Package: pyjerasure
pyjerasurePython Wrapper library for libjerasureOnly basic encoding/decoding methods are implemented.UsageIn this example we have blocks of data that we would like to protect against data loss.data = [
  b"hello",
  b"world",
  b"data-123",
  b"data-0123456789A",
]First we import the library and setup our matrix.There are multiple matrix types available which can be shown withMatrix.TYPESimport pyjerasure

matrix_type = "rs_r6"
k = 4  # Number of data blocks
m = 2  # Number of coding blocks. This is also the maximum number of blocks that can be lost.
w = 8  # Word Size

matrix = pyjerasure.Matrix(matrix_type, k, m, w)Next we encode our data using the matrix.
This adds redundant coding blocks to our data.coded_data = pyjerasure.encode_from_blocks(matrix, data)
print(coded_data)

#  Outputs:
#
#  [b'hello\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
#   b'world\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
#   b'data-123\x00\x00\x00\x00\x00\x00\x00\x00',
#   b'data-0123456789A',
#   b'\x1f\n\x1e\x00\x0b\x01\x03\x013456789A',
#   b'\x0c\r\xc2\x02fY]A\x85\xbd\xb5\xad\xa5\xdd\xd52']
#Notice how some of our data has been padded with zeroed bytes.
This is necessary for encoding our data.
The*_from_blocksmethod automatically pads data to the correct length.Now we're going to simulate a loss of data by deleting 'm' blocks.missing = [1, 3]
for i in missing:
  coded_data[i] = b""
print(coded_data)

#  Outputs:
#
#  [b'hello\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
#   b'',
#   b'data-123\x00\x00\x00\x00\x00\x00\x00\x00',
#   b'',
#   b'\x1f\n\x1e\x00\x0b\x01\x03\x013456789A',
#   b'\x0c\r\xc2\x02fY]A\x85\xbd\xb5\xad\xa5\xdd\xd52']
#Recovering the data can be done if we know the indexes of the missing blocks.restored = pyjerasure.decode_from_blocks(matrix, coded_data, missing)
print(restored)

#  Outputs:
#
#  [b'hello\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
#   b'world\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
#   b'data-123\x00\x00\x00\x00\x00\x00\x00\x00',
#   b'data-0123456789A',
#   b'\x1f\n\x1e\x00\x0b\x01\x03\x013456789A',
#   b'\x0c\r\xc2\x02fY]A\x85\xbd\xb5\xad\xa5\xdd\xd52']
#Blocks can be encoded and decoded as a byte string using the*_from_bytesmethods.
Each block needs to be padded in respect to the longest block. Thealign_sizemethod returns the appropriate size for each block.
TheMatrix.align_blockmethod pads each block.matrix_type = "cauchy"
matrix = pyjerasure.Matrix(matrix_type, k, m, w)
size = max([len(block) for block in data])
padded = [matrix.align_block(block, size) for block in data]
padded_data = b"".join(padded)
encoded = pyjerasure.encode_from_bytes(matrix, padded_data, size)
print(encoded)

#  Outputs:
#
#  b'hello\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
#    world\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
#    data-123\x00\x00\x00\x00\x00\x00\x00\x00
#    data-0123456789A
#    M\x8a\xea\x01+\xb0\xdem\x0f]\xfa\x0e\xa9\xaa\r\x15
#    2\x89\xef\x01RP\xe3\x8d\xc5\rJ\x83\xc4\x0eIW'
#

block_size = len(encoded) // (matrix.k + matrix.m)
erased = bytearray(encoded)
erased[:block_size * 2] = bytes(block_size * 2) # Erase first two blocks.
erased = bytes(erased)
print(erased)

#  Outputs:
#
#  b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
#    \x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00 
#    data-123\x00\x00\x00\x00\x00\x00\x00\x00
#    data-0123456789A
#    M\x8a\xea\x01+\xb0\xdem\x0f]\xfa\x0e\xa9\xaa\r\x15
#    2\x89\xef\x01RP\xe3\x8d\xc5\rJ\x83\xc4\x0eIW'
#

erasures = [0, 1]
restored = pyjerasure.decode_from_bytes(matrix, erased, erasures, size)
print(restored)

#  Outputs:
#
#  b'hello\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
#    world\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
#    data-123\x00\x00\x00\x00\x00\x00\x00\x00
#    data-0123456789A
#    M\x8a\xea\x01+\xb0\xdem\x0f]\xfa\x0e\xa9\xaa\r\x15
#    2\x89\xef\x01RP\xe3\x8d\xc5\rJ\x83\xc4\x0eIW'
#InstallingUsing pippip install pyjerasureFrom SourceInstalling from source requireslibjerasure-devto be installed.
In addition,cythonmay need to be installed as well.pip install cython
python setup.py install build_extOriginal LicenseCopyright (c) 2013, James S. Plank and Kevin Greenan
All rights reserved.Jerasure - A C/C++ Library for a Variety of Reed-Solomon and RAID-6 Erasure Coding TechniquesRevision 2.0: Galois Field backend now links to GF-CompleteRedistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.Neither the name of the University of Tennessee nor the names of its
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.