C # shared memory operations

The following is a class for C # Memory operations. You only need to add the following class to the corresponding project, and this project can directly operate on the memory!

Using system. runtime. interopservices; // to add the following namespace, use dllimport

Public class sharememlib
{

[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, [financialas (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 sharememlib ()

{

}

~ Sharememlib ()

{

Close ();

}

 

// Initialize the memory

Public int Init (string strname, long lngsize)

{

If (lngsize <= 0 | lngsize> 0x00800000) lngsize = 0x00800000;

M_memsize = lngsize;

If (strname. length> 0)

{

// Create a memory shared body (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; // An error occurred while creating the shared body.

}

Else

{

If (getlasterror () = error_already_exists) // already created

{

M_balreadyexist = true;

}

Else

{

M_balreadyexist = false;

}

}

// Create memory ing

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; // failed to create memory ing

}

Else

{

M_binit = true;

If (m_balreadyexist = false)

{

}

}

}

Else

{

Return 1;

}

 

Return 0;

}

// Disable shared memory

Public void close ()

{

If (m_binit)

{

Unmapviewoffile (m_pwdata );

Closehandle (m_hsharedmemoryfile );

}

}

/// Read data

Public int read (ref byte [] bytdata, int lngaddr, int lngsize)

{

If (lngaddr + lngsize> m_memsize) return 2; // exceeds the data Zone

If (m_binit)

{

Marshal. Copy (m_pwdata, bytdata, lngaddr, lngsize );

}

Else

{

Return 1;

}

Return 0;

}

 

// Write data to the shared memory

Public int write (byte [] bytdata, int lngaddr, int lngsize)

{

If (lngaddr + lngsize> m_memsize) return 2; // exceeds the data Zone

If (m_binit)

{

Marshal. Copy (bytdata, lngaddr, m_pwdata, lngsize );

}

Else

{

Return 1;

}

Return 0;

}

}

Call method:

Declare sharememery. sharememlib memdb = new sharememlib (); as a public variable.

// Use the following sentence to call the method for initializing shared memory in the above class

If (memdb. INIT ("yfmemtest", 10240 )! = 0)

Convert data that needs to be written in memory into byte []

Memdb. Write (bytdata, 0, BB. Length); // write data to the shared memory.

Byte [] bytdata = new byte [16];
Int intret = memdb. Read (ref bytdata, 0, 16 );

The above method reads 16 bytes of content in the memory.

The above method has been tested in vs2008.