/*
 * Platform interface to the MacOS X CoreMIDI framework
 * 
 * Jon Parise <jparise at cmu.edu>
 * and subsequent work by Andrew Zeldis and Zico Kolter
 * and Roger B. Dannenberg
 *
 * $Id: pmmacosx.c,v 1.17 2002/01/27 02:40:40 jon Exp $
 */
 
/* Notes:
    since the input and output streams are represented by MIDIEndpointRef
    values and almost no other state, we store the MIDIEndpointRef on
    descriptors[midi->device_id].descriptor. The only other state we need
    is for errors: we need to know if there is an error and if so, what is
    the error text. We use a structure with two kinds of
    host error: "error" and "callback_error". That way, asynchronous callbacks
    do not interfere with other error information.
    
    OS X does not seem to have an error-code-to-text function, so we will
    just use text messages instead of error codes.
 */

#include <stdlib.h>

//#define CM_DEBUG 1

#include "portmidi.h"
#include "pmutil.h"
#include "pminternal.h"
#include "porttime.h"
#include "pmmac.h"
#include "pmmacosxcm.h"

#include <stdio.h>
#include <string.h>

#include <CoreServices/CoreServices.h>
#include <CoreMIDI/MIDIServices.h>
#include <CoreAudio/HostTime.h>
#include <unistd.h>

#define PACKET_BUFFER_SIZE 1024
/* maximum overall data rate (OS X limit is 15000 bytes/second) */
#define MAX_BYTES_PER_S 14000

/* Apple reports that packets are dropped when the MIDI bytes/sec
   exceeds 15000. This is computed by "tracking the number of MIDI 
   bytes scheduled into 1-second buckets over the last six seconds
   and averaging these counts." 

   This is apparently based on timestamps, not on real time, so 
   we have to avoid constructing packets that schedule high speed
   output even if the actual writes are delayed (which was my first
   solution).

   The LIMIT_RATE symbol, if defined, enables code to modify 
   timestamps as follows:
     After each packet is formed, the next allowable timestamp is
     computed as this_packet_time + this_packet_len * delay_per_byte

     This is the minimum timestamp allowed in the next packet. 

     Note that this distorts accurate timestamps somewhat.
 */
#define LIMIT_RATE 1

#define SYSEX_BUFFER_SIZE 128

#define VERBOSE_ON 1
#define VERBOSE if (VERBOSE_ON)

#define MIDI_SYSEX      0xf0
#define MIDI_EOX        0xf7
#define MIDI_STATUS_MASK 0x80

// "Ref"s are pointers on 32-bit machines and ints on 64 bit machines
// NULL_REF is our representation of either 0 or NULL
#ifdef __LP64__
#define NULL_REF 0
#else
#define NULL_REF NULL
#endif

static MIDIClientRef	client = NULL_REF; 	/* Client handle to the MIDI server */
static MIDIPortRef	portIn = NULL_REF;	/* Input port handle */
static MIDIPortRef	portOut = NULL_REF;	/* Output port handle */

extern pm_fns_node pm_macosx_in_dictionary;
extern pm_fns_node pm_macosx_out_dictionary;

typedef struct midi_macosxcm_struct {
    PmTimestamp sync_time; /* when did we last determine delta? */
    UInt64 delta;	/* difference between stream time and real time in ns */
    UInt64 last_time;	/* last output time in host units*/
    int first_message;  /* tells midi_write to sychronize timestamps */
    int sysex_mode;     /* middle of sending sysex */
    uint32_t sysex_word; /* accumulate data when receiving sysex */
    uint32_t sysex_byte_count; /* count how many received */
    char error[PM_HOST_ERROR_MSG_LEN];
    char callback_error[PM_HOST_ERROR_MSG_LEN];
    Byte packetBuffer[PACKET_BUFFER_SIZE];
    MIDIPacketList *packetList; /* a pointer to packetBuffer */
    MIDIPacket *packet;
    Byte sysex_buffer[SYSEX_BUFFER_SIZE]; /* temp storage for sysex data */
    MIDITimeStamp sysex_timestamp; /* timestamp to use with sysex data */
    /* allow for running status (is running status possible here? -rbd): -cpr */
    unsigned char last_command; 
    int32_t last_msg_length;
    /* limit midi data rate (a CoreMidi requirement): */
    UInt64 min_next_time; /* when can the next send take place? */
    int byte_count; /* how many bytes in the next packet list? */
    Float64 us_per_host_tick; /* host clock frequency, units of min_next_time */
    UInt64 host_ticks_per_byte; /* host clock units per byte at maximum rate */
} midi_macosxcm_node, *midi_macosxcm_type;

/* private function declarations */
MIDITimeStamp timestamp_pm_to_cm(PmTimestamp timestamp);
PmTimestamp timestamp_cm_to_pm(MIDITimeStamp timestamp);

char* cm_get_full_endpoint_name(MIDIEndpointRef endpoint);


static int
midi_length(int32_t msg)
{
    int status, high, low;
    static int high_lengths[] = {
        1, 1, 1, 1, 1, 1, 1, 1,         /* 0x00 through 0x70 */
        3, 3, 3, 3, 2, 2, 3, 1          /* 0x80 through 0xf0 */
    };
    static int low_lengths[] = {
        1, 2, 3, 2, 1, 1, 1, 1,         /* 0xf0 through 0xf8 */
        1, 1, 1, 1, 1, 1, 1, 1          /* 0xf9 through 0xff */
    };

    status = msg & 0xFF;
    high = status >> 4;
    low = status & 15;

    return (high != 0xF) ? high_lengths[high] : low_lengths[low];
}

static PmTimestamp midi_synchronize(PmInternal *midi)
{
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    UInt64 pm_stream_time_2 = 
            AudioConvertHostTimeToNanos(AudioGetCurrentHostTime());
    PmTimestamp real_time;
    UInt64 pm_stream_time;
    /* if latency is zero and this is an output, there is no 
       time reference and midi_synchronize should never be called */
    assert(midi->time_proc);
    assert(!(midi->write_flag && midi->latency == 0));
    do {
         /* read real_time between two reads of stream time */
         pm_stream_time = pm_stream_time_2;
         real_time = (*midi->time_proc)(midi->time_info);
         pm_stream_time_2 = AudioConvertHostTimeToNanos(AudioGetCurrentHostTime());
         /* repeat if more than 0.5 ms has elapsed */
    } while (pm_stream_time_2 > pm_stream_time + 500000);
    m->delta = pm_stream_time - ((UInt64) real_time * (UInt64) 1000000);
    m->sync_time = real_time;
    return real_time;
}


static void
process_packet(MIDIPacket *packet, PmEvent *event, 
	       PmInternal *midi, midi_macosxcm_type m)
{
    /* handle a packet of MIDI messages from CoreMIDI */
    /* there may be multiple short messages in one packet (!) */
    unsigned int remaining_length = packet->length;
    unsigned char *cur_packet_data = packet->data;
    while (remaining_length > 0) {
        if (cur_packet_data[0] == MIDI_SYSEX ||
            /* are we in the middle of a sysex message? */
            (m->last_command == 0 &&
             !(cur_packet_data[0] & MIDI_STATUS_MASK))) {
            m->last_command = 0; /* no running status */
            unsigned int amt = pm_read_bytes(midi, cur_packet_data, 
                                             remaining_length, 
                                             event->timestamp);
            remaining_length -= amt;
            cur_packet_data += amt;
        } else if (cur_packet_data[0] == MIDI_EOX) {
            /* this should never happen, because pm_read_bytes should
             * get and read all EOX bytes*/
            midi->sysex_in_progress = FALSE;
            m->last_command = 0;
        } else if (cur_packet_data[0] & MIDI_STATUS_MASK) {
            /* compute the length of the next (short) msg in packet */
	    unsigned int cur_message_length = midi_length(cur_packet_data[0]);
            if (cur_message_length > remaining_length) {
#ifdef DEBUG
                printf("PortMidi debug msg: not enough data");
#endif
		/* since there's no more data, we're done */
		return;
	    }
	    m->last_msg_length = cur_message_length;
	    m->last_command = cur_packet_data[0];
	    switch (cur_message_length) {
	    case 1:
	        event->message = Pm_Message(cur_packet_data[0], 0, 0);
		break; 
	    case 2:
	        event->message = Pm_Message(cur_packet_data[0], 
					    cur_packet_data[1], 0);
		break;
	    case 3:
	        event->message = Pm_Message(cur_packet_data[0],
					    cur_packet_data[1], 
					    cur_packet_data[2]);
		break;
	    default:
                /* PortMIDI internal error; should never happen */
                assert(cur_message_length == 1);
	        return; /* give up on packet if continued after assert */
	    }
	    pm_read_short(midi, event);
	    remaining_length -= m->last_msg_length;
	    cur_packet_data += m->last_msg_length;
	} else if (m->last_msg_length > remaining_length + 1) {
	    /* we have running status, but not enough data */
#ifdef DEBUG
	    printf("PortMidi debug msg: not enough data in CoreMIDI packet");
#endif
	    /* since there's no more data, we're done */
	    return;
	} else { /* output message using running status */
	    switch (m->last_msg_length) {
	    case 1:
	        event->message = Pm_Message(m->last_command, 0, 0);
		break;
	    case 2:
	        event->message = Pm_Message(m->last_command, 
					    cur_packet_data[0], 0);
		break;
	    case 3:
	        event->message = Pm_Message(m->last_command, 
					    cur_packet_data[0], 
					    cur_packet_data[1]);
		break;
	    default:
	        /* last_msg_length is invalid -- internal PortMIDI error */
	        assert(m->last_msg_length == 1);
	    }
	    pm_read_short(midi, event);
	    remaining_length -= (m->last_msg_length - 1);
	    cur_packet_data += (m->last_msg_length - 1);
	}
    }
}



/* called when MIDI packets are received */
static void
readProc(const MIDIPacketList *newPackets, void *refCon, void *connRefCon)
{
    PmInternal *midi;
    midi_macosxcm_type m;
    PmEvent event;
    MIDIPacket *packet;
    unsigned int packetIndex;
    uint32_t now;
    unsigned int status;
    
#ifdef CM_DEBUG
    printf("readProc: numPackets %d: ", newPackets->numPackets);
#endif

    /* Retrieve the context for this connection */
    midi = (PmInternal *) connRefCon;
    m = (midi_macosxcm_type) midi->descriptor;
    assert(m);
    
    /* synchronize time references every 100ms */
    now = (*midi->time_proc)(midi->time_info);
    if (m->first_message || m->sync_time + 100 /*ms*/ < now) { 
        /* time to resync */
        now = midi_synchronize(midi);
        m->first_message = FALSE;
    }
    
    packet = (MIDIPacket *) &newPackets->packet[0];
    /* printf("readproc packet status %x length %d\n", packet->data[0], 
               packet->length); */
    for (packetIndex = 0; packetIndex < newPackets->numPackets; packetIndex++) {
        /* Set the timestamp and dispatch this message */
        event.timestamp = (PmTimestamp) /* explicit conversion */ (
                (AudioConvertHostTimeToNanos(packet->timeStamp) - m->delta) / 
                (UInt64) 1000000);
        status = packet->data[0];
        /* process packet as sysex data if it begins with MIDI_SYSEX, or
           MIDI_EOX or non-status byte with no running status */
#ifdef CM_DEBUG
        printf(" %d", packet->length);
#endif
        if (status == MIDI_SYSEX || status == MIDI_EOX || 
            ((!(status & MIDI_STATUS_MASK)) && !m->last_command)) {
	    /* previously was: !(status & MIDI_STATUS_MASK)) {
             * but this could mistake running status for sysex data
             */
            /* reset running status data -cpr */
	    m->last_command = 0;
	    m->last_msg_length = 0;
            /* printf("sysex packet length: %d\n", packet->length); */
            pm_read_bytes(midi, packet->data, packet->length, event.timestamp);
        } else {
            process_packet(packet, &event, midi, m);
	}
        packet = MIDIPacketNext(packet);
    }
#ifdef CM_DEBUG
    printf("\n");
#endif
}

static PmError
midi_in_open(PmInternal *midi, void *driverInfo)
{
    MIDIEndpointRef endpoint;
    midi_macosxcm_type m;
    OSStatus macHostError;
    
    /* insure that we have a time_proc for timing */
    if (midi->time_proc == NULL) {
        if (!Pt_Started()) 
            Pt_Start(1, 0, 0);
        /* time_get does not take a parameter, so coerce */
        midi->time_proc = (PmTimeProcPtr) Pt_Time;
    }
    endpoint = (MIDIEndpointRef) (long) descriptors[midi->device_id].descriptor;
    if (endpoint == NULL_REF) {
        return pmInvalidDeviceId;
    }

    m = (midi_macosxcm_type) pm_alloc(sizeof(midi_macosxcm_node)); /* create */
    midi->descriptor = m;
    if (!m) {
        return pmInsufficientMemory;
    }
    m->error[0] = 0;
    m->callback_error[0] = 0;
    m->sync_time = 0;
    m->delta = 0;
    m->last_time = 0;
    m->first_message = TRUE;
    m->sysex_mode = FALSE;
    m->sysex_word = 0;
    m->sysex_byte_count = 0;
    m->packetList = NULL;
    m->packet = NULL;
    m->last_command = 0;
    m->last_msg_length = 0;

    macHostError = MIDIPortConnectSource(portIn, endpoint, midi);
    if (macHostError != noErr) {
        pm_hosterror = macHostError;
        sprintf(pm_hosterror_text, 
                "Host error %ld: MIDIPortConnectSource() in midi_in_open()",
                (long) macHostError);
        midi->descriptor = NULL;
        pm_free(m);
        return pmHostError;
    }
    
    return pmNoError;
}

static PmError
midi_in_close(PmInternal *midi)
{
    MIDIEndpointRef endpoint;
    OSStatus macHostError;
    PmError err = pmNoError;
    
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    
    if (!m) return pmBadPtr;

    endpoint = (MIDIEndpointRef) (long) descriptors[midi->device_id].descriptor;
    if (endpoint == NULL_REF) {
        pm_hosterror = pmBadPtr;
    }
    
    /* shut off the incoming messages before freeing data structures */
    macHostError = MIDIPortDisconnectSource(portIn, endpoint);
    if (macHostError != noErr) {
        pm_hosterror = macHostError;
        sprintf(pm_hosterror_text, 
                "Host error %ld: MIDIPortDisconnectSource() in midi_in_close()",
                (long) macHostError);
        err = pmHostError;
    }
    
    midi->descriptor = NULL;
    pm_free(midi->descriptor);
    
    return err;
}


static PmError
midi_out_open(PmInternal *midi, void *driverInfo)
{
    midi_macosxcm_type m;

    m = (midi_macosxcm_type) pm_alloc(sizeof(midi_macosxcm_node)); /* create */
    midi->descriptor = m;
    if (!m) {
        return pmInsufficientMemory;
    }
    m->error[0] = 0;
    m->callback_error[0] = 0;
    m->sync_time = 0;
    m->delta = 0;
    m->last_time = 0;
    m->first_message = TRUE;
    m->sysex_mode = FALSE;
    m->sysex_word = 0;
    m->sysex_byte_count = 0;
    m->packetList = (MIDIPacketList *) m->packetBuffer;
    m->packet = NULL;
    m->last_command = 0;
    m->last_msg_length = 0;
    m->min_next_time = 0;
    m->byte_count = 0;
    m->us_per_host_tick = 1000000.0 / AudioGetHostClockFrequency();
    m->host_ticks_per_byte = (UInt64) (1000000.0 / 
                                       (m->us_per_host_tick * MAX_BYTES_PER_S));
    return pmNoError;
}


static PmError
midi_out_close(PmInternal *midi)
{
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    if (!m) return pmBadPtr;
    
    midi->descriptor = NULL;
    pm_free(midi->descriptor);
    
    return pmNoError;
}

static PmError
midi_abort(PmInternal *midi)
{
    PmError err = pmNoError;
    OSStatus macHostError;
    MIDIEndpointRef endpoint =
            (MIDIEndpointRef) (long) descriptors[midi->device_id].descriptor;
    macHostError = MIDIFlushOutput(endpoint);
    if (macHostError != noErr) {
        pm_hosterror = macHostError;
        sprintf(pm_hosterror_text,
                "Host error %ld: MIDIFlushOutput()", (long) macHostError);
        err = pmHostError;
    }
    return err;
}


static PmError
midi_write_flush(PmInternal *midi, PmTimestamp timestamp)
{
    OSStatus macHostError;
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    MIDIEndpointRef endpoint = 
            (MIDIEndpointRef) (long) descriptors[midi->device_id].descriptor;
    assert(m);
    assert(endpoint);
    if (m->packet != NULL) {
        /* out of space, send the buffer and start refilling it */
        /* before we can send, maybe delay to limit data rate. OS X allows
         * 15KB/s. */
        UInt64 now = AudioGetCurrentHostTime();
        if (now < m->min_next_time) {
            usleep((useconds_t) 
                   ((m->min_next_time - now) * m->us_per_host_tick));
        }
        macHostError = MIDISend(portOut, endpoint, m->packetList);
        m->packet = NULL; /* indicate no data in packetList now */
        m->min_next_time = now + m->byte_count * m->host_ticks_per_byte;
        m->byte_count = 0;
        if (macHostError != noErr) goto send_packet_error;
    }
    return pmNoError;
    
send_packet_error:
    pm_hosterror = macHostError;
    sprintf(pm_hosterror_text, 
            "Host error %ld: MIDISend() in midi_write()",
            (long) macHostError);
    return pmHostError;

}


static PmError
send_packet(PmInternal *midi, Byte *message, unsigned int messageLength, 
            MIDITimeStamp timestamp)
{
    PmError err;
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    assert(m);
    
    /* printf("add %d to packet %p len %d\n", message[0], m->packet, messageLength); */
    m->packet = MIDIPacketListAdd(m->packetList, sizeof(m->packetBuffer), 
                                  m->packet, timestamp, messageLength, 
                                  message);
    m->byte_count += messageLength;
    if (m->packet == NULL) {
        /* out of space, send the buffer and start refilling it */
        /* make midi->packet non-null to fool midi_write_flush into sending */
        m->packet = (MIDIPacket *) 4; 
        /* timestamp is 0 because midi_write_flush ignores timestamp since
         * timestamps are already in packets. The timestamp parameter is here
         * because other API's need it. midi_write_flush can be called 
         * from system-independent code that must be cross-API.
         */
        if ((err = midi_write_flush(midi, 0)) != pmNoError) return err;
        m->packet = MIDIPacketListInit(m->packetList);
        assert(m->packet); /* if this fails, it's a programming error */
        m->packet = MIDIPacketListAdd(m->packetList, sizeof(m->packetBuffer),
                                      m->packet, timestamp, messageLength, 
                                      message);
        assert(m->packet); /* can't run out of space on first message */           
    }
    return pmNoError;
}    


static PmError
midi_write_short(PmInternal *midi, PmEvent *event)
{
    PmTimestamp when = event->timestamp;
    PmMessage what = event->message;
    MIDITimeStamp timestamp;
    UInt64 when_ns;
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    Byte message[4];
    unsigned int messageLength;

    if (m->packet == NULL) {
        m->packet = MIDIPacketListInit(m->packetList);
        /* this can never fail, right? failure would indicate something 
           unrecoverable */
        assert(m->packet);
    }
    
    /* compute timestamp */
    if (when == 0) when = midi->now;
    /* if latency == 0, midi->now is not valid. We will just set it to zero */
    if (midi->latency == 0) when = 0;
    when_ns = ((UInt64) (when + midi->latency) * (UInt64) 1000000) + m->delta;
    timestamp = (MIDITimeStamp) AudioConvertNanosToHostTime(when_ns);

    message[0] = Pm_MessageStatus(what);
    message[1] = Pm_MessageData1(what);
    message[2] = Pm_MessageData2(what);
    messageLength = midi_length(what);
        
    /* make sure we go foreward in time */
    if (timestamp < m->min_next_time) timestamp = m->min_next_time;

    #ifdef LIMIT_RATE
        if (timestamp < m->last_time)
            timestamp = m->last_time;
	m->last_time = timestamp + messageLength * m->host_ticks_per_byte;
    #endif

    /* Add this message to the packet list */
    return send_packet(midi, message, messageLength, timestamp);
}


static PmError 
midi_begin_sysex(PmInternal *midi, PmTimestamp when)
{
    UInt64 when_ns;
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    assert(m);
    m->sysex_byte_count = 0;
    
    /* compute timestamp */
    if (when == 0) when = midi->now;
    /* if latency == 0, midi->now is not valid. We will just set it to zero */
    if (midi->latency == 0) when = 0;
    when_ns = ((UInt64) (when + midi->latency) * (UInt64) 1000000) + m->delta;
    m->sysex_timestamp = (MIDITimeStamp) AudioConvertNanosToHostTime(when_ns);

    if (m->packet == NULL) {
        m->packet = MIDIPacketListInit(m->packetList);
        /* this can never fail, right? failure would indicate something 
           unrecoverable */
        assert(m->packet);
    }
    return pmNoError;
}


static PmError
midi_end_sysex(PmInternal *midi, PmTimestamp when)
{
    PmError err;
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    assert(m);
    
    /* make sure we go foreward in time */
    if (m->sysex_timestamp < m->min_next_time) 
        m->sysex_timestamp = m->min_next_time;

    #ifdef LIMIT_RATE
        if (m->sysex_timestamp < m->last_time) 
            m->sysex_timestamp = m->last_time;
        m->last_time = m->sysex_timestamp + m->sysex_byte_count *
                                            m->host_ticks_per_byte;
    #endif
    
    /* now send what's in the buffer */
    err = send_packet(midi, m->sysex_buffer, m->sysex_byte_count,
                      m->sysex_timestamp);
    m->sysex_byte_count = 0;
    if (err != pmNoError) {
        m->packet = NULL; /* flush everything in the packet list */
        return err;
    }
    return pmNoError;
}


static PmError
midi_write_byte(PmInternal *midi, unsigned char byte, PmTimestamp timestamp)
{
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    assert(m);
    if (m->sysex_byte_count >= SYSEX_BUFFER_SIZE) {
        PmError err = midi_end_sysex(midi, timestamp);
        if (err != pmNoError) return err;
    }
    m->sysex_buffer[m->sysex_byte_count++] = byte;
    return pmNoError;
}


static PmError
midi_write_realtime(PmInternal *midi, PmEvent *event)
{
    /* to send a realtime message during a sysex message, first
       flush all pending sysex bytes into packet list */
    PmError err = midi_end_sysex(midi, 0);
    if (err != pmNoError) return err;
    /* then we can just do a normal midi_write_short */
    return midi_write_short(midi, event);
}

static unsigned int midi_has_host_error(PmInternal *midi)
{
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    return (m->callback_error[0] != 0) || (m->error[0] != 0);
}


static void midi_get_host_error(PmInternal *midi, char *msg, unsigned int len)
{
    midi_macosxcm_type m = (midi_macosxcm_type) midi->descriptor;
    msg[0] = 0; /* initialize to empty string */
    if (m) { /* make sure there is an open device to examine */
        if (m->error[0]) {
            strncpy(msg, m->error, len);
            m->error[0] = 0; /* clear the error */
        } else if (m->callback_error[0]) {
            strncpy(msg, m->callback_error, len);
            m->callback_error[0] = 0; /* clear the error */
        }
        msg[len - 1] = 0; /* make sure string is terminated */
    }
}


MIDITimeStamp timestamp_pm_to_cm(PmTimestamp timestamp)
{
    UInt64 nanos;
    if (timestamp <= 0) {
        return (MIDITimeStamp)0;
    } else {
        nanos = (UInt64)timestamp * (UInt64)1000000;
        return (MIDITimeStamp)AudioConvertNanosToHostTime(nanos);
    }
}

PmTimestamp timestamp_cm_to_pm(MIDITimeStamp timestamp)
{
    UInt64 nanos;
    nanos = AudioConvertHostTimeToNanos(timestamp);
    return (PmTimestamp)(nanos / (UInt64)1000000);
}


//
// Code taken from http://developer.apple.com/qa/qa2004/qa1374.html
//////////////////////////////////////
// Obtain the name of an endpoint without regard for whether it has connections.
// The result should be released by the caller.
CFStringRef EndpointName(MIDIEndpointRef endpoint, bool isExternal)
{
  CFMutableStringRef result = CFStringCreateMutable(NULL, 0);
  CFStringRef str;
  
  // begin with the endpoint's name
  str = NULL;
  MIDIObjectGetStringProperty(endpoint, kMIDIPropertyName, &str);
  if (str != NULL) {
    CFStringAppend(result, str);
    CFRelease(str);
  }
  
  MIDIEntityRef entity = NULL_REF;
  MIDIEndpointGetEntity(endpoint, &entity);
  if (entity == NULL_REF)
    // probably virtual
    return result;
  
  if (CFStringGetLength(result) == 0) {
    // endpoint name has zero length -- try the entity
    str = NULL;
    MIDIObjectGetStringProperty(entity, kMIDIPropertyName, &str);
    if (str != NULL) {
      CFStringAppend(result, str);
      CFRelease(str);
    }
  }
  // now consider the device's name
  MIDIDeviceRef device = NULL_REF;
  MIDIEntityGetDevice(entity, &device);
  if (device == NULL_REF)
    return result;
  
  str = NULL;
  MIDIObjectGetStringProperty(device, kMIDIPropertyName, &str);
  if (CFStringGetLength(result) == 0) {
      CFRelease(result);
      return str;
  }
  if (str != NULL) {
    // if an external device has only one entity, throw away
    // the endpoint name and just use the device name
    if (isExternal && MIDIDeviceGetNumberOfEntities(device) < 2) {
      CFRelease(result);
      return str;
    } else {
      if (CFStringGetLength(str) == 0) {
        CFRelease(str);
        return result;
      }
      // does the entity name already start with the device name?
      // (some drivers do this though they shouldn't)
      // if so, do not prepend
        if (CFStringCompareWithOptions( result, /* endpoint name */
             str /* device name */,
             CFRangeMake(0, CFStringGetLength(str)), 0) != kCFCompareEqualTo) {
        // prepend the device name to the entity name
        if (CFStringGetLength(result) > 0)
          CFStringInsert(result, 0, CFSTR(" "));
        CFStringInsert(result, 0, str);
      }
      CFRelease(str);
    }
  }
  return result;
}


// Obtain the name of an endpoint, following connections.
// The result should be released by the caller.
static CFStringRef ConnectedEndpointName(MIDIEndpointRef endpoint)
{
  CFMutableStringRef result = CFStringCreateMutable(NULL, 0);
  CFStringRef str;
  OSStatus err;
  long i;
  
  // Does the endpoint have connections?
  CFDataRef connections = NULL;
  long nConnected = 0;
  bool anyStrings = false;
  err = MIDIObjectGetDataProperty(endpoint, kMIDIPropertyConnectionUniqueID, &connections);
  if (connections != NULL) {
    // It has connections, follow them
    // Concatenate the names of all connected devices
    nConnected = CFDataGetLength(connections) / (int32_t) sizeof(MIDIUniqueID);
    if (nConnected) {
      const SInt32 *pid = (const SInt32 *)(CFDataGetBytePtr(connections));
      for (i = 0; i < nConnected; ++i, ++pid) {
        MIDIUniqueID id = EndianS32_BtoN(*pid);
        MIDIObjectRef connObject;
        MIDIObjectType connObjectType;
        err = MIDIObjectFindByUniqueID(id, &connObject, &connObjectType);
        if (err == noErr) {
          if (connObjectType == kMIDIObjectType_ExternalSource  ||
              connObjectType == kMIDIObjectType_ExternalDestination) {
            // Connected to an external device's endpoint (10.3 and later).
            str = EndpointName((MIDIEndpointRef)(connObject), true);
          } else {
            // Connected to an external device (10.2) (or something else, catch-all)
            str = NULL;
            MIDIObjectGetStringProperty(connObject, kMIDIPropertyName, &str);
          }
          if (str != NULL) {
            if (anyStrings)
              CFStringAppend(result, CFSTR(", "));
            else anyStrings = true;
            CFStringAppend(result, str);
            CFRelease(str);
          }
        }
      }
    }
    CFRelease(connections);
  }
  if (anyStrings)
    return result;
  
  // Here, either the endpoint had no connections, or we failed to obtain names for any of them.
  return EndpointName(endpoint, false);
}


char* cm_get_full_endpoint_name(MIDIEndpointRef endpoint)
{
#ifdef OLDCODE
    MIDIEntityRef entity;
    MIDIDeviceRef device;

    CFStringRef endpointName = NULL;
    CFStringRef deviceName = NULL;
#endif
    CFStringRef fullName = NULL;
    CFStringEncoding defaultEncoding;
    char* newName;

    /* get the default string encoding */
    defaultEncoding = CFStringGetSystemEncoding();

    fullName = ConnectedEndpointName(endpoint);
    
#ifdef OLDCODE
    /* get the entity and device info */
    MIDIEndpointGetEntity(endpoint, &entity);
    MIDIEntityGetDevice(entity, &device);

    /* create the nicely formated name */
    MIDIObjectGetStringProperty(endpoint, kMIDIPropertyName, &endpointName);
    MIDIObjectGetStringProperty(device, kMIDIPropertyName, &deviceName);
    if (deviceName != NULL) {
        fullName = CFStringCreateWithFormat(NULL, NULL, CFSTR("%@: %@"),
                                            deviceName, endpointName);
    } else {
        fullName = endpointName;
    }
#endif    
    /* copy the string into our buffer */
    newName = (char *) malloc(CFStringGetLength(fullName) + 1);
    CFStringGetCString(fullName, newName, CFStringGetLength(fullName) + 1,
                       defaultEncoding);

    /* clean up */
#ifdef OLDCODE
    if (endpointName) CFRelease(endpointName);
    if (deviceName) CFRelease(deviceName);
#endif
    if (fullName) CFRelease(fullName);

    return newName;
}

 

pm_fns_node pm_macosx_in_dictionary = {
    none_write_short,
    none_sysex,
    none_sysex,
    none_write_byte,
    none_write_short,
    none_write_flush,
    none_synchronize,
    midi_in_open,
    midi_abort,
    midi_in_close,
    success_poll,
    midi_has_host_error,
    midi_get_host_error,
};

pm_fns_node pm_macosx_out_dictionary = {
    midi_write_short,
    midi_begin_sysex,
    midi_end_sysex,
    midi_write_byte,
    midi_write_realtime,
    midi_write_flush,
    midi_synchronize,
    midi_out_open,
    midi_abort,
    midi_out_close,
    success_poll,
    midi_has_host_error,
    midi_get_host_error,
};


/* We do nothing with callbacks, but generating the callbacks also
 * updates CoreMIDI state. Callback may not be essential, but calling
 * the CFRunLoopRunInMode is necessary.
 */
void cm_notify(const MIDINotification *msg, void *refCon)
{
    /*  for debugging, trace change notifications:
    const char *descr[] = {
        "undefined (0)",
        "kMIDIMsgSetupChanged",
        "kMIDIMsgObjectAdded",
        "kMIDIMsgObjectRemoved",
        "kMIDIMsgPropertyChanged",
        "kMIDIMsgThruConnectionsChanged",
        "kMIDIMsgSerialPortOwnerChanged",
        "kMIDIMsgIOError"};

    printf("MIDI Notify, messageID %d (%s)\n", (int) msg->messageID,
           descr[(int) msg->messageID]);
    */
    return;
}


PmError pm_macosxcm_init(void)
{
    ItemCount numInputs, numOutputs, numDevices;
    MIDIEndpointRef endpoint;
    OSStatus macHostError = noErr;
    char *error_text;

    /* Determine the number of MIDI devices on the system */
    numDevices = MIDIGetNumberOfDevices();

    /* Return prematurely if no devices exist on the system
       Note that this is not an error. There may be no devices.
       Pm_CountDevices() will return zero, which is correct and
       useful information
     */
    if (numDevices <= 0) {
        return pmNoError;
    }


    /* Initialize the client handle */
    if (client == NULL_REF) {
        macHostError = MIDIClientCreate(CFSTR("PortMidi"), &cm_notify, NULL,
                                        &client);
    } else {
        for (int i = 0; i < 100; i++) {
            // look for any changes before scanning for devices
            CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0, true);
            if (i % 5 == 0) Pt_Sleep(1);  /* insert 20 delays */
        }
    }
    if (macHostError != noErr) {
        error_text = "MIDIClientCreate() in pm_macosxcm_init()";
        goto error_return;
    }
    numInputs = MIDIGetNumberOfSources();
    numOutputs = MIDIGetNumberOfDestinations();

    /* Create the input port */
    macHostError = MIDIInputPortCreate(client, CFSTR("Input port"), readProc,
                                          NULL, &portIn);
    if (macHostError != noErr) {
        error_text = "MIDIInputPortCreate() in pm_macosxcm_init()";
        goto error_return;
    }

    /* Create the output port */
    macHostError = MIDIOutputPortCreate(client, CFSTR("Output port"), &portOut);
    if (macHostError != noErr) {
        error_text = "MIDIOutputPortCreate() in pm_macosxcm_init()";
        goto error_return;
    }

    /* Iterate over the MIDI input devices */
    for (int i = 0; i < numInputs; i++) {
        endpoint = MIDIGetSource(i);
        if (endpoint == NULL_REF) {
            continue;
        }

        /* set the first input we see to the default */
        if (pm_default_input_device_id == -1)
            pm_default_input_device_id = pm_descriptor_index;

        /* Register this device with PortMidi */
        pm_add_device("CoreMIDI", cm_get_full_endpoint_name(endpoint),
                      TRUE, (void *) (long) endpoint, &pm_macosx_in_dictionary);
    }

    /* Iterate over the MIDI output devices */
    for (int i = 0; i < numOutputs; i++) {
        endpoint = MIDIGetDestination(i);
        if (endpoint == NULL_REF) {
            continue;
        }

        /* set the first output we see to the default */
        if (pm_default_output_device_id == -1)
            pm_default_output_device_id = pm_descriptor_index;

        /* Register this device with PortMidi */
        pm_add_device("CoreMIDI", cm_get_full_endpoint_name(endpoint),
                      FALSE, (void *) (long) endpoint,
                      &pm_macosx_out_dictionary);
    }
    return pmNoError;
    
error_return:
    pm_hosterror = macHostError;
    sprintf(pm_hosterror_text, "Host error %ld: %s\n", (long) macHostError,
            error_text);
    pm_macosxcm_term(); /* clear out any opened ports */
    return pmHostError;
}

void pm_macosxcm_term(void)
{
    /* docs say do not explicitly dispose of client
       if (client != NULL_REF) MIDIClientDispose(client); */
    if (portIn != NULL_REF) MIDIPortDispose(portIn);
    if (portOut != NULL_REF) MIDIPortDispose(portOut);
}
