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Editorial Team
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Asked: 2026-06-07T06:54:06+00:00

I have an app which is creating unique ids in the form of unsigned

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I have an app which is creating unique ids in the form of unsigned long ints. The app needs this precision.

However, I have to send these ids in a protocol that only allows for ints. The receiving application – of the protocol – does not need this precision. So my questions is: how can I convert an unsigned long int to an int, especially when the unsigned long int is larger than an int?

edit:

The protocol only supports int. I would be good to know how to avoid “roll-over problems”

The application sending the message needs to know the uniqueness for a long period of time, whereas the receiver needs to know the uniqueness only over a short period of time.

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1 Answer

  1. Editorial Team

    Here’s one possible approach:

    #include <climits>
unsigned long int uid = ...;
int abbreviated_uid = uid & INT_MAX;

    If int is 32 bits, for example, this discards all but the low-order 31 bits of the UID. It will only yield non-negative values.

    This loses information from the original uid, but you indicated that that’s not a problem.

    But your question is vague enough that it’s hard to tell whether this will suit your purposes.

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