python-bchlib
所属分类：其他
开发工具：Python
文件大小：27KB
下载次数：8
上传日期：2019-03-05 16:50:56
上 传 者：
baugi
说明： BCH编码及解码，可自定义BCH编码类型
(BCH Coding and Decoding)
文件列表:
COPYING (18092, 2018-05-18)
MANIFEST.in (38, 2018-05-18)
bchlib (0, 2018-05-18)
bchlib\bch.c (37500, 2018-05-18)
bchlib\bch.h (2791, 2018-05-18)
bchlib\bchlib.c (15815, 2018-05-18)
exynos-encode-example.py (656, 2018-05-18)
setup.py (1229, 2018-05-18)
python-bchlib
=============
This is a python module for encoding and correcting data using [BCH codes](https://en.wikipedia.org/wiki/BCH_code).
## Requirements
* python3 or python2.7
* python3-dev or python-dev
## Building and Installing
__Python 3:__
$ python3 setup.py build
$ sudo python3 setup.py install
__Python 2.7:__
$ python setup.py build
$ sudo python setup.py install
## Module Documentation
bchlib.__BCH(__ polynomial, t[, reverse] __)__ → bch
> Constructor creates a BCH object with given `polynomial` and `t` bit strength, `reverse` is an optional boolean that flips the bit order of data. The Galois field order is automatically determined from the `polynomial`.
bch.__encode(__ data[, ecc] __)__ → ecc
> Encodes `data` with an optional starting `ecc` and returns an ecc.
bch.__decode(__ data, ecc __)__ → ( bitflips, data, ecc )
> Corrects `data` using `ecc` and returns a tuple.
bch.__decode_inplace(__ data, ecc __)__ → bitflips
> Corrects `data` using `ecc` in place, returning the number of bitflips.
bch.__decode_syndromes(__ data, syndromes __)__ → ( bitflips, data )
> Corrects `data` using a sequence of `syndromes`, of t*2 elements, returning a tuple.
bch.__compute_even_syndromes(__ syndromes __)__ → syndromes
> Computes even syndromes from odd ones. Takes and returns a sequence of t*2 elements.
bch.__ecc_bytes__
> A readonly field; the number of bytes an ecc takes up.
bch.__ecc_bits__
> A readonly field; the number of bits an ecc takes up.
bch.__m__
> A readonly field; the Galois field order.
bch.__n__
> A readonly field; the maximum codeword size in bits.
bch.__syndromes__
> A readonly field; a tuple of syndromes after performing a correct operation.
bch.__t__
> A readonly field; the number bit errors that can be corrected.
## Usage Example
```python
import bchlib
import hashlib
import os
import random
# create a bch object
BCH_POLYNOMIAL = 8219
BCH_BITS = 16
bch = bchlib.BCH(BCH_POLYNOMIAL, BCH_BITS)
# random data
data = bytearray(os.urandom(512))
# encode and make a "packet"
ecc = bch.encode(data)
packet = data + ecc
# print hash of packet
sha1_initial = hashlib.sha1(packet)
print('sha1: %s' % (sha1_initial.hexdigest(),))
def bitflip(packet):
byte_num = random.randint(0, len(packet) - 1)
bit_num = random.randint(0, 7)
packet[byte_num] ^= (1 << bit_num)
# make BCH_BITS errors
for _ in range(BCH_BITS):
bitflip(packet)
# print hash of packet
sha1_corrupt = hashlib.sha1(packet)
print('sha1: %s' % (sha1_corrupt.hexdigest(),))
# de-packetize
data, ecc = packet[:-bch.ecc_bytes], packet[-bch.ecc_bytes:]
# correct
bitflips = bch.decode_inplace(data, ecc)
print('bitflips: %d' % (bitflips))
# packetize
packet = data + ecc
# print hash of packet
sha1_corrected = hashlib.sha1(packet)
print('sha1: %s' % (sha1_corrected.hexdigest(),))
if sha1_initial.digest() == sha1_corrected.digest():
print('Corrected!')
else:
print('Failed')
```
近期下载者：
相关文件：
收藏者：