Re: [hash2] Comments

From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2024-12-08 20:45:51

On 12/8/24 21:31, Peter Dimov via Boost wrote:
>> So, for example, if you have a 32 bit hash function and you need 64 bits, this
>> is how you would do it, ordered from best to worst:
>>
>> // as good as possible
>> uint64_t f1( Hash& hash )
>> {
>>     uint32_t r1 = hash.result();
>>     uint32_t r2 = hash.result();
>>     return (uint64_t(r1) << 32) | r2;
>> }
>>
>> // not that bad, but worse than the above
>> uint64_t f2( Hash& hash )
>> {
>>     return get_integral_result<uint64_t>( hash.result() );
>> }
> 
> All that leads me to the thought that I've got get_integral_result wrong;
> it should take the hash algorithm directly, not its result, and should
> invoke result() as many times as needed to obtain the necessary
> number of bits.

This would be incompatible with algorithms that don't support multiple
calls to finalize().