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POSplitting shared memory?
 

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    <p>A block of shared memory is allocated using <code>CreateFileMapping()</code> and the handle to it is given. Some data were written using <code>MapViewOfFile()</code> -- call it 'source'</p> <p>Now I wish to split the shared memory into many small blocks and to get the handles to them.<br> Is there a way to do that while not calling <code>CreateFileMapping()</code> again and copying from 'source'?</p> <p><code>OpenFileMapping()</code> and <code>MapViewOfFile()</code> with appropriate offsets will work but the problem is, in that case the process that calls <code>OpenFileMapping()</code> get to have access to data written in 'source' by other processes and they might be corrupted by using a wrong offset.</p> <p>Long story short, I'm looking for something like <code>OpenFileMapping(String name, UINT **offset**, ...)</code></p> <hr> <p>The last sentence was misleading.</p> <p>What I'm really trying to do is something like this:</p> <pre><code>&lt;Host process&gt; HANDLE hShm = CreateFileMapping(INVALID_HANDLE_VALUE, ..., "shm"); void* pShm = MapViewOfFile(hShm); UINT numShms = *(UINT*)pShm; // first 4 bytes stores number of shared memory blocks HANDLE *hShmSplit = new HANDLE[numShms]; for(size_t i=0; i&lt;numShms; i++) { TCHAR shmName[32]; wsprintf(shmName, "shm%d", i); // suppose offset is set pShm+=offset; hShmSplit[i] = *CreateFileMappingFromExistingMapping*(pShm, shmName); } CloseHandle(hShm); // no longer used &lt;Client process&gt; TCHAR* shmName="shm1"; HANDLE hShm = OpenFileMapping(shmName); LPVOID p = MapViewOfFile(hShm); // use shared memory // Now the client process has access to shm1 but not to shm2, shm3, or other shm_x's. </code></pre>
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    1. USJeffrey Goines
    1. USJeffrey Goines
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      1. POSplitting shared memory?
      1. USRaymond Chen
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    1. CO... Why can't you just pass around pointers to the middle of it?
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      1. POSplitting shared memory?
      1. USIgnacio Vazquez-Abrams
    2. COIt's a multiprocess project so...
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      1. POSplitting shared memory?
      1. USJeffrey Goines
    3. COHow do you expect the other processes to get at the open file then?
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      1. POSplitting shared memory?
      1. USIgnacio Vazquez-Abrams
 

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