statetrie: nibbles

crypto/statetrie/nibbles/nibbles.go

@@ -0,0 +1,170 @@
+// Copyright (C) 2019-2023 Algorand, Inc.
+// This file is part of go-algorand
+//
+// go-algorand is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// go-algorand 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 Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with go-algorand.  If not, see <https://www.gnu.org/licenses/>.
+
+package nibbles
+
+import (
+	"bytes"
+	"errors"
+)
+
+// Nibbles are 4-bit values stored in an 8-bit byte arrays
+type Nibbles []byte
+
+const (
+	// evenIndicator for serialization when the last nibble in a byte array
+	// is part of the nibble array.
+	evenIndicator = 0x01
+	// oddIndicator for when it is not.
+	oddIndicator = 0x03
+)
+
+// MakeNibbles returns a nibble array from the byte array.  If oddLength is true,
+// the last 4 bits of the last byte of the array are ignored.
+func MakeNibbles(data []byte, oddLength bool) Nibbles {
+	return Unpack(data, oddLength)
+}
+
+// Unpack the byte array into a nibble array.  If oddLength is true, the last 4
+// bits of the last byte of the array are ignored.  Allocates a new byte
+// slice.
+//
+// [0x12, 0x30], true -> [0x1, 0x2, 0x3]
+// [0x12, 0x34], false -> [0x1, 0x2, 0x3, 0x4]
+// [0x12, 0x34], true -> [0x1, 0x2, 0x3]  <-- last byte last 4 bits ignored
+// [], false -> []
+// never to be called with [], true
+func Unpack(data []byte, oddLength bool) Nibbles {
+	length := len(data) * 2
+	if oddLength {
+		length = length - 1
+	}
+	ns := make([]byte, length)
+
+	j := 0
+	for i := 0; i < length; i++ {
+		if i%2 == 0 {
+			ns[i] = data[j] >> 4
+		} else {
+			ns[i] = data[j] & 0x0f
+			j++
+		}
+	}
+	return ns
+}
+
+// Pack the nibble array into a byte array.
+// Return the byte array and a bool indicating if the last byte is a full byte or
+// only the high 4 bits are part of the encoding
+// the last four bits of a oddLength byte encoding will always be zero.
+// Allocates a new byte slice.
+//
+// [0x1, 0x2, 0x3] -> [0x12, 0x30], true
+// [0x1, 0x2, 0x3, 0x4] -> [0x12, 0x34], false
+// [0x1] -> [0x10], true
+// [] -> [], false
+func Pack(nyb Nibbles) ([]byte, bool) {
+	length := len(nyb)
+	data := make([]byte, length/2+length%2)
+	for i := 0; i < length; i++ {
+		if i%2 == 0 {
+			data[i/2] = nyb[i] << 4
+		} else {
+			data[i/2] = data[i/2] | nyb[i]
+		}
+	}
+
+	return data, length%2 != 0
+}
+
+// Equal returns true if the two nibble arrays are equal
+// [0x1, 0x2, 0x3], [0x1, 0x2, 0x3] -> true
+// [0x1, 0x2, 0x3], [0x1, 0x2, 0x4] -> false
+// [0x1, 0x2, 0x3], [0x1] -> false
+// [0x1, 0x2, 0x3], [0x1, 0x2, 0x3, 0x4] -> false
+// [], [] -> true
+// [], [0x1] -> false
+func Equal(nyb1 Nibbles, nyb2 Nibbles) bool {
+	return bytes.Equal(nyb1, nyb2)
+}
+
+// ShiftLeft returns a slice of nyb1 that contains the Nibbles after the first
+// numNibbles
+func ShiftLeft(nyb1 Nibbles, numNibbles int) Nibbles {
+	if numNibbles <= 0 {
+		return nyb1
+	}
+	if numNibbles > len(nyb1) {
+		return nyb1[:0]
+	}
+
+	return nyb1[numNibbles:]
+}
+
+// SharedPrefix returns a slice from nyb1 that contains the shared prefix
+// between nyb1 and nyb2
+func SharedPrefix(nyb1 Nibbles, nyb2 Nibbles) Nibbles {
+	minLength := len(nyb1)
+	if len(nyb2) < minLength {
+		minLength = len(nyb2)
+	}
+	for i := 0; i < minLength; i++ {
+		if nyb1[i] != nyb2[i] {
+			return nyb1[:i]
+		}
+	}
+	return nyb1[:minLength]
+}
+
+// Serialize returns a byte array that represents the Nibbles
+// an empty nibble array is serialized as a single byte with value 0x3
+// as the empty nibble is considered to be full width
+//
+// [0x1, 0x2, 0x3] -> [0x12, 0x30, 0x01]
+// [0x1, 0x2, 0x3, 0x4] -> [0x12, 0x34, 0x03]
+// [] -> [0x03]
+func Serialize(nyb Nibbles) (data []byte) {
+	p, h := Pack(nyb)
+	length := len(p)
+	output := make([]byte, length+1)
+	copy(output, p)
+	if h {
+		// 0x1 is the arbitrary odd length indicator
+		output[length] = evenIndicator
+	} else {
+		// 0x3 is the arbitrary even length indicator
+		output[length] = oddIndicator
+	}
+
+	return output
+}
+
+// Deserialize returns a nibble array from the byte array.
+func Deserialize(encoding []byte) (Nibbles, error) {
+	var ns Nibbles
+	length := len(encoding)
+	if length == 0 {
+		return nil, errors.New("invalid encoding")
+	}
+	if encoding[length-1] == evenIndicator {
+		ns = Unpack(encoding[:length-1], true)
+	} else if encoding[length-1] == oddIndicator {
+		ns = Unpack(encoding[:length-1], false)
+	} else {
+		return nil, errors.New("invalid encoding")
+	}
+	return ns, nil
+}

crypto/statetrie/nibbles/nibbles_test.go

@@ -0,0 +1,200 @@
+// Copyright (C) 2019-2023 Algorand, Inc.
+// This file is part of go-algorand
+//
+// go-algorand is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// go-algorand 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 Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with go-algorand.  If not, see <https://www.gnu.org/licenses/>.
+
+package nibbles
+
+import (
+	"bytes"
+	"github.com/algorand/go-algorand/test/partitiontest"
+	"github.com/stretchr/testify/require"
+	"math/rand"
+	"testing"
+	"time"
+)
+
+func TestNibblesRandom(t *testing.T) {
+	partitiontest.PartitionTest(t)
+	t.Parallel()
+
+	seed := time.Now().UnixNano()
+	localRand := rand.New(rand.NewSource(seed))
+	defer func() {
+		if t.Failed() {
+			t.Logf("The seed was %d", seed)
+		}
+	}()
+
+	for i := 0; i < 1_000; i++ {
+		length := localRand.Intn(8192) + 1
+		data := make([]byte, length)
+		localRand.Read(data)
+		half := localRand.Intn(2) == 0 // half of the time, we have an odd number of nibbles
+		if half && localRand.Intn(2) == 0 {
+			data[len(data)-1] &= 0xf0 // sometimes clear the last nibble, sometimes do not
+		}
+		nibbles := MakeNibbles(data, half)
+
+		data2 := Serialize(nibbles)
+		nibbles2, err := Deserialize(data2)
+		require.NoError(t, err)
+		require.Equal(t, nibbles, nibbles2)
+
+		if half {
+			data[len(data)-1] &= 0xf0 // clear last nibble
+		}
+		packed, odd := Pack(nibbles)
+		require.Equal(t, odd, half)
+		require.Equal(t, packed, data)
+		unpacked := Unpack(packed, odd)
+		require.Equal(t, nibbles, unpacked)
+
+		packed, odd = Pack(nibbles2)
+		require.Equal(t, odd, half)
+		require.Equal(t, packed, data)
+		unpacked = Unpack(packed, odd)
+		require.Equal(t, nibbles2, unpacked)
+	}
+}
+
+func TestNibbles(t *testing.T) {
+	partitiontest.PartitionTest(t)
+	t.Parallel()
+
+	sampleNibbles := []Nibbles{
+		{0x0, 0x1, 0x2, 0x3, 0x4},
+		{0x4, 0x1, 0x2, 0x3, 0x4},
+		{0x0, 0x0, 0x2, 0x3, 0x5},
+		{0x0, 0x1, 0x2, 0x3, 0x4, 0x5},
+		{},
+		{0x1},
+	}
+
+	sampleNibblesPacked := [][]byte{
+		{0x01, 0x23, 0x40},
+		{0x41, 0x23, 0x40},
+		{0x00, 0x23, 0x50},
+		{0x01, 0x23, 0x45},
+		{},
+		{0x10},
+	}
+
+	sampleNibblesShifted1 := []Nibbles{
+		{0x1, 0x2, 0x3, 0x4},
+		{0x1, 0x2, 0x3, 0x4},
+		{0x0, 0x2, 0x3, 0x5},
+		{0x1, 0x2, 0x3, 0x4, 0x5},
+		{},
+		{},
+	}
+
+	sampleNibblesShifted2 := []Nibbles{
+		{0x2, 0x3, 0x4},
+		{0x2, 0x3, 0x4},
+		{0x2, 0x3, 0x5},
+		{0x2, 0x3, 0x4, 0x5},
+		{},
+		{},
+	}
+
+	for i, n := range sampleNibbles {
+		b, oddLength := Pack(n)
+		if oddLength {
+			// require that oddLength packs returns a byte slice with the last nibble set to 0x0
+			require.Equal(t, b[len(b)-1]&0x0f == 0x00, true)
+		}
+
+		require.Equal(t, oddLength == (len(n)%2 == 1), true)
+		require.Equal(t, bytes.Equal(b, sampleNibblesPacked[i]), true)
+
+		unp := Unpack(b, oddLength)
+		require.Equal(t, bytes.Equal(unp, n), true)
+
+	}
+	for i, n := range sampleNibbles {
+		require.Equal(t, bytes.Equal(ShiftLeft(n, -2), sampleNibbles[i]), true)
+		require.Equal(t, bytes.Equal(ShiftLeft(n, -1), sampleNibbles[i]), true)
+		require.Equal(t, bytes.Equal(ShiftLeft(n, 0), sampleNibbles[i]), true)
+		require.Equal(t, bytes.Equal(ShiftLeft(n, 1), sampleNibblesShifted1[i]), true)
+		require.Equal(t, bytes.Equal(ShiftLeft(n, 2), sampleNibblesShifted2[i]), true)
+	}
+
+	sampleSharedNibbles := [][]Nibbles{
+		{{0x0, 0x1, 0x2, 0x9, 0x2}, {0x0, 0x1, 0x2}},
+		{{0x4, 0x1}, {0x4, 0x1}},
+		{{0x9, 0x2, 0x3}, {}},
+		{{0x0}, {0x0}},
+		{{}, {}},
+	}
+	for i, n := range sampleSharedNibbles {
+		shared := SharedPrefix(n[0], sampleNibbles[i])
+		require.Equal(t, bytes.Equal(shared, n[1]), true)
+		shared = SharedPrefix(sampleNibbles[i], n[0])
+		require.Equal(t, bytes.Equal(shared, n[1]), true)
+	}
+
+	sampleSerialization := []Nibbles{
+		{0x0, 0x1, 0x2, 0x9, 0x2},
+		{0x4, 0x1},
+		{0x4, 0x1, 0x4, 0xf},
+		{0x4, 0x1, 0x4, 0xf, 0x0},
+		{0x9, 0x2, 0x3},
+		{},
+		{0x05},
+		{},
+	}
+
+	for _, n := range sampleSerialization {
+		nbytes := Serialize(n)
+		n2, err := Deserialize(nbytes)
+		require.NoError(t, err)
+		require.Equal(t, bytes.Equal(n, n2), true)
+	}
+
+	makeNibblesTestExpected := Nibbles{0x0, 0x1, 0x2, 0x9, 0x2}
+	makeNibblesTestData := []byte{0x01, 0x29, 0x20}
+	mntr := MakeNibbles(makeNibblesTestData, true)
+	require.Equal(t, bytes.Equal(mntr, makeNibblesTestExpected), true)
+	makeNibblesTestExpectedFW := Nibbles{0x0, 0x1, 0x2, 0x9, 0x2, 0x0}
+	mntr2 := MakeNibbles(makeNibblesTestData, false)
+	require.Equal(t, bytes.Equal(mntr2, makeNibblesTestExpectedFW), true)
+
+	sampleEqualFalse := [][]Nibbles{
+		{{0x0, 0x1, 0x2, 0x9, 0x2}, {0x0, 0x1, 0x2, 0x9}},
+		{{0x0, 0x1, 0x2, 0x9}, {0x0, 0x1, 0x2, 0x9, 0x2}},
+		{{0x0, 0x1, 0x2, 0x9, 0x2}, {}},
+		{{}, {0x0, 0x1, 0x2, 0x9, 0x2}},
+		{{0x0}, {}},
+		{{}, {0x0}},
+		{{}, {0x1}},
+	}
+	for _, n := range sampleEqualFalse {
+		ds := Serialize(n[0])
+		us, e := Deserialize(ds)
+		require.NoError(t, e)
+		require.Equal(t, Equal(n[0], us), true)
+		require.Equal(t, Equal(n[0], n[0]), true)
+		require.Equal(t, Equal(us, n[0]), true)
+		require.Equal(t, Equal(n[0], n[1]), false)
+		require.Equal(t, Equal(us, n[1]), false)
+		require.Equal(t, Equal(n[1], n[0]), false)
+		require.Equal(t, Equal(n[1], us), false)
+	}
+
+	_, e := Deserialize([]byte{})
+	require.Error(t, e)
+	_, e = Deserialize([]byte{0x02})
+	require.Error(t, e)
+}