namespace ICSharpCode.SharpZipLib.Checksum
{
	/// <summary>
	/// Interface to compute a data checksum used by checked input/output streams.
	/// A data checksum can be updated by one byte or with a byte array. After each
	/// update the value of the current checksum can be returned by calling
	/// <code>getValue</code>. The complete checksum object can also be reset
	/// so it can be used again with new data.
	/// </summary>
	public interface IChecksum
	{
		/// <summary>
		/// Resets the data checksum as if no update was ever called.
		/// </summary>
		void Reset();

		/// <summary>
		/// Returns the data checksum computed so far.
		/// </summary>
		long Value {
			get;
		}

		/// <summary>
		/// Adds one byte to the data checksum.
		/// </summary>
		/// <param name = "bval">
		/// the data value to add. The high byte of the int is ignored.
		/// </param>
		void Update(int bval);

		/// <summary>
		/// Updates the data checksum with the bytes taken from the array.
		/// </summary>
		/// <param name="buffer">
		/// buffer an array of bytes
		/// </param>
		void Update(byte[] buffer);

		/// <summary>
		/// Adds the byte array to the data checksum.
		/// </summary>
		/// <param name = "buffer">
		/// The buffer which contains the data
		/// </param>
		/// <param name = "offset">
		/// The offset in the buffer where the data starts
		/// </param>
		/// <param name = "count">
		/// the number of data bytes to add.
		/// </param>
		void Update(byte[] buffer, int offset, int count);
	}
}