HttpOpenRequest lplpszAcceptTypes

This is a discussion on HttpOpenRequest lplpszAcceptTypes within the Networking/Device Communication forums, part of the General Programming Boards category; Im trying to implement a simple update function, but I cant get this function to work with binary files. Can ...

  1. #1
    Malum in se abachler's Avatar
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    HttpOpenRequest lplpszAcceptTypes

    Im trying to implement a simple update function, but I cant get this function to work with binary files. Can someone please post a snippet of code showing how to implement this?

    I have tried recasting the lplpszAcceptTypes every which way but loose, and VC keeps complaining about it. A search of the net shows that im nto alone in this problem, but turns up no solution as yet.

    Currently I have it implmented as such:

    const char szMIME[] = "image/bmp";
    LPSTR MIME[3];
    LPVOID lpMIME;

    lpMIME = &MIME[0];

    /* snip code that copies szMIME into allocated memory pointed to by MIME[0]; */


    hRequest = HttpOpenRequest( hConnection , NULL , (char *)&szFile , NULL , NULL , (LPSTR *)lpMIME/*image/bmp*/ , INTERNET_FLAG_KEEP_CONNECTION || INTERNET_FLAG_PRAGMA_NOCACHE , 0 );
    Last edited by abachler; 04-16-2007 at 03:25 PM. Reason: add code

  2. #2
    Malum in se abachler's Avatar
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    OK, I feel dumb now, all i needed to do was recast the lpMIME as (char **)lpMIME and it accepted it.

  3. #3
    and the hat of wrongness Salem's Avatar
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    Of course casting can be used to cover up a multitude of sins, which don't involve reading the manual.

    > INTERNET_FLAG_KEEP_CONNECTION || INTERNET_FLAG_PRAGMA_NOCACHE
    Do you know the difference between | and || ?

    > (char *)&szFile
    Perhaps if you dropped the &, you could drop the cast as well?
    I'm assuming from your use of hungarian notation that this is an array?

    > (LPSTR *)lpMIME
    To quote the manual page
    Quote Originally Posted by msdn
    lplpszAcceptTypes
    [in] A pointer to a null-terminated array of strings that indicates media types accepted by the client. If this parameter is NULL, no types are accepted by the client. Servers generally interpret a lack of accept types to indicate that the client accepts only documents of type "text/*" (that is, only text documents—no pictures or other binary files). For more information and a list of valid media types, see ftp://ftp.isi.edu/in-notes/iana/assi...es/media-types.
    How is your array terminated with a NULL pointer?
    Maybe
    Code:
    char *szMIME[] = {
        "image/bmp",
        NULL
    };
    Then perhaps you can pass szMime as a parameter without any casting, and without any copying?
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  4. #4
    Malum in se abachler's Avatar
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    You cant pass the array directly , the function call requires a pointer to an array of pointers, not a single pointer to a string. In any case, the casting was the problem, since I already had the array of pointers set up properly. The compiler just didnt want to accept the conversion from const char ** to char **

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