C#+无unsafe的非托管大数组(large unmanaged array in c# without 'unsafe' keyword)

C#+无unsafe的非托管大数组(large unmanaged array in c# without 'unsafe' keyword)

+BIT祝威+悄悄在此留下版了个权的信息说：

C#申请一个大数组(Use a large array in C#)

在C#里，有时候我需要能够申请一个很大的数组、使用之、然后立即释放其占用的内存。

Sometimes I need to allocate a large array, use it and then release its memory space immediately.

由于在C#里提供的 int[] array = new int[]; 这样的数组，其内存释放很难由程序员完全控制，在申请一个大数组后，程序可能会变得很慢。

If I use something like  int[] array = new int[]; , it will be difficult to release its memory space by programmer and the app probably runs slower and slower.

特别是在C#+OpenGL编程中，我在使用VAO/VBO时十分需要设计一个非托管的数组，比如在glBufferData时我希望可以使用下面的glBufferData：

Specially in C#+OpenGL routines when I'm using VAO/VBO, I need an unmanaged array for glBufferData:

         /// <summary>
         /// 设置当前VBO的数据。
         /// </summary>
         /// <param name="target"></param>
         /// <param name="data"></param>
         /// <param name="usage"></param>
         public static void glBufferData(uint target, UnmanagedArrayBase data, uint usage)
         {
             GetDelegateFor<glBufferData>()((uint)target,
                 data.ByteLength, // 使用非托管数组
                 data.Header, // 使用非托管数组
                 (uint)usage);
         }
         // ...
         // glBufferData的声明
         private delegate void glBufferData(uint target, int size, IntPtr data, uint usage);

而在指定VBO的数据时，可能是float、vec3等等类型：

And the content in VBO can be float, vec3 and any other structs.

         /// <summary>
         /// 金字塔的posotion array.
         /// </summary>
         static vec3[] positions = new vec3[]
         {
             new vec3(0.0f, 1.0f, 0.0f),
             new vec3(-1.0f, -1.0f, 1.0f),
             // ...
             new vec3(-1.0f, -1.0f, 1.0f),
         };
 //  Create a vertex buffer for the vertex data.
             {
                 uint[] ids = new uint[];
                 GL.GenBuffers(, ids);
                 GL.BindBuffer(GL.GL_ARRAY_BUFFER, ids[]);
                 // 使用vec3作为泛型的非托管数组的参数
                 UnmanagedArray<vec3> positionArray = new UnmanagedArray<vec3>(positions.Length);
                 for (int i = ; i < positions.Length; i++)
                 {
                     // 使用this[i]这样的索引方式来读写非托管数组的元素
                     positionArray[i] = positions[i];
                 }
                 GL.BufferData(BufferDataTarget.ArrayBuffer, positionArray, BufferDataUsage.StaticDraw);
                 GL.VertexAttribPointer(positionLocation, , GL.GL_FLOAT, false, , IntPtr.Zero);
                 GL.EnableVertexAttribArray(positionLocation);
             }

+BIT祝威+悄悄在此留下版了个权的信息说：

UnmanagedArray<T>

所以我设计了这样一个非托管的数组类型：无unsafe，可接收任何struct类型作为泛型参数，可随时释放内存。

So I designed this UnmangedArray<T> : no 'unsafe' keyword, takes any struct as generic parameter, can be released anytime you want.

     /// <summary>
     /// 元素类型为sbyte, byte, char, short, ushort, int, uint, long, ulong, float, double, decimal, bool或其它struct的非托管数组。
     /// <para>不能使用enum类型作为T。</para>
     /// </summary>
     /// <typeparam name="T">sbyte, byte, char, short, ushort, int, uint, long, ulong, float, double, decimal, bool或其它struct, 不能使用enum类型作为T。</typeparam>
     public class UnmanagedArray<T> : UnmanagedArrayBase where T : struct
     {

         /// <summary>
         ///元素类型为sbyte, byte, char, short, ushort, int, uint, long, ulong, float, double, decimal, bool或其它struct的非托管数组。
         /// </summary>
         /// <param name="count"></param>
         [MethodImpl(MethodImplOptions.Synchronized)]
         public UnmanagedArray(int count)
             : base(count, Marshal.SizeOf(typeof(T)))
         {
         }

         /// <summary>
         /// 获取或设置索引为<paramref name="index"/>的元素。
         /// </summary>
         /// <param name="index"></param>
         /// <returns></returns>
         public T this[int index]
         {
             get
             {
                 if (index <  || index >= this.Count)
                     throw new IndexOutOfRangeException("index of UnmanagedArray is out of range");

                 var pItem = this.Header + (index * elementSize);
                 //var obj = Marshal.PtrToStructure(pItem, typeof(T));
                 //T result = (T)obj;
                 T result = Marshal.PtrToStructure<T>(pItem);// works in .net 4.5.1
                 return result;
             }
             set
             {
                 if (index <  || index >= this.Count)
                     throw new IndexOutOfRangeException("index of UnmanagedArray is out of range");

                 var pItem = this.Header + (index * elementSize);
                 //Marshal.StructureToPtr(value, pItem, true);
                 Marshal.StructureToPtr<T>(value, pItem, true);// works in .net 4.5.1
             }
         }

         /// <summary>
         /// 按索引顺序依次获取各个元素。
         /// </summary>
         /// <returns></returns>
         public IEnumerable<T> GetElements()
         {
             if (!this.disposed)
             {
                 for (int i = ; i < this.Count; i++)
                 {
                     yield return this[i];
                 }
             }
         }
     }

     /// <summary>
     /// 非托管数组的基类。
     /// </summary>
     public abstract class UnmanagedArrayBase : IDisposable
     {

         /// <summary>
         /// 数组指针。
         /// </summary>
         public IntPtr Header { get; private set; }

         /// <summary>
         /// 元素数目。
         /// </summary>
         public int Count { get; private set; }

         /// <summary>
         /// 单个元素的字节数。
         /// </summary>
         protected int elementSize;

         /// <summary>
         /// 申请到的字节数。（元素数目 * 单个元素的字节数）。
         /// </summary>
         public int ByteLength
         {
             get { return this.Count * this.elementSize; }
         }

         /// <summary>
         /// 非托管数组。
         /// </summary>
         /// <param name="elementCount">元素数目。</param>
         /// <param name="elementSize">单个元素的字节数。</param>
         [MethodImpl(MethodImplOptions.Synchronized)]
         protected UnmanagedArrayBase(int elementCount, int elementSize)
         {
             this.Count = elementCount;
             this.elementSize = elementSize;

             int memSize = elementCount * elementSize;
             this.Header = Marshal.AllocHGlobal(memSize);

             allocatedArrays.Add(this);
         }

         private static readonly List<IDisposable> allocatedArrays = new List<IDisposable>();

         /// <summary>
         /// 立即释放所有<see cref="UnmanagedArray"/>。
         /// </summary>
         [MethodImpl(MethodImplOptions.Synchronized)]
         public static void FreeAll()
         {
             foreach (var item in allocatedArrays)
             {
                 item.Dispose();
             }
             allocatedArrays.Clear();
         }

         ~UnmanagedArrayBase()
         {
             Dispose();
         }

         #region IDisposable Members

         /// <summary>
         /// Internal variable which checks if Dispose has already been called
         /// </summary>
         protected Boolean disposed;

         /// <summary>
         /// Releases unmanaged and - optionally - managed resources
         /// </summary>
         /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
         protected void Dispose(Boolean disposing)
         {
             if (disposed)
             {
                 return;
             }

             if (disposing)
             {
                 //Managed cleanup code here, while managed refs still valid
             }
             //Unmanaged cleanup code here
             IntPtr ptr = this.Header;

             if (ptr != IntPtr.Zero)
             {
                 this.Count = ;
                 this.Header = IntPtr.Zero;
                 Marshal.FreeHGlobal(ptr);
             }

             disposed = true;
         }

         /// <summary>
         /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
         /// </summary>
         public void Dispose()
         {
             this.Dispose(true);
             GC.SuppressFinalize(this);
         }

         #endregion

     }

UnmanagedArray

+BIT祝威+悄悄在此留下版了个权的信息说：

如何使用(How to use)

UnmanagedArray<T>使用方式十分简单，就像一个普通的数组一样：

Using UnamangedAray<T> is just like a normal array(int[], vec3[], etc.):

         internal static void TypicalScene()
         {
             const int count = ;

             // 测试float类型
             var floatArray = new UnmanagedArray<float>(count);
             for (int i = ; i < count; i++)
             {
                 floatArray[i] = i;
             }
             for (int i = ; i < count; i++)
             {
                 var item = floatArray[i];
                 if (item != i)
                 { throw new Exception(); }
             }

             // 测试int类型
             var intArray = new UnmanagedArray<int>(count);
             for (int i = ; i < count; i++)
             {
                 intArray[i] = i;
             }
             for (int i = ; i < count; i++)
             {
                 var item = intArray[i];
                 if (item != i)
                 { throw new Exception(); }
             }

             // 测试bool类型
             var boolArray = new UnmanagedArray<bool>(count);
             for (int i = ; i < count; i++)
             {
                 boolArray[i] = i %  == ;
             }
             for (int i = ; i < count; i++)
             {
                 var item = boolArray[i];
                 if (item != (i %  == ))
                 { throw new Exception(); }
             }

             // 测试vec3类型
             var vec3Array = new UnmanagedArray<vec3>(count);
             for (int i = ; i < count; i++)
             {
                 vec3Array[i] = new vec3(i *  + , i *  + , i *  + );
             }
             for (int i = ; i < count; i++)
             {
                 var item = vec3Array[i];
                 var old = new vec3(i *  + , i *  + , i *  + );
                 if (item.x != old.x || item.y != old.y || item.z != old.z)
                 { throw new Exception(); }
             }

             // 测试foreach
             foreach (var item in vec3Array.GetElements())
             {
                 Console.WriteLine(item);
             }

             // 释放此数组占用的内存，这之后就不能再使用vec3Array了。
             vec3Array.Dispose();

             // 立即释放所有非托管数组占用的内存，这之后就不能再使用上面申请的数组了。
             UnmanagedArrayBase.FreeAll();
         }

快速读写UnmanagedArray<T>

UnmanagedArrayHelper

由于很多时候需要申请和使用很大的UnmanagedArray<T>，直接使用this[index]索引方式速度会偏慢，所以我添加了几个辅助方法，专门解决快速读写UnmanagedArray<T>的问题。

     public static class UnmanagedArrayHelper
     {
         ///// <summary>
         ///// 错误    1    无法获取托管类型(“T”)的地址和大小，或无法声明指向它的指针
         ///// </summary>
         ///// <typeparam name="T"></typeparam>
         ///// <param name="array"></param>
         ///// <returns></returns>
         //public static unsafe T* FirstElement<T>(this UnmanagedArray<T> array) where T : struct
         //{
         //    var header = (void*)array.Header;
         //    return (T*)header;
         //}

         /// <summary>
         /// 获取非托管数组的第一个元素的地址。
         /// </summary>
         /// <param name="array"></param>
         /// <returns></returns>
         public static unsafe void* FirstElement(this UnmanagedArrayBase array)
         {
             var header = (void*)array.Header;

             return header;
         }

         public static unsafe void* LastElement(this UnmanagedArrayBase array)
         {
             var last = (void*)(array.Header + (array.ByteLength - array.ByteLength / array.Length));

             return last;
         }

         /// <summary>
         /// 获取非托管数组的最后一个元素的地址再向后一个单位的地址。
         /// </summary>
         /// <param name="array"></param>
         /// <returns></returns>
         public static unsafe void* TailAddress(this UnmanagedArrayBase array)
         {
             var tail = (void*)(array.Header + array.ByteLength);

             return tail;
         }
     }

如何使用

这个类型实现了3个扩展方法，可以获取UnmanagedArray<T>的第一个元素的位置、最后一个元素的位置、最后一个元素+1的位置。用这种unsafe的方法可以实现C语言一样的读写速度。

下面是一个例子。用unsafe的方式读写UnmanagedArray<T>，速度比this[index]方式快10到70倍。

         public static void TypicalScene()
         {
             int length = ;
             UnmanagedArray<int> array = new UnmanagedArray<int>(length);
             UnmanagedArray<int> array2 = new UnmanagedArray<int>(length);

             long tick = DateTime.Now.Ticks;
             for (int i = ; i < length; i++)
             {
                 array[i] = i;
             }
             long totalTicks = DateTime.Now.Ticks - tick;

             tick = DateTime.Now.Ticks;
             unsafe
             {
                 int* header = (int*)array2.FirstElement();
                 int* last = (int*)array2.LastElement();
                 int* tailAddress = (int*)array2.TailAddress();
                 int value = ;
                 for (int* ptr = header; ptr <= last/*or: ptr < tailAddress*/; ptr++)
                 {
                     *ptr = value++;
                 }
             }
             long totalTicks2 = DateTime.Now.Ticks - tick;
             Console.WriteLine("ticks: {0}, {1}", totalTicks, totalTicks2);// unsafe method works faster.

             for (int i = ; i < length; i++)
             {
                 if (array[i] != i)
                 {
                     Console.WriteLine("something wrong here");
                 }
                 if (array2[i] != i)
                 {
                     Console.WriteLine("something wrong here");
                 }
             }

             array.Dispose();
             array2.Dispose();
         }

                 unsafe
                 {
                     vec3* header = (vec3*)vec3Array.FirstElement();
                     vec3* last = (vec3*)vec3Array.LastElement();
                     vec3* tailAddress = (vec3*)vec3Array.TailAddress();
                     int i = ;
                     for (vec3* ptr = header; ptr <= last/*or: ptr < tailAddress*/; ptr++)
                     {
                         *ptr = new vec3(i *  + , i *  + , i *  + );
                         i++;
                     }
                     i = ;
                     for (vec3* ptr = header; ptr <= last/*or: ptr < tailAddress*/; ptr++, i++)
                     {
                         var item = *ptr;
                         var old = new vec3(i *  + , i *  + , i *  + );
                         if (item.x != old.x || item.y != old.y || item.z != old.z)
                         { throw new Exception(); }
                     }
                 }

2015-08-25

用StructLayout和MarshalAs支持复杂的struct

在OpenGL中我需要用UnmanagedArray<mat4>，其中mat4定义如下：

     /// <summary>
     /// Represents a 4x4 matrix.
     /// </summary>
     [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Size =  *  * )]
     public struct mat4
     {
         /// <summary>
         /// Gets or sets the <see cref="vec4"/> column at the specified index.
         /// </summary>
         /// <value>
         /// The <see cref="vec4"/> column.
         /// </value>
         /// <param name="column">The column index.</param>
         /// <returns>The column at index <paramref name="column"/>.</returns>
         public vec4 this[int column]
         {
             get { return cols[column]; }
             set { cols[column] = value; }
         }

         /// <summary>
         /// Gets or sets the element at <paramref name="column"/> and <paramref name="row"/>.
         /// </summary>
         /// <value>
         /// The element at <paramref name="column"/> and <paramref name="row"/>.
         /// </value>
         /// <param name="column">The column index.</param>
         /// <param name="row">The row index.</param>
         /// <returns>
         /// The element at <paramref name="column"/> and <paramref name="row"/>.
         /// </returns>
         public float this[int column, int row]
         {
             get { return cols[column][row]; }
             set { cols[column][row] = value; }
         }

         /// <summary>
         /// The columms of the matrix.
         /// </summary>
         [MarshalAs(UnmanagedType.ByValArray, SizeConst = )]
         private vec4[] cols;
     }

     /// <summary>
     /// Represents a four dimensional vector.
     /// </summary>
     [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Size =  * )]
     public struct vec4
     {
         public float x;
         public float y;
         public float z;
         public float w;

         public float this[int index]
         {
             get
             {
                 if (index == ) return x;
                 else if (index == ) return y;
                 else if (index == ) return z;
                 else if (index == ) return w;
                 else throw new Exception("Out of range.");
             }
             set
             {
                 if (index == ) x = value;
                 else if (index == ) y = value;
                 else if (index == ) z = value;
                 else if (index == ) w = value;
                 else throw new Exception("Out of range.");
             }
         }
     }

mat4

注意：UnmanagedArray<T>支持的struct，T的大小必须是确定的。所以在mat4里我们用 [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Size = * * )] 指定mat4的大小为4个 vec4 * 4个 float * 4个字节(每个float) = 64字节，并且在 private vec4[] cols; 上用 [MarshalAs(UnmanagedType.ByValArray, SizeConst = )] 规定了cols的元素数必须是4。之后在 vec4 上的 [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Size = * )] 不写也可以，因为vec4只有4个简单的float字段，不含复杂类型。

下面是测试用例。

             mat4 matrix = glm.scale(mat4.identity(), new vec3(, , ));

             var size = Marshal.SizeOf(typeof(mat4));
             size = Marshal.SizeOf(matrix);

             UnmanagedArray<mat4> array = new UnmanagedArray<mat4>();
             array[] = matrix;

             mat4 newMatirx = array[]; // newMatrix should be equal to matrix

             array.Dispose();

如果matrix和newMatrix相等，就说明上述Attribute配置正确了。