501 lines
19 KiB
Python
501 lines
19 KiB
Python
from __future__ import annotations
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from io import BytesIO
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from typing import TYPE_CHECKING, Any, Literal
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from .core import Adapter, AdaptationError, Pass
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from .lib import int_to_bin, bin_to_int, swap_bytes
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from .lib import FlagsContainer, HexString
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if TYPE_CHECKING:
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from collections.abc import Callable, Hashable, Mapping, Sized
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from .core import Construct, _Pass
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from .lib import Container, ListContainer
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__all__ = [
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"BitIntegerError", "MappingError", "ConstError", "ValidationError", "PaddingError",
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"BitIntegerAdapter", "MappingAdapter", "FlagsAdapter", "StringAdapter", "PaddedStringAdapter",
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"LengthValueAdapter", "CStringAdapter", "TunnelAdapter", "ExprAdapter", "HexDumpAdapter", "ConstAdapter",
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"SlicingAdapter", "IndexingAdapter", "PaddingAdapter",
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"Validator", "OneOf", "NoneOf",
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]
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#===============================================================================
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# exceptions
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#===============================================================================
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class BitIntegerError(AdaptationError):
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__slots__ = ()
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class MappingError(AdaptationError):
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__slots__ = ()
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class ConstError(AdaptationError):
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__slots__ = ()
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class ValidationError(AdaptationError):
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__slots__ = ()
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class PaddingError(AdaptationError):
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__slots__ = ()
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#===============================================================================
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# adapters
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#===============================================================================
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class BitIntegerAdapter(Adapter):
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"""
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Adapter for bit-integers (converts bitstrings to integers, and vice versa).
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See BitField.
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Parameters:
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* subcon - the subcon to adapt
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* width - the size of the subcon, in bits
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* swapped - whether to swap byte order (little endian/big endian).
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default is False (big endian)
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* signed - whether the value is signed (two's complement). the default
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is False (unsigned)
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* bytesize - number of bits per byte, used for byte-swapping (if swapped).
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default is 8.
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"""
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__slots__ = ("width", "swapped", "signed", "bytesize")
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def __init__(self, subcon: Construct, width: int, swapped: bool = False, signed: bool = False,
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bytesize: int = 8) -> None:
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Adapter.__init__(self, subcon)
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self.width = width
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self.swapped = swapped
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self.signed = signed
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self.bytesize = bytesize
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def _encode(self, obj: int, context: Container) -> bytes:
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if obj < 0 and not self.signed:
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raise BitIntegerError("object is negative, but field is not signed",
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obj)
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obj2 = int_to_bin(obj, width = self.width)
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if self.swapped:
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obj2 = swap_bytes(obj2, bytesize = self.bytesize)
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return obj2
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def _decode(self, obj: bytes, context: Container) -> int:
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if self.swapped:
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obj = swap_bytes(obj, bytesize = self.bytesize)
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return bin_to_int(obj, signed = self.signed)
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class MappingAdapter(Adapter):
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"""
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Adapter that maps objects to other objects.
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See SymmetricMapping and Enum.
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Parameters:
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* subcon - the subcon to map
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* decoding - the decoding (parsing) mapping (a dict)
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* encoding - the encoding (building) mapping (a dict)
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* decdefault - the default return value when the object is not found
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in the decoding mapping. if no object is given, an exception is raised.
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if `Pass` is used, the unmapped object will be passed as-is
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* encdefault - the default return value when the object is not found
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in the encoding mapping. if no object is given, an exception is raised.
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if `Pass` is used, the unmapped object will be passed as-is
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"""
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__slots__ = ("encoding", "decoding", "encdefault", "decdefault")
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def __init__(self, subcon: Construct, decoding: Mapping[Any, Any], encoding: Mapping[Any, Any],
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decdefault: Hashable | _Pass = NotImplemented,
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encdefault: Hashable | _Pass = NotImplemented,
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) -> None:
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Adapter.__init__(self, subcon)
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self.decoding = decoding
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self.encoding = encoding
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self.decdefault = decdefault
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self.encdefault = encdefault
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def _encode(self, obj: Hashable, context: Container) -> Hashable:
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try:
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return self.encoding[obj]
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except (KeyError, TypeError):
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if self.encdefault is NotImplemented:
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raise MappingError("no encoding mapping for %r [%s]" % (
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obj, self.subcon.name))
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if self.encdefault is Pass:
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return obj
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return self.encdefault
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def _decode(self, obj: Hashable, context: Container) -> Hashable:
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try:
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return self.decoding[obj]
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except (KeyError, TypeError):
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if self.decdefault is NotImplemented:
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raise MappingError("no decoding mapping for %r [%s]" % (
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obj, self.subcon.name))
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if self.decdefault is Pass:
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return obj
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return self.decdefault
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class FlagsAdapter(Adapter):
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"""
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Adapter for flag fields. Each flag is extracted from the number, resulting
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in a FlagsContainer object. Not intended for direct usage.
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See FlagsEnum.
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Parameters
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* subcon - the subcon to extract
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* flags - a dictionary mapping flag-names to their value
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"""
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__slots__ = ("flags",)
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def __init__(self, subcon: Construct, flags: dict[str, int]) -> None:
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Adapter.__init__(self, subcon)
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self.flags = flags
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def _encode(self, obj: FlagsContainer, context: Container) -> int:
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flags = 0
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for name, value in self.flags.items():
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if getattr(obj, name, False):
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flags |= value
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return flags
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def _decode(self, obj: int, context: Container) -> FlagsContainer:
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obj2 = FlagsContainer()
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for name, value in self.flags.items():
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setattr(obj2, name, bool(obj & value))
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return obj2
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class StringAdapter(Adapter):
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"""
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Adapter for strings. Converts a sequence of characters into a python
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string, and optionally handles character encoding.
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See String.
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Parameters:
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* subcon - the subcon to convert
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* encoding - the character encoding name (e.g., "utf8"), or None to
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return raw bytes (usually 8-bit ASCII).
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"""
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__slots__ = ("encoding",)
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def __init__(self, subcon: Construct, encoding: str | None = None) -> None:
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Adapter.__init__(self, subcon)
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self.encoding = encoding
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def _encode(self, obj: bytes | str, context: Container) -> bytes:
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if self.encoding:
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assert isinstance(obj, str)
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obj = obj.encode(self.encoding)
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assert isinstance(obj, bytes)
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return obj
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def _decode(self, obj: bytes, context: Container) -> bytes | str:
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if self.encoding:
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return obj.decode(self.encoding)
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return obj
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class PaddedStringAdapter(Adapter):
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r"""
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Adapter for padded strings.
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See String.
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Parameters:
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* subcon - the subcon to adapt
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* padchar - the padding character. default is b"\x00".
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* paddir - the direction where padding is placed ("right", "left", or
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"center"). the default is "right".
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* trimdir - the direction where trimming will take place ("right" or
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"left"). the default is "right". trimming is only meaningful for
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building, when the given string is too long.
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"""
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__slots__ = ("padchar", "paddir", "trimdir")
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def __init__(self, subcon: Construct, padchar: bytes = b"\x00", paddir: Literal["right", "left", "center"] = "right",
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trimdir: Literal["right", "left"] = "right") -> None:
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if paddir not in ("right", "left", "center"):
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raise ValueError("paddir must be 'right', 'left' or 'center'",
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paddir)
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if trimdir not in ("right", "left"):
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raise ValueError("trimdir must be 'right' or 'left'", trimdir)
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Adapter.__init__(self, subcon)
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self.padchar = padchar
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self.paddir = paddir
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self.trimdir = trimdir
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def _decode(self, obj: bytes, context: Container) -> bytes:
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if self.paddir == "right":
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obj = obj.rstrip(self.padchar)
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elif self.paddir == "left":
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obj = obj.lstrip(self.padchar)
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else:
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obj = obj.strip(self.padchar)
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return obj
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def _encode(self, obj: bytes, context: Container) -> bytes:
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size = self._sizeof(context)
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if self.paddir == "right":
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obj = obj.ljust(size, self.padchar)
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elif self.paddir == "left":
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obj = obj.rjust(size, self.padchar)
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else:
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obj = obj.center(size, self.padchar)
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if len(obj) > size:
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if self.trimdir == "right":
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obj = obj[:size]
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else:
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obj = obj[-size:]
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return obj
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class LengthValueAdapter(Adapter):
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"""
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Adapter for length-value pairs. It extracts only the value from the
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pair, and calculates the length based on the value.
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See PrefixedArray and PascalString.
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Parameters:
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* subcon - the subcon returning a length-value pair
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"""
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__slots__ = ()
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def _encode(self, obj: Sized, context: Container) -> tuple[int, Sized]:
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return (len(obj), obj)
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def _decode(self, obj: tuple[int, Sized] | ListContainer, context: Container) -> Sized:
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return obj[1]
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class CStringAdapter(StringAdapter):
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r"""
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Adapter for C-style strings (strings terminated by a terminator char).
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Parameters:
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* subcon - the subcon to convert
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* terminators - a sequence of terminator chars. default is b"\x00".
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* encoding - the character encoding to use (e.g., "utf8"), or None to
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return raw-bytes. the terminator characters are not affected by the
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encoding.
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"""
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__slots__ = ("terminators",)
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def __init__(self, subcon: Construct, terminators: bytes = b"\x00", encoding: str | None = None) -> None:
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StringAdapter.__init__(self, subcon, encoding = encoding)
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self.terminators = terminators
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def _encode(self, obj: bytes | str, context: Container) -> bytes:
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return StringAdapter._encode(self, obj, context) + self.terminators[0:1]
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def _decode(self, obj: list[bytes], context: Container) -> bytes | str: # type: ignore[override] # ty: ignore[invalid-method-override]
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# This violates the Liskov Substitution Principle: should be `obj: bytes`, but RepeatUntil() converts `bytes` to `list[byte]`
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return StringAdapter._decode(self, b''.join(obj[:-1]), context)
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class TunnelAdapter(Adapter):
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"""
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Adapter for tunneling (as in protocol tunneling). A tunnel is construct
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nested upon another (layering). For parsing, the lower layer first parses
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the data (note: it must return a string!), then the upper layer is called
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to parse that data (bottom-up). For building it works in a top-down manner;
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first the upper layer builds the data, then the lower layer takes it and
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writes it to the stream.
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Parameters:
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* subcon - the lower layer subcon
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* inner_subcon - the upper layer (tunneled/nested) subcon
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Example:
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# a pascal string containing compressed data (zlib encoding), so first
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# the string is read, decompressed, and finally re-parsed as an array
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# of UBInt16
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TunnelAdapter(
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PascalString("data", encoding = "zlib"),
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GreedyRange(UBInt16("elements"))
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)
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"""
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__slots__ = ("inner_subcon",)
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def __init__(self, subcon: Construct, inner_subcon: Construct) -> None:
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Adapter.__init__(self, subcon)
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self.inner_subcon = inner_subcon
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def _decode(self, obj: bytes, context: Container) -> Any:
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return self.inner_subcon._parse(BytesIO(obj), context)
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def _encode(self, obj: Any, context: Container) -> bytes:
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stream = BytesIO()
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self.inner_subcon._build(obj, stream, context)
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return stream.getvalue()
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class ExprAdapter(Adapter):
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"""
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A generic adapter that accepts 'encoder' and 'decoder' as parameters. You
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can use ExprAdapter instead of writing a full-blown class when only a
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simple expression is needed.
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Parameters:
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* subcon - the subcon to adapt
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* encoder - a function that takes (obj, context) and returns an encoded
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version of obj
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* decoder - a function that takes (obj, context) and returns a decoded
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version of obj
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Example:
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ExprAdapter(UBInt8("foo"),
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encoder = lambda obj, ctx: obj / 4,
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decoder = lambda obj, ctx: obj * 4,
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)
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"""
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__slots__ = ("__encode", "__decode")
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def __init__(self, subcon: Construct, encoder: Callable[[Any, Container], bytes], decoder: Callable[[bytes, Container], Any]) -> None:
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Adapter.__init__(self, subcon)
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self.__encode = encoder
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self.__decode = decoder
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def _encode(self, obj: Any, context: Container) -> Any:
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return self.__encode(obj, context)
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def _decode(self, obj: Any, context: Container) -> Any:
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return self.__decode(obj, context)
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class HexDumpAdapter(Adapter):
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"""
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Adapter for hex-dumping strings. It returns a HexString, which is a string
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"""
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__slots__ = ("linesize",)
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def __init__(self, subcon: Construct, linesize: int = 16) -> None:
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Adapter.__init__(self, subcon)
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self.linesize = linesize
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def _encode(self, obj: Any, context: Container) -> Any:
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return obj
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def _decode(self, obj: bytes, context: Container) -> HexString:
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return HexString(obj, linesize = self.linesize)
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class ConstAdapter(Adapter):
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"""
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Adapter for enforcing a constant value ("magic numbers"). When decoding,
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the return value is checked; when building, the value is substituted in.
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Parameters:
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* subcon - the subcon to validate
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* value - the expected value
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Example:
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Const(Field("signature", 2), "MZ")
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"""
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__slots__ = ("value",)
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def __init__(self, subcon: Construct, value: object) -> None:
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Adapter.__init__(self, subcon)
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self.value = value
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def _encode(self, obj: object, context: Container) -> object:
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if obj is None or obj == self.value:
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return self.value
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else:
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raise ConstError("expected %r, found %r" % (self.value, obj))
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def _decode(self, obj: object, context: Container) -> object:
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if obj != self.value:
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raise ConstError("expected %r, found %r" % (self.value, obj))
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return obj
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class SlicingAdapter(Adapter):
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"""
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Adapter for slicing a list (getting a slice from that list)
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Parameters:
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* subcon - the subcon to slice
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* start - start index
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* stop - stop index (or None for up-to-end)
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* step - step (or None for every element)
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"""
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__slots__ = ("start", "stop", "step")
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def __init__(self, subcon: Construct, start: int, stop: int | None = None) -> None:
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Adapter.__init__(self, subcon)
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self.start = start
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self.stop = stop
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def _encode(self, obj: list[Any], context: Container) -> list[Any]:
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if self.start is None:
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return obj
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return [None] * self.start + obj
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def _decode(self, obj: list[Any], context: Container) -> list[Any]:
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return obj[self.start:self.stop]
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class IndexingAdapter(Adapter):
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"""
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Adapter for indexing a list (getting a single item from that list)
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Parameters:
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* subcon - the subcon to index
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* index - the index of the list to get
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"""
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__slots__ = ("index",)
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def __init__(self, subcon: Construct, index: int) -> None:
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Adapter.__init__(self, subcon)
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if type(index) is not int:
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raise TypeError("index must be an integer", type(index))
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self.index = index
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def _encode(self, obj: Any, context: Container) -> list[Any]:
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return [None] * self.index + [obj]
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def _decode(self, obj: list[Any], context: Container) -> Any:
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return obj[self.index]
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class PaddingAdapter(Adapter):
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r"""
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Adapter for padding.
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Parameters:
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* subcon - the subcon to pad
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* pattern - the padding pattern (character as byte). default is b"\x00"
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* strict - whether or not to verify, during parsing, that the given
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padding matches the padding pattern. default is False (unstrict)
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"""
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__slots__ = ("pattern", "strict")
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def __init__(self, subcon: Construct, pattern: bytes = b"\x00", strict: bool = False) -> None:
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Adapter.__init__(self, subcon)
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self.pattern = pattern
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self.strict = strict
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def _encode(self, obj: None, context: Container) -> bytes:
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return self._sizeof(context) * self.pattern
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def _decode(self, obj: bytes, context: Container) -> bytes:
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if self.strict:
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expected = self._sizeof(context) * self.pattern
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if obj != expected:
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raise PaddingError("expected %r, found %r" % (expected, obj))
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return obj
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#===============================================================================
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# validators
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#===============================================================================
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class Validator(Adapter):
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"""
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Abstract class: validates a condition on the encoded/decoded object.
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Override _validate(obj, context) in deriving classes.
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Parameters:
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* subcon - the subcon to validate
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"""
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__slots__ = ()
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def _decode(self, obj: object, context: Container) -> object:
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if not self._validate(obj, context):
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raise ValidationError("invalid object", obj)
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return obj
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def _encode(self, obj: object, context: Container) -> object:
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return self._decode(obj, context)
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def _validate(self, obj: object, context: Container) -> bool:
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raise NotImplementedError()
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class OneOf(Validator):
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"""
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Validates that the object is one of the listed values.
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:param ``Construct`` subcon: object to validate
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:param iterable valids: a set of valid values
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>>> from ..construct import UBInt8
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>>> OneOf(UBInt8("foo"), [4,5,6,7]).parse(b"\\x05")
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5
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>>> OneOf(UBInt8("foo"), [4,5,6,7]).parse(b"\\x08") # doctest: +IGNORE_EXCEPTION_DETAIL
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Traceback (most recent call last):
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...
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ValidationError: ('invalid object', 8)
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>>>
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>>> OneOf(UBInt8("foo"), [4,5,6,7]).build(5)
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b'\\x05'
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>>> OneOf(UBInt8("foo"), [4,5,6,7]).build(9) # doctest: +IGNORE_EXCEPTION_DETAIL
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Traceback (most recent call last):
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...
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ValidationError: ('invalid object', 9)
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"""
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__slots__ = ("valids",)
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def __init__(self, subcon: Construct, valids: list[object]) -> None:
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Validator.__init__(self, subcon)
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self.valids = valids
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def _validate(self, obj: object, context: Container) -> bool:
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return obj in self.valids
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class NoneOf(Validator):
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"""
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Validates that the object is none of the listed values.
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:param ``Construct`` subcon: object to validate
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:param iterable invalids: a set of invalid values
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>>> from ..construct import UBInt8
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>>> NoneOf(UBInt8("foo"), [4,5,6,7]).parse(b"\\x08")
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8
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>>> NoneOf(UBInt8("foo"), [4,5,6,7]).parse(b"\\x06") # doctest: +IGNORE_EXCEPTION_DETAIL
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Traceback (most recent call last):
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...
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ValidationError: ('invalid object', 6)
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"""
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__slots__ = ("invalids",)
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def __init__(self, subcon: Construct, invalids: list[object]) -> None:
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Validator.__init__(self, subcon)
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self.invalids = invalids
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def _validate(self, obj: object, context: Container) -> bool:
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return obj not in self.invalids
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