Java full runtime: Avoid allocating iterator if UnknownFieldSet's Tre…

…eMap is empty I also considered using Collections.emptyNavigableMap(), which I thought might use a specialized allocation free empty iterator, but it allocates, and its clone() method isn't nicely exposed. PiperOrigin-RevId: 630234849
protocolbuffers · May 3, 2024 · 4f12891 · 4f12891
1 parent cc79f77
commit 4f12891
Showing 1 changed file with 26 additions and 4 deletions.
diff --git a/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java b/java/core/src/main/java/com/google/protobuf/UnknownFieldSet.java
@@ -102,6 102,10 @@ public Field getField(int number) {
  /** Serializes the set and writes it to {@code output}. */
  @Override
  public void writeTo(CodedOutputStream output) throws IOException {
  if (fields.isEmpty()) {
  // Avoid allocating an iterator.
  return;
  }
  for (Map.Entry<Integer, Field> entry : fields.entrySet()) {
  Field field = entry.getValue();
  field.writeTo(entry.getKey(), output);
@@ -174,23 178,33 @@ public void writeDelimitedTo(OutputStream output) throws IOException {
  @Override
  public int getSerializedSize() {
  int result = 0;
- if (!fields.isEmpty()) {
- for (Map.Entry<Integer, Field> entry : fields.entrySet()) {
- result = entry.getValue().getSerializedSize(entry.getKey());
- }
  if (fields.isEmpty()) {
  // Avoid allocating an iterator.
  return result;
  }
  for (Map.Entry<Integer, Field> entry : fields.entrySet()) {
  result = entry.getValue().getSerializedSize(entry.getKey());
  }
  return result;
  }
 
  /** Serializes the set and writes it to {@code output} using {@code MessageSet} wire format. */
  public void writeAsMessageSetTo(CodedOutputStream output) throws IOException {
  if (fields.isEmpty()) {
  // Avoid allocating an iterator.
  return;
  }
  for (Map.Entry<Integer, Field> entry : fields.entrySet()) {
  entry.getValue().writeAsMessageSetExtensionTo(entry.getKey(), output);
  }
  }
 
  /** Serializes the set and writes it to {@code writer}. */
  void writeTo(Writer writer) throws IOException {
  if (fields.isEmpty()) {
  // Avoid allocating an iterator.
  return;
  }
  if (writer.fieldOrder() == Writer.FieldOrder.DESCENDING) {
  // Write fields in descending order.
  for (Map.Entry<Integer, Field> entry : fields.descendingMap().entrySet()) {
@@ -206,6 220,10 @@ void writeTo(Writer writer) throws IOException {
 
  /** Serializes the set and writes it to {@code writer} using {@code MessageSet} wire format. */
  void writeAsMessageSetTo(Writer writer) throws IOException {
  if (fields.isEmpty()) {
  // Avoid allocating an iterator.
  return;
  }
  if (writer.fieldOrder() == Writer.FieldOrder.DESCENDING) {
  // Write fields in descending order.
  for (Map.Entry<Integer, Field> entry : fields.descendingMap().entrySet()) {
@@ -222,6 240,10 @@ void writeAsMessageSetTo(Writer writer) throws IOException {
  /** Get the number of bytes required to encode this set using {@code MessageSet} wire format. */
  public int getSerializedSizeAsMessageSet() {
  int result = 0;
  if (fields.isEmpty()) {
  // Avoid allocating an iterator.
  return result;
  }
  for (Map.Entry<Integer, Field> entry : fields.entrySet()) {
  result = entry.getValue().getSerializedSizeAsMessageSetExtension(entry.getKey());
  }