Memoize isInitialized result for DynamicMessage to improve parsing performance.

PiperOrigin-RevId: 864068668

Author: protobuf-github-bot

java/core/src/main/java/com/google/protobuf/DynamicMessage.java

@@ -33,6 +33,17 @@ public final class DynamicMessage extends AbstractMessage {
   private final UnknownFieldSet unknownFields;
   private int memoizedSize = -1;
 
+  /**
+   * Stores previously-computed {@code isInitialized} results. {@code isInitialized} can be
+   * expensive to compute in situations where a large message is converted to a builder, modified,
+   * and then rebuilt.
+   */
+  private transient byte isInitializedMemo = NO_MEMO_PRESENT;
+
+  private static final byte NO_MEMO_PRESENT = -1;
+  private static final byte IS_INITIALIZED_FALSE = 0;
+  private static final byte IS_INITIALIZED_TRUE = 1;
+
   /**
    * Construct a {@code DynamicMessage} using the given {@code FieldSet}. oneofCases stores the
    * FieldDescriptor for each oneof to indicate which field is set. Caller should make sure the
@@ -215,7 +226,20 @@ static boolean isInitialized(Descriptor type, FieldSet<FieldDescriptor> fields)
 
   @Override
   public boolean isInitialized() {
-    return isInitialized(type, fields);
+    // This section departs slightly from idiomatic style because it is expected that this style
+    // will optimize better on mobile after processing by technologies like AppReduce.
+    if (isInitializedMemo == IS_INITIALIZED_TRUE) {
+      return true;
+    }
+    if (isInitializedMemo == IS_INITIALIZED_FALSE) {
+      return false;
+    }
+    if (isInitialized(type, fields)) {
+      isInitializedMemo = IS_INITIALIZED_TRUE;
+      return true;
+    }
+    isInitializedMemo = IS_INITIALIZED_FALSE;
+    return false;
   }
 
   @Override