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<h1 align="center">CRC</h1>
<p align="center">
Calculate CRC checksums, verify CRC checksum, predefined CRC configurations, custom CRC configurations
</p>
<p align="center">
<a href="https://github.com/Nicoretti/crc/actions">
<img src="https://img.shields.io/github/checks-status/nicoretti/crc/master" alt="Checks Master">
</a>
<a href="https://coveralls.io/github/Nicoretti/crc">
<img src="https://img.shields.io/coverallsCoverage/github/Nicoretti/crc" alt="Coverage">
</a>
<a href="https://opensource.org/licenses/BSD-2-Clause">
<img src="https://img.shields.io/pypi/l/crc" alt="License">
</a>
<a href="https://pypi.org/project/crc/">
<img src="https://img.shields.io/pypi/dm/crc" alt="Downloads">
</a>
<a href="https://pypi.org/project/crc/">
<img src="https://img.shields.io/pypi/pyversions/crc" alt="Supported Python Versions">
</a>
<a href="https://pypi.org/project/crc/">
<img src="https://img.shields.io/pypi/v/crc" alt="PyPi Package">
</a>
</p>
---
* Documentation: [https://nicoretti.github.io/crc](https://nicoretti.github.io/crc)
* Source Code: [https://github.com/Nicoretti/crc](https://github.com/Nicoretti/crc)
---
## Available CRC Configurations
For convenience various frequently used crc configurations ship with the library out of the box.
| CRC8 | CRC16 | CRC32 | CRC64 |
|---------------|----------|---------|-------|
| CCITT | XMODEM | CRC32 | CRC64 |
| AUTOSAR | GSM | AUTOSAR | |
| SAEJ1850 | PROFIBUS | BZIP2 | |
| SAEJ1850_ZERO | MODBUS | POSIX | |
| BLUETOOTH | IBM-3740 | | |
| MAXIM-DOW | KERMIT | | |
If you find yourself in the position, where having a new configuration available out of the
box would be desirable, feel free to create a [PR](https://github.com/Nicoretti/crc/pulls) or file an [issue](https://github.com/Nicoretti/crc/issues).
## Custom Configurations
If you want to create a custom configuration, you should have the following information available:
🗒 Note:
This library currently only supports bit widths of full bytes 8, 16, 24, 32, ...
* **width**
* **polynom**
* **init value**
* **final xor value**
* **reversed input**
* **reversed output**
In case you only have a name of a specific crc configuration/algorithm and you are unsure what are the specific parameters
of it, a look into this [crc-catalogue](http://reveng.sourceforge.net/crc-catalogue/all.htm) might help.
## Requirements
* [\>= Python 3.8](https://www.python.org)
## Installation
```shell
pip install crc
```
## Examples
### Create a Calculator
#### Pre defined configuration
```python
from crc import Calculator, Crc8
calculator = Calculator(Crc8.CCITT)
```
#### Custom configuration
```python
from crc import Calculator, Configuration
config = Configuration(
width=8,
polynomial=0x07,
init_value=0x00,
final_xor_value=0x00,
reverse_input=False,
reverse_output=False,
)
calculator = Calculator(config)
```
### Calculate a checksum
#### Standard
```python
from crc import Calculator, Crc8
expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
calculator = Calculator(Crc8.CCITT)
assert expected == calculator.checksum(data)
```
#### Optimized for speed
```python
from crc import Calculator, Crc8
expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
calculator = Calculator(Crc8.CCITT, optimized=True)
assert expected == calculator.checksum(data)
```
### Verify a checksum
#### Standard
```python
from crc import Calculator, Crc8
expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
calculator = Calculator(Crc8.CCITT)
assert calculator.verify(data, expected)
```
#### Optimized for speed
```python
from crc import Calculator, Crc8
expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
calculator = Calculator(Crc8.CCITT, optimized=True)
assert calculator.verify(data, expected)
```
### Calculate a checksum with raw registers
#### Register
```python
from crc import Crc8, Register
expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
register = Register(Crc8.CCITT)
register.init()
register.update(data)
assert expected == register.digest()
```
#### TableBasedRegister
```python
from crc import Crc8, TableBasedRegister
expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
register = TableBasedRegister(Crc8.CCITT)
register.init()
register.update(data)
assert expected == register.digest()
```
References & Resources
-----------------------
* [A Painless guide to crc error detection algorithms](http://www.zlib.net/crc_v3.txt)
* [CRC-Catalogue](http://reveng.sourceforge.net/crc-catalogue/all.htm)
|
