about the digit size in libtommath

This is a discussion on about the digit size in libtommath within the C Programming forums, part of the General Programming Boards category; In the libtommath library documentation file, what does it mean by the "default value of mp_digit being ISO C unsigned ...

  1. #1
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    about the digit size in libtommath

    In the libtommath library documentation file, what does it mean by the
    "default value of mp_digit being ISO C unsigned long data type, each
    digit is 28 bits long" ? Shouldn't it be 32 bits? It shows 4 bytes
    when I use sizeof and looking at the source code it seems to be
    defined as
    typedef unsigned long mp_digit

  2. #2
    and the hat of wrongness Salem's Avatar
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    My guess is that it simplifies the internal code, when it comes to detecting things like overflow.

    You would have to read the code, read the design documents, or ask on the forum dedicated to libtommath maintainers and developers.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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    Algorithm Dissector iMalc's Avatar
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    I once thought that it would make overflow detection easier, but then I found out that it's easy anyway.
    I use all 32-bits in my own one.
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  4. #4
    and the hat of wrongness Salem's Avatar
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    Take answer, and post elsewhere -> About the digit size in libtommath - Dev Shed
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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