Click here to Skip to main content
Click here to Skip to main content
Articles » Languages » C# » General » Downloads
 
Add your own
alternative version

Tagged as

Lazy Alternatives - LazyAndWeak and BackgroundLoader

, 1 Dec 2011 CPOL
This article will present two alternatives to Lazy.
LazyAlternatives.zip
LazyAlternatives
LazyAlternatives.suo
LazyAlternativesSample
Properties
Settings.settings
Pfz
Caching
Collections
DataTypes
DynamicObjects
Internal
Extensions
Factoring
Pfz.csproj.user
Pfz.Phone.csproj.user
Pfz.ruleset
Pfz.Silverlight.csproj.user
Pfz.snk
Pfz.suo
PhoneSpecific
Properties
Remoting
Instructions
Internal
Serializers
Udp
Serialization
BinaryBuiltIn
Threading
Contexts
Disposers
Unsafe
using System;
using System.Linq;
using System.Collections.Generic;
using System.Collections;

namespace Pfz.Collections
{
	/// <summary>
	/// Struct that holds an immutable array.
	/// The methods that "change" the array will, in fact, create copies of it.
	/// </summary>
	public struct ImmutableArray<T>:
		IEquatable<ImmutableArray<T>>,
		IEnumerable<T>
	{
		private readonly T[] _array;
		
		/// <summary>
		/// Creates an immutable array that is a copy from the given collection.
		/// </summary>
		public ImmutableArray(ICollection<T> collection)
		{
			if (collection == null)
				throw new ArgumentNullException("collection");

			int count = collection.Count;
			if (count == 0)
			{
				_array = null;
				_hashCode = 0;
				return;
			}
			
			_array = new T[count];
			int index = -1;
			int hashCode = 0;
			foreach(T item in collection)
			{
				index++;
				
				_array[index] = item;
				if (item != null)
					hashCode ^= item.GetHashCode();
			}
			
			_hashCode = hashCode;
		}
		
		private ImmutableArray(T[] array, int hashCode)
		{
			_array = array;
			_hashCode = hashCode;
		}

		private readonly int _hashCode;
		/// <summary>
		/// Gets the hash-code of the array, which is the exclusive combination
		/// of all items hash-codes.
		/// </summary>
		public override int GetHashCode()
		{
			return _hashCode;
		}
		
		/// <summary>
		/// Compares this immutable array to another object.
		/// Returns false if the other object is not of the same type.
		/// </summary>
		public override bool Equals(object obj)
		{
			if (obj is ImmutableArray<T>)
			{
				var other = (ImmutableArray<T>)obj;
				return Equals(other);
			}
			
			return false;
		}

		/// <summary>
		/// Compares this immutable array to another one.
		/// </summary>
		public bool Equals(ImmutableArray<T> other)
		{
			if (other._hashCode != _hashCode)
				return false;
			
			if (other._array == _array)
				return true;
			
			if (_array == null || other._array == null)
				return false;
			
			if (other._array.Length != _array.Length)
				return false;
			
			return other._array.SequenceEqual(_array);
		}
		
		/// <summary>
		/// Creates a new immutable array, which all the items from this array and
		/// a new one at the end.
		/// </summary>
		public ImmutableArray<T> Add(T value)
		{
			T[] array;
			int hashCode;
			int valueHashCode = 0;
			if (value != null)
				valueHashCode = value.GetHashCode();
			
			if (_array == null)
			{
				array = new T[]{value};
				hashCode = valueHashCode;
			}
			else
			{
				int length = _array.Length;
				array = new T[length + 1];
				_array.CopyTo(array, 0);
				array[length] = value;
				hashCode = _hashCode ^ valueHashCode;
			}
			
			return new ImmutableArray<T>(array, hashCode);
		}
		
		/// <summary>
		/// Creates a copy of this immutable array, without the last item.
		/// Throws an IndexOutOfRangeException if this is an empty array.
		/// </summary>
		public ImmutableArray<T> RemoveLast()
		{
			if (_array == null)
				throw new ArgumentException("There are no more items to be removed.");
			
			int newLength = _array.Length - 1;
			
			if (newLength == 0)
				return new ImmutableArray<T>();
			
			T lastItem = _array[newLength];
			int lastHashCode = 0;
			if (lastItem != null)
				lastHashCode = lastItem.GetHashCode();
			
			T[] newArray = new T[newLength];
			Array.Copy(_array, newArray, newLength);
			int newHash = _hashCode ^ lastHashCode;
			return new ImmutableArray<T>(newArray, newHash);
		}
		
		/// <summary>
		/// Gets the length of this array.
		/// </summary>
		public int Length
		{
			get
			{
				if (_array == null)
					return 0;
				
				return _array.Length;
			}
		}
		
		/// <summary>
		/// Gets an item by the given index from this array.
		/// </summary>
		public T this[int index]
		{
			get
			{
				return _array[index];
			}
		}

		/// <summary>
		/// Returns the index of the first found value in this array.
		/// If the value does not exists, returns -1.
		/// </summary>
		public int IndexOf(T item)
		{
			if (_array == null)
				return -1;
			
			int count = _array.Length;
			for (int i=0; i<count; i++)
			{
				T otherItem = _array[i];
				
				if (object.Equals(otherItem, item))
					return i;
			}
			
			return -1;
		}

		/// <summary>
		/// Compares two ImmutableArrays for equality.
		/// </summary>
		public static bool operator == (ImmutableArray<T> a, ImmutableArray<T> b)
		{
			return a.Equals(b);
		}

		/// <summary>
		/// Compares two ImmutableArrays for inequality.
		/// </summary>
		public static bool operator != (ImmutableArray<T> a, ImmutableArray<T> b)
		{
			return !a.Equals(b);
		}

		#region IEnumerable<T> Members
			/// <summary>
			/// Gets an enumerator that will returns all items in this array.
			/// </summary>
			public IEnumerator<T> GetEnumerator()
			{
				if (_array == null)
					yield break;
					
				foreach(T value in _array)
					yield return value;
			}
		#endregion
		#region IEnumerable Members
			IEnumerator IEnumerable.GetEnumerator()
			{
				return GetEnumerator();
			}
		#endregion
	}
}

By viewing downloads associated with this article you agree to the Terms of Service and the article's licence.

If a file you wish to view isn't highlighted, and is a text file (not binary), please let us know and we'll add colourisation support for it.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

Paulo Zemek
Engineer Microsoft Corporation
United States United States
I started to program computers when I was 11 years old, as a hobbist, programming in AMOS Basic and Blitz Basic for Amiga.
At 12 I had my first try with assembler, but it was too difficult at the time. Then, in the same year, I learned C and, after learning C, I was finally able to learn assembler (for Motorola 680x0).
Not sure, but probably between 12 and 13, I started to learn C++. I always programmed "in an object oriented way", but using function pointers instead of virtual methods.
 
At 15 I started to learn Pascal at school and to use Delphi. At 16 I started my first internship (using Delphi). At 18 I started to work professionally using C++ and since then I've developed my programming skills as a professional developer in C++ and C#, generally creating libraries that help other developers do they work easier, faster and with less errors.
 
Now I just started working as a Senior Software Engineer at Microsoft.
 
Want more info or simply want to contact me?
Take a look at: http://paulozemek.azurewebsites.net/
Or e-mail me at: paulozemek@outlook.com
 
Codeproject MVP 2012
Microsoft MVP 2013-2014

| Advertise | Privacy | Terms of Use | Mobile
Web02 | 2.8.1411023.1 | Last Updated 1 Dec 2011
Article Copyright 2011 by Paulo Zemek
Everything else Copyright © CodeProject, 1999-2014
Layout: fixed | fluid