python-idzip
Seekable, gzip compatible, compression format
Gzip allows to store extra fields in the gzip header. Idzip stores offsets for the efficient seeking there.
Install
python setup.py install
or
[python-idzip RHEL6 signed RPM] (http://pkgs.bauman.in/repoview/python-idzip.html)
Acknowledgement
based on https://code.google.com/p/idzip/
The file format was designed by Rik Faith for dictzip. Idzip just uses multiple gzip members to have no file size limit.
Idzip means Improved Dictzip.
added a Writer class
Sizing
downloaded
http://textfiles.com/stories/bureau.txt
cat several copies together up to 20GB > input.txt
gzfile generated using standard gzip
dzfile generated using this library
total 50172612
-rw-rw-r--. 1 dan dan 21313751280 May 10 15:58 input.txt
-rw-rw-r--. 1 dan dan 8576570661 May 10 17:21 dzfile.txt.dz
-rw-rw-r--. 1 dan dan 8076548622 May 10 16:28 gzfile.txt.gz
Size is almost the same as standard gzip
Seek Timing
seekpos = 21313751280 - 15
from time import time
start=time()
original = open("/home/dan/ziptest/input.txt")
original.seek(seekpos)
original.close()
print "Raw Seek to end", time() - start, "seconds"
import gzip
start=time()
verify = gzip.open("/home/dan/ziptest/gzfile.txt.gz", "rb")
verify.seek(seekpos)
verify.close()
print "Standard GZIP Seek to end", time() - start, "seconds"
import idzip
start=time()
verify = idzip.open("/home/dan/ziptest/input.txt.dz")
verify.seek(seekpos)
verify.close()
print "idzip Seek to end", time() - start, "seconds" Raw Seek to end 0.000866889953613 seconds
Standard GZIP Seek to end 255.133864164 seconds
idzip Seek to end 0.0381989479065 seconds
Stream Writer
class allows streaming.
from idzip import Writer
outfile = "/home/dan/ziptest/input1.txt.dz"
writer = Writer(outfile, sync_size=1048576*100)
infile = open("/home/dan/ziptest/input.txt", "rb")
while True:
data = infile.read(1048576+1)
if not data:
break
writer.write(data)
writer.close()
infile.close()Alternatively, you can open an IdzipFile in write mode and accomplish the
same task:
import idzip
infile =
infile = open("/home/dan/ziptest/input.txt", "rb")
writer = idzip.IdzipFile("/home/dan/ziptest/input1.txt.dz", "wb", sync_size=1048576*100)
with infile, writer:
while True:
data = infile.read(1048576 + 1)
if not data:
break
writer.write(data)
