108 lines
3.5 KiB
Python
108 lines
3.5 KiB
Python
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# -*- coding: utf-8 -*-
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"""
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hpack/hpack_compat
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~~~~~~~~~~~~~~~~~~
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Provides an abstraction layer over two HPACK implementations.
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This module has a pure-Python greenfield HPACK implementation that can be used
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on all Python platforms. However, this implementation is both slower and more
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memory-hungry than could be achieved with a C-language version. Additionally,
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nghttp2's HPACK implementation currently achieves better compression ratios
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than hyper's in almost all benchmarks.
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For those who care about efficiency and speed in HPACK, this module allows you
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to use nghttp2's HPACK implementation instead of ours. This module detects
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whether the nghttp2 bindings are installed, and if they are it wraps them in
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a hpack-compatible API and uses them instead of its own. If not, it falls back
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to the built-in Python bindings.
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"""
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import logging
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from .hpack import _to_bytes
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log = logging.getLogger(__name__)
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# Attempt to import nghttp2.
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try:
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import nghttp2
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USE_NGHTTP2 = True
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log.debug("Using nghttp2's HPACK implementation.")
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except ImportError:
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USE_NGHTTP2 = False
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log.debug("Using our pure-Python HPACK implementation.")
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if USE_NGHTTP2: # noqa
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class Encoder(object):
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"""
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An HPACK encoder object. This object takes HTTP headers and emits
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encoded HTTP/2 header blocks.
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"""
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def __init__(self):
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self._e = nghttp2.HDDeflater()
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@property
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def header_table_size(self):
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"""
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Returns the header table size. For the moment this isn't
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useful, so we don't use it.
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"""
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raise NotImplementedError()
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@header_table_size.setter
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def header_table_size(self, value):
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log.debug("Setting header table size to %d", value)
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self._e.change_table_size(value)
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def encode(self, headers, huffman=True):
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"""
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Encode the headers. The huffman parameter has no effect, it is
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simply present for compatibility.
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"""
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log.debug("HPACK encoding %s", headers)
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# Turn the headers into a list of tuples if possible. This is the
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# natural way to interact with them in HPACK.
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if isinstance(headers, dict):
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headers = headers.items()
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# Next, walk across the headers and turn them all into bytestrings.
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headers = [(_to_bytes(n), _to_bytes(v)) for n, v in headers]
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# Now, let nghttp2 do its thing.
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header_block = self._e.deflate(headers)
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return header_block
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class Decoder(object):
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"""
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An HPACK decoder object.
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"""
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def __init__(self):
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self._d = nghttp2.HDInflater()
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@property
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def header_table_size(self):
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"""
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Returns the header table size. For the moment this isn't
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useful, so we don't use it.
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"""
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raise NotImplementedError()
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@header_table_size.setter
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def header_table_size(self, value):
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log.debug("Setting header table size to %d", value)
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self._d.change_table_size(value)
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def decode(self, data):
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"""
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Takes an HPACK-encoded header block and decodes it into a header
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set.
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"""
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log.debug("Decoding %s", data)
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headers = self._d.inflate(data)
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return [(n.decode('utf-8'), v.decode('utf-8')) for n, v in headers]
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else:
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# Grab the built-in encoder and decoder.
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from .hpack import Encoder, Decoder # noqa
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