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#!/usr/bin/env python
# $Id: oggtail.py,v 1.1 2001/05/02 01:49:11 andrew Exp $
# Send to stdout an ogg stream composed of the last PERCENT percent of
# file OGGFILE.
#
# example: oggtail.py --percent=PERCENT OGGFILE
#
# (PERCENT is rounded down to the nearest page. Cutting at the
# nearest packet would be more complicated.)
# First version by Mike Coleman <mkc@mathdogs.com>, April 2001
# TODO: This still doesn't work quite right. 'ogg123' complains with
# a warning if we pipe oggtail's output directly into it, so probably
# there's a minor error in the stream formatting somewhere.
import getopt
import ogg
import sys
_debug = 0
def usage():
sys.exit("usage: oggtail.py [--debug] --percent=PERCENT OGGFILE")
def debug(s):
if _debug:
sys.stderr.write(s)
sys.stderr.write('\n')
def copy_packets(from_, to_, outstream=None, count=None, start_pageno=0, start_granulepos=0):
"""
Copy 'count' packets from file 'from_' to file 'to_'. If 'count'
is None, copy the rest of 'from_'. Use 'start_granulepos' as the
initial granulepos tag for pages. Bytes will be skipped in
'from_' to sync, as needed, and copying will stop if a chain
boundary is encountered.
"""
# XXX: warn on desync, except at beginning?
copied = 0
written = 0
pageno = start_pageno
granule_offset = None
instream = None
# get it? insync? get it? i'm so funny you can't stand it!
insync = ogg.OggSyncState()
while count == None or copied < count:
b = from_.read(65536) # size doesn't really matter
if not b:
break
insync.bytesin(b)
skipped = 1
while skipped != 0:
skipped, page = insync.pageseek()
if skipped > 0:
if instream and page.serialno() != serialno:
# we hit a chain boundary
break
if not instream:
serialno = page.serialno()
instream = ogg.OggStreamState(serialno)
outstream = ogg.OggStreamState(serialno)
page.pageno = pageno
debug('*** %s' % page.pageno())
pageno = pageno + 1
instream.pagein(page)
while count == None or copied < count:
p = instream.packetout()
if not p:
break
if p.granulepos != -1:
if granule_offset == None:
granule_offset = p.granulepos
p.granulepos = p.granulepos - granule_offset
debug('copied %s' % p)
outstream.packetin(p)
copied = copied + 1
while 1:
pg = outstream.pageout()
if not pg:
break
debug('writing %s' % pg)
# FIX: should check success of write
written = written + pg.writeout(to_)
elif skipped < 0:
print 'skipped', -skipped, 'bytes'
pg = outstream.flush()
if pg:
written = written + pg.writeout(to_)
return (written, pageno - start_pageno, outstream)
opts, pargs = getopt.getopt(sys.argv[1:], '', ['debug', 'percent='])
print sys.argv, opts, pargs
if len(opts) < 1 or len(pargs) != 1:
usage()
for o, a in opts:
print o, a
if o == '--percent':
try:
percent = float(a)
except ValueError:
usage()
elif o == '--debug':
_debug = 1
else:
usage()
if not 0.0 <= percent <= 100.0:
usage()
file = pargs[0]
f = open(file, 'rb')
f.seek(0, 2)
f_size = f.tell()
f.seek(0)
# first copy the three header packets
n, p, os = copy_packets(f, sys.stdout, None, 3)
debug('copied header: %d bytes, %d pages' % (n, p))
debug(str(os))
# then seek to percent and copy out the rest
f.seek(int((100.0 - percent) / 100.0 * f_size))
n, p, os = copy_packets(f, sys.stdout, os)
debug('copied tail: %d bytes, %d pages' % (n, p))
debug(str(os))
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