# Check

**Repository Path**: JetLab/check

## Basic Information

- **Project Name**: Check
- **Description**: .NetFramework4.5 and .NetCore3.0 c#(CSharp) library for Cyclic Redundancy Check(CRC), contains almost all CRC-8, CRC-16 and CRC-32. OR define a algorithm yourself.
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-03-14
- **Last Updated**: 2021-03-14

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

## About
===========================
.NetFramework4.5 and .NetCore3.0 c#(CSharp) library for Cyclic Redundancy Check(CRC), contains almost all CRC-8, CRC-16 and CRC-32. OR define a algorithm yourself.
## How to
===========================

### 1. Define a new crc algorithm
---------------------------
```cs
CrcAlgorithm algorithm;

// used the standard model
algorithm = CrcAlgorithm.Standard.Crc16X25;

// OR define it yourself
algorithm =
    new CrcAlgorithm(
        "CRC-16/X-25",  //      [Name]: what you call this algorithm
        16,             //     [Width]: of polynomial(Poly)
        0x1021,         //      [Poly]: (CRC-16/X-25)X^16+X^12+X^5+X^0 -> (poly is simplified and not include first bit) | (1 << 12) | (1 << 5) | (1 << 0) = 0X1021
        0xFFFF,         //      [Init]: Initial value for the register
        true,           //  [IsRefInp]: Whether the bits of each byte are REFLECTED(*) before being processed
        true,           //  [IsRefOut]: Whether the algorithm feeds input bytes through the register or xors them with a byte from one end and then straight into the table.
        0xFFFF,         //    [XorOut]: Value to XOR with the final register value.
        0x906E);        //     [Check]: The checksum obtained when the ASCII string "123456789"(Standard.Validate) is fed.

// REFLECTED(*):
// 1100-1110-1010 ->  0101-0111-0011
```

### 2. Validate your algorithm
---------------------------
```cs
bool isChecked = false;
isChecked = algorithm.IsChecked;  //  algorithm.Check == algorithm.ComputeCrc(Standard.Validate, Standard.Validate.Length);
Assert.IsTrue(isChecked);
```

### 3. Define a data to validate
---------------------------
```cs
byte[] data = Encoding.ASCII.GetBytes("123456789");               // string to calcualte -> byte[9]
byte[] checksum = BitConverter.GetBytes((UInt16)algorithm.Check); // checksum 0x906E -> byte[2]
byte[] buff = data.Concat(checksum).ToArray();                    // buff = {data} + {checksum}
```

### 4. Validate from buff or data and checksum
---------------------------
```cs
bool validated = false;
// calcualte from buff
validated = algorithm.Validated(buff, length: buff.Length - 2, offset: 0); // [length]: length of data; [offset]: start index of data
Assert.IsTrue(validated == true);

// OR calcualte from data and checksum
validated = algorithm.Validated(data, checksum);
Assert.IsTrue(validated == true);
```

### 5. If you want to know the expected checksum from data
---------------------------
```cs
UInt64 expectedChecksum = algorithm.ComputeCrc(data, data.Length, offset: 0);
Assert.AreEqual(expectedChecksum, checksum.ToUInt64());
```