Implement caching

Added caching util function with tests and applied in:

- parser.Block.Transactions(),
- parser.Payload.ChannelHeader(),
- parser.Payload.SignatureHeader(),
- parser.NamespaceReadWriteSet.ReadWriteSet(),
- parser.EndorserTransaction.ReadWriteSets(),

methods, as it was in the typescript sample.

Corrected Println usage and added comments to util functions.

Signed-off-by: Stanislav Jakuschevskij <stas@two-giants.com>

off_chain_data/application-go/app.go

@@ -33,7 +33,7 @@ func main() {
 			printUsage()
 			panic(fmt.Errorf("unknown command: %s", name))
 		}
-		fmt.Printf("command: %s\n", name)
+		fmt.Println("command:", name)
 	}
 
 	client := newGrpcConnection()
@@ -47,7 +47,7 @@ func main() {
 
 func printUsage() {
 	fmt.Println("Arguments: <command1> [<command2> ...]")
-	fmt.Printf("Available commands: %v\n", availableCommands())
+	fmt.Println("Available commands:", availableCommands())
 }
 
 func availableCommands() string {

off_chain_data/application-go/getAllAssets.go

@@ -28,7 +28,7 @@ func getAllAssets(clientConnection *grpc.ClientConn) {
 	smartContract := atb.NewAssetTransferBasic(contract)
 	assets := smartContract.GetAllAssets()
 
-	fmt.Printf("%s\n", formatJSON(assets))
+	fmt.Println(formatJSON(assets))
 }
 
 func formatJSON(data []byte) string {

off_chain_data/application-go/listen.go

@@ -108,8 +108,8 @@ func listen(clientConnection *grpc.ClientConn) {
 	}
 	defer checkpointer.Close()
 
-	fmt.Printf("Start event listening from block %d\n", checkpointer.BlockNumber())
+	fmt.Println("Start event listening from block", checkpointer.BlockNumber())
-	fmt.Printf("Last processed transaction ID within block: %s\n", checkpointer.TransactionID())
+	fmt.Println("Last processed transaction ID within block:", checkpointer.TransactionID())
 	if simulatedFailureCount > 0 {
 		fmt.Printf("Simulating a write failure every %d transactions\n", simulatedFailureCount)
 	}

off_chain_data/application-go/parser/blockParser.go

@@ -22,23 +22,38 @@ func (b *Block) Number() uint64 {
 	return header.GetNumber()
 }
 
-// TODO: needs cache
 func (b *Block) Transactions() []*Transaction {
-	envelopes := b.unmarshalEnvelopesFromBlockData()
+	return utils.Cache(func() []*Transaction {
+		envelopes := b.unmarshalEnvelopesFromBlockData()
 
-	commonPayloads := b.unmarshalPayloadsFrom(envelopes)
+		commonPayloads := b.unmarshalPayloadsFrom(envelopes)
 
-	payloads := b.parse(commonPayloads)
+		payloads := b.parse(commonPayloads)
 
-	result := b.createTransactionsFrom(payloads)
+		return b.createTransactionsFrom(payloads)
+	})()
+}
 
+func (b *Block) unmarshalEnvelopesFromBlockData() []*common.Envelope {
+	result := []*common.Envelope{}
+	for _, blockData := range b.block.GetData().GetData() {
+		envelope := &common.Envelope{}
+		if err := proto.Unmarshal(blockData, envelope); err != nil {
+			panic(err)
+		}
+		result = append(result, envelope)
+	}
 	return result
 }
 
-func (*Block) createTransactionsFrom(payloads []*PayloadImpl) []*Transaction {
+func (*Block) unmarshalPayloadsFrom(envelopes []*common.Envelope) []*common.Payload {
-	result := []*Transaction{}
+	result := []*common.Payload{}
-	for _, payload := range payloads {
+	for _, envelope := range envelopes {
-		result = append(result, NewTransaction(payload))
+		commonPayload := &common.Payload{}
+		if err := proto.Unmarshal(envelope.GetPayload(), commonPayload); err != nil {
+			panic(err)
+		}
+		result = append(result, commonPayload)
 	}
 	return result
 }
@@ -62,30 +77,6 @@ func (b *Block) parse(commonPayloads []*common.Payload) []*PayloadImpl {
 	return result
 }
 
-func (*Block) unmarshalPayloadsFrom(envelopes []*common.Envelope) []*common.Payload {
-	result := []*common.Payload{}
-	for _, envelope := range envelopes {
-		commonPayload := &common.Payload{}
-		if err := proto.Unmarshal(envelope.GetPayload(), commonPayload); err != nil {
-			panic(err)
-		}
-		result = append(result, commonPayload)
-	}
-	return result
-}
-
-func (b *Block) unmarshalEnvelopesFromBlockData() []*common.Envelope {
-	result := []*common.Envelope{}
-	for _, blockData := range b.block.GetData().GetData() {
-		envelope := &common.Envelope{}
-		if err := proto.Unmarshal(blockData, envelope); err != nil {
-			panic(err)
-		}
-		result = append(result, envelope)
-	}
-	return result
-}
-
 func (b *Block) extractTransactionValidationCodes() []byte {
 	metadata := utils.AssertDefined(
 		b.block.GetMetadata(),
@@ -98,6 +89,14 @@ func (b *Block) extractTransactionValidationCodes() []byte {
 	)
 }
 
+func (*Block) createTransactionsFrom(payloads []*PayloadImpl) []*Transaction {
+	result := []*Transaction{}
+	for _, payload := range payloads {
+		result = append(result, NewTransaction(payload))
+	}
+	return result
+}
+
 // TODO remove unused?
 func (b *Block) ToProto() *common.Block {
 	return b.block

off_chain_data/application-go/parser/blockParser_test.go

@@ -14,7 +14,7 @@ import (
 	"google.golang.org/protobuf/reflect/protoreflect"
 )
 
-func TestGetReadWriteSetsFromEndorserTransaction(t *testing.T) {
+func Test_GetReadWriteSetsFromEndorserTransaction(t *testing.T) {
 	nsReadWriteSetFake, expectedNamespace, expectedAsset := nsReadWriteSetFake()
 
 	transaction := &peer.Transaction{
@@ -73,7 +73,7 @@ func assertReadWriteSet(
 	}
 }
 
-func TestReadWriteSetWrapping(t *testing.T) {
+func Test_ReadWriteSetWrapping(t *testing.T) {
 	nsReadWriteSetFake, _, _ := nsReadWriteSetFake()
 
 	txReadWriteSetFake := &rwset.TxReadWriteSet{
@@ -86,7 +86,7 @@ func TestReadWriteSetWrapping(t *testing.T) {
 	}
 }
 
-func TestNamespaceReadWriteSetParsing(t *testing.T) {
+func Test_NamespaceReadWriteSetParsing(t *testing.T) {
 	nsReadWriteSetFake, expectedNamespace, expectedAsset := nsReadWriteSetFake()
 
 	parsedNsRwSet := parser.ParseNamespaceReadWriteSet(nsReadWriteSetFake)

off_chain_data/application-go/parser/payload.go

@@ -30,15 +30,16 @@ func ParsePayload(payload *common.Payload, statusCode int32) *PayloadImpl {
 }
 
 func (p *PayloadImpl) ChannelHeader() *common.ChannelHeader {
-	header := utils.AssertDefined(p.payload.GetHeader(), "missing payload header")
+	return utils.Cache(func() *common.ChannelHeader {
+		header := utils.AssertDefined(p.payload.GetHeader(), "missing payload header")
 
-	// TODO add cache, return cachedChannelHeader like in blockParser.ts:77
+		result := &common.ChannelHeader{}
-	result := &common.ChannelHeader{}
+		if err := proto.Unmarshal(header.GetChannelHeader(), result); err != nil {
-	if err := proto.Unmarshal(header.GetChannelHeader(), result); err != nil {
+			panic(err)
-		panic(err)
+		}
-	}
 
-	return result
+		return result
+	})()
 }
 
 func (p *PayloadImpl) EndorserTransaction() EndorserTransaction {
@@ -55,15 +56,16 @@ func (p *PayloadImpl) EndorserTransaction() EndorserTransaction {
 }
 
 func (p *PayloadImpl) SignatureHeader() *common.SignatureHeader {
-	header := utils.AssertDefined(p.payload.GetHeader(), "missing payload header")
+	return utils.Cache(func() *common.SignatureHeader {
+		header := utils.AssertDefined(p.payload.GetHeader(), "missing payload header")
 
-	// TODO add cache, return cachedSignatureHeader like in blockParser.ts:77
+		result := &common.SignatureHeader{}
-	result := &common.SignatureHeader{}
+		if err := proto.Unmarshal(header.GetSignatureHeader(), result); err != nil {
-	if err := proto.Unmarshal(header.GetSignatureHeader(), result); err != nil {
+			panic(err)
-		panic(err)
+		}
-	}
 
-	return result
+		return result
+	})()
 }
 
 func (p *PayloadImpl) TransactionValidationCode() int32 {

off_chain_data/application-go/parser/readWriteSet.go

@@ -1,6 +1,8 @@
 package parser
 
 import (
+	"offChainData/utils"
+
 	"github.com/hyperledger/fabric-protos-go-apiv2/ledger/rwset"
 	"github.com/hyperledger/fabric-protos-go-apiv2/ledger/rwset/kvrwset"
 	"google.golang.org/protobuf/proto"
@@ -53,14 +55,15 @@ func (p *NamespaceReadWriteSetImpl) Namespace() string {
 	return p.nsReadWriteSet.GetNamespace()
 }
 
-// TODO add cache
 func (p *NamespaceReadWriteSetImpl) ReadWriteSet() *kvrwset.KVRWSet {
-	result := kvrwset.KVRWSet{}
+	return utils.Cache(func() *kvrwset.KVRWSet {
-	if err := proto.Unmarshal(p.nsReadWriteSet.GetRwset(), &result); err != nil {
+		result := kvrwset.KVRWSet{}
-		panic(err)
+		if err := proto.Unmarshal(p.nsReadWriteSet.GetRwset(), &result); err != nil {
-	}
+			panic(err)
+		}
 
-	return &result
+		return &result
+	})()
 }
 
 // TODO remove unused

off_chain_data/application-go/parser/transaction.go

@@ -71,21 +71,20 @@ func ParseEndorserTransaction(transaction *peer.Transaction) *EndorserTransactio
 	return &EndorserTransactionImpl{transaction}
 }
 
-// TODO add cache
 func (p *EndorserTransactionImpl) ReadWriteSets() []ReadWriteSet {
-	chaincodeActionPayloads := p.unmarshalChaincodeActionPayloads()
+	return utils.Cache(func() []ReadWriteSet {
+		chaincodeActionPayloads := p.unmarshalChaincodeActionPayloads()
 
-	chaincodeEndorsedActions := p.extractChaincodeEndorsedActionsFrom(chaincodeActionPayloads)
+		chaincodeEndorsedActions := p.extractChaincodeEndorsedActionsFrom(chaincodeActionPayloads)
 
-	proposalResponsePayloads := p.unmarshalProposalResponsePayloadsFrom(chaincodeEndorsedActions)
+		proposalResponsePayloads := p.unmarshalProposalResponsePayloadsFrom(chaincodeEndorsedActions)
 
-	chaincodeActions := p.unmarshalChaincodeActionsFrom(proposalResponsePayloads)
+		chaincodeActions := p.unmarshalChaincodeActionsFrom(proposalResponsePayloads)
 
-	txReadWriteSets := p.unmarshalTxReadWriteSetsFrom(chaincodeActions)
+		txReadWriteSets := p.unmarshalTxReadWriteSetsFrom(chaincodeActions)
 
-	parsedReadWriteSets := p.parseReadWriteSets(txReadWriteSets)
+		return p.parseReadWriteSets(txReadWriteSets)
-
+	})()
-	return parsedReadWriteSets
 }
 
 func (p *EndorserTransactionImpl) unmarshalChaincodeActionPayloads() []*peer.ChaincodeActionPayload {

off_chain_data/application-go/transact.go

@@ -44,7 +44,7 @@ func (t *transactApp) transact() {
 	anAsset := atb.NewAsset()
 
 	t.smartContract.CreateAsset(anAsset)
-	fmt.Printf("\nCreated asset %s\n", anAsset.ID)
+	fmt.Println("Created asset", anAsset.ID)
 
 	// Transfer randomly 1 in 2 assets to a new owner.
 	if utils.RandomInt(2) == 0 {
@@ -56,6 +56,6 @@ func (t *transactApp) transact() {
 	// Delete randomly 1 in 4 created assets.
 	if utils.RandomInt(4) == 0 {
 		t.smartContract.DeleteAsset(anAsset.ID)
-		fmt.Printf("Deleted asset %s\n", anAsset.ID)
+		fmt.Println("Deleted asset", anAsset.ID)
 	}
 }

off_chain_data/application-go/utils/utils.go

@@ -6,11 +6,13 @@ import (
 	"math/big"
 )
 
+// Pick a random element from an array.
 func RandomElement(values []string) string {
 	result := values[RandomInt(len(values))]
 	return result
 }
 
+// Generate a random integer in the range 0 to max - 1.
 func RandomInt(max int) int {
 	result, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
 	if err != nil {
@@ -20,6 +22,7 @@ func RandomInt(max int) int {
 	return int(result.Int64())
 }
 
+// Pick a random element from an array, excluding the current value.
 func DifferentElement(values []string, currentValue string) string {
 	candidateValues := []string{}
 	for _, v := range values {
@@ -30,6 +33,7 @@ func DifferentElement(values []string, currentValue string) string {
 	return RandomElement(candidateValues)
 }
 
+// Return the value if it is defined; otherwise panics with an error message.
 func AssertDefined[T any](value T, message string) T {
 	if any(value) == any(nil) {
 		panic(errors.New(message))
@@ -37,3 +41,17 @@ func AssertDefined[T any](value T, message string) T {
 
 	return value
 }
+
+// Wrap a function call with a cache. On first call the wrapped function is invoked to
+// obtain a result. Subsequent calls return the cached result.
+func Cache[T any](f func() T) func() T {
+	value := any(nil)
+
+	return func() T {
+		if value == nil {
+			value = f()
+		}
+
+		return value.(T)
+	}
+}

off_chain_data/application-go/utils/utils_test.go

@@ -0,0 +1,64 @@
+package utils_test
+
+import (
+	"offChainData/utils"
+	"testing"
+)
+
+func Test_cachePrimitiveFunctionResult(t *testing.T) {
+	counter := 0
+	f := func() int {
+		counter++
+		return 5
+	}
+
+	cachedFunc := utils.Cache(f)
+	result1 := cachedFunc()
+	result2 := cachedFunc()
+
+	if counter != 1 {
+		t.Error("expected counter to be 1, but got", counter)
+	}
+
+	if result1 != 5 || result2 != 5 {
+		t.Fatal("expected results to be 5, but got", result1, result2)
+	}
+}
+
+func Test_cacheWrappedPrimitiveFunctionResult(t *testing.T) {
+	controlValue := 5
+	multiplyControlValueBy := func(n int) int { controlValue *= n; return controlValue }
+
+	cachedFunc := utils.Cache(func() int { return multiplyControlValueBy(5) })
+	result1 := cachedFunc()
+	result2 := cachedFunc()
+
+	if controlValue != 25 {
+		t.Error("expected control value to be 25, but got", controlValue)
+	}
+
+	if result1 != 25 || result2 != 25 {
+		t.Fatal("expected cached results to be 25, but got", result1, result2)
+	}
+}
+
+func Test_cacheWrappedDataStructureResult(t *testing.T) {
+	type GreetMe struct {
+		helloTo string
+	}
+
+	controlStruct := &GreetMe{helloTo: "Hello "}
+	greet := func(name string) *GreetMe { controlStruct.helloTo += name; return controlStruct }
+
+	cachedFunc := utils.Cache(func() *GreetMe { return greet("John Doe") })
+	result1 := cachedFunc().helloTo
+	result2 := cachedFunc().helloTo
+
+	if controlStruct.helloTo != "Hello John Doe" {
+		t.Error("expected control value to be 'Hello John Doe', but got", controlStruct)
+	}
+
+	if result1 != "Hello John Doe" || result2 != "Hello John Doe" {
+		t.Fatal("expected cached results to be 'Hello John Doe', but got", result1, result2)
+	}
+}

off_chain_data/application-typescript/src/utils.ts

@@ -67,7 +67,7 @@ export function assertDefined<T>(value: T | null | undefined, message: string):
  */
 export function cache<T>(f: () => T): () => T {
     let value: T | undefined;
-    return () => {
+    return (): T => {
         if (value === undefined) {
             value = f();
         }