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https://github.com/tahoe-lafs/tahoe-lafs.git
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83 lines
2.7 KiB
Python
83 lines
2.7 KiB
Python
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#!/usr/bin/env python
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from pyutil.assertutil import _assert, precondition
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import random
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import sys
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import fec
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def shuffle(nums_and_shares):
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""" Make sure that if nums_and_shares[i][0] < len(nums_and_shares), that i == nums_and_shares[i][0]. """
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i = 0
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while i < len(nums_and_shares):
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num, share = nums_and_shares[i]
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if num >= len(nums_and_shares) or num == i:
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i += 1
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else:
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nums_and_shares[i] = nums_and_shares[num]
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nums_and_shares[num] = (num, share,)
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_assert([ (i, (num, share,),) for (i, (num, share,),) in enumerate(nums_and_shares) if num < len(nums_and_shares) and num != i ] == [], [ (i, (num, share,),) for (i, (num, share,),) in enumerate(nums_and_shares) if num < len(nums_and_shares) and num != i ])
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def _h(k, m, ss):
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# sys.stdout.write("k: %s, m: %s, len(ss): %r, len(ss[0]): %r" % (k, m, len(ss), len(ss[0]),)) ; sys.stdout.flush()
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encer = fec.Encoder(k, m)
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# sys.stdout.write("constructed.\n") ; sys.stdout.flush()
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nums_and_shares = list(enumerate(encer.encode(ss)))
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# sys.stdout.write("encoded.\n") ; sys.stdout.flush()
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_assert(isinstance(nums_and_shares, list), nums_and_shares)
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_assert(len(nums_and_shares) == m, len(nums_and_shares), m)
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nums_and_shares = random.sample(nums_and_shares, k)
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shuffle(nums_and_shares)
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shares = [ x[1] for x in nums_and_shares ]
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nums = [ x[0] for x in nums_and_shares ]
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# sys.stdout.write("about to construct Decoder.\n") ; sys.stdout.flush()
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decer = fec.Decoder(k, m)
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# sys.stdout.write("about to decode.\n") ; sys.stdout.flush()
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decoded = decer.decode(shares, nums)
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# sys.stdout.write("decoded.\n") ; sys.stdout.flush()
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_assert(len(decoded) == len(ss), len(decoded), len(ss))
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_assert(tuple([str(s) for s in decoded]) == tuple([str(s) for s in ss]), tuple([str(s) for s in decoded]), tuple([str(s) for s in ss]))
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def randstr(n):
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return ''.join(map(chr, map(random.randrange, [0]*n, [256]*n)))
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def div_ceil(n, d):
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"""
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The smallest integer k such that k*d >= n.
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"""
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return (n/d) + (n%d != 0)
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def next_multiple(n, k):
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"""
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The smallest multiple of k which is >= n.
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"""
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return div_ceil(n, k) * k
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def pad_size(n, k):
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"""
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The smallest number that has to be added to n so that n is a multiple of k.
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"""
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if n%k:
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return k - n%k
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else:
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return 0
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def _test_random():
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# m = random.randrange(1, 255)
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m = 99
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# k = random.randrange(1, m+1)
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k = 33
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# l = random.randrange(0, 2**16)
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l = 2**12
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ss = [ randstr(l/k) + '\x00' * pad_size(l/k, k) for x in range(k) ]
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_h(k, m, ss)
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def test_random():
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for i in range(2**9):
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sys.stdout.write(",")
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_test_random()
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sys.stdout.write(".")
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test_random()
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