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Optimize memory operations #3

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Optimize memory operations #3

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21 changes: 11 additions & 10 deletions pyrdiff.py
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Original file line number Diff line number Diff line change
Expand Up @@ -280,41 +280,42 @@ def _generate_delta(signatures, changedfd):
rs = RollSum()

offset = 0
while offset+blocksize < len(buf):
global_shift = 0
while offset+blocksize < len(buf[global_shift:]):
# Prime the rolling sum
if rs.count == 0:
count = min(blocksize, len(buf))
rs.set(faster_rollsum(buf[:count]), count)
rs.set(faster_rollsum(buf[global_shift:global_shift+count]), count)
continue

# Plow through the data, byte at a time
try:
md4_table = sigs[rs.sum()]
md = md4(buf[offset:offset+blocksize])[:md4_truncation]
md = md4(buf[global_shift+offset:offset+blocksize+global_shift])[:md4_truncation]
file_offset = md4_table[md]
if offset > 0:
yield LiteralChange(buf[:offset])
yield LiteralChange(buf[global_shift:offset+global_shift])
yield CopyChange(file_offset, blocksize)
buf = buf[offset+blocksize:]
global_shift += offset+blocksize
offset = 0
rs = RollSum()
except KeyError:
rs.rotate(buf[offset+blocksize], buf[offset])
rs.rotate(buf[offset+blocksize+global_shift], buf[offset+global_shift])
offset += 1

# Processing the last block is a bit different
while offset < len(buf):
while offset < len(buf[global_shift:]):
# See if the last block is still at the end of file
try:
md4_table = sigs[rs.sum()]
md = md4(buf[offset:])[:md4_truncation]
md = md4(buf[global_shift+offset:])[:md4_truncation]
file_offset = md4_table[md]
if offset > 0:
yield LiteralChange(buf[:offset])
yield LiteralChange(buf[global_shift:global_shift+offset])
yield CopyChange(file_offset, blocksize)
return
except KeyError:
rs.rollout(buf[offset])
rs.rollout(buf[offset+global_shift])
offset += 1

# Eh, have the data then
Expand Down