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99 lines
2.7 KiB
Python
99 lines
2.7 KiB
Python
"""
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Utility functions and types:
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Type definition for buffers:
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ctypes_buffer_t
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Custom exception type:
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MemEditError
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Search for a buffer inside another buffer:
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search_buffer(needle_buffer, haystack_buffer)
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Check if two buffers (ctypes objects) store equal values:
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ctypes_equal(a, b)
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"""
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from typing import List, Union
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import ctypes
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ctypes_buffer_t = Union[ctypes._SimpleCData, ctypes.Array, ctypes.Structure, ctypes.Union]
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class MemEditError(Exception):
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pass
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def search_buffer_verbatim(needle_buffer: ctypes_buffer_t,
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haystack_buffer: ctypes_buffer_t,
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) -> List[int]:
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"""
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Search for a buffer inside another buffer, using a direct (bitwise) comparison
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Args:
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needle_buffer: Buffer to search for.
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haystack_buffer: Buffer to search in.
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Returns:
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List of offsets where the `needle_buffer` was found.
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"""
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found = []
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haystack = bytes(haystack_buffer)
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needle = bytes(needle_buffer)
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start = 0
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result = haystack.find(needle, start)
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while start < len(haystack) and result != -1:
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found.append(result)
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start = result + 1
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result = haystack.find(needle, start)
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return found
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def search_buffer(needle_buffer: ctypes_buffer_t,
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haystack_buffer: ctypes_buffer_t,
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) -> List[int]:
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"""
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Search for a buffer inside another buffer, using `ctypes_equal` for comparison.
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Much slower than `search_buffer_verbatim`.
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Args:
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needle_buffer: Buffer to search for.
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haystack_buffer: Buffer to search in.
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Returns:
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List of offsets where the needle_buffer was found.
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"""
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found = []
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read_type = type(needle_buffer)
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for offset in range(0, len(haystack_buffer) - ctypes.sizeof(needle_buffer)):
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v = read_type.from_buffer(haystack_buffer, offset)
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if ctypes_equal(needle_buffer, v):
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found.append(offset)
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return found
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def ctypes_equal(a: ctypes_buffer_t,
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b: ctypes_buffer_t,
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) -> bool:
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"""
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Check if the values stored inside two ctypes buffers are equal.
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"""
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if not type(a) == type(b):
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return False
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if isinstance(a, ctypes.Array):
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return a[:] == b[:]
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elif isinstance(a, ctypes.Structure) or isinstance(a, ctypes.Union):
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for attr_name, attr_type in a._fields_:
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a_attr, b_attr = (getattr(x, attr_name) for x in (a, b))
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if isinstance(a, ctypes_buffer_t):
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if not ctypes_equal(a_attr, b_attr):
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return False
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elif not a_attr == b_attr:
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return False
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return True
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else:
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return a.value == b.value
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