wave.go

// ImpSynth
// Copyright (C) 2026 Carl Frank Otto III
//
// This library is based in part on the Nuked-OPL3 OPL3 emulator by Nuke.YKT.
// It is free software: you can redistribute it and/or modify it under the
// terms of the GNU Lesser General Public License as published by the Free
// Software Foundation, version 2.1 of the License.
//
// This library is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
// details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this library; if not, see <https://www.gnu.org/licenses/>.

package impsynth

var oplLogSinROM = [256]uint16{
	0x859, 0x6c3, 0x607, 0x58b, 0x52e, 0x4e4, 0x4a6, 0x471,
	0x443, 0x41a, 0x3f5, 0x3d3, 0x3b5, 0x398, 0x37e, 0x365,
	0x34e, 0x339, 0x324, 0x311, 0x2ff, 0x2ed, 0x2dc, 0x2cd,
	0x2bd, 0x2af, 0x2a0, 0x293, 0x286, 0x279, 0x26d, 0x261,
	0x256, 0x24b, 0x240, 0x236, 0x22c, 0x222, 0x218, 0x20f,
	0x206, 0x1fd, 0x1f5, 0x1ec, 0x1e4, 0x1dc, 0x1d4, 0x1cd,
	0x1c5, 0x1be, 0x1b7, 0x1b0, 0x1a9, 0x1a2, 0x19b, 0x195,
	0x18f, 0x188, 0x182, 0x17c, 0x177, 0x171, 0x16b, 0x166,
	0x160, 0x15b, 0x155, 0x150, 0x14b, 0x146, 0x141, 0x13c,
	0x137, 0x133, 0x12e, 0x129, 0x125, 0x121, 0x11c, 0x118,
	0x114, 0x10f, 0x10b, 0x107, 0x103, 0x0ff, 0x0fb, 0x0f8,
	0x0f4, 0x0f0, 0x0ec, 0x0e9, 0x0e5, 0x0e2, 0x0de, 0x0db,
	0x0d7, 0x0d4, 0x0d1, 0x0cd, 0x0ca, 0x0c7, 0x0c4, 0x0c1,
	0x0be, 0x0bb, 0x0b8, 0x0b5, 0x0b2, 0x0af, 0x0ac, 0x0a9,
	0x0a7, 0x0a4, 0x0a1, 0x09f, 0x09c, 0x099, 0x097, 0x094,
	0x092, 0x08f, 0x08d, 0x08a, 0x088, 0x086, 0x083, 0x081,
	0x07f, 0x07d, 0x07a, 0x078, 0x076, 0x074, 0x072, 0x070,
	0x06e, 0x06c, 0x06a, 0x068, 0x066, 0x064, 0x062, 0x060,
	0x05e, 0x05c, 0x05b, 0x059, 0x057, 0x055, 0x053, 0x052,
	0x050, 0x04e, 0x04d, 0x04b, 0x04a, 0x048, 0x046, 0x045,
	0x043, 0x042, 0x040, 0x03f, 0x03e, 0x03c, 0x03b, 0x039,
	0x038, 0x037, 0x035, 0x034, 0x033, 0x031, 0x030, 0x02f,
	0x02e, 0x02d, 0x02b, 0x02a, 0x029, 0x028, 0x027, 0x026,
	0x025, 0x024, 0x023, 0x022, 0x021, 0x020, 0x01f, 0x01e,
	0x01d, 0x01c, 0x01b, 0x01a, 0x019, 0x018, 0x017, 0x017,
	0x016, 0x015, 0x014, 0x014, 0x013, 0x012, 0x011, 0x011,
	0x010, 0x00f, 0x00f, 0x00e, 0x00d, 0x00d, 0x00c, 0x00c,
	0x00b, 0x00a, 0x00a, 0x009, 0x009, 0x008, 0x008, 0x007,
	0x007, 0x007, 0x006, 0x006, 0x005, 0x005, 0x005, 0x004,
	0x004, 0x004, 0x003, 0x003, 0x003, 0x002, 0x002, 0x002,
	0x002, 0x001, 0x001, 0x001, 0x001, 0x001, 0x001, 0x001,
	0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
}

var oplExpROM = [256]uint16{
	0x7fa, 0x7f5, 0x7ef, 0x7ea, 0x7e4, 0x7df, 0x7da, 0x7d4,
	0x7cf, 0x7c9, 0x7c4, 0x7bf, 0x7b9, 0x7b4, 0x7ae, 0x7a9,
	0x7a4, 0x79f, 0x799, 0x794, 0x78f, 0x78a, 0x784, 0x77f,
	0x77a, 0x775, 0x770, 0x76a, 0x765, 0x760, 0x75b, 0x756,
	0x751, 0x74c, 0x747, 0x742, 0x73d, 0x738, 0x733, 0x72e,
	0x729, 0x724, 0x71f, 0x71a, 0x715, 0x710, 0x70b, 0x706,
	0x702, 0x6fd, 0x6f8, 0x6f3, 0x6ee, 0x6e9, 0x6e5, 0x6e0,
	0x6db, 0x6d6, 0x6d2, 0x6cd, 0x6c8, 0x6c4, 0x6bf, 0x6ba,
	0x6b5, 0x6b1, 0x6ac, 0x6a8, 0x6a3, 0x69e, 0x69a, 0x695,
	0x691, 0x68c, 0x688, 0x683, 0x67f, 0x67a, 0x676, 0x671,
	0x66d, 0x668, 0x664, 0x65f, 0x65b, 0x657, 0x652, 0x64e,
	0x649, 0x645, 0x641, 0x63c, 0x638, 0x634, 0x630, 0x62b,
	0x627, 0x623, 0x61e, 0x61a, 0x616, 0x612, 0x60e, 0x609,
	0x605, 0x601, 0x5fd, 0x5f9, 0x5f5, 0x5f0, 0x5ec, 0x5e8,
	0x5e4, 0x5e0, 0x5dc, 0x5d8, 0x5d4, 0x5d0, 0x5cc, 0x5c8,
	0x5c4, 0x5c0, 0x5bc, 0x5b8, 0x5b4, 0x5b0, 0x5ac, 0x5a8,
	0x5a4, 0x5a0, 0x59c, 0x599, 0x595, 0x591, 0x58d, 0x589,
	0x585, 0x581, 0x57e, 0x57a, 0x576, 0x572, 0x56f, 0x56b,
	0x567, 0x563, 0x560, 0x55c, 0x558, 0x554, 0x551, 0x54d,
	0x549, 0x546, 0x542, 0x53e, 0x53b, 0x537, 0x534, 0x530,
	0x52c, 0x529, 0x525, 0x522, 0x51e, 0x51b, 0x517, 0x514,
	0x510, 0x50c, 0x509, 0x506, 0x502, 0x4ff, 0x4fb, 0x4f8,
	0x4f4, 0x4f1, 0x4ed, 0x4ea, 0x4e7, 0x4e3, 0x4e0, 0x4dc,
	0x4d9, 0x4d6, 0x4d2, 0x4cf, 0x4cc, 0x4c8, 0x4c5, 0x4c2,
	0x4be, 0x4bb, 0x4b8, 0x4b5, 0x4b1, 0x4ae, 0x4ab, 0x4a8,
	0x4a4, 0x4a1, 0x49e, 0x49b, 0x498, 0x494, 0x491, 0x48e,
	0x48b, 0x488, 0x485, 0x482, 0x47e, 0x47b, 0x478, 0x475,
	0x472, 0x46f, 0x46c, 0x469, 0x466, 0x463, 0x460, 0x45d,
	0x45a, 0x457, 0x454, 0x451, 0x44e, 0x44b, 0x448, 0x445,
	0x442, 0x43f, 0x43c, 0x439, 0x436, 0x433, 0x430, 0x42d,
	0x42a, 0x428, 0x425, 0x422, 0x41f, 0x41c, 0x419, 0x416,
	0x414, 0x411, 0x40e, 0x40b, 0x408, 0x406, 0x403, 0x400,
}

func oplEnvelopeCalcExp(level uint32) int {
	if level > 0x1fff {
		level = 0x1fff
	}
	return int((oplExpROM[level&0xff] << 1) >> (level >> 8))
}

func oplWaveOutput(wave uint8, phase uint16, envelope uint16) int {
	switch wave & 0x07 {
	case 0:
		return oplWaveOutput0(phase, envelope)
	case 1:
		return oplWaveOutput1(phase, envelope)
	case 2:
		return oplWaveOutput2(phase, envelope)
	case 3:
		return oplWaveOutput3(phase, envelope)
	case 4:
		return oplWaveOutput4(phase, envelope)
	case 5:
		return oplWaveOutput5(phase, envelope)
	case 6:
		return oplWaveOutput6(phase, envelope)
	default:
		return oplWaveOutput7(phase, envelope)
	}
}

func oplSignedOutput(raw int, neg bool) int {
	if !neg {
		return raw
	}
	return int(int16(^uint16(raw)))
}

func oplWaveOutput0(phase uint16, envelope uint16) int {
	phase &= 0x3ff
	neg := (phase & 0x200) != 0
	out := oplLogSinROM[phase&0xff]
	if (phase & 0x100) != 0 {
		out = oplLogSinROM[(phase&0xff)^0xff]
	}
	return oplSignedOutput(oplEnvelopeCalcExp(uint32(out)+(uint32(envelope)<<3)), neg)
}

func oplWaveOutput1(phase uint16, envelope uint16) int {
	phase &= 0x3ff
	out := uint16(0)
	if (phase & 0x200) != 0 {
		out = 0x1000
	} else if (phase & 0x100) != 0 {
		out = oplLogSinROM[(phase&0xff)^0xff]
	} else {
		out = oplLogSinROM[phase&0xff]
	}
	return oplEnvelopeCalcExp(uint32(out) + (uint32(envelope) << 3))
}

func oplWaveOutput2(phase uint16, envelope uint16) int {
	phase &= 0x3ff
	out := oplLogSinROM[phase&0xff]
	if (phase & 0x100) != 0 {
		out = oplLogSinROM[(phase&0xff)^0xff]
	}
	return oplEnvelopeCalcExp(uint32(out) + (uint32(envelope) << 3))
}

func oplWaveOutput3(phase uint16, envelope uint16) int {
	phase &= 0x3ff
	out := uint16(0)
	if (phase & 0x100) != 0 {
		out = 0x1000
	} else {
		out = oplLogSinROM[phase&0xff]
	}
	return oplEnvelopeCalcExp(uint32(out) + (uint32(envelope) << 3))
}

func oplWaveOutput4(phase uint16, envelope uint16) int {
	phase &= 0x3ff
	neg := (phase & 0x300) == 0x100
	out := uint16(0)
	if (phase & 0x200) != 0 {
		out = 0x1000
	} else if (phase & 0x80) != 0 {
		out = oplLogSinROM[((phase^0xff)<<1)&0xff]
	} else {
		out = oplLogSinROM[(phase<<1)&0xff]
	}
	return oplSignedOutput(oplEnvelopeCalcExp(uint32(out)+(uint32(envelope)<<3)), neg)
}

func oplWaveOutput5(phase uint16, envelope uint16) int {
	phase &= 0x3ff
	out := uint16(0)
	if (phase & 0x200) != 0 {
		out = 0x1000
	} else if (phase & 0x80) != 0 {
		out = oplLogSinROM[((phase^0xff)<<1)&0xff]
	} else {
		out = oplLogSinROM[(phase<<1)&0xff]
	}
	return oplEnvelopeCalcExp(uint32(out) + (uint32(envelope) << 3))
}

func oplWaveOutput6(phase uint16, envelope uint16) int {
	phase &= 0x3ff
	return oplSignedOutput(oplEnvelopeCalcExp(uint32(envelope)<<3), (phase&0x200) != 0)
}

func oplWaveOutput7(phase uint16, envelope uint16) int {
	phase &= 0x3ff
	neg := false
	if (phase & 0x200) != 0 {
		neg = true
		phase = (phase & 0x1ff) ^ 0x1ff
	}
	out := uint32(phase << 3)
	return oplSignedOutput(oplEnvelopeCalcExp(out+(uint32(envelope)<<3)), neg)
}