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Date: Thu, 28 Jul 2022 13:35:07 -0700
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To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
References: <20220728124528.39169-1-adhemerval.zanella@linaro.org>
From: Paul Eggert <eggert@cs.ucla.edu>
Organization: UCLA Computer Science Department
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH] stdlib: Simplify arc4random_uniform
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On 7/28/22 05:45, Adhemerval Zanella via Libc-alpha wrote:
> It uses the bitmask with rejection [1], which calculates a mask
> being the lowest power of two bounding the request upper bound,
> successively queries new random values, and rejects values
> outside the requested range.
> 
> Performance-wise, there is no much gain in trying to converse

converse -> conserve

> bits since arc4random is wrapper on getrandom syscall.  It should
> be cheaper to just query a uint32_t value.  The algorithm also
> avoids mudulo and divide operations, which might be costly

mudulo -> modulo


> +      int bits_left = z;
> +      while (bits_left >= bits)
> +	{
...
> +	  bits_left -= bits;
> +	}

Clearer would be "for (int bits_left = z; bits_left >= bits; bits_left 
-= bits)".

Looks good otherwise; thanks.