DLL shared data segment to achieve multi-process data sharing Summary

 

DLL shared data segment to achieve multi-process data sharing Summary

Some time ago, wm_copydata messages were used to implement process data communication. I want to learn about this software upgrade. dll shared data segment application, because it is easier than shared memory, I have consulted many vckbase predecessors, finally, I understood the following:

Problem description

Imagine using DLL to share process data?

Implementation

Step 1: Define the shared data segment in the DLL. cpp File

# Pragma data_seg ("shared_opcdataset ")

/* Volatile */opcdataset m_gopcdataset [opcdataset_max_len] = {0 };

# Pragma data_seg ()

# Pragma comment (linker, "/section: shared_opcdataset, RWS ")

 

/*

If no Initialization is available, perform the following operations:

_ Declspec (allocate ("shared_opcdataset") opcdataset m_gopcdataset [opcdataset_max_len];

*/

Step 2: Export shared segment Variables

Extern "C"

{

// Export the shared Block Variable

Opcdataset_api opcdataset extern m_gopcdataset [opcdataset_max_len];

}

Step 3: Call

# Include "opcdataset. H"

# Pragma comment (Lib, "copcdataset. lib ")

// Process A: write data to the shared segment

Char opcdatabuffer [56] = {0 };

M_gopcdataset [0]. dval = formatvarval (pvar, opcdatabuffer );

File * fp = fopen ("D: // set.txt", "");

Fprintf (FP, "% F", m_gopcdataset [0]. dval );

Fclose (FP );

// Process B: read data from the shared segment

File * fp = fopen ("D: // get.txt", "");

Fprintf (FP, "% F", m_gopcdataset [0]. dval );

Fclose (FP );

Note: It is best to place these processes in the same directory as your DLL or put your DLL in the System32 directory.

Highlights guide:

Reply to: vc_student (entry) 9:45:56

You can use DLL to export a function to operate the shared memory!

Only one process writes to this space. Other processes are read-only. Are you still using synchronization?

Reply to: vc_student (entry) 9:50:28

What should I do if I write it to half of others?

Reply: Happy ghost (bookboy) 10:03:57

Synchronization is required, but key code segments cannot be cross-process !!!

Reply to: vc_student (entry) 10:04:29

Haha, remember, the key code segment does not seem to support multi-process?

Reply to: vc_student (entry) 10:09:46

You can use mutex objects and event objects.

Reply to: folklore (entry) 10:34:26

Because you have not actually shared it. To share it, use MMAP. Thank you.

Reply: Happy ghost (bookboy) 10:39:59

This kind of software design is strong

Access to shared segments should be encapsulated in the DLL, which is a good design.