smf_load.c

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/*-
 * Copyright (c) 2007, 2008 Edward Tomasz Napierała <trasz@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * ALTHOUGH THIS SOFTWARE IS MADE OF WIN AND SCIENCE, IT IS PROVIDED BY THE
 * AUTHOR AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

/* Reference: http://www.borg.com/~jglatt/tech/midifile.htm */

#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <math.h>
#include <errno.h>
#include <ctype.h>
#ifdef __MINGW32__
#include <windows.h>
#else /* ! __MINGW32__ */
#include <arpa/inet.h>
#endif /* ! __MINGW32__ */
#include "smf.h"
#include "smf_private.h"

static struct chunk_header_struct *
next_chunk(smf_t *smf)
{
        struct chunk_header_struct *chunk;
        void *next_chunk_ptr;

        assert(smf->file_buffer != NULL);
        assert(smf->file_buffer_length > 0);
        assert(smf->next_chunk_offset >= 0);

        if (smf->next_chunk_offset + sizeof(struct chunk_header_struct) >= smf->file_buffer_length) {
                g_critical("SMF warning: no more chunks left.");
                return (NULL);
        }

        next_chunk_ptr = (unsigned char *)smf->file_buffer + smf->next_chunk_offset;

        chunk = (struct chunk_header_struct *)next_chunk_ptr;

        if (!isalpha(chunk->id[0]) || !isalpha(chunk->id[1]) || !isalpha(chunk->id[2]) || !isalpha(chunk->id[3])) {
                g_critical("SMF error: chunk signature contains at least one non-alphanumeric byte.");
                return (NULL);
        }

        /*
         * XXX: On SPARC, after compiling with "-fast" option there will be SIGBUS here.
         * Please compile with -xmemalign=8i".
         */
        smf->next_chunk_offset += sizeof(struct chunk_header_struct) + ntohl(chunk->length);

        if (smf->next_chunk_offset > smf->file_buffer_length) {
                g_critical("SMF warning: malformed chunk; truncated file?");
                smf->next_chunk_offset = smf->file_buffer_length;
        }

        return (chunk);
}

static int
chunk_signature_matches(const struct chunk_header_struct *chunk, const char *signature)
{
        if (!memcmp(chunk->id, signature, 4))
                return (1);

        return (0);
}

static int
parse_mthd_header(smf_t *smf)
{
        int len;
        struct chunk_header_struct *mthd, *tmp_mthd;

        /* Make sure compiler didn't do anything stupid. */
        assert(sizeof(struct chunk_header_struct) == 8);

        /*
         * We could just do "mthd = smf->file_buffer;" here, but this way we wouldn't
         * get useful error messages.
         */
        if (smf->file_buffer_length < 6) {
                g_critical("SMF error: file is too short, it cannot be a MIDI file.");

                return (-1);
        }

        tmp_mthd = smf->file_buffer;

        if (!chunk_signature_matches(tmp_mthd, "MThd")) {
                g_critical("SMF error: MThd signature not found, is that a MIDI file?");
                
                return (-2);
        }

        /* Ok, now use next_chunk(). */
        mthd = next_chunk(smf);
        if (mthd == NULL)
                return (-3);

        assert(mthd == tmp_mthd);

        len = ntohl(mthd->length);
        if (len != 6) {
                g_critical("SMF error: MThd chunk length %d, must be 6.", len);

                return (-4);
        }

        return (0);
}

static int
parse_mthd_chunk(smf_t *smf)
{
        signed char first_byte_of_division, second_byte_of_division;

        struct mthd_chunk_struct *mthd;

        assert(sizeof(struct mthd_chunk_struct) == 14);

        if (parse_mthd_header(smf))
                return (1);

        mthd = (struct mthd_chunk_struct *)smf->file_buffer;

        smf->format = ntohs(mthd->format);
        if (smf->format < 0 || smf->format > 2) {
                g_critical("SMF error: bad MThd format field value: %d, valid values are 0-2, inclusive.", smf->format);
                return (-1);
        }

        if (smf->format == 2) {
                g_critical("SMF file uses format #2, no support for that yet.");
                return (-2);
        }

        smf->expected_number_of_tracks = ntohs(mthd->number_of_tracks);
        if (smf->expected_number_of_tracks <= 0) {
                g_critical("SMF error: bad number of tracks: %d, must be greater than zero.", smf->expected_number_of_tracks);
                return (-3);
        }

        /* XXX: endianess? */
        first_byte_of_division = *((signed char *)&(mthd->division));
        second_byte_of_division = *((signed char *)&(mthd->division) + 1);

        if (first_byte_of_division >= 0) {
                smf->ppqn = ntohs(mthd->division);
                smf->frames_per_second = 0;
                smf->resolution = 0;
        } else {
                smf->ppqn = 0;
                smf->frames_per_second = - first_byte_of_division;
                smf->resolution = second_byte_of_division;
        }

        if (smf->ppqn == 0) {
                g_critical("SMF file uses FPS timing instead of PPQN, no support for that yet.");
                return (-4);
        }
        
        return (0);
}

static int
extract_vlq(const unsigned char *buf, const int buffer_length, int *value, int *len)
{
        int val = 0;
        const unsigned char *c = buf;

        assert(buffer_length > 0);

        for (;;) {
                if (c >= buf + buffer_length) {
                        g_critical("End of buffer in extract_vlq().");
                        return (-1);
                }

                val = (val << 7) + (*c & 0x7F);

                if (*c & 0x80)
                        c++;
                else
                        break;
        };

        *value = val;
        *len = c - buf + 1;

        if (*len > 4) {
                g_critical("SMF error: Variable Length Quantities longer than four bytes are not supported yet.");
                return (-2);
        }

        return (0);
}

int
is_status_byte(const unsigned char status)
{
        return (status & 0x80);
}

static int
is_sysex_byte(const unsigned char status)
{
        if (status == 0xF0)
                return (1);

        return (0);
}

static int
is_escape_byte(const unsigned char status)
{
        if (status == 0xF7)
                return (1);

        return (0);
}

static int
expected_sysex_length(const unsigned char status, const unsigned char *second_byte, const int buffer_length, int *consumed_bytes)
{
        int sysex_length, len;

        assert(status == 0xF0);

        if (buffer_length < 3) {
                g_critical("SMF error: end of buffer in expected_sysex_length().");
                return (-1);
        }

        if (extract_vlq(second_byte, buffer_length, &sysex_length, &len))
                return (-1);

        if (consumed_bytes != NULL)
                *consumed_bytes = len;

        /* +1, because the length does not include status byte. */
        return (sysex_length + 1);
}

static int
expected_escaped_length(const unsigned char status, const unsigned char *second_byte, const int buffer_length, int *consumed_bytes)
{
        /* -1, because we do not want to account for 0x7F status. */
        return (expected_sysex_length(status, second_byte, buffer_length, consumed_bytes) - 1);
}

static int
expected_message_length(unsigned char status, const unsigned char *second_byte, const int buffer_length)
{
        /* Make sure this really is a valid status byte. */
        assert(is_status_byte(status));

        /* We cannot use this routine for sysexes. */
        assert(!is_sysex_byte(status));

        /* We cannot use this routine for escaped events. */
        assert(!is_escape_byte(status));

        /* Buffer length may be zero, for e.g. realtime messages. */
        assert(buffer_length >= 0);

        /* Is this a metamessage? */
        if (status == 0xFF) {
                if (buffer_length < 2) {
                        g_critical("SMF error: end of buffer in expected_message_length().");
                        return (-1);
                }

                /*
                 * Format of this kind of messages is like this: 0xFF 0xwhatever 0xlength and then "length" bytes.
                 * Second byte points to this:                        ^^^^^^^^^^
                 */
                return (*(second_byte + 1) + 3);
        }

        if ((status & 0xF0) == 0xF0) {
                switch (status) {
                        case 0xF2: /* Song Position Pointer. */
                                return (3);

                        case 0xF1: /* MTC Quarter Frame. */
                        case 0xF3: /* Song Select. */
                                return (2);

                        case 0xF6: /* Tune Request. */
                        case 0xF8: /* MIDI Clock. */
                        case 0xF9: /* Tick. */
                        case 0xFA: /* MIDI Start. */
                        case 0xFB: /* MIDI Continue. */
                        case 0xFC: /* MIDI Stop. */
                        case 0xFE: /* Active Sense. */
                                return (1);

                        default:
                                g_critical("SMF error: unknown 0xFx-type status byte '0x%x'.", status);
                                return (-2);
                }
        }

        /* Filter out the channel. */
        status &= 0xF0;

        switch (status) {
                case 0x80: /* Note Off. */
                case 0x90: /* Note On. */
                case 0xA0: /* AfterTouch. */
                case 0xB0: /* Control Change. */
                case 0xE0: /* Pitch Wheel. */
                        return (3);     

                case 0xC0: /* Program Change. */
                case 0xD0: /* Channel Pressure. */
                        return (2);

                default:
                        g_critical("SMF error: unknown status byte '0x%x'.", status);
                        return (-3);
        }
}

static int
extract_sysex_event(const unsigned char *buf, const int buffer_length, smf_event_t *event, int *len, int last_status)
{
        int status, message_length, vlq_length;
        const unsigned char *c = buf;

        status = *buf;

        assert(is_sysex_byte(status));

        c++;

        message_length = expected_sysex_length(status, c, buffer_length - 1, &vlq_length);

        if (message_length < 0)
                return (-3);

        c += vlq_length;

        if (vlq_length + message_length >= buffer_length) {
                g_critical("End of buffer in extract_sysex_event().");
                return (-5);
        }

        event->midi_buffer_length = message_length;
        event->midi_buffer = malloc(event->midi_buffer_length);
        if (event->midi_buffer == NULL) {
                g_critical("Cannot allocate memory in extract_sysex_event(): %s", strerror(errno));
                return (-4);
        }

        event->midi_buffer[0] = status;
        memcpy(event->midi_buffer + 1, c, message_length - 1);

        *len = vlq_length + message_length;

        return (0);
}

static int
extract_escaped_event(const unsigned char *buf, const int buffer_length, smf_event_t *event, int *len, int last_status)
{
        int status, message_length, vlq_length;
        const unsigned char *c = buf;

        status = *buf;

        assert(is_escape_byte(status));

        c++;

        message_length = expected_escaped_length(status, c, buffer_length - 1, &vlq_length);

        if (message_length < 0)
                return (-3);

        c += vlq_length;

        if (vlq_length + message_length >= buffer_length) {
                g_critical("End of buffer in extract_escaped_event().");
                return (-5);
        }

        event->midi_buffer_length = message_length;
        event->midi_buffer = malloc(event->midi_buffer_length);
        if (event->midi_buffer == NULL) {
                g_critical("Cannot allocate memory in extract_escaped_event(): %s", strerror(errno));
                return (-4);
        }

        memcpy(event->midi_buffer, c, message_length);

        if (smf_event_is_valid(event)) {
                g_critical("Escaped event is invalid.");
                return (-1);
        }

        if (smf_event_is_system_realtime(event) || smf_event_is_system_common(event)) {
                g_warning("Escaped event is not System Realtime nor System Common.");
        }

        *len = vlq_length + message_length;

        return (0);
}


static int
extract_midi_event(const unsigned char *buf, const int buffer_length, smf_event_t *event, int *len, int last_status)
{
        int status, message_length;
        const unsigned char *c = buf;

        assert(buffer_length > 0);

        /* Is the first byte the status byte? */
        if (is_status_byte(*c)) {
                status = *c;
                c++;

        } else {
                /* No, we use running status then. */
                status = last_status;
        }

        if (!is_status_byte(status)) {
                g_critical("SMF error: bad status byte (MSB is zero).");
                return (-1);
        }

        if (is_sysex_byte(status))
                return (extract_sysex_event(buf, buffer_length, event, len, last_status));

        if (is_escape_byte(status))
                return (extract_escaped_event(buf, buffer_length, event, len, last_status));

        /* At this point, "c" points to first byte following the status byte. */
        message_length = expected_message_length(status, c, buffer_length - (c - buf));

        if (message_length < 0)
                return (-3);

        if (message_length - 1 > buffer_length - (c - buf)) {
                g_critical("End of buffer in extract_midi_event().");
                return (-5);
        }

        event->midi_buffer_length = message_length;
        event->midi_buffer = malloc(event->midi_buffer_length);
        if (event->midi_buffer == NULL) {
                g_critical("Cannot allocate memory in extract_midi_event(): %s", strerror(errno));
                return (-4);
        }

        event->midi_buffer[0] = status;
        memcpy(event->midi_buffer + 1, c, message_length - 1);

        *len = c + message_length - 1 - buf;

        return (0);
}

static smf_event_t *
parse_next_event(smf_track_t *track)
{
        int time = 0, len, buffer_length;
        unsigned char *c, *start;

        smf_event_t *event = smf_event_new();
        if (event == NULL)
                goto error;

        c = start = (unsigned char *)track->file_buffer + track->next_event_offset;

        assert(track->file_buffer != NULL);
        assert(track->file_buffer_length > 0);
        assert(track->next_event_offset > 0);

        buffer_length = track->file_buffer_length - track->next_event_offset;
        assert(buffer_length > 0);

        /* First, extract time offset from previous event. */
        if (extract_vlq(c, buffer_length, &time, &len))
                goto error;

        c += len;
        buffer_length -= len;

        if (buffer_length <= 0)
                goto error;

        /* Now, extract the actual event. */
        if (extract_midi_event(c, buffer_length, event, &len, track->last_status))
                goto error;

        c += len;
        buffer_length -= len;
        track->last_status = event->midi_buffer[0];
        track->next_event_offset += c - start;

        smf_track_add_event_delta_pulses(track, event, time);

        return (event);

error:
        if (event != NULL)
                smf_event_delete(event);

        return (NULL);
}

static char *
make_string(const unsigned char *buf, const int buffer_length, int len)
{
        char *str;

        assert(buffer_length > 0);
        assert(len > 0);

        if (len > buffer_length) {
                g_critical("End of buffer in make_string().");

                len = buffer_length;
        }

        str = malloc(len + 1);
        if (str == NULL) {
                g_critical("Cannot allocate memory in make_string().");
                return (NULL);
        }

        memcpy(str, buf, len);
        str[len] = '\0';

        return (str);
}

int
smf_event_is_textual(const smf_event_t *event)
{
        if (!smf_event_is_metadata(event))
                return (0);

        if (event->midi_buffer_length < 4)
                return (0);

        if (event->midi_buffer[3] < 1 && event->midi_buffer[3] > 9)
                return (0);

        return (1);
}

char *
smf_event_extract_text(const smf_event_t *event)
{
        int string_length = -1, length_length = -1;

        if (!smf_event_is_textual(event))
                return (NULL);

        if (event->midi_buffer_length < 3) {
                g_critical("smf_event_extract_text: truncated MIDI message.");
                return (NULL);
        }

        extract_vlq((void *)&(event->midi_buffer[2]), event->midi_buffer_length - 2, &string_length, &length_length);

        if (string_length <= 0) {
                g_critical("smf_event_extract_text: truncated MIDI message.");
                return (NULL);
        }

        return (make_string((void *)(&event->midi_buffer[2] + length_length), event->midi_buffer_length - 2 - length_length, string_length));
}

static int
parse_mtrk_header(smf_track_t *track)
{
        struct chunk_header_struct *mtrk;

        /* Make sure compiler didn't do anything stupid. */
        assert(sizeof(struct chunk_header_struct) == 8);
        assert(track->smf != NULL);

        mtrk = next_chunk(track->smf);

        if (mtrk == NULL)
                return (-1);

        if (!chunk_signature_matches(mtrk, "MTrk")) {
                g_warning("SMF warning: Expected MTrk signature, got %c%c%c%c instead; ignoring this chunk.",
                                mtrk->id[0], mtrk->id[1], mtrk->id[2], mtrk->id[3]);
                
                return (-2);
        }

        track->file_buffer = mtrk;
        track->file_buffer_length = sizeof(struct chunk_header_struct) + ntohl(mtrk->length);
        track->next_event_offset = sizeof(struct chunk_header_struct);

        return (0);
}

static int
event_is_end_of_track(const smf_event_t *event)
{
        if (event->midi_buffer[0] == 0xFF && event->midi_buffer[1] == 0x2F)
                return (1);

        return (0);
}

int
smf_event_length_is_valid(const smf_event_t *event)
{
        assert(event);
        assert(event->midi_buffer);

        if (event->midi_buffer_length < 1)
                return (0);

        /* We cannot use expected_message_length on sysexes. */
        if (smf_event_is_sysex(event))
                return (1);

        if (event->midi_buffer_length != expected_message_length(event->midi_buffer[0],
                &(event->midi_buffer[1]), event->midi_buffer_length - 1)) {

                return (0);
        }

        return (1);
}

/* XXX: this routine requires some more work to detect more errors. */
int
smf_event_is_valid(const smf_event_t *event)
{
        assert(event);
        assert(event->midi_buffer);
        assert(event->midi_buffer_length >= 1);

        if (!is_status_byte(event->midi_buffer[0])) {
                g_critical("First byte of MIDI message is not a valid status byte.");

                return (0);
        }

        if (!smf_event_length_is_valid(event))
                return (0);

        return (1);
}

static int
parse_mtrk_chunk(smf_track_t *track)
{
        smf_event_t *event;

        if (parse_mtrk_header(track))
                return (-1);

        for (;;) {
                event = parse_next_event(track);

                /* Couldn't parse an event? */
                if (event == NULL) {
                        g_critical("Unable to parse MIDI event; truncating track.");
                        if (smf_track_add_eot_delta_pulses(track, 0) != 0) {
                                g_critical("smf_track_add_eot_delta_pulses failed.");
                                return (-2);
                        }
                        break;
                }

                assert(smf_event_is_valid(event));

                if (event_is_end_of_track(event))
                        break;
        }

        track->file_buffer = NULL;
        track->file_buffer_length = 0;
        track->next_event_offset = -1;

        return (0);
}

static int
load_file_into_buffer(void **file_buffer, int *file_buffer_length, const char *file_name)
{
        FILE *stream = fopen(file_name, "rb");

        if (stream == NULL) {
                g_critical("Cannot open input file: %s", strerror(errno));

                return (-1);
        }

        if (fseek(stream, 0, SEEK_END)) {
                g_critical("fseek(3) failed: %s", strerror(errno));

                return (-2);
        }

        *file_buffer_length = ftell(stream);
        if (*file_buffer_length == -1) {
                g_critical("ftell(3) failed: %s", strerror(errno));

                return (-3);
        }

        if (fseek(stream, 0, SEEK_SET)) {
                g_critical("fseek(3) failed: %s", strerror(errno));

                return (-4);
        }

        *file_buffer = malloc(*file_buffer_length);
        if (*file_buffer == NULL) {
                g_critical("malloc(3) failed: %s", strerror(errno));

                return (-5);
        }

        if (fread(*file_buffer, 1, *file_buffer_length, stream) != *file_buffer_length) {
                g_critical("fread(3) failed: %s", strerror(errno));

                return (-6);
        }
        
        if (fclose(stream)) {
                g_critical("fclose(3) failed: %s", strerror(errno));

                return (-7);
        }

        return (0);
}

smf_t *
smf_load_from_memory(const void *buffer, const int buffer_length)
{
        int i;

        smf_t *smf = smf_new();

        smf->file_buffer = (void *)buffer;
        smf->file_buffer_length = buffer_length;
        smf->next_chunk_offset = 0;

        if (parse_mthd_chunk(smf))
                return (NULL);

        for (i = 1; i <= smf->expected_number_of_tracks; i++) {
                smf_track_t *track = smf_track_new();
                if (track == NULL)
                        return (NULL);

                smf_add_track(smf, track);

                /* Skip unparseable chunks. */
                if (parse_mtrk_chunk(track)) {
                        g_warning("SMF warning: Cannot load track.");
                        smf_track_delete(track);
                }

                track->file_buffer = NULL;
                track->file_buffer_length = 0;
                track->next_event_offset = -1;
        }

        if (smf->expected_number_of_tracks != smf->number_of_tracks) {
                g_warning("SMF warning: MThd header declared %d tracks, but only %d found; continuing anyway.",
                                smf->expected_number_of_tracks, smf->number_of_tracks);

                smf->expected_number_of_tracks = smf->number_of_tracks;
        }

        smf->file_buffer = NULL;
        smf->file_buffer_length = 0;
        smf->next_chunk_offset = -1;

        return (smf);
}

smf_t *
smf_load(const char *file_name)
{
        int file_buffer_length;
        void *file_buffer;
        smf_t *smf;

        if (load_file_into_buffer(&file_buffer, &file_buffer_length, file_name))
                return (NULL);

        smf = smf_load_from_memory(file_buffer, file_buffer_length);

        memset(file_buffer, 0, file_buffer_length);
        free(file_buffer);

        if (smf == NULL)
                return (NULL);

        smf_rewind(smf);

        return (smf);
}

---