coap_writer.h

// Copyright 2024-2025 The Aerospace Corporation.
// This file is a part of SatCat5, licensed under CERN-OHL-W v2 or later.
// Message formatting for the Constrained Applications Protocol (CoAP)
 
#pragma once
 
#include <satcat5/coap_constants.h>
#include <satcat5/coap_reader.h>
#include <satcat5/io_writeable.h>
 
namespace satcat5 {
    namespace coap {
        class Writer final {
        public:
            constexpr Writer(
                satcat5::io::Writeable* dst,
                bool write_max_age = true)
                : m_dst(dst), m_last_opt(0), m_insert_max_age(write_max_age) {}
 
            inline bool ready() const
                { return m_dst && m_dst->get_write_space(); }
 
            bool write_header(
                u8 type, Code code, u16 msg_id,
                u64 token = 0, u8 tkl = 0);
 
            bool write_header(Code code, Connection* request);
 
            bool write_option(u16 id, unsigned len, const void* data);
            bool write_option(u16 id, const char* str);
            bool write_option(u16 id, u64 value);
 
            bool write_uri(u16 id, const char* str);
 
            satcat5::io::Writeable* write_data();
 
            inline bool write_finalize()
                { insert_max_age(); return m_dst->write_finalize(); }
 
        protected:
            // Internal write methods.
            bool write_optid(u16 id, unsigned len);
            void write_varint(u64 x, unsigned len);
            void insert_max_age(u16 next_id = 0);
 
            satcat5::io::Writeable* const m_dst;
            u16 m_last_opt;                 
            bool m_insert_max_age;          
        };
    }
}