共享内存操作类(C#源码)[转]

VC++的共享内存操作代码实现起来相对比较容易，但是用C#语言来实现，就有一定难度，由于工作需要，把以前VC开发的共享内存代码要用C#实现，别说，还费了不少周折，毕竟C#操作API函数和地址指针不是那么直接，还好，总算完成了，效果还不错。



共享内存操作类：

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace ShareMemLib
{
public class ShareMem
{
[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, int wParam, IntPtr lParam);

[DllImport("Kernel32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr CreateFileMapping(int hFile, IntPtr lpAttributes, uint flProtect, uint dwMaxSizeHi, uint dwMaxSizeLow, string lpName);

[DllImport("Kernel32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr OpenFileMapping(int dwDesiredAccess,[MarshalAs(UnmanagedType.Bool)] bool bInheritHandle,string lpName);

[DllImport("Kernel32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr MapViewOfFile(IntPtr hFileMapping,uint dwDesiredAccess, uint dwFileOffsetHigh, uint dwFileOffsetLow,uint dwNumberOfBytesToMap);

[DllImport("Kernel32.dll", CharSet = CharSet.Auto)]
public static extern bool UnmapViewOfFile(IntPtr pvBaseAddress);

[DllImport("Kernel32.dll", CharSet = CharSet.Auto)]
public static extern bool CloseHandle(IntPtr handle);

[DllImport("kernel32", EntryPoint="GetLastError")]
public static extern int GetLastError ();

const int ERROR_ALREADY_EXISTS = 183;

const int FILE_MAP_COPY = 0x0001;
const int FILE_MAP_WRITE = 0x0002;
const int FILE_MAP_READ = 0x0004;
const int FILE_MAP_ALL_ACCESS = 0x0002 | 0x0004;

const int PAGE_READONLY = 0x02;
const int PAGE_READWRITE = 0x04;
const int PAGE_WRITECOPY = 0x08;
const int PAGE_EXECUTE = 0x10;
const int PAGE_EXECUTE_READ = 0x20;
const int PAGE_EXECUTE_READWRITE = 0x40;

const int SEC_COMMIT = 0x8000000;
const int SEC_IMAGE = 0x1000000;
const int SEC_NOCACHE = 0x10000000;
const int SEC_RESERVE = 0x4000000;

const int INVALID_HANDLE_VALUE = -1;

IntPtr m_hSharedMemoryFile = IntPtr.Zero;
IntPtr m_pwData = IntPtr.Zero;
bool m_bAlreadyExist = false;
bool m_bInit = false;
long m_MemSize=0;

public ShareMem()
{
}
~ShareMem()
{
Close();
}

/// <summary>
/// 初始化共享内存
/// </summary>
/// <param name="strName">共享内存名称</param>
/// <param name="lngSize">共享内存大小</param>
/// <returns></returns>
public int Init(string strName, long lngSize)
{
if (lngSize <= 0 || lngSize > 0x00800000) lngSize = 0x00800000;
m_MemSize = lngSize;
if (strName.Length > 0)
{
//创建内存共享体(INVALID_HANDLE_VALUE)
m_hSharedMemoryFile = CreateFileMapping(INVALID_HANDLE_VALUE, IntPtr.Zero, (uint)PAGE_READWRITE, 0, (uint)lngSize, strName);
if (m_hSharedMemoryFile == IntPtr.Zero)
{
m_bAlreadyExist = false;
m_bInit = false;
return 2; //创建共享体失败
}
else
{
if (GetLastError() == ERROR_ALREADY_EXISTS) //已经创建
{
m_bAlreadyExist = true;
}
else //新创建
{
m_bAlreadyExist = false;
}
}
//---------------------------------------
//创建内存映射
m_pwData = MapViewOfFile(m_hSharedMemoryFile, FILE_MAP_WRITE, 0, 0, (uint)lngSize);
if (m_pwData == IntPtr.Zero)
{
m_bInit = false;
CloseHandle(m_hSharedMemoryFile);
return 3; //创建内存映射失败
}
else
{
m_bInit = true;
if (m_bAlreadyExist == false)
{
//初始化
}
}
//----------------------------------------
}
else
{
return 1; //参数错误
}

return 0; //创建成功
}
/// <summary>
/// 关闭共享内存
/// </summary>
public void Close()
{
if (m_bInit)
{
UnmapViewOfFile(m_pwData);
CloseHandle(m_hSharedMemoryFile);
}
}

/// <summary>
/// 读数据
/// </summary>
/// <param name="bytData">数据</param>
/// <param name="lngAddr">起始地址</param>
/// <param name="lngSize">个数</param>
/// <returns></returns>
public int Read(ref byte[] bytData, int lngAddr, int lngSize)
{
if (lngAddr + lngSize > m_MemSize) return 2; //超出数据区
if (m_bInit)
{
Marshal.Copy(m_pwData, bytData, lngAddr, lngSize);
}
else
{
return 1; //共享内存未初始化
}
return 0; //读成功
}

/// <summary>
/// 写数据
/// </summary>
/// <param name="bytData">数据</param>
/// <param name="lngAddr">起始地址</param>
/// <param name="lngSize">个数</param>
/// <returns></returns>
public int Write(byte[] bytData, int lngAddr, int lngSize)
{
if (lngAddr + lngSize > m_MemSize) return 2; //超出数据区
if (m_bInit)
{
Marshal.Copy(bytData, lngAddr, m_pwData, lngSize);
}
else
{
return 1; //共享内存未初始化
}
return 0; //写成功
}
}
}

测试例程：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using ShareMemLib;

namespace YFShareMem
{
public partial class frmShareMem : Form
{
ShareMem MemDB=new ShareMem();
public frmShareMem()
{
InitializeComponent();
}

private void btnOpen_Click(object sender, EventArgs e)
{
if (MemDB.Init("YFMemTest", 10240) != 0)
{
//初始化失败
MessageBox.Show("初始化失败");
}
else
{
btnOpen.Enabled = false;
chkWrite.Enabled = true;
tmrTime.Enabled = true;
}
}

private void tmrTime_Tick(object sender, EventArgs e)
{
byte[] bytData = new byte[16];
int intRet = MemDB.Read(ref bytData, 0, 16);
lstData.Items.Clear();
if (intRet == 0)
{
for (int i = 0; i < 16; i++)
{
lstData.Items.Add(bytData[i].ToString());
}

if (chkWrite.Checked)
{
bytData[0]++;
bytData[1] += 2;
if (bytData[0] > 200) bytData[0] = 0;
if (bytData[1] > 200) bytData[1] = 0;
MemDB.Write(bytData, 0, 16);
}
}
}

}
}

全文】

首先还是定义非托管调用，如下：

const int INVALID_HANDLE_VALUE = -1;
const int PAGE_READWRITE = 0x04;
//共享内存
[DllImport("Kernel32.dll",EntryPoint="CreateFileMapping")]
private static extern IntPtr CreateFileMapping(IntPtr hFile, //HANDLE hFile,
UInt32 lpAttributes,//LPSECURITY_ATTRIBUTES lpAttributes, //0
UInt32 flProtect,//DWORD flProtect
UInt32 dwMaximumSizeHigh,//DWORD dwMaximumSizeHigh,
UInt32 dwMaximumSizeLow,//DWORD dwMaximumSizeLow,
string lpName//LPCTSTR lpName
);

[DllImport("Kernel32.dll",EntryPoint="OpenFileMapping")]
private static extern IntPtr OpenFileMapping(
UInt32 dwDesiredAccess,//DWORD dwDesiredAccess,
int bInheritHandle,//BOOL bInheritHandle,
string lpName//LPCTSTR lpName
);

const int FILE_MAP_ALL_ACCESS = 0x0002;
const int FILE_MAP_WRITE = 0x0002;

[DllImport("Kernel32.dll",EntryPoint="MapViewOfFile")]
private static extern IntPtr MapViewOfFile(
IntPtr hFileMappingObject,//HANDLE hFileMappingObject,
UInt32 dwDesiredAccess,//DWORD dwDesiredAccess
UInt32 dwFileOffsetHight,//DWORD dwFileOffsetHigh,
UInt32 dwFileOffsetLow,//DWORD dwFileOffsetLow,
UInt32 dwNumberOfBytesToMap//SIZE_T dwNumberOfBytesToMap
);

[DllImport("Kernel32.dll",EntryPoint="UnmapViewOfFile")]
private static extern int UnmapViewOfFile(IntPtr lpBaseAddress);

[DllImport("Kernel32.dll",EntryPoint="CloseHandle")]
private static extern int CloseHandle(IntPtr hObject);

然后分别在AB两个进程中定义如下两个信号量及相关变量；

private Semaphore m_Write; //可写的信号
private Semaphore m_Read; //可读的信号
private IntPtr handle; //文件句柄
private IntPtr addr; //共享内存地址
uint mapLength; //共享内存长

定义这两个信号量是为读写互斥用的。
在A进程中创建共享内存：

m_Write = new Semaphore(1,1,"WriteMap");
m_Read = new Semaphore(0,1,"ReadMap");
mapLength = 1024;
IntPtr hFile = new IntPtr(INVALID_HANDLE_VALUE);
handle = CreateFileMapping(hFile,0,PAGE_READWRITE,0,mapLength,"shareMemory");
addr = MapViewOfFile(handle,FILE_MAP_ALL_ACCESS,0,0,0);

然后再向共享内存中写入数据：

m_Write.WaitOne();
byte[] sendStr = Encoding.Default.GetBytes(txtMsg.Text + '/0');
//如果要是超长的话，应另外处理，最好是分配足够的内存
if(sendStr.Length < mapLength)
Copy(sendStr,addr);
m_Read.Release();

这是在一个单独的方法中实现的，可多次调用，但受信号量的控制。其中txtMsg是一个文本框控件，实际中可用任意字符串，加最后的'/0'是为了让在共享内存中的字符串有一个结束符，否则在内存中取出时是以'/0'为准的，就会出现取多的情况。
Copy方法的实现如下：

static unsafe void Copy(byte[] byteSrc,IntPtr dst)
{
fixed (byte* pSrc = byteSrc)
{
byte* pDst = (byte*)dst;
byte* psrc = pSrc;
for(int i=0;i<byteSrc.Length;i++)
{
*pDst = *psrc;
pDst++;
psrc ++;
}
}
}

注意unsafe 关键字，在编译时一定要打开非安全代码开关。
最后不要忘了在A进程中关闭共享内存对象，以免内存泄露。

UnmapViewOfFile(addr);
CloseHandle(handle);

要在B进程中读取共享内存中的数据，首先要打开共享内存对象：

m_Write = Semaphore.OpenExisting("WriteMap");
m_Read = Semaphore.OpenExisting("ReadMap");
handle = OpenFileMapping(0x0002,0,"shareMemory");

读取共享内存中的数据：

m_Read.WaitOne();
string str = MapViewOfFile(handle,FILE_MAP_ALL_ACCESS,0,0,0);
txtMsg.Text = str;
m_Write.Release();