1 files changed, 205 insertions, 0 deletions
diff --git a/midi/midi.ha b/midi/midi.ha
new file mode 100644
index 0000000..7da6689
--- /dev/null
+++ b/midi/midi.ha
@@ -0,0 +1,205 @@
+use fmt;
+use endian;
+use strings;
+use io;
+use os;
+use strconv;
+
+def HEADER: [4]u8 = ['M', 'T', 'h', 'd'];
+def TRACK: [4]u8 = ['M', 'T', 'r', 'k'];
+
+def SOUNDOFF: [2]u8 = [0x78, 0x00];
+
+export type chunk = struct {
+	chktype: [4]u8,
+	length: u32,
+};
+
+export type hchunk = struct {
+	chk: chunk,
+	format: u16,
+	ntrks: u16,
+	division: u16,
+};
+
+export type trchunk = struct {
+	chk: chunk,
+	ev: []event,
+};
+
+export type vlen = u32;
+
+export type event = struct {
+	deltatime: vlen,
+	ev: (midi | sysex | meta),
+};
+
+export type midi = struct {
+	status: u8,
+	data: [2]u8,
+};
+
+export type sysex = void;
+export type meta = void;
+
+export def HEADERCHUNK = chunk {
+	chktype = HEADER,
+	// MIDI 1.0
+	length = 6,
+};
+
+def TRACKCHUNK = chunk {
+	chktype = TRACK,
+	...
+};
+
+export type note = enum u8 {
+	A = 0x39,
+	AS = 0x3A,
+	B = 0x3B,
+	BS = 0x3C,
+	C = 0x3C,
+	CS = 0x3D,
+	D = 0x3E,
+	DS = 0x3F,
+	E = 0x40,
+	ES = 0x41,
+	F = 0x41,
+	FS = 0x42,
+	G = 0x43,
+	GS = 0x44,
+};
+
+export fn finishtrack(c: trchunk) void = {
+	free(c.ev);
+};
+
+export fn newtrack() trchunk = {
+	return trchunk {
+		chk = TRACKCHUNK,
+		ev = [],
+	};
+};
+
+export fn addevent(c: *trchunk, e: event) void = {
+	append(c.ev, e);
+};
+
+export fn noteon(c: *trchunk, d: vlen, n: note, vel: u8 = 0x40, oct: uint = 0) void = {
+	const np = n + (oct * 12): u8;
+	const e = event {
+		deltatime = d,
+		ev = midi {
+			status = 0x90,
+			data = [n, vel],
+		},
+	};
+	append(c.ev, e);
+};
+
+export fn noteoff(c: *trchunk, d: vlen, n: note, vel: u8 = 0x40, oct: uint = 0) void = {
+	const np = n + (oct * 12): u8;
+	const e = event {
+		deltatime = d,
+		ev = midi {
+			status = 0x80,
+			data = [n, vel],
+		},
+	};
+	append(c.ev, e);
+};
+
+export fn writeheader(c: hchunk) void = {
+	io::writeall(os::stdout, c.chk.chktype)!;
+	let buf: [4]u8 = [0...];
+	let l = c.chk.length;
+	endian::beputu32(buf, l);
+	io::writeall(os::stdout, buf)!;
+
+	let bf: [2]u8 = [0...];
+	endian::beputu16(bf, c.format);
+	io::writeall(os::stdout, bf)!;
+	let bf: [2]u8 = [0...];
+	endian::beputu16(bf, c.ntrks);
+	io::writeall(os::stdout, bf)!;
+	let bf: [2]u8 = [0...];
+	endian::beputu16(bf, c.division);
+	io::writeall(os::stdout, bf)!;
+};
+
+export fn writechunk(c: trchunk) void = {
+	io::writeall(os::stdout, c.chk.chktype)!;
+	let buf: [4]u8 = [0...];
+	let l = calclength(c);
+	//let l = c.chk.length;
+	endian::beputu32(buf, l);
+	io::writeall(os::stdout, buf)!;
+
+	for (const ev .. c.ev) {
+		let dt = encodevlen(ev.deltatime);
+		endian::beputu32(buf, dt);
+		if (dt <= 127) {
+			io::writeall(os::stdout, [buf[3]])!;
+		} else if (dt <= 0xFF7F) {
+			io::writeall(os::stdout, buf[2..])!;
+		} else if (dt <= 0xFFFF7F) {
+			io::writeall(os::stdout, buf[1..])!;
+		} else {
+			io::writeall(os::stdout, buf)!;
+		};
+		match (ev.ev) {
+		case let m: midi =>
+			io::writeall(os::stdout, [m.status])!;
+			io::writeall(os::stdout, m.data)!;
+		case =>
+			abort();
+		};
+	};
+};
+
+fn calclength(c: trchunk) u32 = {
+	let length = 0u32;
+	for (const ev .. c.ev) {
+		let dt = encodevlen(ev.deltatime);
+		if (dt <= 127) {
+			length += 1;
+		} else if (dt <= 0xFF7F) {
+			length += 2;
+		} else if (dt <= 0xFFFF7F) {
+			length += 3;
+		} else {
+			length += 4;
+		};
+		match (ev.ev) {
+		case let m: midi =>
+			length += 3;
+		case =>
+			abort();
+		};
+	};
+	return length;
+};
+
+fn encodevlen(v: vlen) u32 = {
+	if (v < 128) {
+		return v;
+	};
+
+	let n = v: u32;
+	let b: [4]u8 = [0...];
+	endian::beputu32(b, v);
+	for (let i = 3z; i >= 0; i -= 1) {
+		b[i] = (n & 0x7F): u8;
+
+		if (i < 3) {
+			b[i] |= 0x80;
+		};
+
+		n >>= 7;
+
+		if (n < 1) {
+			break;
+		};
+	};
+	return endian::begetu32(b);
+};