Class ChecksumCRC16

CRC-16-CCITT checksum algorithm implementation using the generator polynomial x^16 + x^12 + x^5 + 1 (hex: 0x1021). Produces a 16-bit cyclic redundancy check value suitable for protocol and packet integrity verification.

Inheritance

object

ChecksumCRC16

Implements

IChecksum

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: Scylla.Core.Util.Checksum

Assembly: ScyllaCore.dll

Syntax

public sealed class ChecksumCRC16 : IChecksum

Remarks

Algorithm details:

• Polynomial (normal representation): 0x1021 - the CCITT / CRC-CCITT polynomial.
• Initial value: 0xFFFF (all ones), matching the XMODEM and CRC-B variants.
• Input / output reflection: none (non-reflected, big-endian bit order).
• Final XOR: none; the accumulated CRC register is returned as-is.
• Output width: 16 bits.

Lookup-table acceleration is used: the 256-entry table is computed once at class initialisation and shared across all instances via a static field.

Common use cases:

• Serial communication protocols: HDLC, X.25, XMODEM.
• Wireless and embedded protocols: Bluetooth, SD card, DNP3.
• Small data packet integrity checks where a 16-bit result is sufficient.

Comparison with CRC-32: CRC-16 produces a 16-bit result (65,536 possible values) versus CRC-32's 32-bit result (~4 billion values). It is faster and more compact but has a higher probability of undetected errors for large messages. For file integrity or application data checksums, prefer ChecksumCRC32.

Security note: CRC-16 is NOT cryptographically secure. For security-sensitive hashing use the Scylla Crypto module instead.

Properties

Value

Gets the current CRC-16-CCITT checksum value.

Declaration

public long Value { get; }

Property Value

Type	Description
long	A non-negative long in the range [0, 65535]. No final XOR is applied; the value of the internal CRC register is returned directly. Returns 0xFFFF (65535) when no data has been processed.

Methods

Reset()

Resets the CRC-16-CCITT checksum to its initial state (0xFFFF), discarding any previously processed data.

Declaration

public void Reset()

Remarks

After calling Reset, Value returns 0xFFFF. Subsequent Update(byte[]) calls begin a fresh CRC computation. Use this to reuse the same instance for multiple independent checksums without allocating a new object.

Update(byte[])

Updates the CRC-16-CCITT checksum by incorporating all bytes in buffer.

Declaration

public void Update(byte[] buffer)

Parameters

Type	Name	Description
byte[]	buffer	The byte array to process. If null or empty, the call is a no-op and the checksum state is unchanged.

Update(byte[], int, int)

Updates the CRC-16-CCITT checksum by incorporating count bytes from buffer starting at offset.

Declaration

public void Update(byte[] buffer, int offset, int count)

Parameters

Type	Name	Description
byte[]	buffer	The source byte array. If null, or if count is zero, the call is a no-op.
int	offset	Zero-based index of the first byte to read in buffer.
int	count	Number of bytes to process. Must not cause offset + count to exceed buffer.Length.

Remarks

Each byte is processed using a single table lookup into the precomputed _table array: crc = table[(crc >> 8) ^ byte] ^ (crc << 8). Multiple calls accumulate into the same CRC register and produce the same final result as a single call with the concatenated input.

Implements

IChecksum

Extension Methods

FileExtensions.SaveSecureToFileAsync<T>(T, string, string, CancellationToken)

FileExtensions.SaveSecureToFile<T>(T, string, string)

FileExtensions.SaveToFileAsync<T>(T, string, CancellationToken)

FileExtensions.SaveToFile<T>(T, string)

FileExtensions.SaveToFile<T>(T, string, SerializationSettings)

See Also

IChecksum

ChecksumCRC32