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69 lines
2.0 KiB
69 lines
2.0 KiB
from struct import unpack_from as _unpack_from, calcsize as _calcsize
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class StructReader(object):
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def __init__(self, data):
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"""Simplifies parsing of struct data from bytes
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:param data: data bytes
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:type data: :class:`bytes`
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"""
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if not isinstance(data, bytes):
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raise ValueError("Only works with bytes")
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self.data = data
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self.offset = 0
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def __len__(self):
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return len(self.data)
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def rlen(self):
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"""Number of remaining bytes that can be read
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:return: number of remaining bytes
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:rtype: :class:`int`
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"""
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return max(0, len(self) - self.offset)
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def read(self, n=1):
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"""Return n bytes
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:param n: number of bytes to return
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:type n: :class:`int`
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:return: bytes
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:rtype: :class:`bytes`
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"""
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self.offset += n
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return self.data[self.offset - n:self.offset]
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def read_cstring(self, terminator=b'\x00'):
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"""Reads a single null termianted string
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:return: string without bytes
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:rtype: :class:`bytes`
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"""
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null_index = self.data.find(terminator, self.offset)
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if null_index == -1:
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raise RuntimeError("Reached end of buffer")
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result = self.data[self.offset:null_index] # bytes without the terminator
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self.offset = null_index + len(terminator) # advance offset past terminator
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return result
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def unpack(self, format_text):
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"""Unpack bytes using struct modules format
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:param format_text: struct's module format
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:type format_text: :class:`str`
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:return data: result from :func:`struct.unpack_from`
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:rtype: :class:`tuple`
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"""
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data = _unpack_from(format_text, self.data, self.offset)
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self.offset += _calcsize(format_text)
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return data
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def skip(self, n):
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"""Skips the next ``n`` bytes
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:param n: number of bytes to skip
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:type n: :class:`int`
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"""
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self.offset += n
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