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Delphix Engineering committed Sep 15, 2022
2 parents 3eb8ff2 + 69ac146 commit 266d0d8
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220 changes: 3 additions & 217 deletions drgn/helpers/__init__.py
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-------
The ``drgn.helpers`` package contains subpackages which provide helpers for
working with particular types of programs. Currently, there are only helpers
for the Linux kernel. In the future, there may be helpers for, e.g., glibc and
libstdc++.
Generic Helpers
===============
The top-level ``drgn.helpers`` module provides generic helpers that may be
useful for scripts or for implementing other helpers.
working with particular types of programs. Currently, there are common helpers
and helpers for the Linux kernel. In the future, there may be helpers for,
e.g., glibc and libstdc++.
"""

import enum
import typing
from typing import Container, Iterable, Tuple

from drgn import IntegerLike, Type


class ValidationError(Exception):
"""
Error raised by a :ref:`validator <validators>` when an inconsistent or
invalid state is detected.
"""


def escape_ascii_character(
c: int,
escape_single_quote: bool = False,
escape_double_quote: bool = False,
escape_backslash: bool = False,
) -> str:
"""
Format an ASCII byte value as a character, possibly escaping it.
Non-printable characters are always escaped. Non-printable characters other
than ``\\0``, ``\\a``, ``\\b``, ``\\t``, ``\\n``, ``\\v``, ``\\f``, and
``\\r`` are escaped in hexadecimal format (e.g., ``\\x7f``). By default,
printable characters are never escaped.
:param c: The character to escape.
:param escape_single_quote: Whether to escape single quotes to ``\\'``.
:param escape_double_quote: Whether to escape double quotes to ``\\"``.
:param escape_backslash: Whether to escape backslashes to ``\\\\``.
"""
if c == 0:
return r"\0"
elif c == 7:
return r"\a"
elif c == 8:
return r"\b"
elif c == 9:
return r"\t"
elif c == 10:
return r"\n"
elif c == 11:
return r"\v"
elif c == 12:
return r"\f"
elif c == 13:
return r"\r"
elif escape_double_quote and c == 34:
return r"\""
elif escape_single_quote and c == 39:
return r"\'"
elif escape_backslash and c == 92:
return r"\\"
elif 32 <= c <= 126:
return chr(c)
else:
return f"\\x{c:02x}"


def escape_ascii_string(
buffer: Iterable[int],
escape_single_quote: bool = False,
escape_double_quote: bool = False,
escape_backslash: bool = False,
) -> str:
"""
Escape an iterable of ASCII byte values (e.g., :class:`bytes` or
:class:`bytearray`). See :func:`escape_ascii_character()`.
:param buffer: The byte array.
"""
return "".join(
escape_ascii_character(
c,
escape_single_quote=escape_single_quote,
escape_double_quote=escape_double_quote,
escape_backslash=escape_backslash,
)
for c in buffer
)


def enum_type_to_class(
type: Type, name: str, exclude: Container[str] = (), prefix: str = ""
) -> typing.Type[enum.IntEnum]:
"""
Get an :class:`enum.IntEnum` class from an enumerated :class:`drgn.Type`.
:param type: The enumerated type to convert.
:param name: The name of the ``IntEnum`` type to create.
:param exclude: Container (e.g., list or set) of enumerator names to
exclude from the created ``IntEnum``.
:param prefix: Prefix to strip from the beginning of enumerator names.
"""
if type.enumerators is None:
raise TypeError("enum type is incomplete")
enumerators = [
(name[len(prefix) :] if name.startswith(prefix) else name, value)
for (name, value) in type.enumerators
if name not in exclude
]
return enum.IntEnum(name, enumerators) # type: ignore # python/mypy#4865


def decode_flags(
value: IntegerLike,
flags: Iterable[Tuple[str, int]],
bit_numbers: bool = True,
) -> str:
"""
Get a human-readable representation of a bitmask of flags.
By default, flags are specified by their bit number:
>>> decode_flags(2, [("BOLD", 0), ("ITALIC", 1), ("UNDERLINE", 2)])
'ITALIC'
They can also be specified by their value:
>>> decode_flags(2, [("BOLD", 1), ("ITALIC", 2), ("UNDERLINE", 4)],
... bit_numbers=False)
'ITALIC'
Multiple flags are combined with "|":
>>> decode_flags(5, [("BOLD", 0), ("ITALIC", 1), ("UNDERLINE", 2)])
'BOLD|UNDERLINE'
If there are multiple names for the same bit, they are all included:
>>> decode_flags(2, [("SMALL", 0), ("BIG", 1), ("LARGE", 1)])
'BIG|LARGE'
If there are any unknown bits, their raw value is included:
>>> decode_flags(27, [("BOLD", 0), ("ITALIC", 1), ("UNDERLINE", 2)])
'BOLD|ITALIC|0x18'
Zero is returned verbatim:
>>> decode_flags(0, [("BOLD", 0), ("ITALIC", 1), ("UNDERLINE", 2)])
'0'
:param value: Bitmask to decode.
:param flags: List of flag names and their bit numbers or values.
:param bit_numbers: Whether *flags* specifies the bit numbers (where 0 is
the least significant bit) or values of the flags.
"""
value = value.__index__()
if value == 0:
return "0"

parts = []
mask = 0
for name, flag in flags:
if bit_numbers:
flag = 1 << flag
if value & flag:
parts.append(name)
mask |= flag

if value & ~mask:
parts.append(hex(value & ~mask))

return "|".join(parts)


def decode_enum_type_flags(
value: IntegerLike,
type: Type,
bit_numbers: bool = True,
) -> str:
"""
Get a human-readable representation of a bitmask of flags where the flags
are specified by an enumerated :class:`drgn.Type`.
This supports enums where the values are bit numbers:
>>> print(bits_enum)
enum style_bits {
BOLD = 0,
ITALIC = 1,
UNDERLINE = 2,
}
>>> decode_enum_type_flags(5, bits_enum)
'BOLD|UNDERLINE'
Or the values of the flags:
>>> print(flags_enum)
enum style_flags {
BOLD = 1,
ITALIC = 2,
UNDERLINE = 4,
}
>>> decode_enum_type_flags(5, flags_enum, bit_numbers=False)
'BOLD|UNDERLINE'
See :func:`decode_flags()`.
:param value: Bitmask to decode.
:param type: Enumerated type with bit numbers for enumerators.
:param bit_numbers: Whether the enumerator values specify the bit numbers
or values of the flags.
"""
enumerators = type.enumerators
if enumerators is None:
raise TypeError("cannot decode incomplete enumerated type")
return decode_flags(
value,
enumerators, # type: ignore # python/mypy#592
bit_numbers,
)
30 changes: 30 additions & 0 deletions drgn/helpers/common/__init__.py
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# Copyright (c) Meta Platforms, Inc. and affiliates.
# SPDX-License-Identifier: GPL-3.0-or-later

"""
Common
------
The ``drgn.helpers.common`` package provides helpers that can be used with any
program. The helpers are available from the individual modules in which they
are defined and from this top-level package. E.g., the following are both
valid:
>>> from drgn.helpers.common.memory import identify_address
>>> from drgn.helpers.common import identify_address
Some of these helpers may have additional program-specific behavior but are
otherwise generic.
"""

import importlib
import pkgutil
from typing import List

__all__: List[str] = []
for _module_info in pkgutil.iter_modules(__path__, prefix=__name__ + "."):
_submodule = importlib.import_module(_module_info.name)
_submodule_all = getattr(_submodule, "__all__", ())
__all__.extend(_submodule_all)
for _name in _submodule_all:
globals()[_name] = getattr(_submodule, _name)
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