Move Maybe to its own package (ava-labs#1817)

x/merkledb/maybe.go → utils/maybe/maybe.go

@@ -1,7 +1,7 @@
 // Copyright (C) 2019-2023, Ava Labs, Inc. All rights reserved.
 // See the file LICENSE for licensing terms.
 
-package merkledb
+package maybe
 
 // Maybe T = Some T | Nothing.
 // A data wrapper that allows values to be something [Some T] or nothing [Nothing].
@@ -42,23 +42,23 @@ func (m Maybe[T]) Value() T {
 	return m.value
 }
 
-// MaybeBind returns Nothing, if [m] is Nothing.
+// Bind returns Nothing iff [m] is Nothing.
 // Otherwise applies [f] to the value of [m] and returns the result as a Some.
-func MaybeBind[T, U any](m Maybe[T], f func(T) U) Maybe[U] {
+func Bind[T, U any](m Maybe[T], f func(T) U) Maybe[U] {
 	if m.IsNothing() {
 		return Nothing[U]()
 	}
 	return Some(f(m.Value()))
 }
 
-// MaybeEqual returns true if both m1 and m2 are nothing or have the same value according to the equality function
-func MaybeEqual[T any](m1 Maybe[T], m2 Maybe[T], equality func(T, T) bool) bool {
+// Equal returns true if both m1 and m2 are nothing or have the same value according to [equalFunc].
+func Equal[T any](m1 Maybe[T], m2 Maybe[T], equalFunc func(T, T) bool) bool {
 	if m1.IsNothing() {
 		return m2.IsNothing()
 	}
 
 	if m2.IsNothing() {
 		return false
 	}
-	return equality(m1.Value(), m2.Value())
+	return equalFunc(m1.Value(), m2.Value())
 }

x/merkledb/maybe_test.go → utils/maybe/maybe_test.go

@@ -1,7 +1,7 @@
 // Copyright (C) 2019-2023, Ava Labs, Inc. All rights reserved.
 // See the file LICENSE for licensing terms.
 
-package merkledb
+package maybe
 
 import (
 	"testing"
@@ -18,7 +18,7 @@ func TestMaybeClone(t *testing.T) {
 		val := []byte{1, 2, 3}
 		originalVal := slices.Clone(val)
 		m := Some(val)
-		mClone := MaybeBind(m, slices.Clone[[]byte])
+		mClone := Bind(m, slices.Clone[[]byte])
 		m.value[0] = 0
 		require.NotEqual(mClone.value, m.value)
 		require.Equal(originalVal, mClone.value)
@@ -27,23 +27,23 @@ func TestMaybeClone(t *testing.T) {
 	// Case: Value is nothing
 	{
 		m := Nothing[[]byte]()
-		mClone := MaybeBind(m, slices.Clone[[]byte])
+		mClone := Bind(m, slices.Clone[[]byte])
 		require.True(mClone.IsNothing())
 	}
 }
 
 func TestMaybeEquality(t *testing.T) {
 	require := require.New(t)
-	require.True(MaybeEqual(Nothing[int](), Nothing[int](), func(i int, i2 int) bool {
+	require.True(Equal(Nothing[int](), Nothing[int](), func(i int, i2 int) bool {
 		return i == i2
 	}))
-	require.False(MaybeEqual(Nothing[int](), Some(1), func(i int, i2 int) bool {
+	require.False(Equal(Nothing[int](), Some(1), func(i int, i2 int) bool {
 		return i == i2
 	}))
-	require.False(MaybeEqual(Some(1), Nothing[int](), func(i int, i2 int) bool {
+	require.False(Equal(Some(1), Nothing[int](), func(i int, i2 int) bool {
 		return i == i2
 	}))
-	require.True(MaybeEqual(Some(1), Some(1), func(i int, i2 int) bool {
+	require.True(Equal(Some(1), Some(1), func(i int, i2 int) bool {
 		return i == i2
 	}))
 }

x/merkledb/codec.go

@@ -13,6 +13,7 @@ import (
 	"sync"
 
 	"github.com/ava-labs/avalanchego/ids"
+	"github.com/ava-labs/avalanchego/utils/maybe"
 )
 
 const (
@@ -274,7 +275,7 @@ func (c *codecImpl) encodeInt64(dst io.Writer, value int64) error {
 	return err
 }
 
-func (c *codecImpl) encodeMaybeByteSlice(dst io.Writer, maybeValue Maybe[[]byte]) error {
+func (c *codecImpl) encodeMaybeByteSlice(dst io.Writer, maybeValue maybe.Maybe[[]byte]) error {
 	if err := c.encodeBool(dst, !maybeValue.IsNothing()); err != nil {
 		return err
 	}
@@ -284,21 +285,21 @@ func (c *codecImpl) encodeMaybeByteSlice(dst io.Writer, maybeValue Maybe[[]byte]
 	return c.encodeByteSlice(dst, maybeValue.Value())
 }
 
-func (c *codecImpl) decodeMaybeByteSlice(src *bytes.Reader) (Maybe[[]byte], error) {
+func (c *codecImpl) decodeMaybeByteSlice(src *bytes.Reader) (maybe.Maybe[[]byte], error) {
 	if minMaybeByteSliceLen > src.Len() {
-		return Nothing[[]byte](), io.ErrUnexpectedEOF
+		return maybe.Nothing[[]byte](), io.ErrUnexpectedEOF
 	}
 
 	if hasValue, err := c.decodeBool(src); err != nil || !hasValue {
-		return Nothing[[]byte](), err
+		return maybe.Nothing[[]byte](), err
 	}
 
 	bytes, err := c.decodeByteSlice(src)
 	if err != nil {
-		return Nothing[[]byte](), err
+		return maybe.Nothing[[]byte](), err
 	}
 
-	return Some(bytes), nil
+	return maybe.Some(bytes), nil
 }
 
 func (c *codecImpl) decodeByteSlice(src *bytes.Reader) ([]byte, error) {

x/merkledb/codec_test.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/ava-labs/avalanchego/ids"
 	"github.com/ava-labs/avalanchego/utils/hashing"
+	"github.com/ava-labs/avalanchego/utils/maybe"
 )
 
 // TODO add more codec tests
@@ -36,7 +37,7 @@ func newRandomProofNode(r *rand.Rand) ProofNode {
 	}
 
 	hasValue := rand.Intn(2) == 1 // #nosec G404
-	var valueOrHash Maybe[[]byte]
+	var valueOrHash maybe.Maybe[[]byte]
 	if hasValue {
 		// use the hash instead when length is greater than the hash length
 		if len(val) >= HashLength {
@@ -50,7 +51,7 @@ func newRandomProofNode(r *rand.Rand) ProofNode {
 			// variable on the struct
 			val = nil
 		}
-		valueOrHash = Some(val)
+		valueOrHash = maybe.Some(val)
 	}
 
 	return ProofNode{
@@ -229,7 +230,7 @@ func FuzzCodecDBNodeDeterministic(f *testing.F) {
 
 			r := rand.New(rand.NewSource(int64(randSeed))) // #nosec G404
 
-			value := Nothing[[]byte]()
+			value := maybe.Nothing[[]byte]()
 			if hasValue {
 				if len(valueBytes) == 0 {
 					// We do this because when we encode a value of []byte{}
@@ -240,7 +241,7 @@ func FuzzCodecDBNodeDeterministic(f *testing.F) {
 					// private variable on the struct
 					valueBytes = nil
 				}
-				value = Some(valueBytes)
+				value = maybe.Some(valueBytes)
 			}
 
 			numChildren := r.Intn(NodeBranchFactor) // #nosec G404
@@ -294,7 +295,7 @@ func TestCodec_DecodeDBNode(t *testing.T) {
 	require.ErrorIs(err, io.ErrUnexpectedEOF)
 
 	proof := dbNode{
-		value:    Some([]byte{1}),
+		value:    maybe.Some([]byte{1}),
 		children: map[byte]child{},
 	}
 

x/merkledb/db.go

@@ -25,6 +25,7 @@ import (
 	"github.com/ava-labs/avalanchego/trace"
 	"github.com/ava-labs/avalanchego/utils"
 	"github.com/ava-labs/avalanchego/utils/math"
+	"github.com/ava-labs/avalanchego/utils/maybe"
 	"github.com/ava-labs/avalanchego/utils/set"
 )
 
@@ -61,7 +62,7 @@ type ChangeProofer interface {
 		startRootID ids.ID,
 		endRootID ids.ID,
 		start []byte,
-		end Maybe[[]byte],
+		end maybe.Maybe[[]byte],
 		maxLength int,
 	) (*ChangeProof, error)
 
@@ -83,7 +84,7 @@ type ChangeProofer interface {
 		ctx context.Context,
 		proof *ChangeProof,
 		start []byte,
-		end Maybe[[]byte],
+		end maybe.Maybe[[]byte],
 		expectedEndRootID ids.ID,
 	) error
 
@@ -98,7 +99,7 @@ type RangeProofer interface {
 		ctx context.Context,
 		rootID ids.ID,
 		start []byte,
-		end Maybe[[]byte],
+		end maybe.Maybe[[]byte],
 		maxLength int,
 	) (*RangeProof, error)
 
@@ -201,7 +202,7 @@ func newDatabase(
 	// add current root to history (has no changes)
 	trieDB.history.record(&changeSummary{
 		rootID: root,
-		values: map[path]*change[Maybe[[]byte]]{},
+		values: map[path]*change[maybe.Maybe[[]byte]]{},
 		nodes:  map[path]*change[*node]{},
 	})
 
@@ -267,7 +268,7 @@ func (db *merkleDB) rebuild(ctx context.Context) error {
 		}
 		if n.hasValue() {
 			serializedPath := path.Serialize()
-			if err := currentView.Insert(ctx, serializedPath.Value, n.value.value); err != nil {
+			if err := currentView.Insert(ctx, serializedPath.Value, n.value.Value()); err != nil {
 				return err
 			}
 			currentViewSize++
@@ -433,7 +434,7 @@ func (db *merkleDB) getValue(key path, lock bool) ([]byte, error) {
 	if n.value.IsNothing() {
 		return nil, database.ErrNotFound
 	}
-	return n.value.value, nil
+	return n.value.Value(), nil
 }
 
 func (db *merkleDB) GetMerkleRoot(ctx context.Context) (ids.ID, error) {
@@ -481,7 +482,7 @@ func (db *merkleDB) getProof(ctx context.Context, key []byte) (*Proof, error) {
 func (db *merkleDB) GetRangeProof(
 	ctx context.Context,
 	start []byte,
-	end Maybe[[]byte],
+	end maybe.Maybe[[]byte],
 	maxLength int,
 ) (*RangeProof, error) {
 	db.commitLock.RLock()
@@ -496,7 +497,7 @@ func (db *merkleDB) GetRangeProofAtRoot(
 	ctx context.Context,
 	rootID ids.ID,
 	start []byte,
-	end Maybe[[]byte],
+	end maybe.Maybe[[]byte],
 	maxLength int,
 ) (*RangeProof, error) {
 	db.commitLock.RLock()
@@ -510,7 +511,7 @@ func (db *merkleDB) getRangeProofAtRoot(
 	ctx context.Context,
 	rootID ids.ID,
 	start []byte,
-	end Maybe[[]byte],
+	end maybe.Maybe[[]byte],
 	maxLength int,
 ) (*RangeProof, error) {
 	if db.closed {
@@ -532,7 +533,7 @@ func (db *merkleDB) GetChangeProof(
 	startRootID ids.ID,
 	endRootID ids.ID,
 	start []byte,
-	end Maybe[[]byte],
+	end maybe.Maybe[[]byte],
 	maxLength int,
 ) (*ChangeProof, error) {
 	if end.HasValue() && bytes.Compare(start, end.Value()) == 1 {
@@ -578,13 +579,13 @@ func (db *merkleDB) GetChangeProof(
 		result.KeyChanges = append(result.KeyChanges, KeyChange{
 			Key: serializedKey,
 			// create a copy so edits of the []byte don't affect the db
-			Value: MaybeBind(change.after, slices.Clone[[]byte]),
+			Value: maybe.Bind(change.after, slices.Clone[[]byte]),
 		})
 	}
 
 	largestKey := end
 	if len(result.KeyChanges) > 0 {
-		largestKey = Some(result.KeyChanges[len(result.KeyChanges)-1].Key)
+		largestKey = maybe.Some(result.KeyChanges[len(result.KeyChanges)-1].Key)
 	}
 
 	// Since we hold [db.commitlock] we must still have sufficient
@@ -958,7 +959,7 @@ func (db *merkleDB) VerifyChangeProof(
 	ctx context.Context,
 	proof *ChangeProof,
 	start []byte,
-	end Maybe[[]byte],
+	end maybe.Maybe[[]byte],
 	expectedEndRootID ids.ID,
 ) error {
 	if end.HasValue() && bytes.Compare(start, end.Value()) > 0 {
@@ -1004,20 +1005,20 @@ func (db *merkleDB) VerifyChangeProof(
 	// Find the greatest key in [proof.KeyChanges]
 	// Note that [proof.EndProof] is a proof for this key.
 	// [largestPath] is also used when we add children of proof nodes to [trie] below.
-	largestPath := MaybeBind(end, newPath)
+	largestPath := maybe.Bind(end, newPath)
 	if len(proof.KeyChanges) > 0 {
 		// If [proof] has key-value pairs, we should insert children
 		// greater than [end] to ancestors of the node containing [end]
 		// so that we get the expected root ID.
-		largestPath = Some(newPath(proof.KeyChanges[len(proof.KeyChanges)-1].Key))
+		largestPath = maybe.Some(newPath(proof.KeyChanges[len(proof.KeyChanges)-1].Key))
 	}
 
 	// Make sure the end proof, if given, is well-formed.
 	if err := verifyProofPath(proof.EndProof, largestPath.Value()); err != nil {
 		return err
 	}
 
-	keyValues := make(map[path]Maybe[[]byte], len(proof.KeyChanges))
+	keyValues := make(map[path]maybe.Maybe[[]byte], len(proof.KeyChanges))
 	for _, keyValue := range proof.KeyChanges {
 		keyValues[newPath(keyValue.Key)] = keyValue.Value
 	}
@@ -1069,9 +1070,9 @@ func (db *merkleDB) VerifyChangeProof(
 	// keys are less than [insertChildrenLessThan] or whose keys are greater
 	// than [insertChildrenGreaterThan] into the trie so that we get the
 	// expected root ID (if this proof is valid).
-	insertChildrenLessThan := Nothing[path]()
+	insertChildrenLessThan := maybe.Nothing[path]()
 	if len(smallestPath) > 0 {
-		insertChildrenLessThan = Some(smallestPath)
+		insertChildrenLessThan = maybe.Some(smallestPath)
 	}
 	if err := addPathInfo(
 		view,
@@ -1165,7 +1166,7 @@ func (db *merkleDB) initializeRootIfNeeded() (ids.ID, error) {
 func (db *merkleDB) getHistoricalViewForRange(
 	rootID ids.ID,
 	start []byte,
-	end Maybe[[]byte],
+	end maybe.Maybe[[]byte],
 ) (*trieView, error) {
 	currentRootID := db.getMerkleRoot()
 
@@ -1299,7 +1300,7 @@ func (db *merkleDB) prepareChangeProofView(proof *ChangeProof) (*trieView, error
 			if err := view.remove(kv.Key); err != nil {
 				return nil, err
 			}
-		} else if err := view.insert(kv.Key, kv.Value.value); err != nil {
+		} else if err := view.insert(kv.Key, kv.Value.Value()); err != nil {
 			return nil, err
 		}
 	}