/* get_sysex_dump.c
 * cc -Wall -Wformat -g -o get_sysex_dump get_sysex_dump.c
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

#define SYSEX_START 0xf0
#define SYSEX_END   0xf7

struct sysex {
	unsigned int length;
	unsigned char *data;
};

static struct sysex *sysex_new(void);
static void sysex_delete(struct sysex *);
static void sysex_set_length(struct sysex *, unsigned int);
static void sysex_read(int, struct sysex *, int);
static void sysex_write(int, struct sysex *);
static int sysex_checksum(struct sysex *, int, int);

int
main(int argc, char *argv[])
{
	int fd, i;
	struct sysex *se;

	fd = open("/dev/rmidi2", O_RDWR|O_SYNC);
	if (fd == -1) {
		fprintf(stderr, "open() failed: %s\n", strerror(errno));
		return 1;
	}

	se = sysex_new();

	sysex_set_length(se, 11);

	se->data[0]  = 0x41; /* Roland's ID */
	se->data[1]  = 0x10; /* Device Number - default appears to be 0x10 */
	se->data[2]  = 0x16; /* Model ID */
	se->data[3]  = 0x11; /* Command ID - "Request Data" */

	se->data[4]  = 0x04; /* Address MSB */
	se->data[5]  = 0x01; /* Address */
	se->data[6]  = 0x76; /* Address LSB */

	se->data[7]  = 0x00; /* Size MSB */
	se->data[8]  = 0x01; /* Size */
	se->data[9]  = 0x76; /* Size LSB */

	se->data[10] = 0x0e; /* Checksum */

	sysex_write(fd, se);

	sysex_set_length(se, 252); /* 8 bytes to wrap data, and 246 bytes of data */

	sysex_read(fd, se, 1);
	printf("Read %d bytes\n", se->length);
	for (i = 0; i < se->length; i++)
		printf("0x%0x\n", se->data[i]);

	sysex_delete(se);

	if (close(fd) == -1) {
		fprintf(stderr, "close() failed: %s\n", strerror(errno));
		return 1;
	}

	return 0;
}

/* Receives a MIDI System Exclusive message */
void
sysex_read(int fd, struct sysex *se, int autostop)
{
	int n, length = 0;
	unsigned char c;

	if (fd == -1) {
		fprintf(stderr, "sysex_read() failed: invalid fd\n");
		return;
	}

	if (se == NULL) {
		fprintf(stderr, "sysex_read() failed: null sysex argument\n");
		return;
	}

	while ((n = read(fd, &c, 1)) == 1 && c != SYSEX_START)
		usleep(40);
  
	if (n != 1)
		return;

	while (length < se->length) {
		n = read(fd, &c, 1);

		if (n == 1) {
			se->data[length++] = c;
			if (autostop && se->data[length - 1] == SYSEX_END)
				break;
		}
	}
  
	if (length < se->length) {
		se->length = length;
		se->data = realloc(se->data, se->length);
	}
}

/* Sends a MIDI System Exclusive message */
void
sysex_write(int fd, struct sysex *se)
{
	unsigned char *data;

	if (fd == -1) {
		fprintf(stderr, "sysex_write() failed: invalid fd\n");
		return;
	}

	if (se == NULL) {
		fprintf(stderr, "sysex_write() failed: null sysex argument\n");
		return;
	}

	data = calloc(se->length + 2, sizeof(unsigned char));

	data[0] = SYSEX_START;
	memcpy(data + 1, se->data, se->length);
	data[se->length + 1] = SYSEX_END;
  
	write(fd, data, se->length + 2);

	free(data);
}

static struct sysex *sysex_new(void)
{
	struct sysex *se;

	se = calloc(1, sizeof(struct sysex));

	return se;
}

static void sysex_delete(struct sysex *se)
{
	if (se->length != 0)
		free(se->data);

	free(se);
}

/* Sets the length of a MIDI System Exclusive message */
void
sysex_set_length(struct sysex *se, unsigned int length)
{
	if (se == NULL) {
		fprintf(stderr, "sysex_set_length() failed: null sysex argument\n");
		return;
	}

	se->length = length;
	se->data = realloc(se->data, se->length);
}

/* Determine a Roland System Exclusive checksum */
int
sysex_checksum(struct sysex *se, int start, int length)
{
	int checksum, i;

	if (se == NULL) {
		fprintf(stderr, "sysex_checksum() failed: null sysex argument\n");
		return 0;
	}

	checksum = 0;

	for (i = start; i < start + length; i++) {
		checksum += se->data[i];
		if (checksum > 127)
			checksum -= 128;
	}

	checksum = 128 - checksum;

	return checksum;
}