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"""
Unicode Handling
----------------
See also: http://lucumr.pocoo.org/2013/7/2/the-updated-guide-to-unicode/
"""
from __future__ import absolute_import, print_function, division
import re
try:
from collections.abc import MutableMapping
except ImportError: # pragma: no cover
from collections import MutableMapping # Workaround for Python < 3.3
import six
from netlib.utils import always_byte_args, always_bytes, Serializable
if six.PY2: # pragma: no cover
_native = lambda x: x
_always_bytes = lambda x: x
_always_byte_args = lambda x: x
else:
# While headers _should_ be ASCII, it's not uncommon for certain headers to be utf-8 encoded.
_native = lambda x: x.decode("utf-8", "surrogateescape")
_always_bytes = lambda x: always_bytes(x, "utf-8", "surrogateescape")
_always_byte_args = always_byte_args("utf-8", "surrogateescape")
class Headers(MutableMapping, Serializable):
"""
Header class which allows both convenient access to individual headers as well as
direct access to the underlying raw data. Provides a full dictionary interface.
Example:
.. code-block:: python
# Create headers with keyword arguments
>>> h = Headers(host="example.com", content_type="application/xml")
# Headers mostly behave like a normal dict.
>>> h["Host"]
"example.com"
# HTTP Headers are case insensitive
>>> h["host"]
"example.com"
# Headers can also be creatd from a list of raw (header_name, header_value) byte tuples
>>> h = Headers([
[b"Host",b"example.com"],
[b"Accept",b"text/html"],
[b"accept",b"application/xml"]
])
# Multiple headers are folded into a single header as per RFC7230
>>> h["Accept"]
"text/html, application/xml"
# Setting a header removes all existing headers with the same name.
>>> h["Accept"] = "application/text"
>>> h["Accept"]
"application/text"
# bytes(h) returns a HTTP1 header block.
>>> print(bytes(h))
Host: example.com
Accept: application/text
# For full control, the raw header fields can be accessed
>>> h.fields
Caveats:
For use with the "Set-Cookie" header, see :py:meth:`get_all`.
"""
@_always_byte_args
def __init__(self, fields=None, **headers):
"""
Args:
fields: (optional) list of ``(name, value)`` header byte tuples,
e.g. ``[(b"Host", b"example.com")]``. All names and values must be bytes.
**headers: Additional headers to set. Will overwrite existing values from `fields`.
For convenience, underscores in header names will be transformed to dashes -
this behaviour does not extend to other methods.
If ``**headers`` contains multiple keys that have equal ``.lower()`` s,
the behavior is undefined.
"""
self.fields = fields or []
for name, value in self.fields:
if not isinstance(name, bytes) or not isinstance(value, bytes):
raise ValueError("Headers passed as fields must be bytes.")
# content_type -> content-type
headers = {
_always_bytes(name).replace(b"_", b"-"): value
for name, value in six.iteritems(headers)
}
self.update(headers)
def __bytes__(self):
if self.fields:
return b"\r\n".join(b": ".join(field) for field in self.fields) + b"\r\n"
else:
return b""
if six.PY2: # pragma: no cover
__str__ = __bytes__
@_always_byte_args
def __getitem__(self, name):
values = self.get_all(name)
if not values:
raise KeyError(name)
return ", ".join(values)
@_always_byte_args
def __setitem__(self, name, value):
idx = self._index(name)
# To please the human eye, we insert at the same position the first existing header occured.
if idx is not None:
del self[name]
self.fields.insert(idx, [name, value])
else:
self.fields.append([name, value])
@_always_byte_args
def __delitem__(self, name):
if name not in self:
raise KeyError(name)
name = name.lower()
self.fields = [
field for field in self.fields
if name != field[0].lower()
]
def __iter__(self):
seen = set()
for name, _ in self.fields:
name_lower = name.lower()
if name_lower not in seen:
seen.add(name_lower)
yield _native(name)
def __len__(self):
return len(set(name.lower() for name, _ in self.fields))
# __hash__ = object.__hash__
def _index(self, name):
name = name.lower()
for i, field in enumerate(self.fields):
if field[0].lower() == name:
return i
return None
def __eq__(self, other):
if isinstance(other, Headers):
return self.fields == other.fields
return False
def __ne__(self, other):
return not self.__eq__(other)
@_always_byte_args
def get_all(self, name):
"""
Like :py:meth:`get`, but does not fold multiple headers into a single one.
This is useful for Set-Cookie headers, which do not support folding.
See also: https://tools.ietf.org/html/rfc7230#section-3.2.2
"""
name_lower = name.lower()
values = [_native(value) for n, value in self.fields if n.lower() == name_lower]
return values
@_always_byte_args
def set_all(self, name, values):
"""
Explicitly set multiple headers for the given key.
See: :py:meth:`get_all`
"""
values = map(_always_bytes, values) # _always_byte_args does not fix lists
if name in self:
del self[name]
self.fields.extend(
[name, value] for value in values
)
def get_state(self):
return tuple(tuple(field) for field in self.fields)
def set_state(self, state):
self.fields = [list(field) for field in state]
@classmethod
def from_state(cls, state):
return cls([list(field) for field in state])
@_always_byte_args
def replace(self, pattern, repl, flags=0):
"""
Replaces a regular expression pattern with repl in each "name: value"
header line.
Returns:
The number of replacements made.
"""
pattern = re.compile(pattern, flags)
replacements = 0
fields = []
for name, value in self.fields:
line, n = pattern.subn(repl, name + b": " + value)
try:
name, value = line.split(b": ", 1)
except ValueError:
# We get a ValueError if the replacement removed the ": "
# There's not much we can do about this, so we just keep the header as-is.
pass
else:
replacements += n
fields.append([name, value])
self.fields = fields
return replacements
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