feat(vm): add support for gm.dls samples in the go virtual machine (closes #75)

CHANGELOG.md

@@ -5,6 +5,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## Unreleased
 ### Added
+- Support for gm.dls samples in the go-written virtual machine
 - Ability to lock delay relative to beat duration
 - Ability to import 4klang patches (.4kp) and instruments (.4ki)
 - Ability to run sointu as a vsti plugin, inside vsti host

README.md

@@ -358,12 +358,13 @@ New features since fork
     ports / 4 stereo ports, so even this method of routing is unlikely to run
     out of ports in small intros.
   - **Pattern length does not have to be a power of 2**.
-  - **Sample-based oscillators, with samples imported from gm.dls**. Reading
-    gm.dls is obviously Windows only, but with some effort the sample mechanism
-    can be used also without it, in case you are working on a 64k and have some
-    kilobytes to spare. See [this example](tests/test_oscillat_sample.yml), and
-    this go generate [program](cmd/sointu-generate/main.go) parses the gm.dls
-    file and dumps the sample offsets from it.
+  - **Sample-based oscillators, with samples imported from gm.dls**. The
+    gm.dls is available from system folder only on Windows, but the
+    non-native tracker looks for it also in the current folder, so
+    should you somehow magically get hold of gm.dls on Linux or Mac, you
+    can drop it in the same folder with the tracker. See [this example](tests/test_oscillat_sample.yml),
+    and this go generate [program](cmd/sointu-generate/main.go) parses
+    the gm.dls file and dumps the sample offsets from it.
   - **Unison oscillators**. Multiple copies of the oscillator running slightly
     detuned and added up to together. Great for trance leads (supersaw). Unison
     of up to 4, or 8 if you make stereo unison oscillator and add up both left

vm/interpreter.go

@@ -1,9 +1,12 @@
 package vm
 
 import (
+	"encoding/binary"
 	"errors"
 	"fmt"
 	"math"
+	"os"
+	"path/filepath"
 
 	"github.com/vsariola/sointu"
 )
@@ -63,6 +66,27 @@ const (
 	envStateRelease
 )
 
+var su_sample_table [3440660]byte
+
+func init() {
+	var f *os.File
+	var err error
+	if f, err = os.Open("gm.dls"); err == nil { // try to open from current directory first
+		goto success
+	}
+	if f, err = os.Open(filepath.Join(os.Getenv("SystemRoot"), "system32", "drivers", "gm.dls")); err == nil {
+		goto success
+	}
+	if f, err = os.Open(filepath.Join(os.Getenv("SystemRoot"), "SysWOW64", "drivers", "gm.dls")); err == nil {
+		goto success
+	}
+	return
+success:
+	defer f.Close()
+	// read file, ignoring errors
+	f.Read(su_sample_table[:])
+}
+
 func Synth(patch sointu.Patch, bpm int) (sointu.Synth, error) {
 	bytePatch, err := Encode(patch, AllFeatures{}, bpm)
 	if err != nil {
@@ -429,37 +453,53 @@ func (s *Interpreter) Render(buffer []float32, maxtime int) (samples int, time i
 						} else {
 							omega *= 0.000038 //  pretty random scaling constant to get LFOs into reasonable range. Historical reasons, goes all the way back to 4klang
 						}
-						*statevar += float32(omega)
-						*statevar -= float32(int(*statevar+1) - 1)
-						phase := *statevar
-						phase += params[2]
-						phase -= float32(int(phase))
-						color := params[3]
 						var amplitude float32
-						switch {
-						case flags&0x40 == 0x40: // Sine
-							if phase < color {
-								amplitude = float32(math.Sin(2 * math.Pi * float64(phase/color)))
+						*statevar += float32(omega)
+						if flags&0x80 == 0x80 { // if this is a sample oscillator
+							phase := *statevar
+							phase += params[2]
+							sampleno := valuesAtTransform[3] // reuse color as the sample number
+							sampleoffset := s.bytePatch.SampleOffsets[sampleno]
+							sampleindex := int(phase*84.28074964676522 + 0.5)
+							loopstart := int(sampleoffset.LoopStart)
+							if sampleindex >= loopstart {
+								sampleindex -= loopstart
+								sampleindex %= int(sampleoffset.LoopLength)
+								sampleindex += loopstart
 							}
-						case flags&0x20 == 0x20: // Trisaw
-							if phase >= color {
-								phase = 1 - phase
-								color = 1 - color
+							sampleindex += int(sampleoffset.Start)
+							amplitude = float32(int16(binary.LittleEndian.Uint16(su_sample_table[sampleindex*2:]))) / 32767.0
+						} else {
+							*statevar -= float32(int(*statevar+1) - 1)
+							phase := *statevar
+							phase += params[2]
+							phase -= float32(int(phase))
+							color := params[3]
+							switch {
+							case flags&0x40 == 0x40: // Sine
+								if phase < color {
+									amplitude = float32(math.Sin(2 * math.Pi * float64(phase/color)))
+								}
+							case flags&0x20 == 0x20: // Trisaw
+								if phase >= color {
+									phase = 1 - phase
+									color = 1 - color
+								}
+								amplitude = phase/color*2 - 1
+							case flags&0x10 == 0x10: // Pulse
+								if phase >= color {
+									amplitude = -1
+								} else {
+									amplitude = 1
+								}
+							case flags&0x4 == 0x4: // Gate
+								maskLow, maskHigh := valuesAtTransform[3], valuesAtTransform[4]
+								gateBits := (int(maskHigh) << 8) + int(maskLow)
+								amplitude = float32((gateBits >> (int(phase*16+.5) & 15)) & 1)
+								g := unit.state[4+i] // warning: still fucks up with unison = 3
+								amplitude += 0.99609375 * (g - amplitude)
+								unit.state[4+i] = amplitude
 							}
-							amplitude = phase/color*2 - 1
-						case flags&0x10 == 0x10: // Pulse
-							if phase >= color {
-								amplitude = -1
-							} else {
-								amplitude = 1
-							}
-						case flags&0x4 == 0x4: // Gate
-							maskLow, maskHigh := valuesAtTransform[3], valuesAtTransform[4]
-							gateBits := (int(maskHigh) << 8) + int(maskLow)
-							amplitude = float32((gateBits >> (int(phase*16+.5) & 15)) & 1)
-							g := unit.state[4+i] // warning: still fucks up with unison = 3
-							amplitude += 0.99609375 * (g - amplitude)
-							unit.state[4+i] = amplitude
 						}
 						if flags&0x4 == 0 {
 							output += waveshape(amplitude, params[4]) * params[5]

vm/interpreter_test.go

@@ -28,8 +28,8 @@ func TestAllRegressionTests(t *testing.T) {
 		basename := filepath.Base(filename)
 		testname := strings.TrimSuffix(basename, path.Ext(basename))
 		t.Run(testname, func(t *testing.T) {
-			if strings.Contains(testname, "sample") {
-				t.Skip("Samples (gm.dls) not available in the interpreter VM at the moment")
+			if runtime.GOOS != "windows" && strings.Contains(testname, "sample") {
+				t.Skip("Samples (gm.dls) available only on Windows")
 				return
 			}
 			asmcode, err := ioutil.ReadFile(filename)