ReadFile();

This is a discussion on ReadFile(); within the Windows Programming forums, part of the Platform Specific Boards category; Could someone show me how to properley use the ReadFile(); function? I can't seem to figure out how to use ...

  1. #1
    Registered User Queatrix's Avatar
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    ReadFile();

    Could someone show me how to properley use the ReadFile(); function? I can't seem to figure out how to use it. Thanks.

  2. #2
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    Code:
    BOOL ReadFile(
      HANDLE hFile,                // handle of file to read
      LPVOID lpBuffer,             // pointer to buffer that receives data
      DWORD nNumberOfBytesToRead,  // number of bytes to read
      LPDWORD lpNumberOfBytesRead, // pointer to number of bytes read
      LPOVERLAPPED lpOverlapped    // pointer to structure for data
    );

  3. #3
    Registered User Queatrix's Avatar
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    I think I understand what everything does now, but I still can't seem to make it work.
    Could you give me an example to work with? Thanks.

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    To read 10 bytes from a file:
    Code:
    char Buffer[10];
    DWORD dwBytes;
    HANDLE hFile;
    
    
    hFile=CreateFile... 
    ReadFile(hFile, Buffer, 10, &dwBytes, NULL);
    If a function dosen't work check the return code and call GetLastError to get an error code which will describe the problem in more detail.

  5. #5
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    hFile=CreateFile...

    I don't get it. Why would you create a file just to read a file?

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    Because Create file is used to open files as well as create them.

  7. #7
    Registered User Queatrix's Avatar
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    I tried this, but if something is in my file it erases the contence then reads it. How can I prevent that?
    Code:
     char Buffer[10];
    DWORD dwBytes;
    HANDLE hFile; 
    hFile=CreateFile("draft.txt", GENERIC_READ, FILE_SHARE_READ, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
    ReadFile(hFile, Buffer, 10, &dwBytes, NULL);
    MessageBox(NULL, Buffer, "Found", MB_OK);
    Thanks.

  8. #8
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    change CREATE_ALWAYS to OPEN_EXISTING

  9. #9
    Registered User Queatrix's Avatar
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    Now it works. Thank for your help Quantum1024!

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