# -*- 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: (, ). 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()