midi-utils/midi-utils.c

#include "midi-utils.h"

#if !defined _WIN32
/**
 * Converts a string to lowercase.
 * @param dest - The string to convert.
 */
void _strlwr(char* dest) {
	for (unsigned int i = 0; i < strlen(dest); i += 1) {
		if ('A' <= dest[i] && dest[i] <= 'Z') {
			dest[i] += 0x20;
		}
	}
}
#endif

/**
 * Gets the name of a MIDI note value.
 * @param midi_note - The MIDI note value.
 * @note Valid values are from 0-127.
 * @return The MIDI note name.
 * @see MIDI_GetNoteFromName()
 */
char* MIDI_GetNoteName(unsigned char midi_note) {
	static const char* pitch_names[] = {
		"C",
		"C#",
		"D",
		"D#",
		"E",
		"F",
		"F#",
		"G",
		"G#",
		"A",
		"A#",
		"B"
	};

	const unsigned char pitch_class = midi_note % 12;
	const unsigned char octave = midi_note / 12;
	static char note_name[8];
	sprintf(note_name, "%s%u", pitch_names[pitch_class], octave);
	return note_name;
}

/**
 * Gets the note value from a MIDI note name
 * @param name - The MIDI note name.
 * @return The MIDI note value, or 255 if an invalid name is passed.
 * @see MIDI_GetNoteName()
 */
unsigned char MIDI_GetNoteFromName(const char* name) {
	if (!name) {
		return 255u;
	}

	char name_copy[8];
	strcpy(name_copy, name);
	_strlwr(name_copy);

	unsigned char octave = 0;
	unsigned char has_accidental = name_copy[1] == '#' || name_copy[1] == 'b';
	unsigned char octave_start = has_accidental ? 2 : 1;
	unsigned char pitch_class;
	char octave_offset = 0;

	for (unsigned char i = octave_start; '0' <= name_copy[i] && name_copy[i] <= '9'; i += 1) {
		octave *= 10;
		octave += name_copy[i] - '0';
	}

	if (strstr(name_copy, "c#") || strstr(name_copy, "db")) {
		pitch_class = 1;
	} else if (strstr(name_copy, "d#") || strstr(name_copy, "eb")) {
		pitch_class = 3;
	} else if (strstr(name_copy, "fb")) {
		pitch_class = 4;
	} else if (strstr(name_copy, "e#")) {
		pitch_class = 5;
	} else if (strstr(name_copy, "f#") || strstr(name_copy, "gb")) {
		pitch_class = 6;
	} else if (strstr(name_copy, "g#") || strstr(name_copy, "ab")) {
		pitch_class = 8;
	} else if (strstr(name_copy, "a#") || strstr(name_copy, "bb")) {
		pitch_class = 10;
	} else if (strstr(name_copy, "cb")) {
		pitch_class = 11;
		octave_offset = -1;
	} else if (strstr(name_copy, "b#")) {
		pitch_class = 0;
		octave_offset = 1;
	} else if (strstr(name_copy, "c")) {
		pitch_class = 0;
	} else if (strstr(name_copy, "d")) {
		pitch_class = 2;
	} else if (strstr(name_copy, "e")) {
		pitch_class = 4;
	} else if (strstr(name_copy, "f")) {
		pitch_class = 5;
	} else if (strstr(name_copy, "g")) {
		pitch_class = 7;
	} else if (strstr(name_copy, "a")) {
		pitch_class = 9;
	} else if (strstr(name_copy, "b")) {
		pitch_class = 11;
	} else {
		return 255u;
	}

	if (octave == 0 && octave_offset < 0) {
		return 255u;
	}

	return ((octave * 12) + octave_offset) + pitch_class;
}