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# -*- coding: utf-8 -*-
# flake8: noqa
from collections import deque
import logging
from .exceptions import InvalidTableIndex
log = logging.getLogger(__name__)
def table_entry_size(name, value):
"""
Calculates the size of a single entry
This size is mostly irrelevant to us and defined
specifically to accommodate memory management for
lower level implementations. The 32 extra bytes are
considered the "maximum" overhead that would be
required to represent each entry in the table.
See RFC7541 Section 4.1
"""
return 32 + len(name) + len(value)
class HeaderTable:
"""
Implements the combined static and dynamic header table
The name and value arguments for all the functions
should ONLY be byte strings (b'') however this is not
strictly enforced in the interface.
See RFC7541 Section 2.3
"""
#: Default maximum size of the dynamic table. See
#: RFC7540 Section 6.5.2.
DEFAULT_SIZE = 4096
#: Constant list of static headers. See RFC7541 Section
#: 2.3.1 and Appendix A
STATIC_TABLE = (
(b':authority' , b'' ), # noqa
(b':method' , b'GET' ), # noqa
(b':method' , b'POST' ), # noqa
(b':path' , b'/' ), # noqa
(b':path' , b'/index.html' ), # noqa
(b':scheme' , b'http' ), # noqa
(b':scheme' , b'https' ), # noqa
(b':status' , b'200' ), # noqa
(b':status' , b'204' ), # noqa
(b':status' , b'206' ), # noqa
(b':status' , b'304' ), # noqa
(b':status' , b'400' ), # noqa
(b':status' , b'404' ), # noqa
(b':status' , b'500' ), # noqa
(b'accept-charset' , b'' ), # noqa
(b'accept-encoding' , b'gzip, deflate'), # noqa
(b'accept-language' , b'' ), # noqa
(b'accept-ranges' , b'' ), # noqa
(b'accept' , b'' ), # noqa
(b'access-control-allow-origin' , b'' ), # noqa
(b'age' , b'' ), # noqa
(b'allow' , b'' ), # noqa
(b'authorization' , b'' ), # noqa
(b'cache-control' , b'' ), # noqa
(b'content-disposition' , b'' ), # noqa
(b'content-encoding' , b'' ), # noqa
(b'content-language' , b'' ), # noqa
(b'content-length' , b'' ), # noqa
(b'content-location' , b'' ), # noqa
(b'content-range' , b'' ), # noqa
(b'content-type' , b'' ), # noqa
(b'cookie' , b'' ), # noqa
(b'date' , b'' ), # noqa
(b'etag' , b'' ), # noqa
(b'expect' , b'' ), # noqa
(b'expires' , b'' ), # noqa
(b'from' , b'' ), # noqa
(b'host' , b'' ), # noqa
(b'if-match' , b'' ), # noqa
(b'if-modified-since' , b'' ), # noqa
(b'if-none-match' , b'' ), # noqa
(b'if-range' , b'' ), # noqa
(b'if-unmodified-since' , b'' ), # noqa
(b'last-modified' , b'' ), # noqa
(b'link' , b'' ), # noqa
(b'location' , b'' ), # noqa
(b'max-forwards' , b'' ), # noqa
(b'proxy-authenticate' , b'' ), # noqa
(b'proxy-authorization' , b'' ), # noqa
(b'range' , b'' ), # noqa
(b'referer' , b'' ), # noqa
(b'refresh' , b'' ), # noqa
(b'retry-after' , b'' ), # noqa
(b'server' , b'' ), # noqa
(b'set-cookie' , b'' ), # noqa
(b'strict-transport-security' , b'' ), # noqa
(b'transfer-encoding' , b'' ), # noqa
(b'user-agent' , b'' ), # noqa
(b'vary' , b'' ), # noqa
(b'via' , b'' ), # noqa
(b'www-authenticate' , b'' ), # noqa
) # noqa
STATIC_TABLE_LENGTH = len(STATIC_TABLE)
def __init__(self):
self._maxsize = HeaderTable.DEFAULT_SIZE
self._current_size = 0
self.resized = False
self.dynamic_entries = deque()
def get_by_index(self, index):
"""
Returns the entry specified by index
Note that the table is 1-based ie an index of 0 is
invalid. This is due to the fact that a zero value
index signals that a completely unindexed header
follows.
The entry will either be from the static table or
the dynamic table depending on the value of index.
"""
original_index = index
index -= 1
if 0 <= index:
if index < HeaderTable.STATIC_TABLE_LENGTH:
return HeaderTable.STATIC_TABLE[index]
index -= HeaderTable.STATIC_TABLE_LENGTH
if index < len(self.dynamic_entries):
return self.dynamic_entries[index]
raise InvalidTableIndex("Invalid table index %d" % original_index)
def __repr__(self):
return "HeaderTable(%d, %s, %r)" % (
self._maxsize,
self.resized,
self.dynamic_entries
)
def add(self, name, value):
"""
Adds a new entry to the table
We reduce the table size if the entry will make the
table size greater than maxsize.
"""
# We just clear the table if the entry is too big
size = table_entry_size(name, value)
if size > self._maxsize:
self.dynamic_entries.clear()
self._current_size = 0
else:
# Add new entry
self.dynamic_entries.appendleft((name, value))
self._current_size += size
self._shrink()
def search(self, name, value):
"""
Searches the table for the entry specified by name
and value
Returns one of the following:
- ``None``, no match at all
- ``(index, name, None)`` for partial matches on name only.
- ``(index, name, value)`` for perfect matches.
"""
partial = None
header_name_search_result = HeaderTable.STATIC_TABLE_MAPPING.get(name)
if header_name_search_result:
index = header_name_search_result[1].get(value)
if index is not None:
return index, name, value
else:
partial = (header_name_search_result[0], name, None)
offset = HeaderTable.STATIC_TABLE_LENGTH + 1
for (i, (n, v)) in enumerate(self.dynamic_entries):
if n == name:
if v == value:
return i + offset, n, v
elif partial is None:
partial = (i + offset, n, None)
return partial
@property
def maxsize(self):
return self._maxsize
@maxsize.setter
def maxsize(self, newmax):
newmax = int(newmax)
log.debug("Resizing header table to %d from %d", newmax, self._maxsize)
oldmax = self._maxsize
self._maxsize = newmax
self.resized = (newmax != oldmax)
if newmax <= 0:
self.dynamic_entries.clear()
self._current_size = 0
elif oldmax > newmax:
self._shrink()
def _shrink(self):
"""
Shrinks the dynamic table to be at or below maxsize
"""
cursize = self._current_size
while cursize > self._maxsize:
name, value = self.dynamic_entries.pop()
cursize -= table_entry_size(name, value)
log.debug("Evicting %s: %s from the header table", name, value)
self._current_size = cursize
def _build_static_table_mapping():
"""
Build static table mapping from header name to tuple with next structure:
(<minimal index of header>, <mapping from header value to it index>).
static_table_mapping used for hash searching.
"""
static_table_mapping = {}
for index, (name, value) in enumerate(HeaderTable.STATIC_TABLE, 1):
header_name_search_result = static_table_mapping.setdefault(name, (index, {}))
header_name_search_result[1][value] = index
return static_table_mapping
HeaderTable.STATIC_TABLE_MAPPING = _build_static_table_mapping()