F refactor iterators

platform/common/core/generic/vault/vault.go

@@ -349,18 +349,16 @@ func (db *Vault[V]) Statuses(ctx context.Context, txIDs ...driver.TxID) ([]drive
 	if err != nil {
 		return nil, err
 	}
-	statuses := make([]driver.TxValidationStatus[V], 0, len(txIDs))
-	for status, err := it.Next(); status != nil; status, err = it.Next() {
-		if err != nil {
-			return nil, err
+	return collections.ReadAll(collections.Map(it, func(status *driver.TxStatus) (*driver.TxValidationStatus[V], error) {
+		if status == nil {
+			return nil, nil
 		}
-		statuses = append(statuses, driver.TxValidationStatus[V]{
+		return &driver.TxValidationStatus[V]{
 			TxID:           status.TxID,
 			ValidationCode: db.vcProvider.FromInt32(status.Code),
 			Message:        status.Message,
-		})
-	}
-	return statuses, nil
+		}, nil
+	}))
 }
 
 func (db *Vault[V]) SetStatus(ctx context.Context, txID driver.TxID, code V) error {

platform/common/utils/cache/map.go

@@ -9,10 +9,11 @@ package cache
 // NewMapCache creates a dummy implementation of the Cache interface.
 // It is backed by a map with unlimited capacity.
 func NewMapCache[K comparable, V any]() *mapCache[K, V] {
-	return &mapCache[K, V]{
-		m: map[K]V{},
-		l: &noLock{},
-	}
+	return NewMapCacheWithLock[K, V](&noLock{})
+}
+
+func NewMapCacheWithLock[K comparable, V any](l rwLock) *mapCache[K, V] {
+	return &mapCache[K, V]{m: map[K]V{}, l: l}
 }
 
 type mapCache[K comparable, V any] struct {

platform/common/utils/collections/iterators.go

@@ -10,6 +10,7 @@ import (
 	"math/rand"
 
 	"github.com/hyperledger-labs/fabric-smart-client/platform/common/utils"
+	"github.com/hyperledger-labs/fabric-smart-client/platform/common/utils/functions"
 )
 
 type baseIterator[k any] interface {
@@ -68,6 +69,18 @@ func ReadAll[T any](it Iterator[*T]) ([]T, error) {
 	return items, nil
 }
 
+func ToSlice[T any](it Iterator[*T]) ([]*T, error) {
+	defer it.Close()
+	items := make([]*T, 0)
+	for item, err := it.Next(); item != nil || err != nil; item, err = it.Next() {
+		if err != nil {
+			return nil, err
+		}
+		items = append(items, item)
+	}
+	return items, nil
+}
+
 func NewSingleIterator[T any](item T) *sliceIterator[T] {
 	return NewSliceIterator[T]([]T{item})
 }
@@ -123,13 +136,34 @@ func (it *permutationIterator[T]) Close() {
 	it.perm = nil
 }
 
-func Map[A any, B any](iterator Iterator[A], transformer func(A) (B, error)) Iterator[B] {
+func Filter[A any](iterator Iterator[A], filter functions.Filter[A]) Iterator[A] {
+	return &filteredIterator[A]{Iterator: iterator, filter: filter}
+}
+
+type filteredIterator[A any] struct {
+	Iterator[A]
+	filter func(A) bool
+}
+
+func (it *filteredIterator[A]) Next() (A, error) {
+	if next, err := it.Iterator.Next(); err != nil {
+		return next, err
+	} else if utils.IsNil(next) {
+		return utils.Zero[A](), nil
+	} else if !it.filter(next) {
+		return it.Next()
+	} else {
+		return next, nil
+	}
+}
+
+func Map[A any, B any](iterator Iterator[A], transformer functions.Mapper[A, B]) Iterator[B] {
 	return &mappedIterator[A, B]{Iterator: iterator, transformer: transformer}
 }
 
 type mappedIterator[A any, B any] struct {
 	Iterator[A]
-	transformer func(A) (B, error)
+	transformer functions.Mapper[A, B]
 }
 
 func (it *mappedIterator[A, B]) Next() (B, error) {

platform/common/utils/functions/functions.go

@@ -0,0 +1,15 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package functions
+
+type Mapper[A any, B any] func(A) (B, error)
+
+type Filter[T any] func(T) bool
+
+func Not[T any](f Filter[T]) Filter[T] {
+	return func(t T) bool { return !f(t) }
+}

platform/common/utils/nulls.go

@@ -6,6 +6,8 @@ SPDX-License-Identifier: Apache-2.0
 
 package utils
 
+import "reflect"
+
 func Zero[A any]() A {
 	var a A
 	return a
@@ -54,3 +56,21 @@ func DefaultString(a interface{}, b string) string {
 	}
 	return b
 }
+
+var nullableTypes = map[reflect.Kind]struct{}{
+	reflect.Ptr:       {},
+	reflect.Map:       {},
+	reflect.Chan:      {},
+	reflect.Func:      {},
+	reflect.Slice:     {},
+	reflect.Interface: {},
+}
+
+func isNullable(k reflect.Kind) bool {
+	_, ok := nullableTypes[k]
+	return ok
+}
+
+func IsNil(a any) bool {
+	return a == nil || isNullable(reflect.TypeOf(a).Kind()) && reflect.ValueOf(a).IsNil()
+}

platform/view/services/db/driver/sql/common/binding.go

@@ -10,6 +10,7 @@ import (
 	"database/sql"
 	"fmt"
 
+	"github.com/hyperledger-labs/fabric-smart-client/platform/common/utils/collections"
 	"github.com/hyperledger-labs/fabric-smart-client/platform/view/services/db/driver"
 	"github.com/hyperledger-labs/fabric-smart-client/platform/view/view"
 	"github.com/pkg/errors"
@@ -53,13 +54,10 @@ func (db *BindingPersistence) HaveSameBinding(this, that view.Identity) (bool, e
 	}
 	defer rows.Close()
 
-	longTermIds := make([]view.Identity, 0, 2)
-	for rows.Next() {
-		var longTerm view.Identity
-		if err := rows.Scan(&longTerm); err != nil {
-			return false, err
-		}
-		longTermIds = append(longTermIds, longTerm)
+	it := QueryIterator(rows, func(r RowScanner, id *view.Identity) error { return r.Scan(id) })
+	longTermIds, err := collections.ReadAll(it)
+	if err != nil {
+		return false, err
 	}
 	if len(longTermIds) != 2 {
 		return false, errors.Errorf("%d entries found instead of 2", len(longTermIds))

platform/view/services/db/driver/sql/common/helpers.go

@@ -500,13 +500,10 @@ func TTestCompositeKeys(t *testing.T, db driver.UnversionedPersistence) {
 
 	itr, err := db.GetStateRangeScanIterator(ns, startKey, endKey)
 	assert.NoError(t, err)
-	defer itr.Close()
 
-	res := make([]driver.UnversionedRead, 0, 4)
-	for n, err := itr.Next(); n != nil; n, err = itr.Next() {
-		assert.NoError(t, err)
-		res = append(res, *n)
-	}
+	res, err := collections.ReadAll(itr)
+	assert.NoError(t, err)
+
 	assert.Len(t, res, 4)
 	assert.Equal(t, []driver.UnversionedRead{
 		{Key: "\x00prefix0a0b0", Raw: []uint8{0x0, 0x70, 0x72, 0x65, 0x66, 0x69, 0x78, 0x30, 0x61, 0x30, 0x62, 0x30}},
@@ -522,13 +519,10 @@ func TTestCompositeKeys(t *testing.T, db driver.UnversionedPersistence) {
 
 	itr, err = db.GetStateRangeScanIterator(ns, startKey, endKey)
 	assert.NoError(t, err)
-	defer itr.Close()
 
-	res = make([]driver.UnversionedRead, 0, 2)
-	for n, err := itr.Next(); n != nil; n, err = itr.Next() {
-		assert.NoError(t, err)
-		res = append(res, *n)
-	}
+	res, err = collections.ReadAll(itr)
+	assert.NoError(t, err)
+
 	assert.Len(t, res, 3)
 	assert.Equal(t, []driver.UnversionedRead{
 		{Key: "\x00prefix0a0b0", Raw: []uint8{0x0, 0x70, 0x72, 0x65, 0x66, 0x69, 0x78, 0x30, 0x61, 0x30, 0x62, 0x30}},
@@ -623,13 +617,10 @@ func TTestUnversionedRange(t *testing.T, db driver.UnversionedPersistence) {
 
 	itr, err := db.GetStateRangeScanIterator(ns, "", "")
 	assert.NoError(t, err)
-	defer itr.Close()
 
-	res := make([]driver.UnversionedRead, 0, 4)
-	for n, err := itr.Next(); n != nil; n, err = itr.Next() {
-		assert.NoError(t, err)
-		res = append(res, *n)
-	}
+	res, err := collections.ReadAll(itr)
+	assert.NoError(t, err)
+
 	assert.Len(t, res, 4)
 	assert.Equal(t, []driver.UnversionedRead{
 		{Key: "k1", Raw: []byte("k1_value")},
@@ -640,13 +631,10 @@ func TTestUnversionedRange(t *testing.T, db driver.UnversionedPersistence) {
 
 	itr, err = db.GetStateRangeScanIterator(ns, "k1", "k3")
 	assert.NoError(t, err)
-	defer itr.Close()
 
-	res = make([]driver.UnversionedRead, 0, 3)
-	for n, err := itr.Next(); n != nil; n, err = itr.Next() {
-		assert.NoError(t, err)
-		res = append(res, *n)
-	}
+	res, err = collections.ReadAll(itr)
+	assert.NoError(t, err)
+
 	assert.Len(t, res, 3)
 	assert.Equal(t, []driver.UnversionedRead{
 		{Key: "k1", Raw: []byte("k1_value")},
@@ -656,12 +644,10 @@ func TTestUnversionedRange(t *testing.T, db driver.UnversionedPersistence) {
 
 	itr, err = db.GetStateSetIterator(ns, "k1", "k2")
 	assert.NoError(t, err)
-	defer itr.Close()
-	res = make([]driver.UnversionedRead, 0, 2)
-	for n, err := itr.Next(); n != nil; n, err = itr.Next() {
-		assert.NoError(t, err)
-		res = append(res, *n)
-	}
+
+	res, err = collections.ReadAll(itr)
+	assert.NoError(t, err)
+
 	assert.Len(t, res, 2)
 	expected := []driver.UnversionedRead{
 		{Key: "k1", Raw: []byte("k1_value")},

platform/view/services/db/driver/sql/common/signerinfo.go

@@ -10,6 +10,7 @@ import (
 	"database/sql"
 	"fmt"
 
+	"github.com/hyperledger-labs/fabric-smart-client/platform/common/utils/collections"
 	"github.com/hyperledger-labs/fabric-smart-client/platform/view/services/db/driver"
 	"github.com/hyperledger-labs/fabric-smart-client/platform/view/view"
 	"github.com/pkg/errors"
@@ -35,11 +36,11 @@ type SignerInfoPersistence struct {
 
 func (db *SignerInfoPersistence) FilterExistingSigners(ids ...view.Identity) ([]view.Identity, error) {
 	idHashes := make([]string, len(ids))
-	inverseMap := make(map[string]view.Identity, len(ids))
+	inverseMap := make(map[string]*view.Identity, len(ids))
 	for i, id := range ids {
 		idHash := id.UniqueID()
 		idHashes[i] = idHash
-		inverseMap[idHash] = id
+		inverseMap[idHash] = &id
 	}
 	where, params := Where(db.ci.InStrings("id", idHashes))
 	query := fmt.Sprintf("SELECT id FROM %s %s", db.table, where)
@@ -51,13 +52,16 @@ func (db *SignerInfoPersistence) FilterExistingSigners(ids ...view.Identity) ([]
 	}
 	defer rows.Close()
 
-	existingSigners := make([]view.Identity, 0)
-	for rows.Next() {
-		var idHash string
-		if err := rows.Scan(&idHash); err != nil {
-			return nil, errors.Wrapf(err, "failed scanning row")
+	idHashItr := QueryIterator(rows, func(r RowScanner, h *string) error { return r.Scan(h) })
+	idItr := collections.Map(idHashItr, func(h *string) (*view.Identity, error) {
+		if h == nil {
+			return nil, nil
 		}
-		existingSigners = append(existingSigners, inverseMap[idHash])
+		return inverseMap[*h], nil
+	})
+	existingSigners, err := collections.ReadAll[view.Identity](idItr)
+	if err != nil {
+		return nil, err
 	}
 	logger.Debugf("Found %d out of %d signers", len(existingSigners), len(ids))
 	return existingSigners, nil

platform/view/services/db/driver/sql/common/unversioned.go

@@ -60,7 +60,7 @@ func (db *UnversionedPersistence) GetStateRangeScanIterator(ns driver2.Namespace
 		return nil, errors2.Wrapf(err, "query error: %s", query)
 	}
 
-	return &readIterator{txs: rows}, nil
+	return QueryIterator(rows, func(r RowScanner, read *driver.UnversionedRead) error { return r.Scan(&read.Key, &read.Raw) }), nil
 }
 
 func (db *UnversionedPersistence) GetState(namespace driver2.Namespace, key driver2.PKey) (driver.UnversionedValue, error) {
@@ -87,7 +87,7 @@ func (db *UnversionedPersistence) GetStateSetIterator(ns driver2.Namespace, keys
 		return nil, errors2.Wrapf(err, "query error: %s", query)
 	}
 
-	return &readIterator{txs: rows}, nil
+	return QueryIterator(rows, func(r RowScanner, read *driver.UnversionedRead) error { return r.Scan(&read.Key, &read.Raw) }), nil
 }
 
 func (db *UnversionedPersistence) Close() error {
@@ -231,23 +231,6 @@ func (db *UnversionedPersistence) Stats() any {
 	return nil
 }
 
-type readIterator struct {
-	txs *sql.Rows
-}
-
-func (t *readIterator) Close() {
-	t.txs.Close()
-}
-
-func (t *readIterator) Next() (*driver.UnversionedRead, error) {
-	if !t.txs.Next() {
-		return nil, nil
-	}
-	var r driver.UnversionedRead
-	err := t.txs.Scan(&r.Key, &r.Raw)
-	return &r, err
-}
-
 func (db *UnversionedPersistence) CreateSchema() error {
 	return InitSchema(db.writeDB, fmt.Sprintf(`
 	CREATE TABLE IF NOT EXISTS %s (