tcp_core.h

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// Copyright 2025 The Aerospace Corporation.
// This file is a part of SatCat5, licensed under CERN-OHL-W v2 or later.
 
#pragma once
 
#include <satcat5/ip_core.h>
 
namespace satcat5 {
    namespace tcp {
        // Alias for address and port types in the "tcp" namespace.
        typedef satcat5::ip::Addr Addr;
        typedef satcat5::ip::Port Port;
 
        constexpr unsigned HDR_MIN_WORDS        = 5;
        constexpr unsigned HDR_MIN_SHORTS       = 2 * HDR_MIN_WORDS;
        constexpr unsigned HDR_MIN_BYTES        = 4 * HDR_MIN_WORDS;
        constexpr unsigned HDR_MAX_WORDS        = 15;
        constexpr unsigned HDR_MAX_SHORTS       = 2 * HDR_MAX_WORDS;
        constexpr unsigned HDR_MAX_BYTES        = 4 * HDR_MAX_WORDS;
 
        struct Header {
            u16 data[HDR_MAX_SHORTS];
 
            // Explicitly declare default constructor and assignment methods.
            Header() = default;
            Header(const Header& t) = default;
            Header& operator=(const Header& t) = default;
 
            // Accessors for specific sub-fields.
            // https://en.wikipedia.org/wiki/Transmission_Control_Protocol#TCP_segment_structure
            constexpr satcat5::tcp::Port src() const    
                { return satcat5::tcp::Port{data[0]}; }
            constexpr satcat5::tcp::Port dst() const    
                { return satcat5::tcp::Port{data[1]}; }
            constexpr unsigned ihl() const              
                { return (data[6] >> 12) & 0x0F; }
            constexpr u16 chk() const                   
                { return data[8]; }
 
            void chk_incr16(u16 prev, u16 next);
            void chk_incr32(u32 prev, u32 next);
 
            void write_to(satcat5::io::Writeable* wr) const;
 
            bool read_core(satcat5::io::Readable* rd);
 
            bool read_from(satcat5::io::Readable* rd);
        };
    }
}