我已经使用C＃来解决以下要求.. - 创建一个可以快速接收大量数据的应用程序 - 您必须能够分析收到的数据，同时传入更多数据。 - 使用尽可能少的CPU和磁盘
我对算法的想法是......
SIZE = 10MB
Create a mmf with the size of SIZE
On data recived:
if data can't fit mmf: increase mmf.size by SIZE
write the data to mmf
- >使用之前的“房间/空间”时，光盘上的大小会以10MB的块数增加。
如何在C＃中“通过SIZE增加mmf.size”？我已经找到了许多关于创建mmfs和视图的简单示例，但唯一的地方（link）我看到了实际增加mmfs区域的代码使用了无法编译的代码。任何帮助都将受到极大的关注。
编辑这会导致异常：
private void IncreaseFileSize()
{
int theNewMax = this.currentMax + INCREMENT_SIZE;
this.currentMax = theNewMax;
this.mmf.Dispose();
this.mmf = MemoryMappedFile.CreateFromFile(this.FileName, FileMode.Create, "MyMMF", theNewMax);
this.view = mmf.CreateViewAccessor(0, theNewMax);
}
抛出此异常：进程无法访问文件'C：\ Users \ moberg \ Documents \ data.bin'，因为它正由另一个进程使用。
Once you map a file in memory, you cannot increase its size.这是内存映射文件的已知限制。
...您必须计算或估计已完成文件的大小，因为文件映射对象的大小是静态的;一旦创建，它们的大小就不能增加或减少。
一种策略是使用存储在non-persisted memory mapped files of a given size中的块，比如说1GB或2GB。你可以通过你自己设计的顶级ViewAccessor管理这些（可能是你需要从MemoryMappedViewAccessor那里获得的基本方法）。
编辑：或者您可以创建一个您希望使用的最大大小的非持久内存映射文件（比如启动8GB，在应用程序启动时使用参数调整它）并检索每个逻辑块的MemoryMappedViewAccessor。在请求每个视图之前，非持久文件不会使用物理资源。
好吧，你可以!!
这是我对可增长内存映射文件的实现：
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.IO;
using System.IO.MemoryMappedFiles;
namespace MmbpTree
{
public unsafe sealed class GrowableMemoryMappedFile : IDisposable
{
private const int AllocationGranularity = 64 * 1024;
private class MemoryMappedArea
{
public MemoryMappedFile Mmf;
public byte* Address;
public long Size;
}
private FileStream fs;
private List<MemoryMappedArea> areas = new List<MemoryMappedArea>();
private long[] offsets;
private byte*[] addresses;
public long Length
{
get {
CheckDisposed();
return fs.Length;
}
}
public GrowableMemoryMappedFile(string filePath, long initialFileSize)
{
if (initialFileSize <= 0 || initialFileSize % AllocationGranularity != 0)
{
throw new ArgumentException("The initial file size must be a multiple of 64Kb and grater than zero");
}
bool existingFile = File.Exists(filePath);
fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);
if (existingFile)
{
if (fs.Length <= 0 || fs.Length % AllocationGranularity != 0)
{
throw new ArgumentException("Invalid file. Its lenght must be a multiple of 64Kb and greater than zero");
}
}
else
{
fs.SetLength(initialFileSize);
}
CreateFirstArea();
}
private void CreateFirstArea()
{
var mmf = MemoryMappedFile.CreateFromFile(fs, null, fs.Length, MemoryMappedFileAccess.ReadWrite, null, HandleInheritability.None, true);
var address = Win32FileMapping.MapViewOfFileEx(mmf.SafeMemoryMappedFileHandle.DangerousGetHandle(),
Win32FileMapping.FileMapAccess.Read | Win32FileMapping.FileMapAccess.Write,
0, 0, new UIntPtr((ulong) fs.Length), null);
if (address == null) throw new Win32Exception();
var area = new MemoryMappedArea
{
Address = address,
Mmf = mmf,
Size = fs.Length
};
areas.Add(area);
addresses = new byte*[] { address };
offsets = new long[] { 0 };
}
public void Grow(long bytesToGrow)
{
CheckDisposed();
if (bytesToGrow <= 0 || bytesToGrow % AllocationGranularity != 0) {
throw new ArgumentException("The growth must be a multiple of 64Kb and greater than zero");
}
long offset = fs.Length;
fs.SetLength(fs.Length + bytesToGrow);
var mmf = MemoryMappedFile.CreateFromFile(fs, null, fs.Length, MemoryMappedFileAccess.ReadWrite, null, HandleInheritability.None, true);
uint* offsetPointer = (uint*)&offset;
var lastArea = areas[areas.Count - 1];
byte* desiredAddress = lastArea.Address + lastArea.Size;
var address = Win32FileMapping.MapViewOfFileEx(mmf.SafeMemoryMappedFileHandle.DangerousGetHandle(),
Win32FileMapping.FileMapAccess.Read | Win32FileMapping.FileMapAccess.Write,
offsetPointer[1], offsetPointer[0], new UIntPtr((ulong)bytesToGrow), desiredAddress);
if (address == null) {
address = Win32FileMapping.MapViewOfFileEx(mmf.SafeMemoryMappedFileHandle.DangerousGetHandle(),
Win32FileMapping.FileMapAccess.Read | Win32FileMapping.FileMapAccess.Write,
offsetPointer[1], offsetPointer[0], new UIntPtr((ulong)bytesToGrow), null);
}
if (address == null) throw new Win32Exception();
var area = new MemoryMappedArea {
Address = address,
Mmf = mmf,
Size = bytesToGrow
};
areas.Add(area);
if (desiredAddress != address) {
offsets = offsets.Add(offset);
addresses = addresses.Add(address);
}
}
public byte* GetPointer(long offset)
{
CheckDisposed();
int i = offsets.Length;
if (i <= 128) // linear search is more efficient for small arrays. Experiments show 140 as the cutpoint on x64 and 100 on x86.
{
while (--i > 0 && offsets[i] > offset);
}
else // binary search is more efficient for large arrays
{
i = Array.BinarySearch<long>(offsets, offset);
if (i < 0) i = ~i - 1;
}
return addresses[i] + offset - offsets[i];
}
private bool isDisposed;
public void Dispose()
{
if (isDisposed) return;
isDisposed = true;
foreach (var a in this.areas)
{
Win32FileMapping.UnmapViewOfFile(a.Address);
a.Mmf.Dispose();
}
fs.Dispose();
areas.Clear();
}
private void CheckDisposed()
{
if (isDisposed) throw new ObjectDisposedException(this.GetType().Name);
}
public void Flush()
{
CheckDisposed();
foreach (var area in areas)
{
if (!Win32FileMapping.FlushViewOfFile(area.Address, new IntPtr(area.Size))) {
throw new Win32Exception();
}
}
fs.Flush(true);
}
}
}
这是Win32FileMapping类：
using System;
using System.Runtime.InteropServices;
namespace MmbpTree
{
public static unsafe class Win32FileMapping
{
[Flags]
public enum FileMapAccess : uint
{
Copy = 0x01,
Write = 0x02,
Read = 0x04,
AllAccess = 0x08,
Execute = 0x20,
}
[DllImport("kernel32.dll", SetLastError = true)]
public static extern byte* MapViewOfFileEx(IntPtr mappingHandle,
FileMapAccess access,
uint offsetHigh,
uint offsetLow,
UIntPtr bytesToMap,
byte* desiredAddress);
[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool UnmapViewOfFile(byte* address);
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool FlushViewOfFile(byte* address, IntPtr bytesToFlush);
}
}
在这里你有Extensions类：
using System;
namespace MmbpTree
{
public static class Extensions
{
public static T[] Add<T>(this T[] array, T element)
{
var result = new T[array.Length + 1];
Array.Copy(array, result, array.Length);
result[array.Length] = element;
return result;
}
public static unsafe byte*[] Add(this byte*[] array, byte* element)
{
var result = new byte*[array.Length + 1];
Array.Copy(array, result, array.Length);
result[array.Length] = element;
return result;
}
}
}
如你所见，我采取了不安全的方法。这是获得内存映射文件的性能优势的唯一方法。
要使用它，您需要考虑以下概念：
例如，您可能希望使用页面大小为1Mb，文件增长为64Mb，初始大小为1Gb。您可以通过调用GetPointer获取指向页面的指针，使用Grow生成文件并使用Flush刷新文件：
const int InitialSize = 1024 * 1024 * 1024;
const int FileGrowth = 64 * 1024 * 1024;
const int PageSize = 1024 * 1024;
using (var gmmf = new GrowableMemoryMappedFile("mmf.bin", InitialSize))
{
var pageNumber = 32;
var pointer = gmmf.GetPointer(pageNumber * PageSize);
// you can read the page content:
byte firstPageByte = pointer[0];
byte lastPageByte = pointer[PageSize - 1];
// or write it
pointer[0] = 3;
pointer[PageSize -1] = 43;
/* allocate more pages when needed */
gmmf.Grow(FileGrowth);
/* use new allocated pages */
/* flushing the file writes to the underlying file */
gmmf.Flush();
}
代码无法编译的原因是因为它使用了不存在的重载。要么自己创建一个文件流并将其传递给正确的重载（假设2000将是你的新大小）：
FileStream fs = new FileStream("C:\MyFile.dat", FileMode.Open);
MemoryMappedFile mmf = MemoryMappedFile.CreateFromFile(fs, "someName", 2000,
MemoryMappedFileAccess.ReadWriteExecute, null, HandleInheritablity.None, false);
或者使用此重载来跳过filstream创建：
MemoryMappedFile mmf = MemoryMappedFile.CreateFromFile("C:\MyFile.dat",
FileMode.Open, "someName", 2000);
使用带有MemoryMappedFile.CreateFromFile参数的capacity的重载。
我发现关闭并重新创建具有相同名称但新尺寸的mmf适用于所有意图和目的
using (var mmf = MemoryMappedFile.CreateOrOpen(SenderMapName, 1))
{
mmf.SafeMemoryMappedFileHandle.Close();
}
using (var sender = MemoryMappedFile.CreateNew(SenderMapName, bytes.Length))
而且它真的很快。