains data for doing float or integer conversion via the strconv package |
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44 // in conjunction with the input bytes. |
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45 type number struct { |
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46 kind uint8 |
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47 neg bool |
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48 size int |
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49 } |
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50 |
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51 // parseNumber constructs a number object from given input. It allows for the |
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52 // following patterns: |
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53 // integer: ^-?([1-9][0-9]*|0[xX][0-9a-fA-F]+|0[0-7]*) |
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54 // float: ^-?((0|[1-9][0-9]*)?([.][0-9]*)?([eE][+-]?[0-9]+)?[fF]?) |
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55 // It also returns the number of parsed bytes for the given number, 0 if it is |
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56 // not a number. |
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57 func parseNumber(input []byte) number { |
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58 kind := numDec |
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59 var size int |
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60 var neg bool |
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61 |
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62 s := input |
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63 if len(s) == 0 { |
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64 return number{} |
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65 } |
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66 |
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67 // Optional - |
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68 if s[0] == '-' { |
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69 neg = true |
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70 s = s[1:] |
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71 size++ |
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72 if len(s) == 0 { |
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73 return number{} |
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74 } |
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75 } |
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76 |
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77 // C++ allows for whitespace and comments in between the negative sign and |
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78 // the rest of the number. This logic currently does not but is consistent |
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79 // with v1. |
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80 |
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81 switch { |
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82 case s[0] == '0': |
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83 if len(s) > 1 { |
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84 switch { |
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85 case s[1] == 'x' || s[1] == 'X': |
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86 // Parse as hex number. |
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87 kind = numHex |
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88 n := 2 |
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89 s = s[2:] |
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90 for len(s) > 0 && (('0' <= s[0] && s[0] <= '9') || |
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91 ('a' <= s[0] && s[0] <= 'f') || |
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92 ('A' <= s[0] && s[0] <= 'F')) { |
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93 s = s[1:] |
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94 n++ |
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95 } |
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96 if n == 2 { |
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97 return number{} |
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98 } |
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99 size += n |
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100 |
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101 case '0' <= s[1] && s[1] <= '7': |
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102 // Parse as octal number. |
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103 kind = numOct |
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104 n := 2 |
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105 s = s[2:] |
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106 for len(s) > 0 && '0' <= s[0] && s[0] <= '7' { |
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107 s = s[1:] |
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108 n++ |
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109 } |
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110 size += n |
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111 } |
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112 |
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113 if kind&(numHex|numOct) > 0 { |
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114 if len(s) > 0 && !isDelim(s[0]) { |
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115 return number{} |
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116 } |
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117 return number{kind: kind, neg: neg, size: size} |
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118 } |
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119 } |
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120 s = s[1:] |
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121 size++ |
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122 |
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123 case '1' <= s[0] && s[0] <= '9': |
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124 n := 1 |
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125 s = s[1:] |
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126 for len(s) > 0 && '0' <= s[0] && s[0] <= '9' { |
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127 s = s[1:] |
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128 n++ |
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129 } |
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130 size += n |
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131 |
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132 case s[0] == '.': |
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133 // Set kind to numFloat to signify the intent to parse as float. And |
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134 // that it needs to have other digits after '.'. |
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135 kind = numFloat |
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136 |
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137 default: |
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138 return number{} |
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139 } |
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140 |
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141 // . followed by 0 or more digits. |
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142 if len(s) > 0 && s[0] == '.' { |
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143 n := 1 |
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144 s = s[1:] |
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145 // If decimal point was before any digits, it should be followed by |
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146 // other digits. |
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147 if len(s) == 0 && kind == numFloat { |
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148 return number{} |
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149 } |
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150 for len(s) > 0 && '0' <= s[0] && s[0] <= '9' { |
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151 s = s[1:] |
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152 n++ |
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153 } |
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154 size += n |
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155 kind = numFloat |
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156 } |
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157 |
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158 // e or E followed by an optional - or + and 1 or more digits. |
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159 if len(s) >= 2 && (s[0] == 'e' || s[0] == 'E') { |
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160 kind = numFloat |
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161 s = s[1:] |
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162 n := 1 |
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163 if s[0] == '+' || s[0] == '-' { |
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164 s = s[1:] |
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165 n++ |
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166 if len(s) == 0 { |
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167 return number{} |
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168 } |
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169 } |
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170 for len(s) > 0 && '0' <= s[0] && s[0] <= '9' { |
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171 s = s[1:] |
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172 n++ |
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173 } |
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174 size += n |
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175 } |
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176 |
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177 // Optional suffix f or F for floats. |
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178 if len(s) > 0 && (s[0] == 'f' || s[0] == 'F') { |
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179 kind = numFloat |
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180 s = s[1:] |
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181 size++ |
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182 } |
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183 |
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184 // Check that next byte is a delimiter or it is at the end. |
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185 if len(s) > 0 && !isDelim(s[0]) { |
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186 return number{} |
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187 } |
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188 |
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189 return number{kind: kind, neg: neg, size: size} |
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190 } |