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# cborutil.py - CBOR extensions
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#
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# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>
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#
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# This software may be used and distributed according to the terms of the
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# GNU General Public License version 2 or any later version.
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from __future__ import absolute_import
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import struct
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import sys
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from .. import pycompat
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# Very short very of RFC 7049...
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#
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# Each item begins with a byte. The 3 high bits of that byte denote the
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# "major type." The lower 5 bits denote the "subtype." Each major type
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# has its own encoding mechanism.
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#
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# Most types have lengths. However, bytestring, string, array, and map
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# can be indefinite length. These are denotes by a subtype with value 31.
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# Sub-components of those types then come afterwards and are terminated
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# by a "break" byte.
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MAJOR_TYPE_UINT = 0
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MAJOR_TYPE_NEGINT = 1
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MAJOR_TYPE_BYTESTRING = 2
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MAJOR_TYPE_STRING = 3
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MAJOR_TYPE_ARRAY = 4
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MAJOR_TYPE_MAP = 5
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MAJOR_TYPE_SEMANTIC = 6
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MAJOR_TYPE_SPECIAL = 7
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SUBTYPE_MASK = 0b00011111
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SUBTYPE_FALSE = 20
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SUBTYPE_TRUE = 21
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SUBTYPE_NULL = 22
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SUBTYPE_HALF_FLOAT = 25
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SUBTYPE_SINGLE_FLOAT = 26
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SUBTYPE_DOUBLE_FLOAT = 27
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SUBTYPE_INDEFINITE = 31
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SEMANTIC_TAG_FINITE_SET = 258
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# Indefinite types begin with their major type ORd with information value 31.
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BEGIN_INDEFINITE_BYTESTRING = struct.pack(
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r'>B', MAJOR_TYPE_BYTESTRING << 5 | SUBTYPE_INDEFINITE
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)
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BEGIN_INDEFINITE_ARRAY = struct.pack(
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r'>B', MAJOR_TYPE_ARRAY << 5 | SUBTYPE_INDEFINITE
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)
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BEGIN_INDEFINITE_MAP = struct.pack(
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r'>B', MAJOR_TYPE_MAP << 5 | SUBTYPE_INDEFINITE
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)
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ENCODED_LENGTH_1 = struct.Struct(r'>B')
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ENCODED_LENGTH_2 = struct.Struct(r'>BB')
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ENCODED_LENGTH_3 = struct.Struct(r'>BH')
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ENCODED_LENGTH_4 = struct.Struct(r'>BL')
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ENCODED_LENGTH_5 = struct.Struct(r'>BQ')
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# The break ends an indefinite length item.
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BREAK = b'\xff'
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BREAK_INT = 255
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def encodelength(majortype, length):
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"""Obtain a value encoding the major type and its length."""
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if length < 24:
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return ENCODED_LENGTH_1.pack(majortype << 5 | length)
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elif length < 256:
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return ENCODED_LENGTH_2.pack(majortype << 5 | 24, length)
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elif length < 65536:
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return ENCODED_LENGTH_3.pack(majortype << 5 | 25, length)
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elif length < 4294967296:
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return ENCODED_LENGTH_4.pack(majortype << 5 | 26, length)
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else:
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return ENCODED_LENGTH_5.pack(majortype << 5 | 27, length)
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def streamencodebytestring(v):
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yield encodelength(MAJOR_TYPE_BYTESTRING, len(v))
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yield v
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def streamencodebytestringfromiter(it):
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"""Convert an iterator of chunks to an indefinite bytestring.
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Given an input that is iterable and each element in the iterator is
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representable as bytes, emit an indefinite length bytestring.
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"""
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yield BEGIN_INDEFINITE_BYTESTRING
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for chunk in it:
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yield encodelength(MAJOR_TYPE_BYTESTRING, len(chunk))
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yield chunk
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yield BREAK
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def streamencodeindefinitebytestring(source, chunksize=65536):
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"""Given a large source buffer, emit as an indefinite length bytestring.
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This is a generator of chunks constituting the encoded CBOR data.
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"""
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yield BEGIN_INDEFINITE_BYTESTRING
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i = 0
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l = len(source)
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while True:
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chunk = source[i : i + chunksize]
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i += len(chunk)
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yield encodelength(MAJOR_TYPE_BYTESTRING, len(chunk))
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yield chunk
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if i >= l:
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break
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yield BREAK
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def streamencodeint(v):
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if v >= 18446744073709551616 or v < -18446744073709551616:
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raise ValueError(b'big integers not supported')
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if v >= 0:
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yield encodelength(MAJOR_TYPE_UINT, v)
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else:
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yield encodelength(MAJOR_TYPE_NEGINT, abs(v) - 1)
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def streamencodearray(l):
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"""Encode a known size iterable to an array."""
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yield encodelength(MAJOR_TYPE_ARRAY, len(l))
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for i in l:
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for chunk in streamencode(i):
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yield chunk
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def streamencodearrayfromiter(it):
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"""Encode an iterator of items to an indefinite length array."""
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yield BEGIN_INDEFINITE_ARRAY
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for i in it:
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for chunk in streamencode(i):
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yield chunk
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yield BREAK
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def _mixedtypesortkey(v):
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return type(v).__name__, v
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def streamencodeset(s):
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# https://www.iana.org/assignments/cbor-tags/cbor-tags.xhtml defines
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# semantic tag 258 for finite sets.
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yield encodelength(MAJOR_TYPE_SEMANTIC, SEMANTIC_TAG_FINITE_SET)
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for chunk in streamencodearray(sorted(s, key=_mixedtypesortkey)):
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yield chunk
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def streamencodemap(d):
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"""Encode dictionary to a generator.
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Does not supporting indefinite length dictionaries.
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"""
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yield encodelength(MAJOR_TYPE_MAP, len(d))
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for key, value in sorted(
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pycompat.iteritems(d), key=lambda x: _mixedtypesortkey(x[0])
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):
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for chunk in streamencode(key):
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yield chunk
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for chunk in streamencode(value):
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yield chunk
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def streamencodemapfromiter(it):
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"""Given an iterable of (key, value), encode to an indefinite length map."""
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yield BEGIN_INDEFINITE_MAP
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for key, value in it:
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for chunk in streamencode(key):
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yield chunk
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for chunk in streamencode(value):
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yield chunk
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yield BREAK
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def streamencodebool(b):
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# major type 7, simple value 20 and 21.
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yield b'\xf5' if b else b'\xf4'
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def streamencodenone(v):
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# major type 7, simple value 22.
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yield b'\xf6'
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STREAM_ENCODERS = {
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bytes: streamencodebytestring,
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int: streamencodeint,
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pycompat.long: streamencodeint,
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list: streamencodearray,
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tuple: streamencodearray,
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dict: streamencodemap,
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set: streamencodeset,
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bool: streamencodebool,
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type(None): streamencodenone,
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}
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def streamencode(v):
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"""Encode a value in a streaming manner.
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Given an input object, encode it to CBOR recursively.
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Returns a generator of CBOR encoded bytes. There is no guarantee
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that each emitted chunk fully decodes to a value or sub-value.
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Encoding is deterministic - unordered collections are sorted.
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"""
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fn = STREAM_ENCODERS.get(v.__class__)
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if not fn:
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# handle subtypes such as encoding.localstr and util.sortdict
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for ty in STREAM_ENCODERS:
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if not isinstance(v, ty):
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continue
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fn = STREAM_ENCODERS[ty]
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break
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if not fn:
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raise ValueError(b'do not know how to encode %s' % type(v))
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return fn(v)
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class CBORDecodeError(Exception):
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"""Represents an error decoding CBOR."""
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if sys.version_info.major >= 3:
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def _elementtointeger(b, i):
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return b[i]
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else:
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def _elementtointeger(b, i):
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return ord(b[i])
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STRUCT_BIG_UBYTE = struct.Struct(r'>B')
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STRUCT_BIG_USHORT = struct.Struct(b'>H')
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STRUCT_BIG_ULONG = struct.Struct(b'>L')
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STRUCT_BIG_ULONGLONG = struct.Struct(b'>Q')
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SPECIAL_NONE = 0
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SPECIAL_START_INDEFINITE_BYTESTRING = 1
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SPECIAL_START_ARRAY = 2
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SPECIAL_START_MAP = 3
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SPECIAL_START_SET = 4
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SPECIAL_INDEFINITE_BREAK = 5
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def decodeitem(b, offset=0):
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"""Decode a new CBOR value from a buffer at offset.
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This function attempts to decode up to one complete CBOR value
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from ``b`` starting at offset ``offset``.
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The beginning of a collection (such as an array, map, set, or
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indefinite length bytestring) counts as a single value. For these
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special cases, a state flag will indicate that a special value was seen.
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When called, the function either returns a decoded value or gives
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a hint as to how many more bytes are needed to do so. By calling
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the function repeatedly given a stream of bytes, the caller can
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build up the original values.
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Returns a tuple with the following elements:
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* Bool indicating whether a complete value was decoded.
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* A decoded value if first value is True otherwise None
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* Integer number of bytes. If positive, the number of bytes
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read. If negative, the number of bytes we need to read to
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decode this value or the next chunk in this value.
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* One of the ``SPECIAL_*`` constants indicating special treatment
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for this value. ``SPECIAL_NONE`` means this is a fully decoded
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simple value (such as an integer or bool).
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"""
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initial = _elementtointeger(b, offset)
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offset += 1
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majortype = initial >> 5
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subtype = initial & SUBTYPE_MASK
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if majortype == MAJOR_TYPE_UINT:
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complete, value, readcount = decodeuint(subtype, b, offset)
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if complete:
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return True, value, readcount + 1, SPECIAL_NONE
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else:
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return False, None, readcount, SPECIAL_NONE
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elif majortype == MAJOR_TYPE_NEGINT:
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# Negative integers are the same as UINT except inverted minus 1.
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complete, value, readcount = decodeuint(subtype, b, offset)
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if complete:
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return True, -value - 1, readcount + 1, SPECIAL_NONE
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else:
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return False, None, readcount, SPECIAL_NONE
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elif majortype == MAJOR_TYPE_BYTESTRING:
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# Beginning of bytestrings are treated as uints in order to
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# decode their length, which may be indefinite.
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complete, size, readcount = decodeuint(
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subtype, b, offset, allowindefinite=True
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)
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# We don't know the size of the bytestring. It must be a definitive
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# length since the indefinite subtype would be encoded in the initial
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# byte.
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if not complete:
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return False, None, readcount, SPECIAL_NONE
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# We know the length of the bytestring.
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if size is not None:
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# And the data is available in the buffer.
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if offset + readcount + size <= len(b):
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value = b[offset + readcount : offset + readcount + size]
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return True, value, readcount + size + 1, SPECIAL_NONE
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# And we need more data in order to return the bytestring.
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else:
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wanted = len(b) - offset - readcount - size
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return False, None, wanted, SPECIAL_NONE
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# It is an indefinite length bytestring.
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else:
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return True, None, 1, SPECIAL_START_INDEFINITE_BYTESTRING
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elif majortype == MAJOR_TYPE_STRING:
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raise CBORDecodeError(b'string major type not supported')
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elif majortype == MAJOR_TYPE_ARRAY:
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# Beginning of arrays are treated as uints in order to decode their
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# length. We don't allow indefinite length arrays.
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complete, size, readcount = decodeuint(subtype, b, offset)
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if complete:
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return True, size, readcount + 1, SPECIAL_START_ARRAY
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else:
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return False, None, readcount, SPECIAL_NONE
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elif majortype == MAJOR_TYPE_MAP:
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# Beginning of maps are treated as uints in order to decode their
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# number of elements. We don't allow indefinite length arrays.
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complete, size, readcount = decodeuint(subtype, b, offset)
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if complete:
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return True, size, readcount + 1, SPECIAL_START_MAP
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else:
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return False, None, readcount, SPECIAL_NONE
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elif majortype == MAJOR_TYPE_SEMANTIC:
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# Semantic tag value is read the same as a uint.
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complete, tagvalue, readcount = decodeuint(subtype, b, offset)
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if not complete:
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return False, None, readcount, SPECIAL_NONE
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# This behavior here is a little wonky. The main type being "decorated"
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# by this semantic tag follows. A more robust parser would probably emit
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# a special flag indicating this as a semantic tag and let the caller
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# deal with the types that follow. But since we don't support many
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# semantic tags, it is easier to deal with the special cases here and
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# hide complexity from the caller. If we add support for more semantic
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# tags, we should probably move semantic tag handling into the caller.
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if tagvalue == SEMANTIC_TAG_FINITE_SET:
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if offset + readcount >= len(b):
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return False, None, -1, SPECIAL_NONE
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complete, size, readcount2, special = decodeitem(
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b, offset + readcount
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)
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if not complete:
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return False, None, readcount2, SPECIAL_NONE
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if special != SPECIAL_START_ARRAY:
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raise CBORDecodeError(
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b'expected array after finite set semantic tag'
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)
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return True, size, readcount + readcount2 + 1, SPECIAL_START_SET
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else:
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raise CBORDecodeError(b'semantic tag %d not allowed' % tagvalue)
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elif majortype == MAJOR_TYPE_SPECIAL:
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# Only specific values for the information field are allowed.
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if subtype == SUBTYPE_FALSE:
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return True, False, 1, SPECIAL_NONE
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elif subtype == SUBTYPE_TRUE:
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return True, True, 1, SPECIAL_NONE
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elif subtype == SUBTYPE_NULL:
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return True, None, 1, SPECIAL_NONE
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elif subtype == SUBTYPE_INDEFINITE:
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return True, None, 1, SPECIAL_INDEFINITE_BREAK
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# If value is 24, subtype is in next byte.
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else:
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raise CBORDecodeError(b'special type %d not allowed' % subtype)
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else:
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assert False
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def decodeuint(subtype, b, offset=0, allowindefinite=False):
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"""Decode an unsigned integer.
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``subtype`` is the lower 5 bits from the initial byte CBOR item
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"header." ``b`` is a buffer containing bytes. ``offset`` points to
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the index of the first byte after the byte that ``subtype`` was
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derived from.
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``allowindefinite`` allows the special indefinite length value
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indicator.
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Returns a 3-tuple of (successful, value, count).
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The first element is a bool indicating if decoding completed. The 2nd
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is the decoded integer value or None if not fully decoded or the subtype
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is 31 and ``allowindefinite`` is True. The 3rd value is the count of bytes.
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If positive, it is the number of additional bytes decoded. If negative,
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it is the number of additional bytes needed to decode this value.
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"""
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# Small values are inline.
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if subtype < 24:
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return True, subtype, 0
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# Indefinite length specifier.
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|
|
elif subtype == 31:
|
|
|
if allowindefinite:
|
|
|
return True, None, 0
|
|
|
else:
|
|
|
raise CBORDecodeError(b'indefinite length uint not allowed here')
|
|
|
elif subtype >= 28:
|
|
|
raise CBORDecodeError(
|
|
|
b'unsupported subtype on integer type: %d' % subtype
|
|
|
)
|
|
|
|
|
|
if subtype == 24:
|
|
|
s = STRUCT_BIG_UBYTE
|
|
|
elif subtype == 25:
|
|
|
s = STRUCT_BIG_USHORT
|
|
|
elif subtype == 26:
|
|
|
s = STRUCT_BIG_ULONG
|
|
|
elif subtype == 27:
|
|
|
s = STRUCT_BIG_ULONGLONG
|
|
|
else:
|
|
|
raise CBORDecodeError(b'bounds condition checking violation')
|
|
|
|
|
|
if len(b) - offset >= s.size:
|
|
|
return True, s.unpack_from(b, offset)[0], s.size
|
|
|
else:
|
|
|
return False, None, len(b) - offset - s.size
|
|
|
|
|
|
|
|
|
class bytestringchunk(bytes):
|
|
|
"""Represents a chunk/segment in an indefinite length bytestring.
|
|
|
|
|
|
This behaves like a ``bytes`` but in addition has the ``isfirst``
|
|
|
and ``islast`` attributes indicating whether this chunk is the first
|
|
|
or last in an indefinite length bytestring.
|
|
|
"""
|
|
|
|
|
|
def __new__(cls, v, first=False, last=False):
|
|
|
self = bytes.__new__(cls, v)
|
|
|
self.isfirst = first
|
|
|
self.islast = last
|
|
|
|
|
|
return self
|
|
|
|
|
|
|
|
|
class sansiodecoder(object):
|
|
|
"""A CBOR decoder that doesn't perform its own I/O.
|
|
|
|
|
|
To use, construct an instance and feed it segments containing
|
|
|
CBOR-encoded bytes via ``decode()``. The return value from ``decode()``
|
|
|
indicates whether a fully-decoded value is available, how many bytes
|
|
|
were consumed, and offers a hint as to how many bytes should be fed
|
|
|
in next time to decode the next value.
|
|
|
|
|
|
The decoder assumes it will decode N discrete CBOR values, not just
|
|
|
a single value. i.e. if the bytestream contains uints packed one after
|
|
|
the other, the decoder will decode them all, rather than just the initial
|
|
|
one.
|
|
|
|
|
|
When ``decode()`` indicates a value is available, call ``getavailable()``
|
|
|
to return all fully decoded values.
|
|
|
|
|
|
``decode()`` can partially decode input. It is up to the caller to keep
|
|
|
track of what data was consumed and to pass unconsumed data in on the
|
|
|
next invocation.
|
|
|
|
|
|
The decoder decodes atomically at the *item* level. See ``decodeitem()``.
|
|
|
If an *item* cannot be fully decoded, the decoder won't record it as
|
|
|
partially consumed. Instead, the caller will be instructed to pass in
|
|
|
the initial bytes of this item on the next invocation. This does result
|
|
|
in some redundant parsing. But the overhead should be minimal.
|
|
|
|
|
|
This decoder only supports a subset of CBOR as required by Mercurial.
|
|
|
It lacks support for:
|
|
|
|
|
|
* Indefinite length arrays
|
|
|
* Indefinite length maps
|
|
|
* Use of indefinite length bytestrings as keys or values within
|
|
|
arrays, maps, or sets.
|
|
|
* Nested arrays, maps, or sets within sets
|
|
|
* Any semantic tag that isn't a mathematical finite set
|
|
|
* Floating point numbers
|
|
|
* Undefined special value
|
|
|
|
|
|
CBOR types are decoded to Python types as follows:
|
|
|
|
|
|
uint -> int
|
|
|
negint -> int
|
|
|
bytestring -> bytes
|
|
|
map -> dict
|
|
|
array -> list
|
|
|
True -> bool
|
|
|
False -> bool
|
|
|
null -> None
|
|
|
indefinite length bytestring chunk -> [bytestringchunk]
|
|
|
|
|
|
The only non-obvious mapping here is an indefinite length bytestring
|
|
|
to the ``bytestringchunk`` type. This is to facilitate streaming
|
|
|
indefinite length bytestrings out of the decoder and to differentiate
|
|
|
a regular bytestring from an indefinite length bytestring.
|
|
|
"""
|
|
|
|
|
|
_STATE_NONE = 0
|
|
|
_STATE_WANT_MAP_KEY = 1
|
|
|
_STATE_WANT_MAP_VALUE = 2
|
|
|
_STATE_WANT_ARRAY_VALUE = 3
|
|
|
_STATE_WANT_SET_VALUE = 4
|
|
|
_STATE_WANT_BYTESTRING_CHUNK_FIRST = 5
|
|
|
_STATE_WANT_BYTESTRING_CHUNK_SUBSEQUENT = 6
|
|
|
|
|
|
def __init__(self):
|
|
|
# TODO add support for limiting size of bytestrings
|
|
|
# TODO add support for limiting number of keys / values in collections
|
|
|
# TODO add support for limiting size of buffered partial values
|
|
|
|
|
|
self.decodedbytecount = 0
|
|
|
|
|
|
self._state = self._STATE_NONE
|
|
|
|
|
|
# Stack of active nested collections. Each entry is a dict describing
|
|
|
# the collection.
|
|
|
self._collectionstack = []
|
|
|
|
|
|
# Fully decoded key to use for the current map.
|
|
|
self._currentmapkey = None
|
|
|
|
|
|
# Fully decoded values available for retrieval.
|
|
|
self._decodedvalues = []
|
|
|
|
|
|
@property
|
|
|
def inprogress(self):
|
|
|
"""Whether the decoder has partially decoded a value."""
|
|
|
return self._state != self._STATE_NONE
|
|
|
|
|
|
def decode(self, b, offset=0):
|
|
|
"""Attempt to decode bytes from an input buffer.
|
|
|
|
|
|
``b`` is a collection of bytes and ``offset`` is the byte
|
|
|
offset within that buffer from which to begin reading data.
|
|
|
|
|
|
``b`` must support ``len()`` and accessing bytes slices via
|
|
|
``__slice__``. Typically ``bytes`` instances are used.
|
|
|
|
|
|
Returns a tuple with the following fields:
|
|
|
|
|
|
* Bool indicating whether values are available for retrieval.
|
|
|
* Integer indicating the number of bytes that were fully consumed,
|
|
|
starting from ``offset``.
|
|
|
* Integer indicating the number of bytes that are desired for the
|
|
|
next call in order to decode an item.
|
|
|
"""
|
|
|
if not b:
|
|
|
return bool(self._decodedvalues), 0, 0
|
|
|
|
|
|
initialoffset = offset
|
|
|
|
|
|
# We could easily split the body of this loop into a function. But
|
|
|
# Python performance is sensitive to function calls and collections
|
|
|
# are composed of many items. So leaving as a while loop could help
|
|
|
# with performance. One thing that may not help is the use of
|
|
|
# if..elif versus a lookup/dispatch table. There may be value
|
|
|
# in switching that.
|
|
|
while offset < len(b):
|
|
|
# Attempt to decode an item. This could be a whole value or a
|
|
|
# special value indicating an event, such as start or end of a
|
|
|
# collection or indefinite length type.
|
|
|
complete, value, readcount, special = decodeitem(b, offset)
|
|
|
|
|
|
if readcount > 0:
|
|
|
self.decodedbytecount += readcount
|
|
|
|
|
|
if not complete:
|
|
|
assert readcount < 0
|
|
|
return (
|
|
|
bool(self._decodedvalues),
|
|
|
offset - initialoffset,
|
|
|
-readcount,
|
|
|
)
|
|
|
|
|
|
offset += readcount
|
|
|
|
|
|
# No nested state. We either have a full value or beginning of a
|
|
|
# complex value to deal with.
|
|
|
if self._state == self._STATE_NONE:
|
|
|
# A normal value.
|
|
|
if special == SPECIAL_NONE:
|
|
|
self._decodedvalues.append(value)
|
|
|
|
|
|
elif special == SPECIAL_START_ARRAY:
|
|
|
self._collectionstack.append(
|
|
|
{b'remaining': value, b'v': [],}
|
|
|
)
|
|
|
self._state = self._STATE_WANT_ARRAY_VALUE
|
|
|
|
|
|
elif special == SPECIAL_START_MAP:
|
|
|
self._collectionstack.append(
|
|
|
{b'remaining': value, b'v': {},}
|
|
|
)
|
|
|
self._state = self._STATE_WANT_MAP_KEY
|
|
|
|
|
|
elif special == SPECIAL_START_SET:
|
|
|
self._collectionstack.append(
|
|
|
{b'remaining': value, b'v': set(),}
|
|
|
)
|
|
|
self._state = self._STATE_WANT_SET_VALUE
|
|
|
|
|
|
elif special == SPECIAL_START_INDEFINITE_BYTESTRING:
|
|
|
self._state = self._STATE_WANT_BYTESTRING_CHUNK_FIRST
|
|
|
|
|
|
else:
|
|
|
raise CBORDecodeError(
|
|
|
b'unhandled special state: %d' % special
|
|
|
)
|
|
|
|
|
|
# This value becomes an element of the current array.
|
|
|
elif self._state == self._STATE_WANT_ARRAY_VALUE:
|
|
|
# Simple values get appended.
|
|
|
if special == SPECIAL_NONE:
|
|
|
c = self._collectionstack[-1]
|
|
|
c[b'v'].append(value)
|
|
|
c[b'remaining'] -= 1
|
|
|
|
|
|
# self._state doesn't need changed.
|
|
|
|
|
|
# An array nested within an array.
|
|
|
elif special == SPECIAL_START_ARRAY:
|
|
|
lastc = self._collectionstack[-1]
|
|
|
newvalue = []
|
|
|
|
|
|
lastc[b'v'].append(newvalue)
|
|
|
lastc[b'remaining'] -= 1
|
|
|
|
|
|
self._collectionstack.append(
|
|
|
{b'remaining': value, b'v': newvalue,}
|
|
|
)
|
|
|
|
|
|
# self._state doesn't need changed.
|
|
|
|
|
|
# A map nested within an array.
|
|
|
elif special == SPECIAL_START_MAP:
|
|
|
lastc = self._collectionstack[-1]
|
|
|
newvalue = {}
|
|
|
|
|
|
lastc[b'v'].append(newvalue)
|
|
|
lastc[b'remaining'] -= 1
|
|
|
|
|
|
self._collectionstack.append(
|
|
|
{b'remaining': value, b'v': newvalue}
|
|
|
)
|
|
|
|
|
|
self._state = self._STATE_WANT_MAP_KEY
|
|
|
|
|
|
elif special == SPECIAL_START_SET:
|
|
|
lastc = self._collectionstack[-1]
|
|
|
newvalue = set()
|
|
|
|
|
|
lastc[b'v'].append(newvalue)
|
|
|
lastc[b'remaining'] -= 1
|
|
|
|
|
|
self._collectionstack.append(
|
|
|
{b'remaining': value, b'v': newvalue,}
|
|
|
)
|
|
|
|
|
|
self._state = self._STATE_WANT_SET_VALUE
|
|
|
|
|
|
elif special == SPECIAL_START_INDEFINITE_BYTESTRING:
|
|
|
raise CBORDecodeError(
|
|
|
b'indefinite length bytestrings '
|
|
|
b'not allowed as array values'
|
|
|
)
|
|
|
|
|
|
else:
|
|
|
raise CBORDecodeError(
|
|
|
b'unhandled special item when '
|
|
|
b'expecting array value: %d' % special
|
|
|
)
|
|
|
|
|
|
# This value becomes the key of the current map instance.
|
|
|
elif self._state == self._STATE_WANT_MAP_KEY:
|
|
|
if special == SPECIAL_NONE:
|
|
|
self._currentmapkey = value
|
|
|
self._state = self._STATE_WANT_MAP_VALUE
|
|
|
|
|
|
elif special == SPECIAL_START_INDEFINITE_BYTESTRING:
|
|
|
raise CBORDecodeError(
|
|
|
b'indefinite length bytestrings '
|
|
|
b'not allowed as map keys'
|
|
|
)
|
|
|
|
|
|
elif special in (
|
|
|
SPECIAL_START_ARRAY,
|
|
|
SPECIAL_START_MAP,
|
|
|
SPECIAL_START_SET,
|
|
|
):
|
|
|
raise CBORDecodeError(
|
|
|
b'collections not supported as map keys'
|
|
|
)
|
|
|
|
|
|
# We do not allow special values to be used as map keys.
|
|
|
else:
|
|
|
raise CBORDecodeError(
|
|
|
b'unhandled special item when '
|
|
|
b'expecting map key: %d' % special
|
|
|
)
|
|
|
|
|
|
# This value becomes the value of the current map key.
|
|
|
elif self._state == self._STATE_WANT_MAP_VALUE:
|
|
|
# Simple values simply get inserted into the map.
|
|
|
if special == SPECIAL_NONE:
|
|
|
lastc = self._collectionstack[-1]
|
|
|
lastc[b'v'][self._currentmapkey] = value
|
|
|
lastc[b'remaining'] -= 1
|
|
|
|
|
|
self._state = self._STATE_WANT_MAP_KEY
|
|
|
|
|
|
# A new array is used as the map value.
|
|
|
elif special == SPECIAL_START_ARRAY:
|
|
|
lastc = self._collectionstack[-1]
|
|
|
newvalue = []
|
|
|
|
|
|
lastc[b'v'][self._currentmapkey] = newvalue
|
|
|
lastc[b'remaining'] -= 1
|
|
|
|
|
|
self._collectionstack.append(
|
|
|
{b'remaining': value, b'v': newvalue,}
|
|
|
)
|
|
|
|
|
|
self._state = self._STATE_WANT_ARRAY_VALUE
|
|
|
|
|
|
# A new map is used as the map value.
|
|
|
elif special == SPECIAL_START_MAP:
|
|
|
lastc = self._collectionstack[-1]
|
|
|
newvalue = {}
|
|
|
|
|
|
lastc[b'v'][self._currentmapkey] = newvalue
|
|
|
lastc[b'remaining'] -= 1
|
|
|
|
|
|
self._collectionstack.append(
|
|
|
{b'remaining': value, b'v': newvalue,}
|
|
|
)
|
|
|
|
|
|
self._state = self._STATE_WANT_MAP_KEY
|
|
|
|
|
|
# A new set is used as the map value.
|
|
|
elif special == SPECIAL_START_SET:
|
|
|
lastc = self._collectionstack[-1]
|
|
|
newvalue = set()
|
|
|
|
|
|
lastc[b'v'][self._currentmapkey] = newvalue
|
|
|
lastc[b'remaining'] -= 1
|
|
|
|
|
|
self._collectionstack.append(
|
|
|
{b'remaining': value, b'v': newvalue,}
|
|
|
)
|
|
|
|
|
|
self._state = self._STATE_WANT_SET_VALUE
|
|
|
|
|
|
elif special == SPECIAL_START_INDEFINITE_BYTESTRING:
|
|
|
raise CBORDecodeError(
|
|
|
b'indefinite length bytestrings not '
|
|
|
b'allowed as map values'
|
|
|
)
|
|
|
|
|
|
else:
|
|
|
raise CBORDecodeError(
|
|
|
b'unhandled special item when '
|
|
|
b'expecting map value: %d' % special
|
|
|
)
|
|
|
|
|
|
self._currentmapkey = None
|
|
|
|
|
|
# This value is added to the current set.
|
|
|
elif self._state == self._STATE_WANT_SET_VALUE:
|
|
|
if special == SPECIAL_NONE:
|
|
|
lastc = self._collectionstack[-1]
|
|
|
lastc[b'v'].add(value)
|
|
|
lastc[b'remaining'] -= 1
|
|
|
|
|
|
elif special == SPECIAL_START_INDEFINITE_BYTESTRING:
|
|
|
raise CBORDecodeError(
|
|
|
b'indefinite length bytestrings not '
|
|
|
b'allowed as set values'
|
|
|
)
|
|
|
|
|
|
elif special in (
|
|
|
SPECIAL_START_ARRAY,
|
|
|
SPECIAL_START_MAP,
|
|
|
SPECIAL_START_SET,
|
|
|
):
|
|
|
raise CBORDecodeError(
|
|
|
b'collections not allowed as set values'
|
|
|
)
|
|
|
|
|
|
# We don't allow non-trivial types to exist as set values.
|
|
|
else:
|
|
|
raise CBORDecodeError(
|
|
|
b'unhandled special item when '
|
|
|
b'expecting set value: %d' % special
|
|
|
)
|
|
|
|
|
|
# This value represents the first chunk in an indefinite length
|
|
|
# bytestring.
|
|
|
elif self._state == self._STATE_WANT_BYTESTRING_CHUNK_FIRST:
|
|
|
# We received a full chunk.
|
|
|
if special == SPECIAL_NONE:
|
|
|
self._decodedvalues.append(
|
|
|
bytestringchunk(value, first=True)
|
|
|
)
|
|
|
|
|
|
self._state = self._STATE_WANT_BYTESTRING_CHUNK_SUBSEQUENT
|
|
|
|
|
|
# The end of stream marker. This means it is an empty
|
|
|
# indefinite length bytestring.
|
|
|
elif special == SPECIAL_INDEFINITE_BREAK:
|
|
|
# We /could/ convert this to a b''. But we want to preserve
|
|
|
# the nature of the underlying data so consumers expecting
|
|
|
# an indefinite length bytestring get one.
|
|
|
self._decodedvalues.append(
|
|
|
bytestringchunk(b'', first=True, last=True)
|
|
|
)
|
|
|
|
|
|
# Since indefinite length bytestrings can't be used in
|
|
|
# collections, we must be at the root level.
|
|
|
assert not self._collectionstack
|
|
|
self._state = self._STATE_NONE
|
|
|
|
|
|
else:
|
|
|
raise CBORDecodeError(
|
|
|
b'unexpected special value when '
|
|
|
b'expecting bytestring chunk: %d' % special
|
|
|
)
|
|
|
|
|
|
# This value represents the non-initial chunk in an indefinite
|
|
|
# length bytestring.
|
|
|
elif self._state == self._STATE_WANT_BYTESTRING_CHUNK_SUBSEQUENT:
|
|
|
# We received a full chunk.
|
|
|
if special == SPECIAL_NONE:
|
|
|
self._decodedvalues.append(bytestringchunk(value))
|
|
|
|
|
|
# The end of stream marker.
|
|
|
elif special == SPECIAL_INDEFINITE_BREAK:
|
|
|
self._decodedvalues.append(bytestringchunk(b'', last=True))
|
|
|
|
|
|
# Since indefinite length bytestrings can't be used in
|
|
|
# collections, we must be at the root level.
|
|
|
assert not self._collectionstack
|
|
|
self._state = self._STATE_NONE
|
|
|
|
|
|
else:
|
|
|
raise CBORDecodeError(
|
|
|
b'unexpected special value when '
|
|
|
b'expecting bytestring chunk: %d' % special
|
|
|
)
|
|
|
|
|
|
else:
|
|
|
raise CBORDecodeError(
|
|
|
b'unhandled decoder state: %d' % self._state
|
|
|
)
|
|
|
|
|
|
# We could have just added the final value in a collection. End
|
|
|
# all complete collections at the top of the stack.
|
|
|
while True:
|
|
|
# Bail if we're not waiting on a new collection item.
|
|
|
if self._state not in (
|
|
|
self._STATE_WANT_ARRAY_VALUE,
|
|
|
self._STATE_WANT_MAP_KEY,
|
|
|
self._STATE_WANT_SET_VALUE,
|
|
|
):
|
|
|
break
|
|
|
|
|
|
# Or we are expecting more items for this collection.
|
|
|
lastc = self._collectionstack[-1]
|
|
|
|
|
|
if lastc[b'remaining']:
|
|
|
break
|
|
|
|
|
|
# The collection at the top of the stack is complete.
|
|
|
|
|
|
# Discard it, as it isn't needed for future items.
|
|
|
self._collectionstack.pop()
|
|
|
|
|
|
# If this is a nested collection, we don't emit it, since it
|
|
|
# will be emitted by its parent collection. But we do need to
|
|
|
# update state to reflect what the new top-most collection
|
|
|
# on the stack is.
|
|
|
if self._collectionstack:
|
|
|
self._state = {
|
|
|
list: self._STATE_WANT_ARRAY_VALUE,
|
|
|
dict: self._STATE_WANT_MAP_KEY,
|
|
|
set: self._STATE_WANT_SET_VALUE,
|
|
|
}[type(self._collectionstack[-1][b'v'])]
|
|
|
|
|
|
# If this is the root collection, emit it.
|
|
|
else:
|
|
|
self._decodedvalues.append(lastc[b'v'])
|
|
|
self._state = self._STATE_NONE
|
|
|
|
|
|
return (
|
|
|
bool(self._decodedvalues),
|
|
|
offset - initialoffset,
|
|
|
0,
|
|
|
)
|
|
|
|
|
|
def getavailable(self):
|
|
|
"""Returns an iterator over fully decoded values.
|
|
|
|
|
|
Once values are retrieved, they won't be available on the next call.
|
|
|
"""
|
|
|
|
|
|
l = list(self._decodedvalues)
|
|
|
self._decodedvalues = []
|
|
|
return l
|
|
|
|
|
|
|
|
|
class bufferingdecoder(object):
|
|
|
"""A CBOR decoder that buffers undecoded input.
|
|
|
|
|
|
This is a glorified wrapper around ``sansiodecoder`` that adds a buffering
|
|
|
layer. All input that isn't consumed by ``sansiodecoder`` will be buffered
|
|
|
and concatenated with any new input that arrives later.
|
|
|
|
|
|
TODO consider adding limits as to the maximum amount of data that can
|
|
|
be buffered.
|
|
|
"""
|
|
|
|
|
|
def __init__(self):
|
|
|
self._decoder = sansiodecoder()
|
|
|
self._chunks = []
|
|
|
self._wanted = 0
|
|
|
|
|
|
def decode(self, b):
|
|
|
"""Attempt to decode bytes to CBOR values.
|
|
|
|
|
|
Returns a tuple with the following fields:
|
|
|
|
|
|
* Bool indicating whether new values are available for retrieval.
|
|
|
* Integer number of bytes decoded from the new input.
|
|
|
* Integer number of bytes wanted to decode the next value.
|
|
|
"""
|
|
|
# We /might/ be able to support passing a bytearray all the
|
|
|
# way through. For now, let's cheat.
|
|
|
if isinstance(b, bytearray):
|
|
|
b = bytes(b)
|
|
|
|
|
|
# Our strategy for buffering is to aggregate the incoming chunks in a
|
|
|
# list until we've received enough data to decode the next item.
|
|
|
# This is slightly more complicated than using an ``io.BytesIO``
|
|
|
# or continuously concatenating incoming data. However, because it
|
|
|
# isn't constantly reallocating backing memory for a growing buffer,
|
|
|
# it prevents excessive memory thrashing and is significantly faster,
|
|
|
# especially in cases where the percentage of input chunks that don't
|
|
|
# decode into a full item is high.
|
|
|
|
|
|
if self._chunks:
|
|
|
# A previous call said we needed N bytes to decode the next item.
|
|
|
# But this call doesn't provide enough data. We buffer the incoming
|
|
|
# chunk without attempting to decode.
|
|
|
if len(b) < self._wanted:
|
|
|
self._chunks.append(b)
|
|
|
self._wanted -= len(b)
|
|
|
return False, 0, self._wanted
|
|
|
|
|
|
# Else we may have enough data to decode the next item. Aggregate
|
|
|
# old data with new and reset the buffer.
|
|
|
newlen = len(b)
|
|
|
self._chunks.append(b)
|
|
|
b = b''.join(self._chunks)
|
|
|
self._chunks = []
|
|
|
oldlen = len(b) - newlen
|
|
|
|
|
|
else:
|
|
|
oldlen = 0
|
|
|
|
|
|
available, readcount, wanted = self._decoder.decode(b)
|
|
|
self._wanted = wanted
|
|
|
|
|
|
if readcount < len(b):
|
|
|
self._chunks.append(b[readcount:])
|
|
|
|
|
|
return available, readcount - oldlen, wanted
|
|
|
|
|
|
def getavailable(self):
|
|
|
return self._decoder.getavailable()
|
|
|
|
|
|
|
|
|
def decodeall(b):
|
|
|
"""Decode all CBOR items present in an iterable of bytes.
|
|
|
|
|
|
In addition to regular decode errors, raises CBORDecodeError if the
|
|
|
entirety of the passed buffer does not fully decode to complete CBOR
|
|
|
values. This includes failure to decode any value, incomplete collection
|
|
|
types, incomplete indefinite length items, and extra data at the end of
|
|
|
the buffer.
|
|
|
"""
|
|
|
if not b:
|
|
|
return []
|
|
|
|
|
|
decoder = sansiodecoder()
|
|
|
|
|
|
havevalues, readcount, wantbytes = decoder.decode(b)
|
|
|
|
|
|
if readcount != len(b):
|
|
|
raise CBORDecodeError(b'input data not fully consumed')
|
|
|
|
|
|
if decoder.inprogress:
|
|
|
raise CBORDecodeError(b'input data not complete')
|
|
|
|
|
|
return decoder.getavailable()
|
|
|
|
