c# 内存共享、内存映射文件、适合读取大文件

using System;  

using System.Collections.Generic;  

using System.Text;  

using System.Runtime.InteropServices;  

using System.IO;  

using System.Data.SqlClient;  

 

namespace WinApp  

{  

   public class Sequence  

   {  

       [DllImport("kernel32.dll")]  

       public static extern IntPtr CreateFileMapping(IntPtr hFile,IntPtr lpFileMappingAttributes, uint flProtect,uint dwMaximumSizeHigh,  

           uint dwMaximumSizeLow, string lpName);  

 

       [DllImport("kernel32.dll")]  

       public static extern IntPtr MapViewOfFile(IntPtr hFileMappingObject, uint 

           dwDesiredAccess, uint dwFileOffsetHigh, uint dwFileOffsetLow, IntPtr dwNumberOfBytesToMap);  

 

       [DllImport("kernel32.dll")]  

       public static extern bool UnmapViewOfFile(IntPtr lpBaseAddress);  

 

       [DllImport("kernel32.dll")]  

       public static extern bool CloseHandle(IntPtr hObject);  

 

       [DllImport("kernel32.dll")]  

       public static extern IntPtr CreateFile(string lpFileName,int dwDesiredAccess, FileShare dwShareMode, IntPtr securityAttrs,  

           FileMode dwCreationDisposition, int dwFlagsAndAttributes, IntPtr hTemplateFile);  

 

       [DllImport("kernel32.dll")]  

       public static extern uint GetFileSize(IntPtr hFile, IntPtr lpFileSizeHigh);  

 

       public const int GENERIC_READ = -2147483648; //0x80000000  

       public const int GENERIC_WRITE = 0x40000000;  

       public const int GENERIC_EXECUTE = 0x20000000;  

       public const int GENERIC_ALL = 0x10000000;  

       public const int FILE_ATTRIBUTE_NORMAL = 0x80;  

       public const int FILE_FLAG_SEQUENTIAL_SCAN = 0x8000000;  

       public const int INVALID_HANDLE_VALUE = -1;  

 

       public const int PAGE_NOACCESS = 1;  

       public const int PAGE_READONLY = 2;  

       public const int PAGE_READWRITE = 4;  

 

       public const int FILE_MAP_COPY = 1;  

       public const int FILE_MAP_WRITE = 2;  

       public const int FILE_MAP_READ = 4;  

 

       public static string MappingFileRead()  

       {  

           string result = "";  

           try 

           {  

               IntPtr vFileHandle = CreateFile(@"c:/test.txt", GENERIC_READ | GENERIC_WRITE, FileShare.Read | FileShare.Write,IntPtr.Zero, FileMode.Open,  

               FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, IntPtr.Zero);  

               if (INVALID_HANDLE_VALUE != (int)vFileHandle)  

               {  

                   IntPtr vMappingHandle = CreateFileMapping(vFileHandle, IntPtr.Zero, PAGE_READWRITE, 0, 0, "~MappingTemp");  

                   if (vMappingHandle != IntPtr.Zero)  

                   {  

                       IntPtr vHead = MapViewOfFile(vMappingHandle, FILE_MAP_COPY | FILE_MAP_READ | FILE_MAP_WRITE, 0, 0, IntPtr.Zero);  

                       if (vHead != IntPtr.Zero)  

                       {                            

                           uint vSize = GetFileSize(vFileHandle, IntPtr.Zero);  

                           byte[] res = new byte[vSize];  

                           Marshal.Copy(vHead, res, 0, (int)vSize);  

                           result = ASCIIEncoding.Default.GetString(res);  

                           string[] _str = result.Split('|');  

                           result = _str[0];  

                           /* 

                           //*************************************** 

                           //_IntPtr = Marshal.ReadIntPtr(vHead);                              

                           byte[] contentbyte1 = new byte[vSize]; 

                           for (int i = 0; i < vSize; i++) 

                           { 

                               byte vTemp = Marshal.ReadByte((IntPtr)((int)vHead + i)); 

                               contentbyte1[i] = vTemp;                                

                           } 

                           Console.WriteLine(ASCIIEncoding.Default.GetString(contentbyte1));//全部值 

                           //*************************************** 

                           byte[] contentbyte = new byte[vSize]; 

                           for (int i = 0; i < vSize; i++) 

                           { 

                               byte vTemp = Marshal.ReadByte((IntPtr)((int)vHead + i)); 

                               contentbyte[i] = vTemp; 

                               if (vTemp == '|')//设定标识结束符合 

                               { 

                                   break; 

                               } 

                           }                             

                           Console.WriteLine(ASCIIEncoding.Default.GetString(contentbyte));//要取的值 

                           result = ASCIIEncoding.Default.GetString(contentbyte); 

                           //*************************************** 

                           */ 

                           UnmapViewOfFile(vHead);  

                       }  

                       CloseHandle(vMappingHandle);  

                   }  

                   CloseHandle(vFileHandle);  

                }  

 

            }  

            catch 

            { }  

            return result;  

        }  

        public static IntPtr InvalidHandleValue = new IntPtr(-1);  

        public static void MappingFileWrite(string val)  

        {  

            try 

            {                  

                IntPtr vFileHandle = CreateFile(@"c:/test.txt", GENERIC_READ | GENERIC_WRITE, FileShare.Read | FileShare.Write, IntPtr.Zero, FileMode.Open,  

                FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, IntPtr.Zero);  

                if (INVALID_HANDLE_VALUE != (int)vFileHandle)  

                {  

                    IntPtr vMappingHandle = CreateFileMapping(vFileHandle, IntPtr.Zero, PAGE_READWRITE, 0, (UInt32)(val.Length + 1), "~MappingTemp");  

                    if (vMappingHandle != IntPtr.Zero)  

                    {  

                        IntPtr vHead = MapViewOfFile(vMappingHandle, FILE_MAP_COPY | FILE_MAP_READ | FILE_MAP_WRITE, 0, 0, IntPtr.Zero);  

                        if (vHead != IntPtr.Zero)  

                        {                                 

                            byte[] by = ASCIIEncoding.Default.GetBytes(val + "|"); //设定标识结束符合  |     

                            Marshal.Copy(by, 0, vHead, by.Length);                              

                            UnmapViewOfFile(vHead);  

                        }  

                        CloseHandle(vMappingHandle);  

                    }  

                    CloseHandle(vFileHandle);  

                }  

 

            }  

            catch 

            { }  

        }  

         

        public static void MappingWrite1(string val)  

        {  

            try 

            {  

                IntPtr vMappingHandle = CreateFileMapping(InvalidHandleValue, IntPtr.Zero, PAGE_READWRITE, 0, (UInt32)(val.Length + 1), "~MappingTemp");  

                if (vMappingHandle != IntPtr.Zero)  

                {  

                    IntPtr vHead = MapViewOfFile(vMappingHandle, FILE_MAP_COPY | FILE_MAP_READ | FILE_MAP_WRITE, 0, 0, IntPtr.Zero);  

                    if (vHead != IntPtr.Zero)  

                    {  

                        byte[] by = ASCIIEncoding.Default.GetBytes(val + "|"); //设定标识结束符合  |    

                        Marshal.Copy(by, 0, vHead, by.Length);  

                        UnmapViewOfFile(vHead);  

                    }  

                    //CloseHandle(vMappingHandle);  

                }  

 

            }  

            catch 

            { }  

        }  

        public static string MappingRead1()  

        {  

            string result = "";  

            try 

            {  

                IntPtr vMappingHandle = CreateFileMapping(InvalidHandleValue, IntPtr.Zero, PAGE_READWRITE, 0, 7, "~MappingTemp");  

                if (vMappingHandle != IntPtr.Zero)  

                {  

                    IntPtr vHead = MapViewOfFile(vMappingHandle, FILE_MAP_COPY | FILE_MAP_READ | FILE_MAP_WRITE, 0, 0, IntPtr.Zero);  

                    if (vHead != IntPtr.Zero)  

                    {  

                        byte[] bytData = new byte[7];  

                        Marshal.Copy(vHead, bytData, 0, 7);  

                        result = ASCIIEncoding.Default.GetString(bytData);  

                        UnmapViewOfFile(vHead);  

                    }  

                    CloseHandle(vMappingHandle);  

                }  

            }  

            catch 

            {  

            }  

            return result;  

        }  

    }     

} 

本文来自CSDN博客，出处：http://blog.csdn.net/gaozhigang/archive/2010/05/25/5622319.aspx