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1 #!/usr/bin/python2.5 |
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2 # |
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3 # Copyright 2008 the Melange authors. |
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4 # |
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5 # Licensed under the Apache License, Version 2.0 (the "License"); |
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6 # you may not use this file except in compliance with the License. |
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7 # You may obtain a copy of the License at |
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8 # |
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9 # http://www.apache.org/licenses/LICENSE-2.0 |
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10 # |
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11 # Unless required by applicable law or agreed to in writing, software |
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12 # distributed under the License is distributed on an "AS IS" BASIS, |
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13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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14 # See the License for the specific language governing permissions and |
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15 # limitations under the License. |
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16 |
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17 """Helpers for manipulating HTTP requests. |
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18 """ |
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19 |
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20 __authors__ = [ |
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21 '"Todd Larsen" <tlarsen@google.com>', |
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22 ] |
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23 |
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24 import urlparse |
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25 |
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26 |
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27 def getSingleIndexedParamValue(request, param_name, values=()): |
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28 """Returns a value indexed by a query parameter in the HTTP request. |
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29 |
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30 Args: |
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31 request: the Django HTTP request object |
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32 param_name: name of the query parameter in the HTTP request |
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33 values: list (or tuple) of ordered values; one of which is |
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34 retrieved by the index value of the param_name argument in |
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35 the HTTP request |
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36 |
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37 Returns: |
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38 None if the query parameter was not present, was not an integer, or |
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39 was an integer that is not a valid [0..len(values)-1] index into |
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40 the values list. |
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41 Otherwise, returns values[int(param_name value)] |
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42 """ |
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43 value_idx = request.GET.get(param_name) |
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44 |
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45 if isinstance(value_idx, (tuple, list)): |
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46 # keep only the first argument if multiple are present |
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47 value_idx = value_idx[0] |
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48 |
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49 try: |
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50 # GET parameter 'param_name' should be an integer value index |
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51 value_idx = int(value_idx) |
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52 except: |
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53 # ignore bogus or missing parameter values, so return None (no message) |
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54 return None |
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55 |
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56 if value_idx < 0: |
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57 # value index out of range, so return None (no value) |
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58 return None |
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59 |
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60 if value_idx >= len(values): |
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61 # value index out of range, so return None (no value) |
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62 return None |
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63 |
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64 # return value associated with valid value index |
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65 return values[value_idx] |
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66 |
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67 |
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68 def getSingleIndexedParamValueIfMissing(value, request, param_name, |
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69 values=()): |
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70 """Returns missing value indexed by a query parameter in the HTTP request. |
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71 |
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72 Args: |
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73 value: an existing value, or a "False" value such as None |
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74 request, param_name, values: see getSingleIndexParamValue() |
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75 |
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76 Returns: |
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77 value, if value is "non-False" |
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78 Otherwise, returns getSingleIndexedParamValue() result. |
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79 """ |
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80 if value: |
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81 # value already present, so return it |
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82 return value |
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83 |
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84 return getSingleIndexedParamValue(request, param_name, values=values) |
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85 |
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86 |
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87 # TODO(tlarsen): write getMultipleIndexParamValues() that returns a |
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88 # list of values if present, omitting those values that are |
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89 # out of range |
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90 |
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91 |
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92 def isReferrerSelf(request, |
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93 expected_prefix=None, suffix=None): |
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94 """Returns True if HTTP referrer path starts with the HTTP request path. |
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95 |
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96 Args: |
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97 request: the Django HTTP request object; request.path is used if |
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98 expected_path is not supplied (the most common usage) |
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99 expected_prefix: optional HTTP path to use instead of the one in |
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100 request.path; default is None (use request.path) |
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101 suffix: suffix to remove from the HTTP request path before comparing |
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102 it to the HTTP referrer path in the HTTP request object headers |
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103 (this is often an link name, for example, that may be changing from |
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104 a POST referrer to a GET redirect target) |
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105 |
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106 Returns: |
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107 True if HTTP referrer path begins with the HTTP request path (either |
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108 request.path or expected_prefix instead if it was supplied), after |
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109 any suffix was removed from that request path |
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110 False otherwise |
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111 |
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112 """ |
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113 http_from = request.META.get('HTTP_REFERER') |
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114 |
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115 if not http_from: |
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116 # no HTTP referrer, so cannot possibly start with expected prefix |
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117 return False |
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118 |
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119 from_path = urlparse.urlparse(http_from).path |
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120 |
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121 if not expected_prefix: |
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122 # use HTTP request path, since expected_prefix was not supplied |
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123 expected_prefix = request.path |
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124 |
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125 if suffix: |
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126 # remove suffix (such as a link name) before comparison |
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127 chars_to_remove = len(suffix) |
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128 |
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129 if not suffix.startswith('/'): |
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130 chars_to_remove = chars_to_remove + 1 |
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131 |
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132 expected_prefix = expected_prefix[:-chars_to_remove] |
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133 |
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134 if not from_path.startswith(expected_prefix): |
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135 # expected prefix did not match first part of HTTP referrer path |
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136 return False |
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137 |
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138 # HTTP referrer started with (possibly truncated) expected prefix |
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139 return True |
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140 |
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141 |
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142 def replaceSuffix(path, old_suffix, new_suffix=None, params=None): |
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143 """Replace the last part of a URL path with something else. |
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144 |
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145 Also appends an optional list of query parameters. Used for |
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146 replacing, for example, one link name at the end of a relative |
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147 URL path with another. |
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148 |
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149 Args: |
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150 path: HTTP request relative URL path (with no query arguments) |
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151 old_suffix: expected suffix at the end of request.path component; |
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152 if any False value (such as None), the empty string '' is used |
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153 new_suffix: if non-False, appended to request.path along with a |
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154 '/' separator (after removing old_suffix if necessary) |
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155 params: an optional dictionary of query parameters to append to |
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156 the redirect target; appended as ?<key1>=<value1>&<key2>=... |
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157 |
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158 Returns: |
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159 /path/with/new_suffix?a=1&b=2 |
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160 """ |
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161 if not old_suffix: |
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162 old_suffix = '' |
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163 |
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164 old_suffix = '/' + old_suffix |
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165 |
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166 if path.endswith(old_suffix): |
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167 # also removes any trailing '/' if old_suffix was empty |
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168 path = path[:-len(old_suffix)] |
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169 |
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170 if new_suffix: |
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171 # if present, appends new_suffix, after '/' separator |
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172 path = '%s/%s' % (path, new_suffix) |
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173 |
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174 if params: |
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175 # appends any query parameters, after a '?' and separated by '&' |
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176 path = '%s?%s' % (path, '&'.join( |
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177 ['%s=%s' % (p,v) for p,v in params.iteritems()])) |
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178 |
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179 return path |