RTPMIDI.h

/* Copyright (c) 2021 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef RTPMIDI_H
#define RTPMIDI_H

// TODO: Clean up includes
#include <stdint.h>
#include "mbed.h"
#include "NetworkInterface.h"
#include "UDPSocket.h"

// TODO: Include this header without having to include mbed-usb
#include "MIDIMessage.h"

#if BYTE_ORDER == LITTLE_ENDIAN
    #define htonll(x) ((((uint64_t)lwip_htonl(x)) << 32) + lwip_htonl((x) >> 32))
#else
    #define htonll(x) ((uint64_t)x)
#endif /* BYTE_ORDER == LITTLE_ENDIAN */

#define CONTROL_PORT    5004
#define MIDI_PORT       5005

#define MAX_NAME_LENGTH 32

#define MAX_MIDI_COMMAND_LEN    8

#define EXCHANGE_SIGNATURE   0xFFFF
#define INV_COMMAND          0x494E
#define ACCEPT_INV_COMMAND   0x4F4B
#define REJECT_INV_COMMAND   0x4E4F
#define END_COMMAND          0x4259
#define PROTOCOL_VERSION     2

#define SYNC_CK0    0
#define SYNC_CK1    1
#define SYNC_CK2    2

#define RTP_VERSION_SHIFT   6
#define RTP_VERSION_2       2

#define RTP_P_FIELD      0x20
#define RTP_X_FIELD      0x10
#define RTP_CC_FIELD     0xF
#define RTP_M_FIELD      0x80
#define RTP_PAYLOAD_TYPE 0x61

#define RTP_CS_FLAG_B    0x80
#define RTP_CS_FLAG_J    0x40
#define RTP_CS_FLAG_Z    0x20
#define RTP_CS_FLAG_P    0x10
//TODO: Variable Length Headers
#define RTP_CS_LEN       0xF

/* Header Defaults */
#define VPXCC       ((RTP_VERSION_2 << RTP_VERSION_SHIFT) & (~RTP_P_FIELD & ~RTP_X_FIELD & ~RTP_CC_FIELD))
#define MPAYLOAD    (~RTP_M_FIELD & RTP_PAYLOAD_TYPE)
#define SEQ_NR      1

/* TODO: Generate these somehow, rather than defining them */
#define SSRC_NUMBER          0x2d5d5ff3
#define NAME                 "k66f"

/* Session Exchange Packet */
typedef struct {
    uint16_t signature;
    uint16_t command;
    uint32_t protocol_version;
    uint32_t initiator_token;
    uint32_t sender_ssrc;
    char name[MAX_NAME_LENGTH];
} __packed exchange_packet_t;

/* Timestamp Packet */
typedef struct {
    uint16_t signature;
    uint16_t command;
    uint32_t sender_ssrc;
    uint8_t count;
    uint8_t padding[3];
    uint64_t timestamp[3];
} __packed timestamp_packet_t;

/* MIDI Packet Header */
typedef struct {
    uint8_t vpxcc;
    uint8_t mpayload;
    uint16_t sequence_number;
    uint32_t timestamp;
    uint32_t sender_ssrc;
} __packed midi_packet_header_t;

// TODO: Support variable length headers
/* MIDI Command Section Header */
typedef uint8_t midi_command_header_t;

class RTPMIDI {
public:

    /**
    * Basic Constructor using default NetworkInterface
    */
    RTPMIDI();

    /**
    * Constructor specifying NetworkInterface
    */
    RTPMIDI(NetworkInterface *net);

    /**
    * Destroy this object
    */
    ~RTPMIDI();

    /**
    * Begin session initiation as participant
    */
    void participate();


    /**
    * Send a MIDIMessage
    *
    * @param msg The MIDIMessage to send
    */
    void write(MIDIMessage msg);

private:
    // TODO: Support variable length headers
    static constexpr uint32_t MidiHeaderLength = sizeof(midi_packet_header_t) + sizeof(midi_command_header_t);
    static constexpr uint32_t MaxPacketSize = MidiHeaderLength + MAX_MIDI_COMMAND_LEN;

    uint8_t _out_buffer[MaxPacketSize];
    uint32_t _out_buffer_pos;
    uint32_t _out_buffer_size;

    uint16_t _sequence_number;

    NetworkInterface *_net;
    UDPSocket _control_socket;
    UDPSocket _midi_socket;
    SocketAddress _peer_address;

    Thread _rtp_thread;
    EventQueue _rtp_queue;

    /**
     * Perform Initialisation steps
     */
    void _init();

    /**
     * Get the current timestamp
     */
    uint64_t _calculate_current_timestamp();

    /**
     * Send and clear the buffer
     */
    void _send_midi_buffer();

    /**
     * Perform synchronisation handshake
     */
    void _synchronise();
};

#endif