hton

This is a discussion on hton within the C Programming forums, part of the General Programming Boards category; To further my knowledge of bitshifting, I decided to rewrite htons/htonl. htons was easy. Only two bytes. Keep in mind ...

  1. #1
    Registered User carrotcake1029's Avatar
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    hton

    To further my knowledge of bitshifting, I decided to rewrite htons/htonl.

    htons was easy. Only two bytes. Keep in mind I am not checking for endianness yet, I am just getting the byte reversing down.
    Code:
    unsigned short htons (unsigned short hostshort)
    {
    	return (hostshort << 8) | (hostshort >> 8);
    }
    Then I went to tackle htonl, and it was a bit tougher.
    Code:
    unsigned long htonl (unsigned long hostlong)
    {
    	return (hostlong << 16) | (hostlong >> 16);
    }
    If I feed it 0x11223344, it comes out 0x33441122. I have tried for a while now and cannot understand how to get it to finish the reverse. The closest I got was with this line (I know, get pretty messy):
    Code:
    (((hostlong << 16) << 8) | ((hostlong << 16) >> 8)) | (((hostlong >> 16) << 8) | ((hostlong >> 16) >> 8));
    Can anyone help me with thinking logically about this. I just seem to be at a block.

  2. #2
    Algorithm Dissector iMalc's Avatar
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    htonl should involve two calls to htons. One with the upper 16 bits and one with the lower 16 bits. Then reconstruct the result with those answers the other way around.
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