midi_output.c

/*
Copyright (C) 2024 Eugene Chernyh (mrf-r)

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

#include "midi_output.h"
#include "midi_internals.h"

#ifndef MIDI_TX_NRPN_LIFETIME_TICKS
#define MIDI_TX_NRPN_LIFETIME_TICKS ((uint32_t)(MIDI_CLOCK_RATE * 2)) // 2 seconds probably ok
#endif

static const uint32_t m_compare_mask[16] = {
    // RIGHT TO LEFT: cin-cn, status_byte, data_bytes
    0xFFFFFFFF, // 0x0 1, 2 or 3 Miscellaneous function codes. Reserved for future extensions.        | --
    0xFFFFFFFF, // 0x1 1, 2 or 3 Cable events. Reserved for future expansion.                         | --
    0x0000FF00, // 0x2 2 Two-byte System Common messages like MTC, SongSelect, etc.                   |
    0x0000FF00, // 0x3 3 Three-byte System Common messages like SPP, etc.                             |
    0xFFFFFF00, // 0x4 3 SysEx starts or continues                                                    | -- //sysex must not go through that method
    0xFFFFFF00, // 0x5 1 Single-byte System Common Message or SysEx ends with following single byte.  | --
    0xFFFFFF00, // 0x6 2 SysEx ends with following two bytes.                                         | --
    0xFFFFFF00, // 0x7 3 SysEx ends with following three bytes.                                       | --
    0x00FFEF00, // 0x8 3 Note-off                                                                     |
    0x00FFEF00, // 0x9 3 Note-on                                                                      |
    0x00FFFF00, // 0xA 3 Poly-KeyPress                                                                |
    0x00FFFF00, // 0xB 3 Control Change                                                               | used in CC handler
    0x0000FF00, // 0xC 2 Program Change                                                               | --
    0x0000FF00, // 0xD 2 Channel Pressure                                                             | --
    0x0000FF00, // 0xE 3 PitchBend Change                                                             |
    0x0000FF00, // 0xF 1 Single Byte                                                                  | --
};

static MidiRet mOptWr________na(MidiOutPortContextT* cx, MidiMessageT m);
static MidiRet mOptWr_SyxStaCon(MidiOutPortContextT* cx, MidiMessageT m);
static MidiRet mOptWr____SyxEnd(MidiOutPortContextT* cx, MidiMessageT m);
static MidiRet mOptWr___Regular(MidiOutPortContextT* cx, MidiMessageT m);
static MidiRet mOptWr____Single(MidiOutPortContextT* cx, MidiMessageT m);
static MidiRet mOptWr________CC(MidiOutPortContextT* cx, MidiMessageT m);

static MidiRet (*const mPortOptWr[16])(MidiOutPortContextT* cx, MidiMessageT m) = {
    mOptWr________na, // 0x0 1, 2 or 3 Miscellaneous function codes. Reserved for future extensions.
    mOptWr________na, // 0x1 1, 2 or 3 Cable events. Reserved for future expansion.
    mOptWr____Single, // 0x2 2 Two-byte System Common messages like MTC, SongSelect, etc.
    mOptWr____Single, // 0x3 3 Three-byte System Common messages like SPP, etc.
    mOptWr_SyxStaCon, // 0x4 3 SysEx starts or continues
    mOptWr____SyxEnd, // 0x5 1 Single-byte System Common Message or SysEx ends with following single byte.
    mOptWr____SyxEnd, // 0x6 2 SysEx ends with following two bytes.
    mOptWr____SyxEnd, // 0x7 3 SysEx ends with following three bytes.
    mOptWr___Regular, // 0x9 3 Note-on
    mOptWr___Regular, // 0xA 3 Poly-KeyPress
    mOptWr___Regular, // 0x8 3 Note-off
    mOptWr________CC, // 0xB 3 Control Change
    mOptWr___Regular, // 0xC 2 Program Change
    mOptWr___Regular, // 0xD 2 Channel Pressure
    mOptWr___Regular, // 0xE 3 PitchBend Change
    mOptWr____Single, // 0xF 1 Single Byte
};

uint16_t midiPortMaxUtilisation(MidiOutPortContextT* cx)
{
    MIDI_ATOMIC_START();
    uint16_t u = cx->max_utilisation;
    cx->max_utilisation = 0;
    MIDI_ATOMIC_END();
    return u;
}

uint16_t midiPortMaxSysexUtilisation(MidiOutPortContextT* cx)
{
    MIDI_ATOMIC_START();
    uint16_t u = cx->max_syx_utilisation;
    cx->max_syx_utilisation = 0;
    MIDI_ATOMIC_END();
    return u;
}

// init output port structure
void midiPortInit(MidiOutPortContextT* cx)
{
    MIDI_ATOMIC_START();
    cx->buf_rp = 0;
    cx->buf_wp = 0;
    cx->status = STATUS_NRPN_UNDEF_BMP;
    cx->sysex_rp = 0;
    cx->sysex_wp = 0;
    cx->nrpn_lsb = 0xFF;
    cx->nrpn_msb = 0xFF;

    cx->max_syx_utilisation = 0;
    cx->max_utilisation = 0;
    cx->messages_flushed = 0;
    cx->messages_optimized = 0;
    MIDI_ATOMIC_END();
}

uint16_t midiPortUtilisation(MidiOutPortContextT* cx)
{
    return (cx->buf_wp - cx->buf_rp) & (MIDI_TX_BUFFER_SIZE - 1);
}
uint16_t midiPortSysexUtilisation(MidiOutPortContextT* cx)
{
    return (cx->sysex_wp - cx->sysex_rp) & (MIDI_TX_SYSEX_BUFFER_SIZE - 1);
}

// get available space in output port
// of channel and sysex buffers lowest value will be returned
uint16_t midiPortFreespaceGet(MidiOutPortContextT* cx)
{
    uint16_t ret;
    MIDI_ATOMIC_START();
    uint16_t mainbu = (cx->buf_rp - cx->buf_wp - 1) & (MIDI_TX_BUFFER_SIZE - 1);
    uint16_t syxbu = (cx->sysex_rp - cx->sysex_wp - 1) & (MIDI_TX_SYSEX_BUFFER_SIZE - 1);
    ret = syxbu < mainbu ? syxbu : mainbu;
    MIDI_ATOMIC_END();
    return ret;
}

static inline void mUtilisationUpdate(MidiOutPortContextT* cx)
{
    uint16_t um = ((cx->buf_wp - cx->buf_rp) & (MIDI_TX_BUFFER_SIZE - 1));
    if (um > cx->max_utilisation) {
        cx->max_utilisation = um;
    }
    uint16_t us = ((cx->sysex_wp - cx->sysex_rp) & (MIDI_TX_SYSEX_BUFFER_SIZE - 1));
    if (us > cx->max_syx_utilisation) {
        cx->max_syx_utilisation = us;
    }
}

unsigned midiMessageCheck(MidiMessageT m)
{
    if (m.cin >= 0x8) {
        return m.cin == m.miditype;
    } else {
        switch (m.cin) {
        case MIDI_CIN_2BYTESYSTEMCOMMON:
            return (0xF1 == m.byte1) || (0xF3 == m.byte1); // MTC or Song select
        case MIDI_CIN_3BYTESYSTEMCOMMON:
            return 0xF2 == m.byte1; // SPP
        case MIDI_CIN_SYSEX3BYTES:
            return 1;
        case MIDI_CIN_SYSEXEND1:
            return 0xF7 == m.byte1;
        case MIDI_CIN_SYSEXEND2:
            return 0xF7 == m.byte2;
        case MIDI_CIN_SYSEXEND3:
            return 0xF7 == m.byte3;
        case MIDI_CIN_SINGLEBYTE:
            return 0xF == m.miditype;
        default:
        case MIDI_CIN_RESERVED1:
        case MIDI_CIN_RESERVED2:
            return 0;
        }
    }
}

// write message to output port with protocol logic optimizations
MidiRet midiPortWrite(MidiOutPortContextT* cx, MidiMessageT m)
{
    MIDI_ASSERT(midiMessageCheck(m));
    uint16_t ret;
    if (cx->status & STATUS_OPTIMIZATION_DISABLED)
        return midiPortWriteRaw(cx, m);

    MIDI_ATOMIC_START();
    ret = mPortOptWr[m.cin](cx, m);
    mUtilisationUpdate(cx);
    // // start transmission if not already started
    // if (p->type == MIDI_TYPE_UART) {
    //     MidiOutUartApiT* uap = (MidiOutUartApiT*)p->api;
    //     if (!(uap->isBusy())) {
    //         midiOutUartTranmissionCompleteCallback(p);
    //     }
    // }
    MIDI_ATOMIC_END();
    return ret;
}

// "midi cable mode" without messages reorganization and
// protocol logic optimization. both channel and sysex
// call port flush to exit from this mode
MidiRet midiPortWriteRaw(MidiOutPortContextT* cx, MidiMessageT m)
{
    MIDI_ASSERT(midiMessageCheck(m));
    MIDI_ASSERT(m.cin >= 0x8 ? m.cin == m.miditype : 1);
    MidiRet ret = MIDI_RET_FAIL;
    MIDI_ATOMIC_START();
    cx->status |= STATUS_OPTIMIZATION_DISABLED;
    uint16_t wp = (cx->buf_wp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
    if (wp != cx->buf_rp) {
        cx->buf[cx->buf_wp] = m;
        cx->buf_wp = wp;
        ret = MIDI_RET_OK;
    }
    mUtilisationUpdate(cx);
    // // start transmission if not already started
    // if (p->type == MIDI_TYPE_UART) {
    //     MidiOutUartApiT* uap = (MidiOutUartApiT*)p->api;
    //     if (!(uap->isBusy())) {
    //         midiOutUartTranmissionCompleteCallback(p);
    //     }
    // }
    MIDI_ATOMIC_END();
    return ret;
}

// free port, also reset nonoptimize mode
// and unlocks sysex
void midiPortFlush(MidiOutPortContextT* cx)
{
    MIDI_ATOMIC_START();
    cx->buf_rp = cx->buf_wp;
    cx->sysex_rp = cx->sysex_wp;
    cx->sysex_cn = SYSEX_CN_UNLOCK;
    cx->status = STATUS_NRPN_UNDEF_BMP;
    cx->nrpn_lsb = 0xFF;
    cx->nrpn_msb = 0xFF;
    MIDI_ATOMIC_END();
}

static const uint16_t m_cin_priorities[16] = {
    // values must be from 0 (filtered out) to (buffer size - 2)
    (MIDI_TX_BUFFER_SIZE - 2) * 0 / 1, // 0x0 1, 2 or 3 Miscellaneous function codes. Reserved for future extensions.        | not used at all
    (MIDI_TX_BUFFER_SIZE - 2) * 0 / 1, // 0x1 1, 2 or 3 Cable events. Reserved for future expansion.                         | not used at all
    (MIDI_TX_BUFFER_SIZE - 2) * 1 / 1, // 0x2 2 Two-byte System Common messages like MTC, SongSelect, etc.                   | 100%
    (MIDI_TX_BUFFER_SIZE - 2) * 1 / 1, // 0x3 3 Three-byte System Common messages like SPP, etc.                             | 100%
    (MIDI_TX_BUFFER_SIZE - 2) * 0 / 1, // 0x4 3 SysEx starts or continues                                                    | --
    (MIDI_TX_BUFFER_SIZE - 2) * 0 / 1, // 0x5 1 Single-byte System Common Message or SysEx ends with following single byte.  | --
    (MIDI_TX_BUFFER_SIZE - 2) * 0 / 1, // 0x6 2 SysEx ends with following two bytes.                                         | --
    (MIDI_TX_BUFFER_SIZE - 2) * 0 / 1, // 0x7 3 SysEx ends with following three bytes.                                       | --
    (MIDI_TX_BUFFER_SIZE - 2) * 7 / 8, // 0x8 3 Note-off                                                                     | 87%
    (MIDI_TX_BUFFER_SIZE - 2) * 5 / 8, // 0x9 3 Note-on                                                                      | 62% - it must be noticable
    (MIDI_TX_BUFFER_SIZE - 2) * 1 / 2, // 0xA 3 Poly-KeyPress                                                                | 50%
    (MIDI_TX_BUFFER_SIZE - 2) * 7 / 8, // 0xB 3 Control Change                                                               | 87% - NOT USED by defaul
    (MIDI_TX_BUFFER_SIZE - 2) * 2 / 3, // 0xC 2 Program Change                                                               | 67%
    (MIDI_TX_BUFFER_SIZE - 2) * 5 / 9, // 0xD 2 Channel Pressure                                                             | 55%
    (MIDI_TX_BUFFER_SIZE - 2) * 4 / 7, // 0xE 3 PitchBend Change                                                             | 57%
    (MIDI_TX_BUFFER_SIZE - 2) * 1 / 1, // 0xF 1 Single Byte                                                                  | 100% always active
};

static const uint16_t m_cc_priorities[3] = {
    // values must be from 0 (filtered out) to (buffer size - 2)
    (MIDI_TX_BUFFER_SIZE - 2) * 5 / 8, // 62% MSB
    (MIDI_TX_BUFFER_SIZE - 2) * 4 / 7, // 57% regular
    (MIDI_TX_BUFFER_SIZE - 2) * 2 / 3, // 67% special
    // CC LSB - not critical, it is possible to flush them without problems
    // CC MSB - by the time LSB is already flushed, so nothing wrong
    // nrpn/rpn data - possible to flush the message without errors - same as CC
    // nrpn/rpn address - by the time data is already flushed, so no errors
    // channel mode - atomic
};

static uint32_t m_cc_prio_bmp[4] = {
    0x00000000,
    0x00000000,
    0x00000001, // damper
    0xFF00003C, // channel modes and rpn addr
};

static inline uint16_t mGetMessagePrio(MidiMessageT m)
{
    uint16_t priority = 0;
    if (m.cin == MIDI_CIN_CONTROLCHANGE) {
        uint8_t cc_pos = m.byte2 >> 5;
        uint8_t cc_msk = m.byte2 & 0x1F;
        if (cc_pos == 0) {
            priority = m_cc_priorities[0];
        } else {
            uint8_t is_high = (m_cc_prio_bmp[cc_pos] >> cc_msk) & 0x1;
            priority = m_cc_priorities[1 + is_high];
        }
    } else {
        priority = m_cin_priorities[m.cin];
    }
    return priority;
}

// flush certain position from port buffer
static inline void mFlushMessage(MidiOutPortContextT* cx, uint16_t pos)
{
    MIDI_ASSERT(cx);
    MIDI_ASSERT(pos < MIDI_TX_BUFFER_SIZE);
    // rp <= pos < wp
    MIDI_ASSERT(((pos - cx->buf_rp) & (MIDI_TX_BUFFER_SIZE - 1)) <= ((cx->buf_wp - cx->buf_rp) & (MIDI_TX_BUFFER_SIZE - 1)));
    cx->messages_flushed++;
    // scan and shift form pos to rp
    for (uint16_t i = pos; i != cx->buf_rp; i = (i - 1) & (MIDI_TX_BUFFER_SIZE - 1)) {
        cx->buf[i] = cx->buf[(i - 1) & (MIDI_TX_BUFFER_SIZE - 1)];
    }
    cx->buf_rp = (cx->buf_rp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
    // // shift from pos to wp
    // cx->buf_wp = (cx->buf_wp - 1) & (MIDI_TX_BUFFER_SIZE - 1);
    // uint16_t next;
    // for (uint16_t i = pos; i != cx->buf_wp; i = next) {
    //     next = (i + 1) & (MIDI_TX_BUFFER_SIZE - 1);
    //     cx->buf[i] = cx->buf[next];
    // }
}

// return MIDI_RET_OK if there is available space in buffer
static inline MidiRet mCheckBufferSpace(MidiOutPortContextT* cx, uint16_t new_prio)
{
    // priorities are not related to the buffer size and can be arbitrary numbers.
    // they use MIDI_TX_BUFFER_SIZE as a reference for historical reasons
    MidiRet ret = MIDI_RET_OK;
    uint16_t utilisation = ((cx->buf_wp - cx->buf_rp) & (MIDI_TX_BUFFER_SIZE - 1));
    if ((MIDI_TX_BUFFER_SIZE - 1) <= utilisation) {
        uint16_t lowest_prio = 0xFFFF;
        uint16_t lowest_prio_pos = cx->buf_rp; // preinit to satisfy compiler
        for (uint16_t i = cx->buf_rp; i != cx->buf_wp; i = (i + 1) & (MIDI_TX_BUFFER_SIZE - 1)) {
            uint16_t prio = mGetMessagePrio(cx->buf[i]);
            if (prio < lowest_prio) { // oldest will be flushed
                lowest_prio = prio;
                lowest_prio_pos = i;
            }
        }
        if (lowest_prio <= new_prio) { // oldest will be flushed
            mFlushMessage(cx, lowest_prio_pos);
        } else {
            cx->messages_flushed++;
            ret = MIDI_RET_FAIL;
        }
    }
    return ret;
}

static MidiRet mOptWr________na(MidiOutPortContextT* cx, MidiMessageT m)
{
    MIDI_ASSERT(0);
    (void)cx;
    (void)m;
    return MIDI_RET_FAIL;
}

// CC is the most complex one
// it uses nrpn special filtering, repeated messages filtering and priority filtering

static inline MidiRet mowccNrpnData(MidiOutPortContextT* cx, MidiMessageT m)
{
    // if this is nrpn data then check it's address validity
    // if either AL or AH was flushed, this data is useless
    if (cx->status & STATUS_NRPN_UNDEF_BMP) {
        cx->messages_flushed++;
        return MIDI_RET_FAIL;
    }
    // scan buffer only up to the last address set, do not replace data of different addresses
    for (uint16_t i = (cx->buf_wp - 1) & (MIDI_TX_BUFFER_SIZE - 1);
         i != ((cx->buf_rp - 1) & (MIDI_TX_BUFFER_SIZE - 1));
         i = (i - 1) & (MIDI_TX_BUFFER_SIZE - 1)) {
        // check that current position is not an address, then we can replace
        uint8_t cc_pos = cx->buf[i].byte2 >> 5;
        uint8_t cc_msk = cx->buf[i].byte2 & 0x1F;
        const uint32_t nrpn_addr_bmp3 = 0x0000003C;
        if ((cc_pos == 3) && ((nrpn_addr_bmp3 >> cc_msk) & 1)) {
            break;
        } else {
            const uint32_t compare_mask = m_compare_mask[MIDI_CIN_CONTROLCHANGE];
            if (((cx->buf[i].full_word ^ m.full_word) & compare_mask) == 0) {
                cx->messages_optimized++;
                // mFlushMessage(cx, i);
                // cx->buf[cx->buf_wp] = m;
                // cx->buf_wp = (cx->buf_wp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
                cx->buf[i] = m; // let's simplify!
                return MIDI_RET_OK;
            }
        }
    }
    // filter by priority
    MidiRet ret = MIDI_RET_FAIL;
    if (MIDI_RET_OK == mCheckBufferSpace(cx, mGetMessagePrio(m))) {
        cx->buf[cx->buf_wp] = m;
        cx->buf_wp = (cx->buf_wp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
        ret = MIDI_RET_OK;
    } else {
        cx->messages_flushed++;
    }
    return ret;
}

static inline MidiRet mowccNrpnAddress(MidiOutPortContextT* cx, MidiMessageT m, uint8_t cc_msk)
{
    // handle RPN-NRPN switch
    if (cx->status & STATUS_NOT_RPN) {
        if (m.byte2 >= 100) {
            cx->status |= STATUS_NRPN_UNDEF_BMP;
            cx->status &= ~STATUS_NOT_RPN;
            cx->nrpn_lsb = 0xFF;
            cx->nrpn_msb = 0xFF;
        }
    } else {
        if (m.byte2 < 100) {
            cx->status |= STATUS_NRPN_UNDEF_BMP | STATUS_NOT_RPN;
            cx->nrpn_lsb = 0xFF;
            cx->nrpn_msb = 0xFF;
        }
    }
    MidiRet ret = MIDI_RET_FAIL;
    const uint16_t prio = m_cc_priorities[2];
    if (MIDI_RET_OK == mCheckBufferSpace(cx, prio)) {
        uint32_t t = MIDI_GET_CLOCK();
        const uint32_t nrpn_al_bmp3 = 0x00000014;
        const uint32_t nrpn_ah_bmp3 = 0x00000028;
        if ((nrpn_al_bmp3 >> cc_msk) & 0x1) {
            if ((m.byte3 == cx->nrpn_lsb) && ((int32_t)(cx->nrpn_lsb_time - t) > 0)) {
                // same address was transmitted recently
                return MIDI_RET_OK;
            } else {
                // different address or timeout
                cx->nrpn_lsb_time = t + MIDI_TX_NRPN_LIFETIME_TICKS;
                cx->nrpn_lsb = m.byte3;
                cx->status &= ~STATUS_NRPNAL_UNDEF;
            }
        } else if ((nrpn_ah_bmp3 >> cc_msk) & 0x1) {
            if ((m.byte3 == cx->nrpn_msb) && ((int32_t)(cx->nrpn_msb_time - t) > 0)) {
                // same address was transmitted recently
                return MIDI_RET_OK;
            } else {
                // different address or timeout
                cx->nrpn_msb_time = t + MIDI_TX_NRPN_LIFETIME_TICKS;
                cx->nrpn_msb = m.byte3;
                cx->status &= ~STATUS_NRPNAH_UNDEF;
            }
        }
        cx->buf[cx->buf_wp] = m;
        cx->buf_wp = (cx->buf_wp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
        ret = MIDI_RET_OK;
    } else {
        // buffer is full
        const uint32_t nrpn_al_bmp3 = 0x00000014;
        const uint32_t nrpn_ah_bmp3 = 0x00000028;
        if ((nrpn_al_bmp3 >> cc_msk) & 0x1) {
            cx->status |= STATUS_NRPNAL_UNDEF;
        } else if ((nrpn_ah_bmp3 >> cc_msk) & 0x1) {
            cx->status |= STATUS_NRPNAH_UNDEF;
        }
        cx->messages_flushed++;
    }
    return ret;
}

static inline MidiRet mowccRegularCC(MidiOutPortContextT* cx, MidiMessageT m)
{
    for (uint16_t i = (cx->buf_wp - 1) & (MIDI_TX_BUFFER_SIZE - 1);
         i != ((cx->buf_rp - 1) & (MIDI_TX_BUFFER_SIZE - 1));
         i = (i - 1) & (MIDI_TX_BUFFER_SIZE - 1)) {
        // optimize repeated events
        const uint32_t compare_mask = m_compare_mask[MIDI_CIN_CONTROLCHANGE];
        if (((cx->buf[i].full_word ^ m.full_word) & compare_mask) == 0) {
            cx->messages_optimized++;
            // mFlushMessage(cx, i); // should we keep order?
            // cx->buf[cx->buf_wp] = m;
            // cx->buf_wp = (cx->buf_wp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
            cx->buf[i] = m; // let's simplify!
            return MIDI_RET_OK;
        }
    }
    // filter by priority
    MidiRet ret = MIDI_RET_FAIL;
    if (MIDI_RET_OK == mCheckBufferSpace(cx, mGetMessagePrio(m))) {
        cx->buf[cx->buf_wp] = m;
        cx->buf_wp = (cx->buf_wp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
        ret = MIDI_RET_OK;
    } else {
        cx->messages_flushed++;
    }
    return ret;
}

static MidiRet mOptWr________CC(MidiOutPortContextT* cx, MidiMessageT m)
{
    const uint32_t nrpn_dat_bmp[4] = {
        0x00000040, // dat msb
        0x00000040, // dat lsb
        0x00000000, //
        0x00000003, // inc dec
    };
    const uint32_t nrpn_addr_bmp3 = 0x0000003C;
    uint8_t cc_pos = m.byte2 >> 5;
    uint8_t cc_msk = m.byte2 & 0x1F;
    if ((nrpn_dat_bmp[cc_pos] >> cc_msk) & 0x1) {
        return mowccNrpnData(cx, m);
    } else if ((cc_pos == 3) && (nrpn_addr_bmp3 >> cc_msk) & 0x1) {
        return mowccNrpnAddress(cx, m, cc_msk);
    } else {
        return mowccRegularCC(cx, m);
    }
}

// Regular is a little bit harder
// it uses messages optimisation and priority filtering
static MidiRet mOptWr___Regular(MidiOutPortContextT* cx, MidiMessageT m)
{
    // find similar messages and delete them
    // scan from last to first
    for (uint16_t i = (cx->buf_wp - 1) & (MIDI_TX_BUFFER_SIZE - 1);
         i != ((cx->buf_rp - 1) & (MIDI_TX_BUFFER_SIZE - 1));
         i = (i - 1) & (MIDI_TX_BUFFER_SIZE - 1)) {
        // check if the same entity got new value before previous was sent
        if (0 == ((cx->buf[i].full_word ^ m.full_word) & m_compare_mask[m.cin])) {
            // shift buffer part and write message to the end
            cx->messages_optimized++;
            // mFlushMessage(cx, i);
            // cx->buf[cx->buf_wp] = m;
            // cx->buf_wp = (cx->buf_wp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
            cx->buf[i] = m;
            return MIDI_RET_OK;
        }
    }
    // filter by priority
    MidiRet ret = MIDI_RET_FAIL;
    if (MIDI_RET_OK == mCheckBufferSpace(cx, mGetMessagePrio(m))) {
        cx->buf[cx->buf_wp] = m;
        cx->buf_wp = (cx->buf_wp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
        ret = MIDI_RET_OK;
    } else {
        cx->messages_flushed++;
    }
    return ret;
}

// Single is the simplest one
// the only optimisation it uses is priority filtering
static MidiRet mOptWr____Single(MidiOutPortContextT* cx, MidiMessageT m)
{
    MidiRet ret = MIDI_RET_FAIL;
    if (MIDI_RET_OK == mCheckBufferSpace(cx, m_cin_priorities[MIDI_CIN_SINGLEBYTE])) {
        cx->buf_rp = (cx->buf_rp - 1) & (MIDI_TX_BUFFER_SIZE - 1);
        uint16_t pos = cx->buf_rp;
        while (pos != cx->buf_wp) {
            uint16_t next = (pos + 1) & (MIDI_TX_BUFFER_SIZE - 1);
            const unsigned t_rt = CINBMP_SINGLEBYTE | CINBMP_2BYTESYSTEMCOMMON | CINBMP_3BYTESYSTEMCOMMON;
            if ((next != cx->buf_wp) && ((t_rt >> cx->buf[next].cin) & 1)) {
                // same kind of message, shift it, so we can insert after
                cx->buf[pos] = cx->buf[next];
            } else {
                cx->buf[pos] = m;
                ret = MIDI_RET_OK;
                break;
            }
            pos = next;
        }
    } else {
        // this is dead code
        cx->messages_flushed++;
    }
    return ret;
}

static MidiRet mOptWr_SyxStaCon(MidiOutPortContextT* cx, MidiMessageT m)
{
    MidiRet ret = MIDI_RET_FAIL;
    if ((SYSEX_CN_UNLOCK == cx->sysex_cn) || (cx->sysex_cn == m.cn)) {
        uint16_t wp = (cx->sysex_wp + 1) & (MIDI_TX_SYSEX_BUFFER_SIZE - 1);
        if (wp != cx->sysex_rp) {
            cx->sysex_cn = m.cn;
            cx->sysex_buf[cx->sysex_wp] = m;
            cx->sysex_wp = wp;
            ret = MIDI_RET_OK;
        }
    }
    return ret;
}

static MidiRet mOptWr____SyxEnd(MidiOutPortContextT* cx, MidiMessageT m)
{
    MidiRet ret = MIDI_RET_FAIL;
    if ((SYSEX_CN_UNLOCK == cx->sysex_cn) || (cx->sysex_cn == m.cn)) {
        uint16_t wp = (cx->sysex_wp + 1) & (MIDI_TX_SYSEX_BUFFER_SIZE - 1);
        if (wp != cx->sysex_rp) {
            cx->sysex_buf[cx->sysex_wp] = m;
            cx->sysex_wp = wp;
            ret = MIDI_RET_OK;
        }
        cx->sysex_cn = SYSEX_CN_UNLOCK;
    }
    return ret;
}

// MidiRet midi_port_check_rt(MidiOutPortContextT* cx, MidiMessageT* m)
// {
//     MidiRet ret = MIDI_RET_FAIL;
//     MidiOutPortContextT* cx = p->context;
//     // TODO critical stuff???
//     if ((0 == (cx->status & (STATUS_OPTIMIZATION_DISABLED | STATUS_OUTPUT_SYX_MODE))) && (cx->buf_rp != cx->buf_wp)) {
//         *m = cx->buf[cx->buf_rp];
//         if (m->cin == MIDI_CIN_SINGLEBYTE) {
//             cx->buf_rp = (cx->buf_rp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
//             m->cn = p->cn;
//             ret = MIDI_RET_OK;
//         }
//     }
//     return ret;
// }

MidiRet midiPortReadNext(MidiOutPortContextT* cx, MidiMessageT* m)
{
    MidiRet ret = MIDI_RET_FAIL;
    MIDI_ATOMIC_START();
    if (cx->status & STATUS_OUTPUT_SYX_MODE) {
        if (cx->sysex_rp != cx->sysex_wp) {
            *m = cx->sysex_buf[cx->sysex_rp];
            cx->sysex_rp = (cx->sysex_rp + 1) & (MIDI_TX_SYSEX_BUFFER_SIZE - 1);
            // CIN SYX END
            const uint16_t t_syxe = CINBMP_SYSEXEND1 | CINBMP_SYSEXEND2 | CINBMP_SYSEXEND3;
            if ((t_syxe >> m->cin) & 0x1) {
                cx->status &= ~STATUS_OUTPUT_SYX_MODE;
            }
            ret = MIDI_RET_OK;
        }
        // else wait for sysex buffer filling
    } else {
        // sysex starts only if main buffer is empty - probably not the best policy
        if (cx->buf_rp != cx->buf_wp) {
            *m = cx->buf[cx->buf_rp];
            cx->buf_rp = (cx->buf_rp + 1) & (MIDI_TX_BUFFER_SIZE - 1);
            ret = MIDI_RET_OK;
        } else {
            if (cx->sysex_rp != cx->sysex_wp) {
                *m = cx->sysex_buf[cx->sysex_rp];
                cx->sysex_rp = (cx->sysex_rp + 1) & (MIDI_TX_SYSEX_BUFFER_SIZE - 1);
                // CIN SYX CONT
                const uint16_t t_syxs = CINBMP_SYSEX3BYTES;
                if ((t_syxs >> m->cin) & 0x1) {
                    cx->status |= STATUS_OUTPUT_SYX_MODE;
                }
                ret = MIDI_RET_OK;
            }
        }
    }
    // m->cn = p->cn;
    MIDI_ATOMIC_END();
    return ret;
}

#if (MIDI_TX_BUFFER_SIZE & (MIDI_TX_BUFFER_SIZE - 1)) != 0
#error "output buffer: please, use only power of 2"
#endif

#if (MIDI_TX_SYSEX_BUFFER_SIZE & (MIDI_TX_SYSEX_BUFFER_SIZE - 1)) != 0
#error "output sysex buffer: please, use only power of 2"
#endif