How can I get the size of a file mapping?

Question

_{Sunday, December 27, 2015 5:29 PM}

Hello! 

I want to use a filemaping to transfer information at two process. For Example, In one process I use

 hfilemap=CreateFileMapping(hfile, NULL,  PAGE_READWRITE ,0,  4096, "mymap" ). At the other process call

 hfilemap=OpenFileMapping( FILE_MAP_READ|FILE_MAP_WRITE , 0,  "mymap" );

Now, if Idon‘t know the size of filemapping is 4096, How can I get the size of filemapping ?

Thanks!

• CJS

All replies (3)

_{Sunday, December 27, 2015 8:14 PM ✅Answered}

Check if this works:

    LPVOID v = MapViewOfFile( hfilemap, FILE_MAP_READ, 0, 0, 0 );

    MEMORY_BASIC_INFORMATION mbi = { 0 };

    VirtualQueryEx( GetCurrentProcess(), v, &mbi, sizeof( mbi ) );

Then see the value of mbi.RegionSize.

However, if the actual amount of transferred data is less than the pre-allocated size of the mapping, then the size can be embedded, for example, in the first four bytes.

_{Monday, December 28, 2015 8:18 AM}

Thank you!

 Please help me to answer another question.

If I want to know which file is associatting with the filemapping object,  How  to do it?

Thanks

-CJS

_{Tuesday, January 5, 2016 3:25 AM}

Hi chencjss,

>>If I want to know which file is associatting with the filemapping object,  How  to do it?

If you have new question, I suggest you post your question in a new thread.

Best Regards,
Herro Wong

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