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  1. #1
    Registered User
    Join Date
    Nov 2005
    Posts
    7

    The error of read data from file

    Hi everybody!
    Recent I encountered two problems.
    First problem:
    I used fread/fwrite function of the standard c, to read or write a structure like:
    typedef struct
    {
    TUint8 i;
    TUint8 j;
    }Teststructure ;
    to a file.when I debug program in simulator ,the file cursor move ahead 2 bytes but move ahead 4 bytes when in real device. So I try to write a TUint8 data to a file ,I find the file cursor move ahead 1 bytes no matter in simulator or real device. I describe in form code like below:

    Teststructure * b;
    FILE* fp = fopen(filePath,"wb");
    fwrite( b;sizeof(Teststructure),1, fp);

    //I suppose the file cursor start at 0;
    TInt addr1 = ftell(fp);

    In simulator
    addr1 = 2;
    In real device
    addr1 = 4;

    And another code
    TUint8 i = 2;
    FILE* fp = fopen(filePath2,"wb");
    fwrite(&i,sizeof(TUint8),1,fp);
    TInt addr2 = ftell(fp);

    No matter in simulator or real device
    addr2 = 1;
    Who can tell me why this happen?


    Another problem,
    I write a TReal data to file:
    TReal i = 0.22;
    FILE* fp = fopen(filePath,"wb");
    fwrite(&i,sizeof(TReal ),1,fp);
    Then, I read this TReal data from file:
    TReal j;
    FILE* fp = fopen(filePath,"rb"):
    fread(&j,sizeof(TReal),1,fp);
    in simulator j = 0.22;but in real device the value of j was a incorrect value;
    who can tell me why?

    My platform is S60 2nd and IDE is VC++ 6.0

  2. #2
    Regular Contributor
    Join Date
    May 2005
    Location
    Sweden
    Posts
    272

    Re: The error of read data from file

    About the first issue, I suppose the struct is padded up to 4 bytes, to avoid alignment problems.
    Mobile Sputnik: http://ptrmobile.blogspot.com/

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