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diff --git a/wsgiref/headers.py b/wsgiref/headers.py
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+"""Manage HTTP Response Headers
+
+Much of this module is red-handedly pilfered from email.Message in the stdlib,
+so portions are Copyright (C) 2001,2002 Python Software Foundation, and were
+written by Barry Warsaw.
+"""
+
+from types import ListType, TupleType
+
+# Regular expression that matches `special' characters in parameters, the
+# existance of which force quoting of the parameter value.
+import re
+tspecials = re.compile(r'[ \(\)<>@,;:\\"/\[\]\?=]')
+
+def _formatparam(param, value=None, quote=1):
+ """Convenience function to format and return a key=value pair.
+
+ This will quote the value if needed or if quote is true.
+ """
+ if value is not None and len(value) > 0:
+ if quote or tspecials.search(value):
+ value = value.replace('\\', '\\\\').replace('"', r'\"')
+ return '%s="%s"' % (param, value)
+ else:
+ return '%s=%s' % (param, value)
+ else:
+ return param
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+class Headers:
+
+ """Manage a collection of HTTP response headers"""
+
+ def __init__(self,headers):
+ if type(headers) is not ListType:
+ raise TypeError("Headers must be a list of name/value tuples")
+ self._headers = headers
+
+ def __len__(self):
+ """Return the total number of headers, including duplicates."""
+ return len(self._headers)
+
+ def __setitem__(self, name, val):
+ """Set the value of a header."""
+ del self[name]
+ self._headers.append((name, val))
+
+ def __delitem__(self,name):
+ """Delete all occurrences of a header, if present.
+
+ Does *not* raise an exception if the header is missing.
+ """
+ name = name.lower()
+ self._headers[:] = [kv for kv in self._headers if kv[0].lower()<>name]
+
+ def __getitem__(self,name):
+ """Get the first header value for 'name'
+
+ Return None if the header is missing instead of raising an exception.
+
+ Note that if the header appeared multiple times, the first exactly which
+ occurrance gets returned is undefined. Use getall() to get all
+ the values matching a header field name.
+ """
+ return self.get(name)
+
+
+
+
+
+ def has_key(self, name):
+ """Return true if the message contains the header."""
+ return self.get(name) is not None
+
+ __contains__ = has_key
+
+
+ def get_all(self, name):
+ """Return a list of all the values for the named field.
+
+ These will be sorted in the order they appeared in the original header
+ list or were added to this instance, and may contain duplicates. Any
+ fields deleted and re-inserted are always appended to the header list.
+ If no fields exist with the given name, returns an empty list.
+ """
+ name = name.lower()
+ return [kv[1] for kv in self._headers if kv[0].lower()==name]
+
+
+ def get(self,name,default=None):
+ """Get the first header value for 'name', or return 'default'"""
+ name = name.lower()
+ for k,v in self._headers:
+ if k.lower()==name:
+ return v
+ return default
+
+
+ def keys(self):
+ """Return a list of all the header field names.
+
+ These will be sorted in the order they appeared in the original header
+ list, or were added to this instance, and may contain duplicates.
+ Any fields deleted and re-inserted are always appended to the header
+ list.
+ """
+ return [k for k, v in self._headers]
+
+
+
+
+ def values(self):
+ """Return a list of all header values.
+
+ These will be sorted in the order they appeared in the original header
+ list, or were added to this instance, and may contain duplicates.
+ Any fields deleted and re-inserted are always appended to the header
+ list.
+ """
+ return [v for k, v in self._headers]
+
+ def items(self):
+ """Get all the header fields and values.
+
+ These will be sorted in the order they were in the original header
+ list, or were added to this instance, and may contain duplicates.
+ Any fields deleted and re-inserted are always appended to the header
+ list.
+ """
+ return self._headers[:]
+
+ def __repr__(self):
+ return "Headers(%s)" % `self._headers`
+
+ def __str__(self):
+ """str() returns the formatted headers, complete with end line,
+ suitable for direct HTTP transmission."""
+ return '\r\n'.join(["%s: %s" % kv for kv in self._headers]+['',''])
+
+ def setdefault(self,name,value):
+ """Return first matching header value for 'name', or 'value'
+
+ If there is no header named 'name', add a new header with name 'name'
+ and value 'value'."""
+ result = self.get(name)
+ if result is None:
+ self._headers.append((name,value))
+ return value
+ else:
+ return result
+
+
+ def add_header(self, _name, _value, **_params):
+ """Extended header setting.
+
+ _name is the header field to add. keyword arguments can be used to set
+ additional parameters for the header field, with underscores converted
+ to dashes. Normally the parameter will be added as key="value" unless
+ value is None, in which case only the key will be added.
+
+ Example:
+
+ h.add_header('content-disposition', 'attachment', filename='bud.gif')
+
+ Note that unlike the corresponding 'email.Message' method, this does
+ *not* handle '(charset, language, value)' tuples: all values must be
+ strings or None.
+ """
+ parts = []
+ if _value is not None:
+ parts.append(_value)
+ for k, v in _params.items():
+ if v is None:
+ parts.append(k.replace('_', '-'))
+ else:
+ parts.append(_formatparam(k.replace('_', '-'), v))
+ self._headers.append((_name, "; ".join(parts)))
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+