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1# Copyright (C) 2015 The Android Open Source Project
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7#      http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
14
15import math
16import os
17import random
18import shutil
19import subprocess
20import sys
21import tempfile
22
23blocksize = 4096
24roots = 2
25
26def corrupt(image, offset, length):
27    print "corrupting %d bytes at offset %d" % (length, offset)
28    f = os.open(image, os.O_WRONLY)
29    os.lseek(f, offset, os.SEEK_SET)
30    os.write(f, os.urandom(length))
31    os.close(f)
32
33def corruptmax(image, roots):
34    size = os.stat(image).st_size
35
36    blocks = int(math.ceil(float(size) / blocksize))
37    rounds = int(math.ceil(float(blocks) / (255 - roots)))
38
39    max_errors = int(math.floor(rounds * roots / 2)) * blocksize
40    offset = random.randrange(0, size - max_errors)
41
42    corrupt(image, offset, max_errors)
43
44def encode(image, fec, roots):
45    if subprocess.call([ "fec", "--roots= " + str(roots), image, fec ]) != 0:
46        raise Exception("encoding failed")
47
48def decode(image, fec, output):
49    return subprocess.call([ "fec", "--decode", image, fec, output ])
50
51def compare(a, b):
52    return subprocess.call([ "cmp", "-s", a, b ])
53
54def simg2img(image, output):
55    print "creating a non-sparse copy of '%s' to '%s'" % (image, output)
56    if subprocess.call([ "simg2img", image, output]) != 0:
57        raise Exception("simg2img failed")
58
59def main(argv):
60    image = argv[0]
61
62    temp_img = tempfile.NamedTemporaryFile()
63    temp_cor = tempfile.NamedTemporaryFile()
64    temp_fec = tempfile.NamedTemporaryFile()
65    temp_out = tempfile.NamedTemporaryFile()
66
67    simg2img(image, temp_img.name)
68    simg2img(image, temp_cor.name)
69
70    encode(image, temp_fec.name, roots)
71    corruptmax(temp_cor.name, roots)
72
73    if decode(temp_cor.name, temp_fec.name, temp_out.name) != 0:
74        raise Exception("FAILED: failed to correct maximum expected errors")
75
76    if compare(temp_img.name, temp_out.name) != 0:
77        raise Exception("FAILED: corrected file not identical")
78    else:
79        print "corrected content matches original"
80
81    corrupt(temp_cor.name, 0, blocksize)
82
83    if decode(temp_cor.name, temp_fec.name, temp_out.name) == 0:
84        raise Exception("FAILED: corrected more than maximum number of errors?")
85
86    print "PASSED"
87
88if __name__ == '__main__':
89    main(sys.argv[1:])
90