rarg, memcpy is annoying

This is a discussion on rarg, memcpy is annoying within the C++ Programming forums, part of the General Programming Boards category; Rarg!!! ok, i'm using memcpy to try and pull out some data from an array of unsigned chars. the way ...

  1. #1
    Software Developer jverkoey's Avatar
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    rarg, memcpy is annoying

    Rarg!!!

    ok, i'm using memcpy to try and pull out some data from an array of unsigned chars.

    the way i'm doing this is: i read data from a file and put it in to a dynamically allocated array of unsigned chars.

    Then, when i need something out of it, i do a memcpy to get the data.

    Now, the way i'm trying to do this is, the files themselves have a bunch of unsigned ints and floats in them, so i need to do a memcpy like so:

    memcpy(floatVar, data, sizeof(float));

    or something like that. But when i try and do that, it won't compile. So, then i add a (void*) to the beginning of floatVar, and it compiles fine, but when i run the program, it crashes........rarg!!!

    anyone know how to copy memory over to a float variable?

    or should i just do it the "old-fashioned" way and just do everything AS i'm reading in the file? (the reason I'm doing it this way is so that if the program crashes mid-read, it won't lose the file data....)

  2. #2
    It's full of stars adrianxw's Avatar
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    Is floatVar a pointer type? How about data? memcpy() wants addresses there.
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    C++ Developer XSquared's Avatar
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    ...rarg?
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    Software Developer jverkoey's Avatar
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    data is an unsigned char*

    floatvar is a float

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    Software Developer jverkoey's Avatar
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    i tried that, but when i run the program, it crashes

  6. #6
    *******argv[] - hu? darksaidin's Avatar
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    Originally posted by jverkoey
    i tried that, but when i run the program, it crashes
    How did you "dynamically" allocate data ?

    Did you create a normal array like a) byte data[iSomeSize] or is data a pointer to something like b)data= new byte[iSomeSize] ?

    In both cases, &data[0] should work thanks to the smart [] operator. This also allows you to specify a position in data from where you want to read the float (assuming there is more than just 4 bytes in "data").

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