plugins/dvdvideo/compositefile.py

   1 # Module:       compositefile.py
   2 # Author:       Eric von Bayer
   3 # Contact:
   4 # Date:         August 18, 2009
   5 # Description:
   6 #     Class that works like a file but is in reality a series of file system
   7 #     files.  Intentionally is a similar API to the file object.
   8 #
   9 # Copyright (c) 2009, Eric von Bayer
  10 # All rights reserved.
  11 #
  12 # Redistribution and use in source and binary forms, with or without
  13 # modification, are permitted provided that the following conditions are met:
  14 #
  15 #    * Redistributions of source code must retain the above copyright notice,
  16 #      this list of conditions and the following disclaimer.
  17 #    * Redistributions in binary form must reproduce the above copyright notice,
  18 #      this list of conditions and the following disclaimer in the documentation
  19 #      and/or other materials provided with the distribution.
  20 #    * The names of the contributors may not be used to endorse or promote
  21 #      products derived from this software without specific prior written
  22 #      permission.
  23 #
  24 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  25 # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  27 # DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  28 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  30 # SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  31 # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  32 # OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  33 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  34
  35 import os
  36 import copy
  37
  38 try:
  39     os.SEEK_SET
  40 except AttributeError:
  41     os.SEEK_SET, os.SEEK_CUR, os.SEEK_END = range(3)
  42
  43 # Handle a series of files as if it's one file
  44 class CompositeFile(object):
  45     """Virtual file that is a composite of other files"""
  46     def __init__( self, *files ):
  47         self.__file_map = list()
  48         self.closed = True
  49
  50         # If we are given a composite file, copy the file map
  51         if len(files) == 1 and isinstance( files[0], CompositeFile ):
  52             self.__file_map = copy.deepcopy( files[0].__file_map )
  53
  54         # Build a file offset map
  55         else:
  56             off = 0L
  57             for cfile in files:
  58                 size = os.path.getsize( cfile )
  59                 if size > 0 and os.path.isfile( cfile ):
  60                     off += size
  61                     self.__file_map.append( ( off, cfile ) )
  62
  63         # Open the first file
  64         self.open()
  65
  66     def __str__( self ):
  67         return ",".join( fm[1] for fm in self.__file_map )
  68
  69     # Advance to the next file
  70     def __next_file( self ):
  71         # If we have an open handle, close it in preparation for the next one
  72         if self.__handle != None and not self.__handle.closed:
  73             self.__handle.close()
  74
  75         # Bump the file number that we're on
  76         self.__fileno += 1
  77
  78         # If there's another file, open it and get the next offset
  79         if self.__fileno < len( self.__file_map ):
  80             self.__handle = open( self.__file_map[ self.__fileno ][1], "rb" )
  81             self.__next_file_off = self.__file_map[ self.__fileno ][0]
  82
  83         # We're done, null the handle and mark as closed
  84         else:
  85             self.close()
  86
  87     # Read a slice, return the data and how many bytes remain to be read
  88     def __read_slice( self, bytes ):
  89         rem = self.__off + bytes - self.__next_file_off
  90
  91         # If the remaining bytes aren't negative, then read a slice and advance
  92         # to the next file.
  93         if rem >= 0L:
  94             bytes = bytes - rem
  95             #print "Read %d[%d]: %d: %s+%d" % ( bytes, rem, self.__off, os.path.basename(self.__handle.name), self.__handle.tell() )
  96             data = self.__handle.read( bytes )
  97             self.__off += len(data)
  98             assert bytes == len(data), "Failed to read the requested number of bytes"
  99             self.__next_file()
 100             return data, rem
 101
 102         # Read the bytes all from this file
 103         else:
 104             #print "Read %d: %d: %s+%d" % ( bytes, self.__off, os.path.basename(self.__handle.name), self.__handle.tell() )
 105             data = self.__handle.read( bytes )
 106             self.__off += len(data)
 107             assert bytes == len(data), "Failed to read the requested number of bytes"
 108             return data, 0
 109
 110     # Get a list of files
 111     def files( self ):
 112         return [ fm[1] for fm in self.__file_map ]
 113
 114     # Return the linear offset
 115     def tell( self ):
 116         return self.__off
 117
 118     # Seek into the composite file
 119     def seek( self, off, whence = os.SEEK_SET ):
 120
 121         # Calculate the new seek offset
 122         if whence == os.SEEK_SET:
 123             new_off = off
 124         elif whence == os.SEEK_CUR:
 125             new_off = self.__off + off
 126         elif whence == os.SEEK_END:
 127             new_off = self.__file_map[-1][0] + off
 128         else:
 129             raise "seek called with an invalid offset type"
 130
 131         # Determine which file this seek offset is part of
 132         soff = 0
 133         fileno = 0
 134         for ( eoff, mfile ) in self.__file_map:
 135             if eoff > new_off:
 136                 break
 137             fileno += 1
 138             soff = eoff
 139
 140         # Make sure this was a valid seek point
 141         if eoff <= new_off:
 142             raise "seek beyond the bounds of the composite file"
 143
 144         # Make sure the correct file is open
 145         if fileno != self.__fileno:
 146             if not self.__handle.closed:
 147                 self.__handle.close()
 148             self.__handle = open( self.__file_map[fileno][1], "rb" )
 149             self.__next_file_off = eoff
 150             self.__fileno = fileno
 151
 152         # Seek the file handle
 153         self.__handle.seek( new_off - soff )
 154         self.__off = new_off
 155
 156     # Read from the file
 157     def read( self, bytes ):
 158         if self.__handle.closed == False:
 159             data = ""
 160             while bytes > 0 and self.closed == False:
 161                 slice_data, bytes = self.__read_slice( bytes )
 162                 data += slice_data
 163             return data
 164         else:
 165             return ""
 166
 167     def open(self):
 168         if self.closed:
 169             self.__fileno = -1
 170             self.__off = 0L
 171             self.__next_file_off = 0L
 172             self.__handle = None
 173             self.closed = False
 174
 175             # Open the first file
 176             self.__next_file()
 177
 178
 179     def close( self ):
 180         if self.__handle != None and self.__handle.closed == False:
 181             self.__handle.close()
 182             self.__handle = None
 183         self.closed = True
 184
 185     def size( self ):
 186         return self.__file_map[-1][0]