共享内存
共享内存指 (shared memory)在多处理器的计算机系统中，可以被不同中央处理器（CPU）访问的大容量内存。由于多个CPU需要快速访问存储器，这样就要对存储器进行缓存（Cache）。任何一个缓存的数据被更新后，由于其他处理器也可能要存取，共享内存就需要立即更新，否则不同的处理器可能用到不同的数据。共享内存是 Unix下的多进程之间的通信方法 ,这种方法通常用于一个程序的多进程间通信，实际上多个程序间也可以通过共享内存来传递信息。
C# 调用Win32 系统APi实现共享内存：
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 > 104857600) lngSize = 104857600;
//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
}
}
ShareMem MemDB = new ShareMem();//声明共享内存操作类
MemDB.Init("shared", 64* 1024 * 1024);//初始化共享内存 返回0表示初始化成功
byte[] bytes = new byte[2];
MemDB.Read(ref bytes, 0, 2);//读取数据，返回0表示读取成功
MemDB.Write(bytes, 0, 2);//写入数据
支付宝扫码打赏
微信打赏
