33 lines
863 B
Python
33 lines
863 B
Python
def pad_up(size, factor):
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"""Pad size up to a multiple of a factor"""
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x = size + factor - 1
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return x - (x % factor)
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def bits(ntotal, nset):
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"""Return a buffer of ntotal bits with the first nset set to 1"""
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assert ntotal % 8 == 0
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nset = max(nset, 0)
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nset = min(nset, ntotal)
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accum = bytearray()
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accum.extend(b'\xFF' * (nset // 8))
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nset -= len(accum) * 8
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partial = nset % 8
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if partial:
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accum.extend([b'\x00', b'\x80', b'\xC0', b'\xE0', b'\xF0', b'\xF8', b'\xFC', b'\xFE', b'\xFF'][partial])
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nset =- partial
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final_len = pad_up(ntotal, 8) // 8
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accum.extend(b'\x00' * (final_len - len(accum)))
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return bytes(accum)
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def chunkify(b, blksize):
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for i in range(0, len(b), blksize):
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ab = b[i:i+blksize]
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if len(ab) < blksize: ab += bytes(blksize-len(ab))
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yield ab
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