page.h

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#pragma once
 
#include "./base.h"
 
#include <cstdint>
#include <optional>
 
namespace emlabcpp::cfg
{
 
template < typename T >
using opt = std::optional< T >;
 
enum class hdr_state : uint8_t
{
        A = 0x40,
        B = A + 0x40,
        C = B + 0x40,
};
 
inline hdr_state next( hdr_state cs ) noexcept
{
        switch ( cs ) {
        case hdr_state::A:
                return hdr_state::B;
        case hdr_state::B:
                return hdr_state::C;
        case hdr_state::C:
                return hdr_state::A;
        default:
                return cs;
        }
}
 
inline opt< hdr_state > byte_to_hdr( std::byte b ) noexcept
{
        switch ( b ) {
        case std::byte{ static_cast< uint8_t >( hdr_state::A ) }:
                return hdr_state::A;
        case std::byte{ static_cast< uint8_t >( hdr_state::B ) }:
                return hdr_state::B;
        case std::byte{ static_cast< uint8_t >( hdr_state::C ) }:
                return hdr_state::C;
        default:
                return {};
        }
}
 
inline opt< hdr_state > hdr_to_hdr_state( std::span< std::byte, cell_size > b ) noexcept
{
        if ( b[0] != ~b[1] )
                return {};
        return byte_to_hdr( b[0] );
}
 
inline std::array< std::byte, 2 > get_hdr( hdr_state hst ) noexcept
{
        std::array< std::byte, 2 > b;
        b[0] = static_cast< std::byte >( hst );
        b[1] = ~static_cast< std::byte >( hst );
        return b;
}
 
}  // namespace emlabcpp::cfg