mirror of https://github.com/dirtbags/netarch.git
74 lines
1.8 KiB
Python
74 lines
1.8 KiB
Python
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#! /usr/bin/python3
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ENDIAN_LITTLE = 1
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ENDIAN_BIG = 2
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ENDIAN_MIDDLE = 3
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ENDIAN_NETWORK = ENDIAN_BIG
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class Unpacker:
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"""Class that lets you peel values off
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>>> u = Unpacker(bytes((1, 0,2, 0,0,0,3, 0,0,0,0,0,0,0,4)))
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>>> u.uint8()
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1
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>>> u.uint16()
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2
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>>> u.uint32()
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3
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>>> u.uint64()
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4
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>>> u = Unpacker(bytes((1,0, 104,105)), ENDIAN_LITTLE)
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>>> u.uint16()
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1
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>>> u.buf
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b'hi'
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>>> u = Unpacker(bytes((1,0, 0,2)))
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>>> u.uint16(ENDIAN_LITTLE)
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1
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>>> u.uint(16, ENDIAN_BIG)
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2
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>>> u = Unpacker(bytes((0,1,2,3)), ENDIAN_MIDDLE)
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>>> '%08x' % u.uint32()
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'01000302'
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"""
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def __init__(self, buf, endian=ENDIAN_NETWORK):
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self.endian = endian
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self.buf = buf
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def uint(self, size, endian=None):
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endian = endian or self.endian
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if size not in (8, 16, 32, 64):
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# XXX: I'm pretty sure this can be done, but I don't want to code it up right now.
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raise ValueError("Can't do weird sizes")
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noctets = size // 8
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if endian == ENDIAN_BIG:
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r = range(0, noctets)
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elif endian == ENDIAN_LITTLE:
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r = range(noctets-1, -1, -1)
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elif endian == ENDIAN_MIDDLE:
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r = (1, 0, 3, 2, 5, 4, 7, 6)[:noctets]
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else:
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raise ValueError("Unsupported byte order")
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pull, self.buf = self.buf[:noctets], self.buf[noctets:]
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acc = 0
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for i in r:
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acc = (acc << 8) | pull[i]
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return acc
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def uint8(self):
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return self.uint(8)
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def uint16(self, endian=None):
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return self.uint(16, endian)
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def uint32(self, endian=None):
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return self.uint(32, endian)
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def uint64(self, endian=None):
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return self.uint(64, endian)
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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