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1 """Manage HTTP Response Headers
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2
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3 Much of this module is red-handedly pilfered from email.message in the stdlib,
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4 so portions are Copyright (C) 2001,2002 Python Software Foundation, and were
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5 written by Barry Warsaw.
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6 """
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7
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8 # Regular expression that matches `special' characters in parameters, the
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9 # existence of which force quoting of the parameter value.
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10 import re
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11 tspecials = re.compile(r'[ \(\)<>@,;:\\"/\[\]\?=]')
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12
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13 def _formatparam(param, value=None, quote=1):
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14 """Convenience function to format and return a key=value pair.
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15
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16 This will quote the value if needed or if quote is true.
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17 """
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18 if value is not None and len(value) > 0:
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19 if quote or tspecials.search(value):
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20 value = value.replace('\\', '\\\\').replace('"', r'\"')
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21 return '%s="%s"' % (param, value)
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22 else:
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23 return '%s=%s' % (param, value)
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24 else:
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25 return param
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26
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27
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28 class Headers:
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29 """Manage a collection of HTTP response headers"""
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30
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31 def __init__(self, headers=None):
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32 headers = headers if headers is not None else []
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33 if type(headers) is not list:
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34 raise TypeError("Headers must be a list of name/value tuples")
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35 self._headers = headers
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36 if __debug__:
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37 for k, v in headers:
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38 self._convert_string_type(k)
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39 self._convert_string_type(v)
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40
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41 def _convert_string_type(self, value):
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42 """Convert/check value type."""
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43 if type(value) is str:
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44 return value
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45 raise AssertionError("Header names/values must be"
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46 " of type str (got {0})".format(repr(value)))
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47
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48 def __len__(self):
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49 """Return the total number of headers, including duplicates."""
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50 return len(self._headers)
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51
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52 def __setitem__(self, name, val):
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53 """Set the value of a header."""
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54 del self[name]
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55 self._headers.append(
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56 (self._convert_string_type(name), self._convert_string_type(val)))
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57
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58 def __delitem__(self,name):
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59 """Delete all occurrences of a header, if present.
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60
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61 Does *not* raise an exception if the header is missing.
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62 """
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63 name = self._convert_string_type(name.lower())
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64 self._headers[:] = [kv for kv in self._headers if kv[0].lower() != name]
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65
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66 def __getitem__(self,name):
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67 """Get the first header value for 'name'
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68
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69 Return None if the header is missing instead of raising an exception.
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70
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71 Note that if the header appeared multiple times, the first exactly which
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72 occurrence gets returned is undefined. Use getall() to get all
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73 the values matching a header field name.
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74 """
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75 return self.get(name)
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76
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77 def __contains__(self, name):
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78 """Return true if the message contains the header."""
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79 return self.get(name) is not None
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80
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81
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82 def get_all(self, name):
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83 """Return a list of all the values for the named field.
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84
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85 These will be sorted in the order they appeared in the original header
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86 list or were added to this instance, and may contain duplicates. Any
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87 fields deleted and re-inserted are always appended to the header list.
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88 If no fields exist with the given name, returns an empty list.
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89 """
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90 name = self._convert_string_type(name.lower())
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91 return [kv[1] for kv in self._headers if kv[0].lower()==name]
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92
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93
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94 def get(self,name,default=None):
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95 """Get the first header value for 'name', or return 'default'"""
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96 name = self._convert_string_type(name.lower())
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97 for k,v in self._headers:
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98 if k.lower()==name:
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99 return v
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100 return default
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101
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102
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103 def keys(self):
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104 """Return a list of all the header field names.
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105
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106 These will be sorted in the order they appeared in the original header
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107 list, or were added to this instance, and may contain duplicates.
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108 Any fields deleted and re-inserted are always appended to the header
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109 list.
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110 """
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111 return [k for k, v in self._headers]
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112
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113 def values(self):
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114 """Return a list of all header values.
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115
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116 These will be sorted in the order they appeared in the original header
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117 list, or were added to this instance, and may contain duplicates.
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118 Any fields deleted and re-inserted are always appended to the header
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119 list.
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120 """
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121 return [v for k, v in self._headers]
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122
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123 def items(self):
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124 """Get all the header fields and values.
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125
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126 These will be sorted in the order they were in the original header
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127 list, or were added to this instance, and may contain duplicates.
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128 Any fields deleted and re-inserted are always appended to the header
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129 list.
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130 """
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131 return self._headers[:]
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132
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133 def __repr__(self):
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134 return "%s(%r)" % (self.__class__.__name__, self._headers)
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135
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136 def __str__(self):
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137 """str() returns the formatted headers, complete with end line,
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138 suitable for direct HTTP transmission."""
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139 return '\r\n'.join(["%s: %s" % kv for kv in self._headers]+['',''])
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140
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141 def __bytes__(self):
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142 return str(self).encode('iso-8859-1')
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143
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144 def setdefault(self,name,value):
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145 """Return first matching header value for 'name', or 'value'
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146
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147 If there is no header named 'name', add a new header with name 'name'
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148 and value 'value'."""
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149 result = self.get(name)
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150 if result is None:
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151 self._headers.append((self._convert_string_type(name),
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152 self._convert_string_type(value)))
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153 return value
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154 else:
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155 return result
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156
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157 def add_header(self, _name, _value, **_params):
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158 """Extended header setting.
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159
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160 _name is the header field to add. keyword arguments can be used to set
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161 additional parameters for the header field, with underscores converted
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162 to dashes. Normally the parameter will be added as key="value" unless
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163 value is None, in which case only the key will be added.
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164
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165 Example:
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166
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167 h.add_header('content-disposition', 'attachment', filename='bud.gif')
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168
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169 Note that unlike the corresponding 'email.message' method, this does
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170 *not* handle '(charset, language, value)' tuples: all values must be
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171 strings or None.
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172 """
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173 parts = []
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174 if _value is not None:
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175 _value = self._convert_string_type(_value)
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176 parts.append(_value)
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177 for k, v in _params.items():
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178 k = self._convert_string_type(k)
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179 if v is None:
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180 parts.append(k.replace('_', '-'))
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181 else:
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182 v = self._convert_string_type(v)
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183 parts.append(_formatparam(k.replace('_', '-'), v))
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184 self._headers.append((self._convert_string_type(_name), "; ".join(parts)))
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