tools/imgutil.py

   1 #!/usr/bin/env python
   2 #
   3 # Copyright (c) 2008 Martin Decky
   4 # Copyright (c) 2011 Martin Sucha
   5 # All rights reserved.
   6 #
   7 # Redistribution and use in source and binary forms, with or without
   8 # modification, are permitted provided that the following conditions
   9 # are met:
  10 #
  11 # - Redistributions of source code must retain the above copyright
  12 #   notice, this list of conditions and the following disclaimer.
  13 # - Redistributions in binary form must reproduce the above copyright
  14 #   notice, this list of conditions and the following disclaimer in the
  15 #   documentation and/or other materials provided with the distribution.
  16 # - The name of the author may not be used to endorse or promote products
  17 #   derived from this software without specific prior written permission.
  18 #
  19 # THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  20 # IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  21 # OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  22 # IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  23 # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  24 # NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  28 # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29 #
  30
  31 """
  32 Utilities for filesystem image creators
  33 """
  34
  35 import os
  36 import stat
  37
  38 exclude_names = set(['.svn', '.bzr'])
  39
  40 def align_up(size, alignment):
  41         "Return size aligned up to alignment"
  42
  43         if (size % alignment == 0):
  44                 return size
  45
  46         return ((size // alignment) + 1) * alignment
  47
  48 def count_up(size, alignment):
  49         "Return units necessary to fit the size"
  50
  51         if (size % alignment == 0):
  52                 return (size // alignment)
  53
  54         return ((size // alignment) + 1)
  55
  56 def num_of_trailing_bin_zeros(num):
  57         "Return number of trailing zeros in binary representation"
  58
  59         i = 0
  60         if (num == 0): raise ValueError()
  61         while num & 1 == 0:
  62                 i += 1
  63                 num = num >> 1
  64         return i
  65
  66 def get_bit(number, n):
  67         "Return True if n-th least-significant bit is set in the given number"
  68
  69         return bool((number >> n) & 1)
  70
  71 def set_bit(number, n):
  72         "Return the number with n-th least-significant bit set"
  73
  74         return number | (1 << n)
  75
  76 class ItemToPack:
  77         "Stores information about one directory item to be added to the image"
  78
  79         def __init__(self, parent, name):
  80                 self.parent = parent
  81                 self.name = name
  82                 self.path = os.path.join(parent, name)
  83                 self.stat = os.stat(self.path)
  84                 self.is_dir = stat.S_ISDIR(self.stat.st_mode)
  85                 self.is_file = stat.S_ISREG(self.stat.st_mode)
  86                 self.size = self.stat.st_size
  87
  88 def listdir_items(path):
  89         "Return a list of items to be packed inside a fs image"
  90
  91         for name in os.listdir(path):
  92                 if name in exclude_names:
  93                         continue
  94
  95                 item = ItemToPack(path, name)
  96
  97                 if not (item.is_dir or item.is_file):
  98                         continue
  99
 100                 yield item
 101
 102 def chunks(item, chunk_size):
 103         "Iterate contents of a file in chunks of a given size"
 104
 105         inf = open(item.path, 'rb')
 106         rd = 0
 107
 108         while (rd < item.size):
 109                 data = bytes(inf.read(chunk_size))
 110                 yield data
 111                 rd += len(data)
 112
 113         inf.close()