我能得到一个内存映射文件的路径？（.NET 4.0）(Can I get a path for

我想，一个non-.NET应用程序访问内存映射文件， 但这个应用程序不知道内存映射文件的存在 ，所以我需要的文件路径。有可能的？

Answer 1:

他们有一些样品这里。

编辑

我认为这将提供答案。基本上，这似乎还需要一些内存指针的内存映射文件，而不是文件系统路径。

Answer 2:

您可以使用GetMappedFileName功能，当它被映射到得到一个内存映射文件的路径。当然，这需要的是内存映射文件实际上是由一个物理文件的支持，但问题使得含糊什么情况到底是。做了一些第三方库的手你MemoryMappedFile，MemoryMappedViewAccessor或MemoryMappedViewStream，但你不知道它是否是由一个物理文件的支持？

这里是在一个怎么会从MemoryMappedFile得到的文件名的示例：

using Microsoft.Win32.SafeHandles;
using System;
using System.ComponentModel;
using System.Diagnostics;
using System.IO.MemoryMappedFiles;
using System.Runtime.InteropServices;
using System.Text;

namespace MMFilePathTest
{
    static class Program
    {
        private static MemoryMappedFile GetMappedPhysicalFile()
        {
            return MemoryMappedFile.CreateFromFile("test.bin", System.IO.FileMode.Create, null, 4096);
        }

        private static MemoryMappedFile GetMappedAnonymousMemory()
        {
            /* The documentation errounously claims that mapName must not be null. Actually anonymous
             * mappings are quite a normal thing on Windows, and is actually both safer and more secure
             * if you don't have a need for a name for them anyways.
             * (Reported as https://github.com/dotnet/docs/issues/5404)
             * Using a name here gives the exact same results (assuming the name isn't already in use). */
            return MemoryMappedFile.CreateNew(null, 4096);
        }

        /* This can be changed to kernel32.dll / K32GetMappedFileNameW if compatibility with Windows Server 2008 and
         * earlier is not needed, but it is not clear what the gain of doing so is, see the remarks about
         * PSAPI_VERSION at https://msdn.microsoft.com/en-us/library/windows/desktop/ms683195(v=vs.85).aspx */
        [DllImport("Psapi.dll", EntryPoint = "GetMappedFileNameW", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
        private static extern int GetMappedFileName(
          SafeProcessHandle hProcess,
          SafeMemoryMappedViewHandle lpv,
          [Out] StringBuilder lpFilename,
          int nSize
        );

        /* Note that the SafeMemoryMappedViewHandle property of SafeMemoryMappedViewAccess and SafeMemoryMappedViewStream
         * is actually the address where the file is mapped */
        private static string GetPathWithGetMappedFileName(SafeMemoryMappedViewHandle memoryMappedViewHandle)
        {
            // The maximum path length in the NT kernel is 32,767 - memory is cheap nowadays so its not a problem 
            // to just allocate the maximum size of 32KB right away.
            StringBuilder filename = new StringBuilder(short.MaxValue);
            int len;
            len = GetMappedFileName(Process.GetCurrentProcess().SafeHandle, memoryMappedViewHandle, filename, short.MaxValue);
            if (len == 0)
                throw new Win32Exception(Marshal.GetLastWin32Error());
            filename.Length = len;
            return filename.ToString();
        }

        private static void PrintFileName(MemoryMappedFile memoryMappedFile)
        {
            try
            {
                using (memoryMappedFile)
                using (MemoryMappedViewAccessor va = memoryMappedFile.CreateViewAccessor())
                {
                    string filename = GetPathWithGetMappedFileName(va.SafeMemoryMappedViewHandle);
                    Console.WriteLine(filename);
                }
            }
            catch (Win32Exception e)
            {
                Console.WriteLine("Error: 0x{0:X08}: {1}", e.NativeErrorCode, e.Message);
            }
        }

        static void Main(string[] args)
        {
            PrintFileName(GetMappedPhysicalFile());
            PrintFileName(GetMappedAnonymousMemory());
        }
    }
}

当我运行此我得到的输出：

\Device\HarddiskVolume5\Users\poizan\Documents\Visual Studio 2017\Projects\MMFilePathTest\MMFilePathTest\bin\Debug\test.bin
Error: 0x000003EE: The volume for a file has been externally altered so that the opened file is no longer valid

注意，路径在本地NT路径格式返回。如果您需要将其转换成DOS / Win32的格式，看这个问题：我如何转换本地（NT）路径为Win32的路径名？

对于当没有文件相关联的错误，该错误信息是有点怪，但错误代码的含义ERROR_FILE_INVALID ，这是有道理的，因为没有文件。