translate int_32 to 8-bit

This is a discussion on translate int_32 to 8-bit within the C Programming forums, part of the General Programming Boards category; hello, So, if I converting ip address from 8-bit to int_32 type. address = (((((ip[0]<<8)+ip[1])<<8)+ip[2])<<8)+ip[3]; But, which's way reverse that? ...

  1. #1
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    translate int_32 to 8-bit

    hello,
    So, if I converting ip address from 8-bit to int_32 type.
    address = (((((ip[0]<<8)+ip[1])<<8)+ip[2])<<8)+ip[3];
    But, which's way reverse that?
    I tried this way
    Code:
    for (;i<4; ++i) id[i] = (address >> (i*8)) & 0xFF;
    printf("%u\n", id[i]);
    However. I've got a value prefix where has been that ip-address.
    How to do converting value from int_32 to 8-bit?

  2. #2
    Registered User carrotcake1029's Avatar
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    It seems you are doing it correct.
    Lets say this ip is stored like this: 0x01020304
    Code:
    ip >> 0 = 0x04
    ip >> 8 = 0x03
    ip >> 16 = 0x02
    ip >> 32 = 0x01
    So you could do something along the lines of this:
    Code:
    char temp;
    
        for (i = 0; i < 4; i++)
            temp = (ip >> (8 * i)) & 0xFF;

  3. #3
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    If I doing whatever like this
    Code:
    for (address=first_address; address<first_address+hosts; ++address){
    printf("%u\n\n", address);
    for (;i<3; i++) id[i] = (address >> (i*8)) & 0xFF;
    printf("%u\n", id[i]);
    }
    I've got it crazy of result
    Code:
    3232240640
    
    0
    3232240641
    
    0
    3232240642
    
    0
    3232240643
    
    0
    But I expect something like this
    3232240640
    192.168.20.0
    3232240641
    192.168.20.1
    3232240642
    192.168.20.2
    3232240643
    192.168.20.3
    Last edited by quantt; 01-25-2009 at 12:41 AM.

  4. #4
    Registered User carrotcake1029's Avatar
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    Could you post the code of how you populate the variable that holds the ip. Also, post what the 32bit ip is, untouched.

  5. #5
    CSharpener vart's Avatar
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    Code:
    for (;i<3; i++) id[i] = (address >> (i*8)) & 0xFF;
    printf("%u\n", id[i]);
    you ar printing id[4] - which is out of bounds access

    as well as your i is never reset to 0 on the next iteration of the outher loop
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  6. #6
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    Quote Originally Posted by vart View Post
    you ar printing id[4] - which is out of bounds access
    as well as your i is never reset to 0 on the next iteration of the outher loop
    ops, I gaming with it and forgot change it before posted.
    Could you post the code of how you populate the variable that holds the ip. Also, post what the 32bit ip is, untouched.
    sure
    Code:
    sscanf(argv[1], "%d.%d.%d.%d/%d", &ip[0], &ip[1], &ip[2], &ip[3], &mask);
    degree = 32 - mask;
    hosts=1 << degree;

  7. #7
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    Could you help me?

  8. #8
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    Are you resetting i in the second for loop, now?

  9. #9
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    Have you updated the code after incorporating suggestions made by the other posters?

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