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FNV-1a hash in C#
/// <summary>
/// A hash combiner that is implemented with the Fowler/Noll/Vo algorithm (FNV-1a). This is a mutable struct for performance reasons.
/// </summary>
public struct FnvHash
{
/// <summary>
/// The starting point of the FNV hash.
/// </summary>
public const int Offset = unchecked((int)2166136261);
/// <summary>
/// The prime number used to compute the FNV hash.
/// </summary>
private const int Prime = 16777619;
/// <summary>
/// Gets the current result of the hash function.
/// </summary>
public int HashCode { get; private set; }
/// <summary>
/// Creates a new FNV hash initialized to <see cref="Offset"/>.
/// </summary>
public static FnvHash Create()
{
var result = new FnvHash();
result.HashCode = Offset;
return result;
}
/// <summary>
/// Adds the specified byte to the hash.
/// </summary>
/// <param name="data">The byte to hash.</param>
public void Combine(byte data)
{
unchecked
{
HashCode ^= data;
HashCode *= Prime;
}
}
/// <summary>
/// Adds the specified integer to this hash, in little-endian order.
/// </summary>
/// <param name="data">The integer to hash.</param>
public void Combine(int data)
{
Combine(unchecked((byte)data));
Combine(unchecked((byte)(data >> 8)));
Combine(unchecked((byte)(data >> 16)));
Combine(unchecked((byte)(data >> 24)));
}
}
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