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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 |
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25 def getSingleIndexedParamValue(request, param_name, values=()): |
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26 """Returns a value indexed by a query parameter in the HTTP request. |
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27 |
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28 Args: |
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29 request: the Django HTTP request object |
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30 param_name: name of the query parameter in the HTTP request |
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31 values: list (or tuple) of ordered values; one of which is |
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32 retrieved by the index value of the param_name argument in |
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33 the HTTP request |
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34 |
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35 Returns: |
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36 None if the query parameter was not present, was not an integer, or |
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37 was an integer that is not a valid [0..len(values)-1] index into |
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38 the values list. |
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39 Otherwise, returns values[int(param_name value)] |
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40 """ |
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41 value_idx = request.GET.get(param_name) |
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42 |
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43 if isinstance(value_idx, (tuple, list)): |
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44 # keep only the first argument if multiple are present |
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45 value_idx = value_idx[0] |
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46 |
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47 try: |
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48 # GET parameter 'param_name' should be an integer value index |
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49 value_idx = int(value_idx) |
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50 except: |
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51 # ignore bogus or missing parameter values, so return None (no message) |
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52 return None |
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53 |
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54 if value_idx < 0: |
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55 # value index out of range, so return None (no value) |
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56 return None |
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57 |
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58 if value_idx >= len(values): |
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59 # value index out of range, so return None (no value) |
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60 return None |
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61 |
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62 # return value associated with valid value index |
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63 return values[value_idx] |
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64 |
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65 |
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66 def getSingleIndexedParamValueIfMissing(value, request, param_name, |
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67 values=()): |
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68 """Returns missing value indexed by a query parameter in the HTTP request. |
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69 |
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70 Args: |
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71 value: an existing value, or a "False" value such as None |
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72 request, param_name, values: see getSingleIndexParamValue() |
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73 |
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74 Returns: |
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75 value, if value is "non-False" |
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76 Otherwise, returns getSingleIndexedParamValue() result. |
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77 """ |
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78 if value: |
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79 # value already present, so return it |
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80 return value |
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81 |
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82 return getSingleIndexedParamValue(request, param_name, values=values) |
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83 |
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84 |
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85 # TODO(tlarsen): write getMultipleIndexParamValues() that returns a |
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86 # list of values if present, omitting those values that are |
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87 # out of range |