111 lines
4.5 KiB
Python
111 lines
4.5 KiB
Python
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import zlib
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import bps.operations as ops
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def make_bps(source, target):
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# This function was adapted from
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# https://github.com/Alcaro/Flips/blob/master/libbps.cpp
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# originally written by Alcaro, used under the GPLv3.0 license
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sourcelen = len(source)
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targetlen = len(target)
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sourcepos = 0
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targetpos = 0
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lastknownchange = 0
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yield ops.Header(sourcelen, targetlen, "")
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while targetpos < targetlen:
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numunchanged = 0
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while (sourcepos+numunchanged < sourcelen and
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targetpos+numunchanged < targetlen and
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source[sourcepos+numunchanged] == target[targetpos+numunchanged]):
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numunchanged += 1
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if numunchanged > 1 or numunchanged == targetlen - targetpos:
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yield ops.SourceRead(numunchanged)
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sourcepos += numunchanged
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targetpos += numunchanged
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numchanged = 0
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if lastknownchange > targetpos:
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numchanged = lastknownchange - targetpos
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while targetpos + numchanged < targetlen and not (
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sourcepos + numchanged < sourcelen and
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source[sourcepos+numchanged] == target[targetpos+numchanged] and
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source[sourcepos+numchanged+1] == target[targetpos+numchanged+1] and
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source[sourcepos+numchanged+2] == target[targetpos+numchanged+2]):
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numchanged += 1
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if sourcepos+numchanged >= sourcelen:
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numchanged = targetlen - targetpos
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lastknownchange = targetpos + numchanged
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if numchanged:
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rle1start = max(targetpos, 1)
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while rle1start+3 < targetpos+numchanged:
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if (target[rle1start-1] == target[rle1start+0] and
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target[rle1start+0] == target[rle1start+1] and
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target[rle1start+1] == target[rle1start+2] and
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target[rle1start+2] == target[rle1start+3]):
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numchanged = rle1start - targetpos
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break
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if rle1start >= 2 and rle1start+4 < targetpos+numchanged:
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if (target[rle1start-2] == target[rle1start+0] and
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target[rle1start-1] == target[rle1start+1] and
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target[rle1start+0] == target[rle1start+2] and
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target[rle1start+1] == target[rle1start+3] and
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target[rle1start+2] == target[rle1start+4]):
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numchanged = rle1start - targetpos
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break
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rle1start += 1
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assert numchanged >= 0, numchanged
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if numchanged:
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yield ops.TargetRead(target[targetpos:targetpos+numchanged])
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sourcepos += numchanged
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targetpos += numchanged
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if (targetpos >= 2 and targetpos+2 < targetlen and
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target[targetpos-2] == target[targetpos+0] and
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target[targetpos-1] == target[targetpos+1] and
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target[targetpos-0] == target[targetpos+2]):
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# Two-byte RLE
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rlelen = 0
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while (targetpos + rlelen < targetlen and
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target[targetpos+0] == target[targetpos+rlelen+0] and
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target[targetpos+1] == target[targetpos+rlelen+1]):
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rlelen += 2
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yield ops.TargetCopy(rlelen, targetpos - 2)
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sourcepos += rlelen
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targetpos += rlelen
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elif (targetpos >= 1 and targetpos+1 < targetlen and
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target[targetpos-1] == target[targetpos+0] and
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target[targetpos-0] == target[targetpos+1]):
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# One-byte RLE
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rlelen = 0
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while (targetpos + rlelen < targetlen and
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target[targetpos] == target[targetpos+rlelen]):
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rlelen += 1
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yield ops.TargetCopy(rlelen, targetpos - 1)
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sourcepos += rlelen
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targetpos += rlelen
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yield ops.SourceCRC32(zlib.crc32(source) & 0xFFFFFFFF)
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yield ops.TargetCRC32(zlib.crc32(target) & 0xFFFFFFFF)
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def main():
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import bps.io
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import bps.apply
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import bps.validate
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import sys
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with open(sys.argv[1], "rb") as f:
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source = f.read()
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with open(sys.argv[2], "rb") as f:
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target = f.read()
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l = list(
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bps.validate.check_stream(
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make_bps(source, target)))
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target2 = bytearray(len(target))
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bps.apply.apply_to_bytearrays(l, source, target2)
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assert target == bytes(target2), "invalid patch created"
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bps.io.write_bps(l, sys.stdout.buffer)
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main()
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