/src/ZebraFlickr/Core/ByteArrayComparer.cs

#region License



// Copyright (c) 2012 Gareth Lennox (garethl@dwakn.com)

// All rights reserved.

// 

// Redistribution and use in source and binary forms, with or without modification,

// are permitted provided that the following conditions are met:

// 

//     * Redistributions of source code must retain the above copyright notice,

//       this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above copyright notice,

//       this list of conditions and the following disclaimer in the documentation

//       and/or other materials provided with the distribution.

//     * Neither the name of Gareth Lennox nor the names of its

//       contributors may be used to endorse or promote products derived from this

//       software without specific prior written permission.

//  

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE

// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER

// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,

// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.



#endregion



using System;

using System.Collections.Generic;



namespace ZebraFlickr.Core

{

	/// <summary>

	/// Byte array equality comparer

	/// </summary>

	public class ByteArrayComparer : IEqualityComparer<byte[]>, IComparer<byte[]>

	{

		private static readonly ByteArrayComparer _instance = new ByteArrayComparer();



		public static ByteArrayComparer Instance

		{

			get { return _instance; }

		}



		#region IComparer<byte[]> Members



		/// <summary>

		/// Compares two objects and returns a value indicating whether one is less than, equal to, or greater than the other.

		/// </summary>

		/// <returns>

		/// Less than zero <paramref name="x"/> is less than <paramref name="y"/>.

		/// Zero <paramref name="x"/> equals <paramref name="y"/>.

		/// Greater than zero <paramref name="x"/> is greater than <paramref name="y"/>.

		/// </returns>

		/// <param name="x">The first object to compare.</param>

		/// <param name="y">The second object to compare.</param>

		public int Compare(byte[] x, byte[] y)

		{

			for (int i = 0; i < x.Length && i < y.Length; ++i)

			{

				int c = x[i] - y[i];

				if (c != 0)

					return c;

			}



			if (x.Length < y.Length)

				return -1;



			if (x.Length > y.Length)

				return 1;



			return 0;

		}



		#endregion



		#region IEqualityComparer<byte[]> Members



		/// <summary>

		/// Determines whether the specified objects are equal.

		/// </summary>

		/// <returns>

		/// true if the specified objects are equal; otherwise, false.

		/// </returns>

		/// <param name="x">The first objectto compare.</param>

		/// <param name="y">The second object to compare.</param>

		public bool Equals(byte[] x, byte[] y)

		{

			if (x == null || y == null || x.Length != y.Length)

				return false;



			for (var i = 0; i < x.Length; i++)

			{

				if (x[i] != y[i])

					return false;

			}



			return true;

		}



		/// <summary>

		/// Returns a hash code for the specified object.

		/// </summary>

		/// <returns>

		/// A hash code for the specified object.

		/// </returns>

		/// <param name="obj">The <see cref="T:System.Object"/> for which a hash code is to be returned.</param>

		/// <exception cref="T:System.ArgumentNullException">The type of <paramref name="obj"/> is a reference type and <paramref name="obj"/> is null.</exception>

		public int GetHashCode(byte[] obj)

		{

			unchecked

			{

				const int p = 16777619;

				var hash = (int) 2166136261;



				for (var i = 0; i < obj.Length; i++)

					hash = (hash ^ obj[i])*p;



				hash += hash << 13;

				hash ^= hash >> 7;

				hash += hash << 3;

				hash ^= hash >> 17;

				hash += hash << 5;

				return hash;

			}

		}



		#endregion



		public int Compare(byte[] x, int offset, int count, byte[] y)

		{

			if (count != y.Length)

				throw new ArgumentOutOfRangeException("Count does not match second argument's length");



			var end = offset + count;

			for (int i = offset; i < end; ++i)

			{

				int c = x[i] - y[i - offset];

				if (c != 0)

					return c;

			}



			return 0;

		}

	}

}