def a2b_l(cs, lengthinbits):
"""
@param lengthinbits the number of bits of data in encoded into cs
a2b_l() will return a result big enough to hold lengthinbits bits. So for example if cs is
4 characters long (encoding at least 15 and up to 20 bits) and lengthinbits is 16, then a2b_l()
will return a string of length 2 (since 2 bytes is sufficient to store 16 bits). If cs is 4
characters long and lengthinbits is 20, then a2b_l() will return a string of length 3 (since
3 bytes is sufficient to store 20 bits).
Please see the warning in the docstring of b2a_l() regarding the use of b2a() versus b2a_l().
@return the data encoded in cs
"""
precondition(could_be_base32_encoded_l(cs, lengthinbits),
"cs is required to be possibly base32 encoded data.",
cs=cs,
lengthinbits=lengthinbits)
qs = [ord(v) for v in string.translate(cs, c2vtranstable)]
numoctets = div_ceil(lengthinbits, 8)
numquintetsofdata = div_ceil(lengthinbits, 5)
# append zero quintets for padding if needed
numquintetsneeded = div_ceil(numoctets * 8, 5)
qs.extend([0] * (numquintetsneeded - len(qs)))
octets = []
pos = 2048
num = qs[0] * pos
readybits = 5
i = 1
while len(octets) < numoctets:
while pos > 256:
pos = pos / 32
num = num + (qs[i] * pos)
i = i + 1
octet = num / 256
octets.append(octet)
num = num - (octet * 256)
num = num * 256
pos = pos * 256
assert len(
octets) == numoctets, "len(octets): %s, numoctets: %s, octets: %s" % (
len(octets),
numoctets,
octets,
)
res = ''.join([chr(o) for o in octets])
precondition(
b2a_l(res, lengthinbits) == cs,
"cs is required to be the canonical base-32 encoding of some data.",
b2a(res),
res=res,
cs=cs)
return res
def recursive_subset_sum(entropy_needed, wordlists):
# Pick a minimalish set of numbers which sum to at least
# entropy_needed.
# Okay now what's the smallest number of words which will give us
# at least this much entropy?
entropy_of_biggest_wordlist = wordlists[-1][0]
assert isinstance(entropy_of_biggest_wordlist, float), wordlists[-1]
needed_words = div_ceil(entropy_needed, entropy_of_biggest_wordlist)
# How much entropy do we need from each word?
needed_entropy_per_word = entropy_needed / needed_words
# What's the smallest wordlist that offers at least this much
# entropy per word?
for (wlentropy, wl) in wordlists:
if wlentropy >= needed_entropy_per_word:
break
assert wlentropy >= needed_entropy_per_word, (wlentropy,
needed_entropy_per_word)
result = [(wlentropy, wl)]
# If we need more, recurse...
if wlentropy < entropy_needed:
rest = recursive_subset_sum(entropy_needed - wlentropy, wordlists)
result.extend(rest)
return result
def a2b_l(cs, lengthinbits):
"""
@param lengthinbits the number of bits of data in encoded into cs
a2b_l() will return a result big enough to hold lengthinbits bits. So for example if cs is
4 characters long (encoding at least 15 and up to 20 bits) and lengthinbits is 16, then a2b_l()
will return a string of length 2 (since 2 bytes is sufficient to store 16 bits). If cs is 4
characters long and lengthinbits is 20, then a2b_l() will return a string of length 3 (since
3 bytes is sufficient to store 20 bits).
Please see the warning in the docstring of b2a_l() regarding the use of b2a() versus b2a_l().
@return the data encoded in cs
"""
precondition(could_be_base32_encoded_l(cs, lengthinbits), "cs is required to be possibly base32 encoded data.", cs=cs, lengthinbits=lengthinbits)
qs = [ord(v) for v in string.translate(cs, c2vtranstable)]
numoctets = div_ceil(lengthinbits, 8)
numquintetsofdata = div_ceil(lengthinbits, 5)
# append zero quintets for padding if needed
numquintetsneeded = div_ceil(numoctets*8, 5)
qs.extend([0]*(numquintetsneeded-len(qs)))
octets = []
pos = 2048
num = qs[0] * pos
readybits = 5
i = 1
while len(octets) < numoctets:
while pos > 256:
pos = pos / 32
num = num + (qs[i] * pos)
i = i + 1
octet = num / 256
octets.append(octet)
num = num - (octet * 256)
num = num * 256
pos = pos * 256
assert len(octets) == numoctets, "len(octets): %s, numoctets: %s, octets: %s" % (len(octets), numoctets, octets,)
res = ''.join([chr(o) for o in octets])
precondition(b2a_l(res, lengthinbits) == cs, "cs is required to be the canonical base-32 encoding of some data.", b2a(res), res=res, cs=cs)
return res
def encode_file_to_streams(file_path, block_size, k, m):
"""
break file into file stripes.
@type file_path : C{str}
@param file_path : abs path of file to encode.
@type block_size : C{int}
@param block_size : encode unit.
@type k : C{int}
@param k : number of necessary file shares to restore.
@type m : C{int}
@param m : m-k redundant file shares.
@rtype : C{list}
@return : m file streams, each stream is a str.
"""
file_size = path.getsize(file_path)
file = open(file_path)
fencoder = Encoder(k, m)
block_count = mathutil.div_ceil(file_size, block_size)
ds = []
ds.extend([""] * k)
# for the last round , block might be not complete or empty
index = 0
results = []
results.extend([""] * m)
for i in range(block_count / k):
for index in range(k):
ds[index] = file.read(block_size)
ds[k - 1] = ds[k - 1] + "\x00" * (block_size - len(ds[k - 1]))
temp = fencoder.encode(ds)
for j in range(m):
results[j] = results[j] + temp[j]
if block_count % k == 0:
return results
# the last round
for i in range(block_count % k):
ds[i] = file.read(block_size)
ds[i] = ds[i] + "\x00" * (block_size - len(ds[i]))
for index in range(i + 1, k):
ds[index] = "\x00" * (len(ds[0]))
temp = fencoder.encode(ds)
for j in range(m):
results[j] = results[j] + temp[j]
return results
def _make_new_rand_data(size, k, m):
global d, easyfecenc, fecenc, K, M
K = k
M = m
d = os.urandom(size)
del ds[:]
ds.extend([None] * k)
blocksize = mathutil.div_ceil(size, k)
for i in range(k):
ds[i] = d[i * blocksize:(i + 1) * blocksize]
ds[-1] = ds[-1] + "\x00" * (len(ds[-2]) - len(ds[-1]))
easyfecenc = easyfec.Encoder(k, m)
fecenc = Encoder(k, m)
def share_size_for_data(shares_needed, datasize):
"""
Calculate the size of a single erasure encoding share for data of the
given size and with the given level of redundancy.
:param int shares_needed: The number of shares (``k``) from the erasure
encoding process which are required to reconstruct original data of
the indicated size.
:param int datasize: The size of the data to consider, in bytes.
:return int: The size of a single erasure encoding share for the given
inputs.
"""
return div_ceil(datasize, shares_needed)
def test_odd_sizes(self):
for j in range(2**6):
lib = random.randrange(1, 2**8)
numos = mathutil.div_ceil(lib, 8)
bs = insecurerandstr(numos)
# zero-out unused least-sig bits
if lib%8:
b=ord(bs[-1])
b = b >> (8 - (lib%8))
b = b << (8 - (lib%8))
bs = bs[:-1] + chr(b)
asl = zbase62.b2a_l(bs, lib)
assert len(asl) == zbase62.num_chars_that_this_many_octets_encode_to(numos) # the size of the base-62 encoding must be just right
bs2l = zbase62.a2b_l(asl, lib)
assert len(bs2l) == numos # the size of the result must be just right
assert bs == bs2l
def decode_files_to_file(files, size, block_size, k, m, destination_path):
"""
decoded file stripes to file.
@type files :C{list}
@param files : list of abs path of file stripes ,
should end with '.n' , n is an integer.
@type size : C{int}
@param size : file original size.
@type block_size : C{int}
@param block_size : processing unit.
@type k : C{int}
@param k : k.
@type m : C{int}
@param m : m.
@type destination_path : C{str}
@param destination_path : abs path to put decoded file to.
"""
fdecoder = Decoder(k, m)
file = open(destination_path, "w")
parts = [int(path.splitext(f)[1][1:]) for f in files]
streams = []
streams.extend([""] * k)
file_shares = [open(f, "r") for f in files]
file_shares_size = path.getsize(files[0]) * k
block_count = mathutil.div_ceil(file_shares_size, block_size)
for count in range(block_count):
for i in range(k):
streams[i] = file_shares[i].read(block_size)
results = fdecoder.decode(streams, parts)
for i in range(len(results)):
file.write(results[i])
file.truncate(size)
file.close()
def fdc_file(parts, block_size, k, m, file_name, file_dir, file_origin_size):
fdecoder = Decoder(k, m)
streams = []
streams.extend([""] * k)
file = open(file_dir ,'w')
files = [ open('./temp/'+ file_name + '.' + str(i),'r') for i in parts ]
file_size = path.getsize('./temp/' + file_name +'.'+str(parts[0])) * k
block_count = mathutil.div_ceil(file_size, block_size)
for count in range(block_count) :
for i in range(k) :
streams[i] = files[i].read(block_size)
results = fdecoder.decode(streams, parts)
for i in range(len(results)) :
file.write(results[i])
file.truncate(file_origin_size)
file.close()
def fec_file(file, block_size, k, m): file_size = path.getsize(file.name) fencoder = Encoder(k, m) block_count = mathutil.div_ceil(file_size, block_size) #block_count_per_k = mathutil.div_ceil(block_count, k) ds = [] ds.extend([""] * k) #for the last round, block might be not complete or empty index = 0 results = [] results.extend([""] * m) for i in range(block_count / k): for index in range(k): ds[index] = file.read(block_size) ds[k-1] = ds[k-1] + "\x00" * (block_size - len(ds[k-1])) temp = fencoder.encode(ds) for j in range(m): results[j] = results[j] + temp[j] if block_count % k == 0 : return results #the last round for i in range(block_count % k): ds[i] = file.read(block_size) ds[i] = ds[i] + "\x00" * (block_size - len(ds[i])) for index in range(i+1,k): ds[index] = "\x00" * (len(ds[0])) temp = fencoder.encode(ds) for j in range(m): results[j] = results[j] + temp[j] return results
def recursive_subset_sum(entropy_needed, wordlists):
# Pick a minimalish set of numbers which sum to at least
# entropy_needed.
# Okay now what's the smallest number of words which will give us
# at least this much entropy?
entropy_of_biggest_wordlist = wordlists[-1][0]
assert isinstance(entropy_of_biggest_wordlist, float), wordlists[-1]
needed_words = div_ceil(entropy_needed, entropy_of_biggest_wordlist)
# How much entropy do we need from each word?
needed_entropy_per_word = entropy_needed / needed_words
# What's the smallest wordlist that offers at least this much
# entropy per word?
for (wlentropy, wl) in wordlists:
if wlentropy >= needed_entropy_per_word:
break
assert wlentropy >= needed_entropy_per_word, (wlentropy, needed_entropy_per_word)
result = [(wlentropy, wl)]
# If we need more, recurse...
if wlentropy < entropy_needed:
rest = recursive_subset_sum(entropy_needed - wlentropy, wordlists)
result.extend(rest)
return result
def b2a_l(os, lengthinbits):
"""
@param os the data to be encoded (a string)
@param lengthinbits the number of bits of data in os to be encoded
b2a_l() will generate a base-32 encoded string big enough to encode
lengthinbits bits. So for example if os is 2 bytes long and lengthinbits is
15, then b2a_l() will generate a 3-character- long base-32 encoded string
(since 3 quintets is sufficient to encode 15 bits). If os is 2 bytes long
and lengthinbits is 16 (or None), then b2a_l() will generate a 4-character
string. Note that if os is 2 bytes long and lengthinbits is 15, then the
least-significant bit of os is ignored.
Warning: if you generate a base-32 encoded string with b2a_l(), and then someone else tries to
decode it by calling a2b() instead of a2b_l(), then they will (probably) get a different
string than the one you encoded! So only use b2a_l() when you are sure that the encoding and
decoding sides know exactly which lengthinbits to use. If you do not have a way for the
encoder and the decoder to agree upon the lengthinbits, then it is best to use b2a() and
a2b(). The only drawback to using b2a() over b2a_l() is that when you have a number of
bits to encode that is not a multiple of 8, b2a() can sometimes generate a base-32 encoded
string that is one or two characters longer than necessary.
@return the contents of os in base-32 encoded form
"""
precondition(isinstance(lengthinbits, (
int,
long,
)),
"lengthinbits is required to be an integer.",
lengthinbits=lengthinbits)
precondition(
div_ceil(lengthinbits, 8) == len(os),
"lengthinbits is required to specify a number of bits storable in exactly len(os) octets.",
lengthinbits=lengthinbits,
lenos=len(os))
# precondition((lengthinbits % 8==0) or ((ord(os[-1]) % (2**(8-(lengthinbits%8))))==0), "Any unused least-significant bits in os are required to be zero bits.", ord(os[-1]), lengthinbits=lengthinbits) # removing this precondition, because I like to use it with random os, like this: base32.b2a_l(file("/dev/urandom", "r").read(9), 65)
os = [ord(o) for o in os]
numquintets = div_ceil(lengthinbits, 5)
numoctetsofdata = div_ceil(lengthinbits, 8)
# print "numoctetsofdata: %s, len(os): %s, lengthinbits: %s, numquintets: %s" % (numoctetsofdata, len(os), lengthinbits, numquintets,)
# zero out any unused bits in the final octet
if lengthinbits % 8 != 0:
os[-1] >>= (8 - (lengthinbits % 8))
os[-1] <<= (8 - (lengthinbits % 8))
# append zero octets for padding if needed
numoctetsneeded = div_ceil(numquintets * 5, 8) + 1
os.extend([0] * (numoctetsneeded - len(os)))
quintets = []
cutoff = 256
num = os[0]
i = 0
while len(quintets) < numquintets:
i = i + 1
assert len(
os
) > i, "len(os): %s, i: %s, len(quintets): %s, numquintets: %s, lengthinbits: %s, numoctetsofdata: %s, numoctetsneeded: %s, os: %s" % (
len(os),
i,
len(quintets),
numquintets,
lengthinbits,
numoctetsofdata,
numoctetsneeded,
os,
)
num = num * 256
num = num + os[i]
if cutoff == 1:
cutoff = 256
continue
cutoff = cutoff * 8
quintet = num / cutoff
quintets.append(quintet)
num = num - (quintet * cutoff)
cutoff = cutoff / 32
quintet = num / cutoff
quintets.append(quintet)
num = num - (quintet * cutoff)
if len(quintets) > numquintets:
assert len(quintets) == (
numquintets +
1), "len(quintets): %s, numquintets: %s, quintets: %s" % (
len(quintets),
numquintets,
quintets,
)
quintets = quintets[:numquintets]
res = string.translate(''.join([chr(q) for q in quintets]), v2ctranstable)
assert could_be_base32_encoded_l(
res, lengthinbits), "lengthinbits: %s, res: %s" % (
lengthinbits,
res,
)
return res
def b2a_l(os, lengthinbits):
"""
@param os the data to be encoded (a string)
@param lengthinbits the number of bits of data in os to be encoded
b2a_l() will generate a base-32 encoded string big enough to encode
lengthinbits bits. So for example if os is 2 bytes long and lengthinbits is
15, then b2a_l() will generate a 3-character- long base-32 encoded string
(since 3 quintets is sufficient to encode 15 bits). If os is 2 bytes long
and lengthinbits is 16 (or None), then b2a_l() will generate a 4-character
string. Note that if os is 2 bytes long and lengthinbits is 15, then the
least-significant bit of os is ignored.
Warning: if you generate a base-32 encoded string with b2a_l(), and then someone else tries to
decode it by calling a2b() instead of a2b_l(), then they will (probably) get a different
string than the one you encoded! So only use b2a_l() when you are sure that the encoding and
decoding sides know exactly which lengthinbits to use. If you do not have a way for the
encoder and the decoder to agree upon the lengthinbits, then it is best to use b2a() and
a2b(). The only drawback to using b2a() over b2a_l() is that when you have a number of
bits to encode that is not a multiple of 8, b2a() can sometimes generate a base-32 encoded
string that is one or two characters longer than necessary.
@return the contents of os in base-32 encoded form
"""
precondition(isinstance(lengthinbits, (int, long,)), "lengthinbits is required to be an integer.", lengthinbits=lengthinbits)
precondition(div_ceil(lengthinbits, 8) == len(os), "lengthinbits is required to specify a number of bits storable in exactly len(os) octets.", lengthinbits=lengthinbits, lenos=len(os))
# precondition((lengthinbits % 8==0) or ((ord(os[-1]) % (2**(8-(lengthinbits%8))))==0), "Any unused least-significant bits in os are required to be zero bits.", ord(os[-1]), lengthinbits=lengthinbits) # removing this precondition, because I like to use it with random os, like this: base32.b2a_l(file("/dev/urandom", "r").read(9), 65)
os = [ord(o) for o in os]
numquintets = div_ceil(lengthinbits, 5)
numoctetsofdata = div_ceil(lengthinbits, 8)
# print "numoctetsofdata: %s, len(os): %s, lengthinbits: %s, numquintets: %s" % (numoctetsofdata, len(os), lengthinbits, numquintets,)
# zero out any unused bits in the final octet
if lengthinbits % 8 != 0:
os[-1] >>= (8-(lengthinbits % 8))
os[-1] <<= (8-(lengthinbits % 8))
# append zero octets for padding if needed
numoctetsneeded = div_ceil(numquintets*5, 8) + 1
os.extend([0]*(numoctetsneeded-len(os)))
quintets = []
cutoff = 256
num = os[0]
i = 0
while len(quintets) < numquintets:
i = i + 1
assert len(os) > i, "len(os): %s, i: %s, len(quintets): %s, numquintets: %s, lengthinbits: %s, numoctetsofdata: %s, numoctetsneeded: %s, os: %s" % (len(os), i, len(quintets), numquintets, lengthinbits, numoctetsofdata, numoctetsneeded, os,)
num = num * 256
num = num + os[i]
if cutoff == 1:
cutoff = 256
continue
cutoff = cutoff * 8
quintet = num / cutoff
quintets.append(quintet)
num = num - (quintet * cutoff)
cutoff = cutoff / 32
quintet = num / cutoff
quintets.append(quintet)
num = num - (quintet * cutoff)
if len(quintets) > numquintets:
assert len(quintets) == (numquintets+1), "len(quintets): %s, numquintets: %s, quintets: %s" % (len(quintets), numquintets, quintets,)
quintets = quintets[:numquintets]
res = string.translate(''.join([chr(q) for q in quintets]), v2ctranstable)
assert could_be_base32_encoded_l(res, lengthinbits), "lengthinbits: %s, res: %s" % (lengthinbits, res,)
return res
