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