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[1000000]; 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[1000000]; , 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:
////// 设置当前VBO的数据。 /// /// /// /// public static void glBufferData(uint target, UnmanagedArrayBase data, uint usage) { GetDelegateFor()((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.
////// 金字塔的posotion array. /// 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[1]; GL.GenBuffers(1, ids); GL.BindBuffer(GL.GL_ARRAY_BUFFER, ids[0]); // 使用vec3作为泛型的非托管数组的参数 UnmanagedArraypositionArray = new UnmanagedArray (positions.Length); for (int i = 0; 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, 3, GL.GL_FLOAT, false, 0, IntPtr.Zero); GL.EnableVertexAttribArray(positionLocation); }
UnmanagedArray
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
1 ///2 /// 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。 3 /// 5 ///不能使用enum类型作为T。 4 ///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。 6 public class UnmanagedArray: UnmanagedArrayBase where T : struct 7 { 8 9 /// 10 ///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。 11 /// 12 /// 13 [MethodImpl(MethodImplOptions.Synchronized)] 14 public UnmanagedArray(int count) 15 : base(count, Marshal.SizeOf(typeof(T))) 16 { 17 } 18 19 ///20 /// 获取或设置索引为 22 /// 23 ///的元素。 21 /// 24 public T this[int index] 25 { 26 get 27 { 28 if (index < 0 || index >= this.Count) 29 throw new IndexOutOfRangeException("index of UnmanagedArray is out of range"); 30 31 var pItem = this.Header + (index * elementSize); 32 //var obj = Marshal.PtrToStructure(pItem, typeof(T)); 33 //T result = (T)obj; 34 T result = Marshal.PtrToStructure (pItem);// works in .net 4.5.1 35 return result; 36 } 37 set 38 { 39 if (index < 0 || index >= this.Count) 40 throw new IndexOutOfRangeException("index of UnmanagedArray is out of range"); 41 42 var pItem = this.Header + (index * elementSize); 43 //Marshal.StructureToPtr(value, pItem, true); 44 Marshal.StructureToPtr (value, pItem, true);// works in .net 4.5.1 45 } 46 } 47 48 /// 49 /// 按索引顺序依次获取各个元素。 50 /// 51 ///52 public IEnumerable GetElements() 53 { 54 if (!this.disposed) 55 { 56 for (int i = 0; i < this.Count; i++) 57 { 58 yield return this[i]; 59 } 60 } 61 } 62 } 63 64 /// 65 /// 非托管数组的基类。 66 /// 67 public abstract class UnmanagedArrayBase : IDisposable 68 { 69 70 ///71 /// 数组指针。 72 /// 73 public IntPtr Header { get; private set; } 74 75 ///76 /// 元素数目。 77 /// 78 public int Count { get; private set; } 79 80 ///81 /// 单个元素的字节数。 82 /// 83 protected int elementSize; 84 85 ///86 /// 申请到的字节数。（元素数目 * 单个元素的字节数）。 87 /// 88 public int ByteLength 89 { 90 get { return this.Count * this.elementSize; } 91 } 92 93 94 ///95 /// 非托管数组。 96 /// 97 /// 元素数目。 98 /// 单个元素的字节数。 99 [MethodImpl(MethodImplOptions.Synchronized)] 100 protected UnmanagedArrayBase(int elementCount, int elementSize) 101 { 102 this.Count = elementCount; 103 this.elementSize = elementSize; 104 105 int memSize = elementCount * elementSize; 106 this.Header = Marshal.AllocHGlobal(memSize); 107 108 allocatedArrays.Add(this); 109 } 110 111 private static readonly ListallocatedArrays = new List (); 112 113 /// 114 /// 立即释放所有 116 [MethodImpl(MethodImplOptions.Synchronized)] 117 public static void FreeAll() 118 { 119 foreach (var item in allocatedArrays) 120 { 121 item.Dispose(); 122 } 123 allocatedArrays.Clear(); 124 } 125 126 ~UnmanagedArrayBase() 127 { 128 Dispose(); 129 } 130 131 #region IDisposable Members 132 133 ///。 115 /// 134 /// Internal variable which checks if Dispose has already been called 135 /// 136 protected Boolean disposed; 137 138 ///139 /// Releases unmanaged and - optionally - managed resources 140 /// 141 ///true to release both managed and unmanaged resources;false to release only unmanaged resources. 142 protected void Dispose(Boolean disposing) 143 { 144 if (disposed) 145 { 146 return; 147 } 148 149 if (disposing) 150 { 151 //Managed cleanup code here, while managed refs still valid 152 } 153 //Unmanaged cleanup code here 154 IntPtr ptr = this.Header; 155 156 if (ptr != IntPtr.Zero) 157 { 158 this.Count = 0; 159 this.Header = IntPtr.Zero; 160 Marshal.FreeHGlobal(ptr); 161 } 162 163 disposed = true; 164 } 165 166 ///167 /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources. 168 /// 169 public void Dispose() 170 { 171 this.Dispose(true); 172 GC.SuppressFinalize(this); 173 } 174 175 #endregion 176 177 } UnmanagedArray
如何使用(How to use)
UnmanagedArray
Using UnamangedAray
internal static void TypicalScene()
{
const int count = 100;
// 测试float类型
var floatArray = new UnmanagedArray(count);
for (int i = 0; i < count; i++)
{
floatArray[i] = i;
}
for (int i = 0; i < count; i++)
{
var item = floatArray[i];
if (item != i)
{ throw new Exception(); }
}
// 测试int类型
var intArray = new UnmanagedArray(count);
for (int i = 0; i < count; i++)
{
intArray[i] = i;
}
for (int i = 0; i < count; i++)
{
var item = intArray[i];
if (item != i)
{ throw new Exception(); }
}
// 测试bool类型
var boolArray = new UnmanagedArray(count);
for (int i = 0; i < count; i++)
{
boolArray[i] = i % 2 == 0;
}
for (int i = 0; i < count; i++)
{
var item = boolArray[i];
if (item != (i % 2 == 0))
{ throw new Exception(); }
}
// 测试vec3类型
var vec3Array = new UnmanagedArray(count);
for (int i = 0; i < count; i++)
{
vec3Array[i] = new vec3(i * 3 + 0, i * 3 + 1, i * 3 + 2);
}
for (int i = 0; i < count; i++)
{
var item = vec3Array[i];
var old = new vec3(i * 3 + 0, i * 3 + 1, i * 3 + 2);
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
UnmanagedArrayHelper
由于很多时候需要申请和使用很大的UnmanagedArray
public static class UnmanagedArrayHelper
{
/////
///// 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
/////
///// (this UnmanagedArray array) where T : struct
//{
// var header = (void*)array.Header;
// return (T*)header;
//}
///
/// 获取非托管数组的第一个元素的地址。
///
///
///
/// 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。
///
///
///
如何使用
这个类型实现了3个扩展方法，可以获取UnmanagedArray
下面是一个例子。用unsafe的方式读写UnmanagedArray
public static void TypicalScene()
{
int length = 1000000;
UnmanagedArray array = new UnmanagedArray(length);
UnmanagedArray array2 = new UnmanagedArray(length);
long tick = DateTime.Now.Ticks;
for (int i = 0; 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 = 0;
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 = 0; 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 = 0;
for (vec3* ptr = header; ptr <= last/*or: ptr < tailAddress*/; ptr++)
{
*ptr = new vec3(i * 3 + 0, i * 3 + 1, i * 3 + 2);
i++;
}
i = 0;
for (vec3* ptr = header; ptr <= last/*or: ptr < tailAddress*/; ptr++, i++)
{
var item = *ptr;
var old = new vec3(i * 3 + 0, i * 3 + 1, i * 3 + 2);
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
1 ///2 /// Represents a 4x4 matrix. 3 /// 4 [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Size = 4 * 4 * 4)] 5 public struct mat4 6 { 7 ///8 /// Gets or sets the 10 ///column at the specified index. 9 /// 11 /// The 13 /// The column index. 14 ///column. 12 /// The column at index 15 public vec4 this[int column] 16 { 17 get { return cols[column]; } 18 set { cols[column] = value; } 19 } 20 21 ///. 22 /// Gets or sets the element at 24 ///and . 23 /// 25 /// The element at 27 /// The column index. 28 /// The row index. 29 ///and . 26 /// 30 /// The element at 32 public float this[int column, int row] 33 { 34 get { return cols[column][row]; } 35 set { cols[column][row] = value; } 36 } 37 38 ///and . 31 /// 39 /// The columms of the matrix. 40 /// 41 [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)] 42 private vec4[] cols; 43 } 44 45 ///46 /// Represents a four dimensional vector. 47 /// 48 [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Size = 4 * 4)] 49 public struct vec4 50 { 51 public float x; 52 public float y; 53 public float z; 54 public float w; 55 56 public float this[int index] 57 { 58 get 59 { 60 if (index == 0) return x; 61 else if (index == 1) return y; 62 else if (index == 2) return z; 63 else if (index == 3) return w; 64 else throw new Exception("Out of range."); 65 } 66 set 67 { 68 if (index == 0) x = value; 69 else if (index == 1) y = value; 70 else if (index == 2) z = value; 71 else if (index == 3) w = value; 72 else throw new Exception("Out of range."); 73 } 74 } 75 } mat4
注意：UnmanagedArray
下面是测试用例。
mat4 matrix = glm.scale(mat4.identity(), new vec3(2, 3, 4)); var size = Marshal.SizeOf(typeof(mat4)); size = Marshal.SizeOf(matrix); UnmanagedArrayarray = new UnmanagedArray (1); array[0] = matrix; mat4 newMatirx = array[0]; // 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。
总结
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