nit: resolve PR comment

Signed-off-by: Ivan Kavaldzhiev <[email protected]>

platform-sdk/platform-apps/tests/StatsSigningTestingTool/src/main/java/com/swirlds/demo/stats/signing/StatsSigningTestingToolMain.java

@@ -36,6 +36,7 @@
 
 import com.hedera.hapi.platform.event.StateSignatureTransaction;
 import com.hedera.pbj.runtime.io.buffer.Bytes;
+import com.hedera.pbj.runtime.io.stream.WritableStreamingData;
 import com.swirlds.common.constructable.ClassConstructorPair;
 import com.swirlds.common.constructable.ConstructableRegistry;
 import com.swirlds.common.constructable.ConstructableRegistryException;
@@ -54,7 +55,8 @@
 import com.swirlds.platform.system.Platform;
 import com.swirlds.platform.system.SwirldMain;
 import edu.umd.cs.findbugs.annotations.NonNull;
-import java.nio.ByteBuffer;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
@@ -66,7 +68,6 @@
 public class StatsSigningTestingToolMain implements SwirldMain {
     // the first four come from the parameters in the config.txt file
 
-    public static final String STATE_SIGNATURE_MARKER = "STATE_SIGNATURE_MARKER";
     private static final Logger logger = LogManager.getLogger(StatsSigningTestingToolMain.class);
 
     static {
@@ -322,17 +323,19 @@ public BasicSoftwareVersion getSoftwareVersion() {
     @Override
     @NonNull
     public Bytes encodeSystemTransaction(@NonNull final StateSignatureTransaction transaction) {
-        final String stateSignatureMarker = STATE_SIGNATURE_MARKER;
-        final int markerSize = stateSignatureMarker.length();
-        final byte[] parsedStateSignatureTransaction =
-                StateSignatureTransaction.PROTOBUF.toBytes(transaction).toByteArray();
-        final int bufferCapacity = Integer.BYTES + markerSize + parsedStateSignatureTransaction.length;
-
-        final ByteBuffer buffer = ByteBuffer.allocate(bufferCapacity);
-        buffer.putInt(markerSize);
-        buffer.put(stateSignatureMarker.getBytes());
-        buffer.put(parsedStateSignatureTransaction);
-
-        return Bytes.wrap(buffer.array());
+        final var bytes = new ByteArrayOutputStream();
+        final var out = new WritableStreamingData(bytes);
+
+        // Add a 1 byte as a marker to indicate the start of a system transaction. This is used
+        // to later differentiate between application transactions and system transactions.
+        final byte marker = 1;
+        out.writeByte(marker);
+        try {
+            StateSignatureTransaction.PROTOBUF.write(transaction, out);
+            return Bytes.wrap(bytes.toByteArray());
+        } catch (final IOException e) {
+            logger.error("Failed to write StateSignatureTransaction to output stream", e);
+            return Bytes.EMPTY;
+        }
     }
 }

platform-sdk/platform-apps/tests/StatsSigningTestingTool/src/main/java/com/swirlds/demo/stats/signing/StatsSigningTestingToolState.java

@@ -48,7 +48,6 @@
 import com.swirlds.platform.system.transaction.ConsensusTransaction;
 import com.swirlds.platform.system.transaction.Transaction;
 import edu.umd.cs.findbugs.annotations.NonNull;
-import java.nio.ByteBuffer;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
@@ -225,13 +224,7 @@ private boolean areTransactionBytesSystemOnes(@NonNull final Transaction transac
             return false;
         }
 
-        final ByteBuffer wrapper = ByteBuffer.wrap(transactionBytes.toByteArray());
-        final var markerSize = wrapper.getInt();
-
-        final var marker = new byte[markerSize];
-        wrapper.get(marker);
-
-        return StatsSigningTestingToolMain.STATE_SIGNATURE_MARKER.equals(new String(marker));
+        return transactionBytes.getByte(0) == (byte) 1;
     }
 
     private void consumeSystemTransaction(
@@ -241,33 +234,17 @@ private void consumeSystemTransaction(
                     final Consumer<ScopedSystemTransaction<StateSignatureTransaction>>
                             stateSignatureTransactionCallback) {
         try {
-            final var stateSignatureTransaction = StateSignatureTransaction.PROTOBUF.parse(
-                    stripSystemTransactionBytes(transaction.getApplicationTransaction()));
+            final Bytes transactionBytes = transaction.getApplicationTransaction();
+            final Bytes strippedSystemTransactionBytes = transactionBytes.slice(1, transactionBytes.length() - 1);
+            final StateSignatureTransaction stateSignatureTransaction =
+                    StateSignatureTransaction.PROTOBUF.parse(strippedSystemTransactionBytes);
             stateSignatureTransactionCallback.accept(new ScopedSystemTransaction<>(
                     event.getCreatorId(), event.getSoftwareVersion(), stateSignatureTransaction));
         } catch (final ParseException e) {
             logger.error("Failed to parse StateSignatureTransaction", e);
         }
     }
 
-    private Bytes stripSystemTransactionBytes(final Bytes transactionBytes) {
-        final byte[] transactionBytesArray = transactionBytes.toByteArray();
-        final ByteBuffer wrapper = ByteBuffer.wrap(transactionBytesArray);
-        final int transactionSize = transactionBytesArray.length;
-
-        // Get the size of the marker string
-        final int markerSize = wrapper.getInt();
-
-        // Get the marker itself
-        final var marker = new byte[markerSize];
-        wrapper.get(marker);
-
-        // Get the StateSignatureTransaction we are interested in
-        final var stateSignatureTransaction = new byte[transactionSize - (markerSize + Integer.BYTES)];
-        wrapper.get(stateSignatureTransaction);
-        return Bytes.wrap(stateSignatureTransaction);
-    }
-
     private void maybeDelay() {
         if (SYNTHETIC_HANDLE_TIME) {
             final long start = System.nanoTime();

platform-sdk/platform-apps/tests/StatsSigningTestingTool/src/main/java/com/swirlds/demo/stats/signing/SttTransactionPool.java

@@ -165,7 +165,7 @@ private void init() {
                     final byte[] sig = exSig.getSignature();
 
                     transactions[i] = TransactionCodec.encode(alg, transactionId, sig, data);
-                } catch (SignatureException e) {
+                } catch (final SignatureException e) {
                     // If we are unable to sign the transaction then log the failure and create an unsigned transaction
                     logger.error(
                             EXCEPTION.getMarker(),
@@ -202,7 +202,7 @@ private void tryAcquirePrimitives() {
                 if (algorithm.isAvailable()) {
                     activeAlgorithms.put(algorithm.getId(), algorithm);
                 }
-            } catch (Exception ex) {
+            } catch (final Exception ex) {
                 logger.error(
                         EXCEPTION.getMarker(),
                         "Failed to Activate Signing Algorithm [ id = {}, class = {} ]",
@@ -212,8 +212,4 @@ private void tryAcquirePrimitives() {
             }
         }
     }
-
-    public int getTransactionSize() {
-        return transactionSize;
-    }
 }

platform-sdk/platform-apps/tests/StatsSigningTestingTool/src/main/java/com/swirlds/demo/stats/signing/TransactionCodec.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2022-2024 Hedera Hashgraph, LLC
+ * Copyright (C) 2022-2025 Hedera Hashgraph, LLC
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,11 +30,11 @@
  * The core transaction encoder and decoder implementation. See below for the binary transaction format specification.
  * <p>
  * Transaction Structure:
- * ------------------------------------------------------------------------------------------------------------
- * | 8 bytes | 1 byte | 1 byte   | 4 bytes   | pklen bytes | 4 bytes | siglen bytes | 4 bytes | datalen bytes |
- * |---------|--------|----------|-----------|-------------|---------|--------------|---------|---------------|
- * | id      | signed | sigAlgId | pklen     | pk          |  siglen | sig          | datalen | data          |
- * ------------------------------------------------------------------------------------------------------------
+ * ---------------------------------------------------------------------------------------------------------------------
+ * | 1 byte | 8 bytes | 1 byte | 1 byte   | 4 bytes   | pklen bytes | 4 bytes | siglen bytes | 4 bytes | datalen bytes |
+ * |--------|---------|--------|----------|-----------|-------------|---------|--------------|---------|---------------|
+ * | marker | id      | signed | sigAlgId | pklen     | pk          |  siglen | sig          | datalen | data          |
+ * ---------------------------------------------------------------------------------------------------------------------
  */
 final class TransactionCodec {
 
@@ -78,11 +78,14 @@ public static int overheadSize(final SigningAlgorithm algorithm) {
 
     public static byte[] encode(
             final SigningAlgorithm algorithm, final long transactionId, final byte[] signature, final byte[] data) {
-        final ByteBuffer buffer = ByteBuffer.allocate(bufferSize(algorithm, (data != null) ? data.length : 0));
+        final ByteBuffer buffer = ByteBuffer.allocate(1 + bufferSize(algorithm, (data != null) ? data.length : 0));
         final boolean signed =
                 algorithm != null && algorithm.isAvailable() && signature != null && signature.length > 0;
-
-        buffer.putLong(transactionId)
+        // Add a 0 byte as a marker to indicate the start of an application transaction. This is used
+        // to later differentiate between application transactions and system transactions.
+        final byte marker = 0;
+        buffer.put(marker)
+                .putLong(transactionId)
                 .put((signed) ? (byte) 1 : 0)
                 .put((signed) ? algorithm.getId() : NO_ALGORITHM_PRESENT)
                 .putInt((signed) ? algorithm.getPublicKeyLength() : 0);

platform-sdk/platform-apps/tests/StatsSigningTestingTool/src/test/java/com/swirlds/demo/stats/signing/StatsSigningTestingToolStateTest.java

@@ -112,7 +112,6 @@ void setUp() {
                 .build();
 
         when(transactionPoolSupplier.get()).thenReturn(transactionPool);
-        when(transactionPool.getTransactionSize()).thenReturn(transactionSize);
     }
 
     @ParameterizedTest