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1 # -*- coding: utf-8 -*-
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2 #
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3 # Copyright (C) 2006 Edgewall Software
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4 # All rights reserved.
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5 #
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6 # This software is licensed as described in the file COPYING, which
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7 # you should have received as part of this distribution. The terms
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8 # are also available at http://trac.edgewall.com/license.html.
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9 #
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10 # This software consists of voluntary contributions made by many
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11 # individuals. For the exact contribution history, see the revision
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12 # history and logs, available at http://projects.edgewall.com/trac/.
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13
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14 """Basic support for evaluating XPath expressions against streams."""
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15
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16 import re
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17
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18 from markup.core import QName, Stream
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19
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20 __all__ = ['Path']
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21
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22 _QUOTES = (("'", "'"), ('"', '"'))
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23
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24 class Path(object):
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25 """Basic XPath support on markup event streams.
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26
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27 >>> from markup.input import XML
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28
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29 Selecting specific tags:
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30
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31 >>> Path('root').select(XML('<root/>')).render()
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32 '<root/>'
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33 >>> Path('//root').select(XML('<root/>')).render()
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34 '<root/>'
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35
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36 Using wildcards for tag names:
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37
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38 >>> Path('*').select(XML('<root/>')).render()
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39 '<root/>'
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40 >>> Path('//*').select(XML('<root/>')).render()
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41 '<root/>'
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42
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43 Selecting attribute values:
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44
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45 >>> Path('@foo').select(XML('<root/>')).render()
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46 ''
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47 >>> Path('@foo').select(XML('<root foo="bar"/>')).render()
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48 'bar'
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49
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50 Selecting descendants:
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51
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52 >>> Path("root/*").select(XML('<root><foo/><bar/></root>')).render()
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53 '<foo/><bar/>'
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54 >>> Path("root/bar").select(XML('<root><foo/><bar/></root>')).render()
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55 '<bar/>'
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56 >>> Path("root/baz").select(XML('<root><foo/><bar/></root>')).render()
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57 ''
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58 >>> Path("root/foo/*").select(XML('<root><foo><bar/></foo></root>')).render()
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59 '<bar/>'
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60
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61 Selecting text nodes:
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62 >>> Path("item/text()").select(XML('<root><item>Foo</item></root>')).render()
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63 'Foo'
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64 >>> Path("item/text()").select(XML('<root><item>Foo</item><item>Bar</item></root>')).render()
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65 'FooBar'
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66
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67 Skipping ancestors:
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68
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69 >>> Path("foo/bar").select(XML('<root><foo><bar/></foo></root>')).render()
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70 '<bar/>'
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71 >>> Path("foo/*").select(XML('<root><foo><bar/></foo></root>')).render()
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72 '<bar/>'
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73 >>> Path("root/bar").select(XML('<root><foo><bar/></foo></root>')).render()
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74 ''
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75 >>> Path("root/bar").select(XML('<root><foo><bar id="1"/></foo><bar id="2"/></root>')).render()
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76 '<bar id="2"/>'
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77 >>> Path("root/*/bar").select(XML('<root><foo><bar/></foo></root>')).render()
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78 '<bar/>'
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79 >>> Path("root//bar").select(XML('<root><foo><bar id="1"/></foo><bar id="2"/></root>')).render()
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80 '<bar id="1"/><bar id="2"/>'
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81 >>> Path("root//bar").select(XML('<root><foo><bar id="1"/></foo><bar id="2"/></root>')).render()
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82 '<bar id="1"/><bar id="2"/>'
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83
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84 Using simple attribute predicates:
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85 >>> Path("root/item[@important]").select(XML('<root><item/><item important="very"/></root>')).render()
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86 '<item important="very"/>'
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87 >>> Path('root/item[@important="very"]').select(XML('<root><item/><item important="very"/></root>')).render()
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88 '<item important="very"/>'
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89 >>> Path("root/item[@important='very']").select(XML('<root><item/><item important="notso"/></root>')).render()
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90 ''
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91 >>> Path("root/item[@important!='very']").select(
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92 ... XML('<root><item/><item important="notso"/></root>')).render()
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93 '<item/><item important="notso"/>'
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94 """
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95
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96 _TOKEN_RE = re.compile('(::|\.\.|\(\)|[/.:\[\]\(\)@=!])|'
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97 '([^/:\[\]\(\)@=!\s]+)|'
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98 '\s+')
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99
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100 def __init__(self, text):
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101 self.source = text
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102
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103 steps = []
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104 cur_op = ''
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105 cur_tag = ''
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106 in_predicate = False
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107 for op, tag in self._TOKEN_RE.findall(text):
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108 if op:
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109 if op == '[':
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110 in_predicate = True
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111 elif op == ']':
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112 in_predicate = False
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113 elif op.startswith('('):
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114 if cur_tag == 'text':
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115 steps[-1] = (False, self.fn_text(), [])
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116 else:
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117 raise NotImplementedError('XPath function "%s" not '
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118 'supported' % cur_tag)
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119 else:
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120 cur_op += op
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121 cur_tag = ''
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122 else:
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123 closure = cur_op in ('', '//')
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124 if cur_op == '@':
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125 if tag == '*':
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126 node_test = self.any_attribute()
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127 else:
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128 node_test = self.attribute_by_name(tag)
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129 else:
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130 if tag == '*':
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131 node_test = self.any_element()
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132 elif in_predicate:
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133 if len(tag) > 1 and (tag[0], tag[-1]) in _QUOTES:
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134 node_test = self.literal_string(tag[1:-1])
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135 if cur_op == '=':
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136 node_test = self.op_eq(steps[-1][2][-1], node_test)
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137 steps[-1][2].pop()
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138 elif cur_op == '!=':
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139 node_test = self.op_neq(steps[-1][2][-1], node_test)
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140 steps[-1][2].pop()
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141 else:
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142 node_test = self.element_by_name(tag)
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143 if in_predicate:
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144 steps[-1][2].append(node_test)
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145 else:
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146 steps.append([closure, node_test, []])
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147 cur_op = ''
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148 cur_tag = tag
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149 self.steps = steps
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150
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151 def __repr__(self):
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152 return '<%s "%s">' % (self.__class__.__name__, self.source)
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153
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154 def select(self, stream):
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155 stream = iter(stream)
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156 def _generate(tests):
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157 test = self.test()
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158 for kind, data, pos in stream:
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159 result = test(kind, data, pos)
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160 if result is True:
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161 yield kind, data, pos
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162 depth = 1
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163 while depth > 0:
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164 ev = stream.next()
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165 if ev[0] is Stream.START:
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166 depth += 1
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167 elif ev[0] is Stream.END:
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168 depth -= 1
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169 yield ev
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170 test(*ev)
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171 elif result:
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172 yield result
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173 return Stream(_generate(self.steps))
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174
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175 def test(self):
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176 stack = [0] # stack of cursors into the location path
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177
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178 def _test(kind, data, pos):
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179 #print '\nTracker %r test [%s] %r' % (self, kind, data)
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180
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181 if not stack:
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182 return False
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183
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184 if kind is Stream.END:
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185 stack.pop()
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186 return None
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187
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188 if kind is Stream.START:
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189 stack.append(stack[-1])
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190
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191 matched = False
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192 closure, node_test, predicates = self.steps[stack[-1]]
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193
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194 #print ' Testing against %r' % node_test
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195 matched = node_test(kind, data, pos)
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196 if matched and predicates:
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197 for predicate in predicates:
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198 if not predicate(kind, data, pos):
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199 matched = None
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200 break
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201
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202 if matched:
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203 if stack[-1] == len(self.steps) - 1:
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204 #print ' Last step %r... returned %r' % (node_test, matched)
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205 return matched
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206
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207 #print ' Matched intermediate step %r... proceed to next step %r' % (node_test, self.steps[stack[-1] + 1])
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208 stack[-1] += 1
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209
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210 elif kind is Stream.START and not closure:
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211 # FIXME: If this step is not a closure, it cannot be matched
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212 # until the current element is closed... so we need to
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213 # move the cursor back to the last closure and retest
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214 # that against the current element
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215 closures = [step for step in self.steps[:stack[-1]] if step[0]]
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216 closures.reverse()
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217 for closure, node_test, predicates in closures:
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218 stack[-1] -= 1
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219 if closure:
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220 matched = node_test(kind, data, pos)
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221 if matched:
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222 stack[-1] += 1
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223 break
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224
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225 return None
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226
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227 return _test
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228
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229 class any_element(object):
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230 def __call__(self, kind, data, pos):
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231 if kind is Stream.START:
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232 return True
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233 return None
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234 def __repr__(self):
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235 return '<%s>' % self.__class__.__name__
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236
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237 class element_by_name(object):
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238 def __init__(self, name):
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239 self.name = QName(name)
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240 def __call__(self, kind, data, pos):
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241 if kind is Stream.START:
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242 return data[0].localname == self.name
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243 return None
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244 def __repr__(self):
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245 return '<%s "%s">' % (self.__class__.__name__, self.name)
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246
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247 class any_attribute(object):
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248 def __call__(self, kind, data, pos):
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249 if kind is Stream.START:
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250 text = ''.join([val for name, val in data[1]])
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251 if text:
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252 return Stream.TEXT, text, pos
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253 return None
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254 return None
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255 def __repr__(self):
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256 return '<%s>' % (self.__class__.__name__)
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257
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258 class attribute_by_name(object):
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259 def __init__(self, name):
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260 self.name = QName(name)
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261 def __call__(self, kind, data, pos):
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262 if kind is Stream.START:
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263 if self.name in data[1]:
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264 return Stream.TEXT, data[1].get(self.name), pos
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265 return None
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266 return None
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267 def __repr__(self):
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268 return '<%s "%s">' % (self.__class__.__name__, self.name)
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269
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270 class fn_text(object):
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271 def __call__(self, kind, data, pos):
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272 if kind is Stream.TEXT:
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273 return kind, data, pos
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274 return None
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275 def __repr__(self):
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276 return '<%s>' % (self.__class__.__name__)
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277
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278 class literal_string(object):
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279 def __init__(self, value):
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280 self.value = value
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281 def __call__(self, kind, data, pos):
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282 return Stream.TEXT, self.value, (-1, -1)
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283 def __repr__(self):
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284 return '<%s>' % (self.__class__.__name__)
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285
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286 class op_eq(object):
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287 def __init__(self, lval, rval):
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288 self.lval = lval
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289 self.rval = rval
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290 def __call__(self, kind, data, pos):
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291 lval = self.lval(kind, data, pos)
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292 rval = self.rval(kind, data, pos)
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293 return (lval and lval[1]) == (rval and rval[1])
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294 def __repr__(self):
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295 return '<%s %r = %r>' % (self.__class__.__name__, self.lval,
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296 self.rval)
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297
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298 class op_neq(object):
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299 def __init__(self, lval, rval):
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300 self.lval = lval
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301 self.rval = rval
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302 def __call__(self, kind, data, pos):
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303 lval = self.lval(kind, data, pos)
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304 rval = self.rval(kind, data, pos)
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305 return (lval and lval[1]) != (rval and rval[1])
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306 def __repr__(self):
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307 return '<%s %r != %r>' % (self.__class__.__name__, self.lval,
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308 self.rval)
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