#encoding:latin-1
#
#  This moduls allows scanning of Tarfile Content with constant
#  memory consumption.
#
#  Python 2.5 tarfile module does internal caching, such that
#  the memory consumption while iterating grows linearly.
#
#  -----------------------------------------------------------------
#
#  (C) July 2008 Uwe Schmitt  <uschmitt@procoders.net>
#
#  This module is inspired by the standard libs tarfile by Lars 
#  Gustäbel #  module and  the work of Tamito KAJIYAMA 
#
#  Permission  is  hereby granted,  free  of charge,  to  any person
#  obtaining a  copy of  this software  and associated documentation
#  files  (the  "Software"),  to   deal  in  the  Software   without
#  restriction,  including  without limitation  the  rights to  use,
#  copy, modify, merge, publish, distribute, sublicense, and/or sell
#  copies  of  the  Software,  and to  permit  persons  to  whom the
#  Software  is  furnished  to  do  so,  subject  to  the  following
#  conditions:
# 
#  The above copyright  notice and this  permission notice shall  be
#  included in all copies or substantial portions of the Software.
# 
#  THE SOFTWARE IS PROVIDED "AS  IS", WITHOUT WARRANTY OF ANY  KIND,
#  EXPRESS OR IMPLIED, INCLUDING  BUT NOT LIMITED TO  THE WARRANTIES
#  OF  MERCHANTABILITY,  FITNESS   FOR  A  PARTICULAR   PURPOSE  AND
#  NONINFRINGEMENT.  IN  NO  EVENT SHALL  THE  AUTHORS  OR COPYRIGHT
#  HOLDERS  BE LIABLE  FOR ANY  CLAIM, DAMAGES  OR OTHER  LIABILITY,
#  WHETHER  IN AN  ACTION OF  CONTRACT, TORT  OR OTHERWISE,  ARISING
#  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
#  OTHER DEALINGS IN THE SOFTWARE.

import gzip, bz2

BLOCKSIZE = 512

def trim_null(v):
    return v[:v.find('\000')]

def oct2int(v):
    return eval('0' + v.strip('\00 '))

def int2int(v):
    v = v.strip('\00 ')
    if v:
        return int(v)
    return None    

class TarInfo:

    def __init__(self, hblock, tar_name, base):

        self.tar_name = tar_name
        self.base     = base

        self.name     = trim_null(hblock[0:100])
        self.mode     = hblock[100:108]
        self.uid      = oct2int(hblock[108:116])
        self.gid      = oct2int(hblock[116:124])
        self.size     = oct2int(hblock[124:136])
        self.mtime    = oct2int(hblock[136:147])
        self.chksum   = int2int(hblock[148:156])
        self.type     = hblock[156]
        self.linkname = trim_null(hblock[157:256])
    
        blocks, remainder = divmod(self.size, BLOCKSIZE)
        if remainder:
            blocks += 1

        self.size_in_block = blocks*BLOCKSIZE

        self.ustar = trim_null(hblock[257:257+6])
        if self.ustar=="ustar":
            self.uname = trim_null(hblock[265:265+32])
            self.gname = trim_null(hblock[297:297+32])
            self.devmajor = int2int(hblock[329:329+8])
            self.devminor = int2int(hblock[337:337+8])
        else:
            self.uname = None
            self.gname = None
            self.devmajor = None
            self.devminor = None


class TarFile:

    @classmethod
    def open(cls, name):
        if name.endswith(".tgz") or name.endswith(".gz"):
            fp = gzip.open(name) 
        elif name.endswith(".bz2"):
            fp = bz2.BZ2File(name)
        else:
            fp = open(name,"r")
        offset = 0
        while 1:
            hblock=fp.read(BLOCKSIZE)
            if not ord(hblock[0]): break
            header = TarInfo(hblock, name, fp.tell())
            yield header
            offset += BLOCKSIZE
            offset += header.size_in_block
            fp.seek(offset)
        

if __name__ == "__main__":

    import sys, time

    if len(sys.argv) == 2:

        for header in TarFile.open(sys.argv[1]):
            print
            print ' name:', header.name
            print ' size:', header.size, 'bytes'
            print 'mtime:', time.ctime(header.mtime)
            print

    else:
        print
        print "need name of tarfile as command line parameter"
        print
        print "extensions .tar, .tar.gz, .tgz and .bz2 are allowed"
        print