Re: [boost] [Endian] Performance

Subject: Re: [boost] [Endian] Performance
From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2011-09-06 12:28:09

Mathias Gaunard wrote:
> On 06/09/2011 00:38, Phil Endecott wrote:
>
>> #elif defined(USE_BEMAN)
>>
>> const char* s (reinterpret_cast<const char*>(&src));
>> uint32_t target;
>> char * t (reinterpret_cast<char*>(&target) + sizeof(target) - 1);
>> *t = *s;
>> *--t = *++s;
>> *--t = *++s;
>> *--t = *++s;
>> return target;
>
> Why isn't that just std::reverse?

Well std::reverse is in-place, and this particular code is not.  But 
yes, std::reverse could be used for some of Beman's functions, and some 
sort of std::copy with reverse iterators could be used here.  There are 
also places where the code could be more concise if std::swap were used.

Fundamentally though, I don't think that casting to bytes is the right 
way to do this; shifts and bitwise ops seem to produce better code, and 
involve less worrying casting.

Regards,  Phil.