MipMapCount.cs

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// Copyright (c) 2014 Silicon Studio Corp. (http://siliconstudio.co.jp)
// This file is distributed under GPL v3. See LICENSE.md for details.
//
// Copyright (c) 2010-2012 SharpDX - Alexandre Mutel
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

using System;
using System.Runtime.InteropServices;

namespace SiliconStudio.Paradox.Graphics
{
    /// <summary>
    /// A simple wrapper to specify number of mipmaps.
    ///  Set to true to specify all mipmaps or sets an integer value >= 1
    /// to specify the exact number of mipmaps.
    /// </summary>
    /// <remarks>
    /// This structure use implicit conversion:
    /// <ul>
    /// <li>Set to <c>true</c> to specify all mipmaps.</li>
    /// <li>Set to <c>false</c> to specify a single mipmap.</li>
    /// <li>Set to an integer value >=1 to specify an exact count of mipmaps.</li>
    /// </ul>
    /// </remarks>
    [StructLayout(LayoutKind.Sequential, Size = 4)]
    public struct MipMapCount : IEquatable<MipMapCount>
    {
        /// <summary>
        /// Automatic mipmap level based on texture size.
        /// </summary>
        public readonly static MipMapCount Auto = new MipMapCount(true);

        /// <summary>
        /// Initializes a new instance of the <see cref="MipMapCount" /> struct.
        /// </summary>
        /// <param name="allMipMaps">if set to <c>true</c> generates all mip maps.</param>
        public MipMapCount(bool allMipMaps)
        {
            this.Count = allMipMaps ? 0 : 1;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="MipMapCount" /> struct.
        /// </summary>
        /// <param name="count">The count.</param>
        public MipMapCount(int count)
        {
            if (count < 0)
                throw new ArgumentException("mipCount must be >= 0");
            this.Count = count;
        }

        /// <summary>
        /// Number of mipmaps.
        /// </summary>
        /// <remarks>
        /// Zero(0) means generate all mipmaps. One(1) generates a single mipmap... etc.
        /// </remarks>
        public readonly int Count;

        public bool Equals(MipMapCount other)
        {
            return this.Count == other.Count;
        }

        public override bool Equals(object obj)
        {
            if (ReferenceEquals(null, obj))
                return false;
            return obj is MipMapCount && Equals((MipMapCount)obj);
        }

        public override int GetHashCode()
        {
            return this.Count;
        }

        public static bool operator ==(MipMapCount left, MipMapCount right)
        {
            return left.Equals(right);
        }

        public static bool operator !=(MipMapCount left, MipMapCount right)
        {
            return !left.Equals(right);
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="MipMapCount"/> to <see cref="bool"/>.
        /// </summary>
        /// <param name="mipMap">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator bool(MipMapCount mipMap)
        {
            return mipMap.Count == 0;
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="bool"/> to <see cref="MipMapCount"/>.
        /// </summary>
        /// <param name="mipMapAll">True to generate all mipmaps, false to use a single mipmap.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator MipMapCount(bool mipMapAll)
        {
            return new MipMapCount(mipMapAll);
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="MipMapCount"/> to <see cref="int"/>.
        /// </summary>
        /// <param name="mipMap">The value.</param>
        /// <returns>The count of mipmap (0 means all mipmaps).</returns>
        public static implicit operator int(MipMapCount mipMap)
        {
            return mipMap.Count;
        }

        /// <summary>
        /// Performs an explicit conversion from <see cref="int"/> to <see cref="MipMapCount"/>.
        /// </summary>
        /// <param name="mipMapCount">True to generate all mipmaps, false to use a single mipmap.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator MipMapCount(int mipMapCount)
        {
            return new MipMapCount(mipMapCount);
        }
    }
}