add autotune

autotune.go

@@ -0,0 +1,66 @@
+package kcp
+
+const maxAutoTuneSamples = 258
+
+// pulse represents a 0/1 signal with time sequence
+type pulse struct {
+	bit bool   // 0 or 1
+	seq uint32 // sequence of the signal
+}
+
+// autoTune object
+type autoTune struct {
+	pulses [maxAutoTuneSamples]pulse
+}
+
+// Sample adds a signal sample to the pulse buffer
+func (tune *autoTune) Sample(bit bool, seq uint32) {
+	tune.pulses[seq%maxAutoTuneSamples] = pulse{bit, seq}
+}
+
+// Find a period for a given signal
+// returns -1 if not found
+//
+//    ---              ------
+//      |              |
+//      |______________|
+//          Period
+//  Falling Edge    Rising Edge
+func (tune *autoTune) FindPeriod(bit bool) int {
+	// find left and right edges for a bit
+	lastPulse := tune.pulses[0]
+	idx := 1
+
+	// left edge
+	var leftEdge int
+	for ; idx < len(tune.pulses); idx++ {
+		if lastPulse.seq+1 == tune.pulses[idx].seq {
+			if lastPulse.bit != bit && tune.pulses[idx].bit == bit {
+				leftEdge = idx
+				break
+			}
+		} else {
+			return -1
+		}
+		lastPulse = tune.pulses[idx]
+	}
+
+	// right edge
+	var rightEdge int
+	lastPulse = tune.pulses[leftEdge]
+	idx = leftEdge + 1
+
+	for ; idx < len(tune.pulses); idx++ {
+		if lastPulse.seq+1 == tune.pulses[idx].seq {
+			if lastPulse.bit == bit && tune.pulses[idx].bit != bit {
+				rightEdge = idx
+				break
+			}
+		} else {
+			return -1
+		}
+		lastPulse = tune.pulses[idx]
+	}
+
+	return rightEdge - leftEdge
+}

autotune_test.go

@@ -0,0 +1,47 @@
+package kcp
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAutoTune(t *testing.T) {
+	signals := []uint32{0, 0, 0, 0, 0, 0}
+
+	tune := autoTune{}
+	for i := 0; i < len(signals); i++ {
+		if signals[i] == 0 {
+			tune.Sample(false, uint32(i))
+		} else {
+			tune.Sample(true, uint32(i))
+		}
+	}
+
+	assert.Equal(t, -1, tune.FindPeriod(false))
+	assert.Equal(t, -1, tune.FindPeriod(true))
+
+	signals = []uint32{1, 0, 1, 0, 0, 1}
+	tune = autoTune{}
+	for i := 0; i < len(signals); i++ {
+		if signals[i] == 0 {
+			tune.Sample(false, uint32(i))
+		} else {
+			tune.Sample(true, uint32(i))
+		}
+	}
+	assert.Equal(t, 1, tune.FindPeriod(false))
+	assert.Equal(t, 1, tune.FindPeriod(true))
+
+	signals = []uint32{1, 0, 0, 0, 0, 1}
+	tune = autoTune{}
+	for i := 0; i < len(signals); i++ {
+		if signals[i] == 0 {
+			tune.Sample(false, uint32(i))
+		} else {
+			tune.Sample(true, uint32(i))
+		}
+	}
+	assert.Equal(t, -1, tune.FindPeriod(true))
+	assert.Equal(t, 4, tune.FindPeriod(false))
+}

go.mod

@@ -5,6 +5,7 @@ require (
 	github.com/klauspost/reedsolomon v1.9.9
 	github.com/mmcloughlin/avo v0.0.0-20200803215136-443f81d77104 // indirect
 	github.com/pkg/errors v0.9.1
+	github.com/stretchr/testify v1.6.1
 	github.com/templexxx/cpu v0.0.7 // indirect
 	github.com/templexxx/xorsimd v0.4.1
 	github.com/tjfoc/gmsm v1.3.2

go.sum

@@ -1,3 +1,5 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/klauspost/cpuid v1.2.4/go.mod h1:Pj4uuM528wm8OyEC2QMXAi2YiTZ96dNQPGgoMS4s3ek=
 github.com/klauspost/cpuid v1.3.1 h1:5JNjFYYQrZeKRJ0734q51WCEEn2huer72Dc7K+R/b6s=
 github.com/klauspost/cpuid v1.3.1/go.mod h1:bYW4mA6ZgKPob1/Dlai2LviZJO7KGI3uoWLd42rAQw4=
@@ -7,6 +9,11 @@ github.com/mmcloughlin/avo v0.0.0-20200803215136-443f81d77104 h1:ULR/QWMgcgRiZLU
 github.com/mmcloughlin/avo v0.0.0-20200803215136-443f81d77104/go.mod h1:wqKykBG2QzQDJEzvRkcS8x6MiSJkF52hXZsXcjaB3ls=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
+github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/templexxx/cpu v0.0.1 h1:hY4WdLOgKdc8y13EYklu9OUTXik80BkxHoWvTO6MQQY=
 github.com/templexxx/cpu v0.0.1/go.mod h1:w7Tb+7qgcAlIyX4NhLuDKt78AHA5SzPmq0Wj6HiEnnk=
 github.com/templexxx/cpu v0.0.7 h1:pUEZn8JBy/w5yzdYWgx+0m0xL9uk6j4K91C5kOViAzo=
@@ -55,4 +62,8 @@ golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IV
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 rsc.io/pdf v0.1.1/go.mod h1:n8OzWcQ6Sp37PL01nO98y4iUCRdTGarVfzxY20ICaU4=