1 | #!/usr/bin/env python |
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2 | # ****************************************************** |
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3 | # Michael Cohen <scudette@users.sourceforge.net> |
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4 | # |
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5 | # ****************************************************** |
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6 | # Version: FLAG $Version: 0.87-pre1 Date: Thu Jun 12 00:48:38 EST 2008$ |
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7 | # ****************************************************** |
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8 | # |
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9 | # * This program is free software; you can redistribute it and/or |
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10 | # * modify it under the terms of the GNU General Public License |
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11 | # * as published by the Free Software Foundation; either version 2 |
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12 | # * of the License, or (at your option) any later version. |
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13 | # * |
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14 | # * This program is distributed in the hope that it will be useful, |
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15 | # * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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16 | # * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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17 | # * GNU General Public License for more details. |
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18 | # * |
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19 | # * You should have received a copy of the GNU General Public License |
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20 | # * along with this program; if not, write to the Free Software |
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21 | # * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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22 | # ****************************************************** |
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23 | """ A simple feed lexer. |
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24 | """ |
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25 | |
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26 | import re,sys |
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27 | |
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28 | class Lexer: |
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29 | """ A generic feed lexer """ |
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30 | ## The following is a description of the states we have and the |
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31 | ## way we move through them: format is an array of |
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32 | ## [ state_re, re, token/action, next state ] |
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33 | tokens = [] |
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34 | state = "INITIAL" |
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35 | buffer = '' |
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36 | error = 0 |
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37 | verbose = 0 |
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38 | state_stack = [] |
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39 | processed = 0 |
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40 | processed_buffer = '' |
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41 | saved_state = None |
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42 | flags = 0 |
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43 | |
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44 | def __init__(self, verbose=0, fd=None): |
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45 | if not self.verbose: |
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46 | self.verbose = verbose |
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47 | |
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48 | if len(self.tokens[0])==4: |
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49 | for row in self.tokens: |
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50 | row.append(re.compile(row[0], re.DOTALL)) |
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51 | row.append(re.compile(row[1], re.DOTALL | re.M | re.S | self.flags )) |
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52 | |
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53 | self.fd = fd |
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54 | |
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55 | def save_state(self, t=None, m=None): |
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56 | """ Returns a dict which represents the current state of the lexer. |
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57 | |
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58 | When provided to restore_state, the lexer is guaranteed to be |
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59 | in the same state as when the save_state was called. |
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60 | |
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61 | Note that derived classes may need to extend this. |
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62 | """ |
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63 | ## Cant save our state if we have errors. We need to guarantee |
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64 | ## that we rewind to a good part of the file. |
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65 | if self.error: return |
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66 | try: |
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67 | end = m.end() |
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68 | except: end = 0 |
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69 | |
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70 | self.saved_state = dict(state_stack = self.state_stack[:], |
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71 | processed = self.processed - end, |
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72 | processed_buffer = self.processed_buffer, |
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73 | readptr = self.fd.tell() - len(self.buffer) - end, |
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74 | state = self.state, |
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75 | objects = self.objects[:], |
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76 | error = self.error, |
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77 | ) |
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78 | |
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79 | if self.verbose>1: |
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80 | print "Saving state %s" % self.processed |
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81 | |
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82 | def restore_state(self): |
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83 | state = self.saved_state |
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84 | if not state: return |
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85 | |
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86 | self.state_stack = state['state_stack'] |
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87 | self.processed = state['processed'] |
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88 | self.processed_buffer = state['processed_buffer'] |
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89 | self.buffer = '' |
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90 | self.fd.seek(state['readptr']) |
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91 | self.state = state['state'] |
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92 | self.objects = state['objects'] |
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93 | self.error = state['error'] |
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94 | if self.verbose>1: |
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95 | print "Restoring state to offset %s" % self.processed |
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96 | |
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97 | def next_token(self, end = True): |
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98 | ## Now try to match any of the regexes in order: |
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99 | current_state = self.state |
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100 | for state_re, re_str, token, next, state, regex in self.tokens: |
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101 | ## Does the rule apply for us now? |
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102 | if state.match(current_state): |
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103 | if self.verbose > 2: |
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104 | print "%s: Trying to match %r with %r" % (self.state, self.buffer[:10], re_str) |
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105 | m = regex.match(self.buffer) |
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106 | if m: |
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107 | if self.verbose > 3: |
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108 | print "%s matched %s" % (re_str, m.group(0).encode("utf8")) |
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109 | ## The match consumes the data off the buffer (the |
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110 | ## handler can put it back if it likes) |
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111 | self.processed_buffer += self.buffer[:m.end()] |
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112 | self.buffer = self.buffer[m.end():] |
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113 | self.processed += m.end() |
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114 | |
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115 | ## Try to iterate over all the callbacks specified: |
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116 | for t in token.split(','): |
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117 | try: |
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118 | if self.verbose > 0: |
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119 | print "0x%X: Calling %s %r" % (self.processed, t, m.group(0)) |
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120 | cb = getattr(self, t, self.default_handler) |
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121 | except AttributeError: |
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122 | continue |
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123 | |
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124 | ## Is there a callback to handle this action? |
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125 | next_state = cb(t, m) |
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126 | if next_state == "CONTINUE": |
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127 | continue |
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128 | |
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129 | elif next_state: |
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130 | next = next_state |
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131 | self.state = next |
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132 | |
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133 | |
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134 | if next: |
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135 | self.state = next |
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136 | |
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137 | return token |
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138 | |
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139 | ## Check that we are making progress - if we are too full, we |
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140 | ## assume we are stuck: |
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141 | if end and len(self.buffer)>0 or len(self.buffer)>1024: |
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142 | self.processed_buffer += self.buffer[:1] |
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143 | self.buffer = self.buffer[1:] |
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144 | self.ERROR("Lexer Stuck, discarding 1 byte (%r) - state %s" % (self.buffer[:10], self.state)) |
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145 | return "ERROR" |
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146 | |
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147 | ## No token were found |
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148 | return None |
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149 | |
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150 | def feed(self, data): |
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151 | self.buffer += data |
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152 | |
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153 | def empty(self): |
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154 | return not len(self.buffer) |
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155 | |
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156 | def default_handler(self, token, match): |
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157 | if self.verbose > 2: |
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158 | print "Default handler: %s with %r" % (token,match.group(0)) |
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159 | |
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160 | def ERROR(self, message = None, weight =1): |
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161 | if self.verbose > 0 and message: |
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162 | print "Error(%s): %s" % (weight,message) |
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163 | |
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164 | self.error += weight |
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165 | |
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166 | def PUSH_STATE(self, token = None, match = None): |
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167 | if self.verbose > 1: |
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168 | print "Storing state %s" % self.state |
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169 | self.state_stack.append(self.state) |
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170 | |
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171 | def POP_STATE(self, token = None, match = None): |
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172 | try: |
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173 | state = self.state_stack.pop() |
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174 | if self.verbose > 1: |
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175 | print "Returned state to %s" % state |
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176 | |
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177 | return state |
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178 | except IndexError: |
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179 | print "Tried to pop the state but failed - possible recursion error" |
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180 | return None |
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181 | |
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182 | def close(self): |
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183 | """ Just a conveniece function to force us to parse all the data """ |
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184 | while self.next_token(): pass |
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185 | |
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186 | class SelfFeederMixIn(Lexer): |
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187 | """ This mixin is used to make a lexer which feeds itself one |
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188 | sector at the time. |
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189 | |
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190 | Note that self.fd must be the fd we read from. |
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191 | """ |
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192 | def parse_fd(self, fd): |
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193 | self.feed(fd.read()) |
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194 | while self.next_token(): pass |
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195 | |
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