Re: [boost] [endian] Project not maintained

Subject: Re: [boost] [endian] Project not maintained
From: Peter Dimov (lists_at_[hidden])
Date: 2016-04-04 11:35:59

Andrey Semashev wrote:

> IMHO, if you need something more than a byte swap then you need a 
> different library.

You're just repeating what you said. My answer remains the same. You never 
need a byte swap. What you need is always something else, to which a byte 
swap is sometimes the answer. Specifically, what you need is to be able to 
read or write integers or floats in non-native formats.

> Well, in some of the projects I work on we have something as simple as:
>
>    void write_be32(std::uint32_t n, void* p);
>    std::uint32_t read_be32(const void* p);
>    // etc.
>
>    template< typename T, std::size_t Size = sizeof(T) >
>    struct big_endian;
>
>    // Specializations for different values of Size
>    template< typename T >
>    struct big_endian< T, 4 >
>    {
>      static void write(T n, void* p)
>      {
>        write_be32(n, p);
>      }

That's more or less what I have, too. Where do we disagree?

Note that

>    void write_be32(std::uint32_t n, void* p);

needs not assume presence of uint32_t or a particular representation of n. 
Given any integer n in any representation, it could still portably write a 
big-endian 32 bit integer into p.

void write_be32( uint_least32_t n, unsigned char p[4] )
{
    // I assume CHAR_BIT of 8 here

    /* assert( n < 2^32 ); */

    p[0] = ( n >> 24 ) & 0xFF;
    p[1] = ( n >> 16 ) & 0xFF;
    p[2] = ( n >> 8 ) & 0xFF;
    p[3] = n & 0xFF;
}

This is, however, not what Boost.Endian does.