Adds a pool for PresenceBitmap instances.

src/main/java/com/amazon/ion/impl/IonCursorBinary.java

@@ -392,6 +392,13 @@ private static class ArgumentGroupMarker {
      */
     TaglessEncoding taglessType = null;
 
+    /**
+     * A pool for PresenceBitmap instances that can be scoped to the current value. This is used when skipping macro
+     * invocations. PresenceBitmap instances that need to stay in scope after the cursor moves to the next value
+     * cannot come from this pool; an externally managed pool must be used in that case.
+     */
+    private final PresenceBitmap.Companion.PooledFactory presenceBitmapPool = new PresenceBitmap.Companion.PooledFactory();
+
     /**
      * @return the given configuration's DataHandler, or null if that DataHandler is a no-op.
      */
@@ -1907,12 +1914,12 @@ private boolean slowIsDelimitedEnd_1_1() {
      * Loads the presence bitmap for the given signature. Upon calling this method, `peekIndex` must point to the
      * first byte in the argument encoding bitmap (if applicable for the signature).
      * @param signature the signature of the macro invocation for which to read a presence bitmap.
+     * @param pool the PresenceBitmap pool to use.
      * @return the presence bitmap.
      */
-    protected PresenceBitmap loadPresenceBitmap(List<Macro.Parameter> signature) {
-        // TODO performance: reuse or pool the presence bitmaps.
+    protected PresenceBitmap loadPresenceBitmap(List<Macro.Parameter> signature, PresenceBitmap.Companion.PooledFactory pool) {
         // Note: when there is no AEB, the following initializes the presence bitmap to "EXPRESSION" for each parameter.
-        PresenceBitmap presenceBitmap = PresenceBitmap.create(signature);
+        PresenceBitmap presenceBitmap = PresenceBitmap.create(signature, pool);
         if (presenceBitmap.getByteSize() > 0) {
             if (fillArgumentEncodingBitmap(presenceBitmap.getByteSize()) == IonCursor.Event.NEEDS_DATA) {
                 throw new UnsupportedOperationException("TODO: support continuable parsing of AEBs.");
@@ -2041,7 +2048,7 @@ private boolean skipMacroInvocation() {
         }
         stepIntoEExpression();
         List<Macro.Parameter > signature = macro.getSignature();
-        PresenceBitmap presenceBitmap = loadPresenceBitmap(signature);
+        PresenceBitmap presenceBitmap = loadPresenceBitmap(signature, presenceBitmapPool);
         for (int i = 0; i < signature.size(); i++) {
             Macro.Parameter parameter = signature.get(i);
             long parameterPresence = presenceBitmap.get(i);
@@ -2335,6 +2342,7 @@ private void reset() {
         macroInvocationId = -1;
         isSystemInvocation = false;
         taglessType = null;
+        presenceBitmapPool.clear();
     }
 
     /**

src/main/java/com/amazon/ion/impl/IonReaderContinuableCoreBinary.java

@@ -1727,7 +1727,7 @@ protected Macro loadMacro() {
 
         @Override
         protected PresenceBitmap loadPresenceBitmapIfNecessary(List<Macro.Parameter> signature) {
-            return IonReaderContinuableCoreBinary.this.loadPresenceBitmap(signature);
+            return IonReaderContinuableCoreBinary.this.loadPresenceBitmap(signature, presenceBitmapPool);
         }
 
         @Override

src/main/java/com/amazon/ion/impl/bin/PresenceBitmap.kt

@@ -3,8 +3,13 @@
 package com.amazon.ion.impl.bin
 
 import com.amazon.ion.*
+import com.amazon.ion.impl.bin.PresenceBitmap.Companion.EXPRESSION
+import com.amazon.ion.impl.bin.PresenceBitmap.Companion.GROUP
+import com.amazon.ion.impl.bin.PresenceBitmap.Companion.VOID
 import com.amazon.ion.impl.macro.*
 import com.amazon.ion.impl.macro.Macro.*
+import com.amazon.ion.impl.macro.MacroEvaluator.*
+import java.util.*
 
 /**
  * Utility class for setting, storing, reading, and writing presence bits.
@@ -70,16 +75,40 @@ internal class PresenceBitmap(
 
         const val MAX_SUPPORTED_PARAMETERS = PB_SLOTS_PER_LONG * 4
 
-        private val ZERO_PARAMETERS: PresenceBitmap = allRequired(0)
-        private val ONE_REQUIRED_PARAMETER: PresenceBitmap = allRequired(1)
-        private val TWO_REQUIRED_PARAMETERS: PresenceBitmap = allRequired(2)
-        private val THREE_REQUIRED_PARAMETERS: PresenceBitmap = allRequired(3)
-        private val FOUR_REQUIRED_PARAMETERS: PresenceBitmap = allRequired(4)
+        private val ZERO_PARAMETERS: PresenceBitmap = allRequired(0) { PresenceBitmap() }
+        private val ONE_REQUIRED_PARAMETER: PresenceBitmap = allRequired(1) { PresenceBitmap() }
+        private val TWO_REQUIRED_PARAMETERS: PresenceBitmap = allRequired(2) { PresenceBitmap() }
+        private val THREE_REQUIRED_PARAMETERS: PresenceBitmap = allRequired(3) { PresenceBitmap() }
+        private val FOUR_REQUIRED_PARAMETERS: PresenceBitmap = allRequired(4) { PresenceBitmap() }
+
+        /** Pool for PresenceBitmap instances. */
+        class PooledFactory {
+
+            private var index = 0
+
+            private var pool: Array<PresenceBitmap?> = Array(32) { null }
+
+            /** Gets an instance from the pool, allocating a new one only if necessary. The returned instance must be reset. */
+            fun get(): PresenceBitmap {
+                if (index >= pool.size) {
+                    pool = pool.copyOf(pool.size * 2)
+                }
+                if (pool[index] == null) {
+                    pool[index] = PresenceBitmap()
+                }
+                return pool[index++]!!
+            }
+
+            /** Clears the pool. Calling this method invalidates all instances previously returned by [get]. */
+            fun clear() {
+                index = 0
+            }
+        }
 
         /** Creates a PresenceBitmap for the given number of required parameters */
-        private fun allRequired(numberOfParameters: Int): PresenceBitmap {
+        private inline fun allRequired(numberOfParameters: Int, supplier: () -> PresenceBitmap): PresenceBitmap {
             if (numberOfParameters > MAX_SUPPORTED_PARAMETERS) throw IonException("Macros with more than 128 parameters are not supported by this implementation.")
-            val bitmap = PresenceBitmap(emptyList(), 0, numberOfParameters)
+            val bitmap = supplier().reset(emptyList(), 0, numberOfParameters)
             for (i in 0 until numberOfParameters) {
                 bitmap.setUnchecked(i, EXPRESSION)
             }
@@ -88,22 +117,30 @@ internal class PresenceBitmap(
 
         /** Creates or reuses a [PresenceBitmap] for the given signature. */
         @JvmStatic
-        fun create(signature: List<Parameter>): PresenceBitmap {
+        fun create(signature: List<Parameter>, pool: PooledFactory): PresenceBitmap {
             if (signature.size > MAX_SUPPORTED_PARAMETERS) throw IonException("Macros with more than 128 parameters are not supported by this implementation.")
             // Calculate the actual number of presence bits that will be encoded for the given signature.
-            val nonRequiredParametersCount = signature.count { it.cardinality != ParameterCardinality.ExactlyOne }
-            val usePresenceBits = nonRequiredParametersCount > PRESENCE_BITS_SIZE_THRESHOLD || signature.any { it.type.taglessEncodingKind != null }
+            var nonRequiredParametersCount = 0
+            var usePresenceBits = false
+            for (i in signature.indices) {
+                val parameter = signature[i]
+                if (parameter.cardinality != ParameterCardinality.ExactlyOne) {
+                    nonRequiredParametersCount++
+                }
+                usePresenceBits = usePresenceBits or (parameter.type.taglessEncodingKind != null)
+            }
+            usePresenceBits = usePresenceBits or (nonRequiredParametersCount > PRESENCE_BITS_SIZE_THRESHOLD)
             val size = if (usePresenceBits) nonRequiredParametersCount else 0
             return if (size > 0) {
-                PresenceBitmap(signature, nonRequiredParametersCount, signature.size)
+                pool.get().reset(signature, nonRequiredParametersCount, signature.size)
             } else {
                 when (signature.size) {
                     0 -> ZERO_PARAMETERS
                     1 -> ONE_REQUIRED_PARAMETER
                     2 -> TWO_REQUIRED_PARAMETERS
                     3 -> THREE_REQUIRED_PARAMETERS
                     4 -> FOUR_REQUIRED_PARAMETERS
-                    else -> allRequired(signature.size)
+                    else -> allRequired(signature.size, pool::get)
                 }
             }
         }
@@ -122,6 +159,21 @@ internal class PresenceBitmap(
     val byteSize: Int
         get() = size divideByRoundingUp PB_SLOTS_PER_BYTE
 
+    /**
+     * Resets this [PresenceBitmap] for the given signature, size, and parameter count. After this method is called,
+     * callers must set the bitmap as necessary, such as by calling [readFrom].
+     */
+    fun reset(signature: List<Parameter>, size: Int, totalParameterCount: Int): PresenceBitmap {
+        this.signature = signature
+        this.size = size
+        this.totalParameterCount = totalParameterCount
+        a = 0
+        b = 0
+        c = 0
+        d = 0
+        return this
+    }
+
     /** Resets this [PresenceBitmap] for the given signature. */
     fun initialize(signature: List<Parameter>) {
         if (signature.size > MAX_SUPPORTED_PARAMETERS) throw IonException("Macros with more than 128 parameters are not supported by this implementation.")

src/main/java/com/amazon/ion/impl/macro/EExpressionArgsReader.java

@@ -29,6 +29,8 @@ public abstract class EExpressionArgsReader {
 
     protected final PooledExpressionFactory expressionPool = new PooledExpressionFactory();
 
+    protected final PresenceBitmap.Companion.PooledFactory presenceBitmapPool = new PresenceBitmap.Companion.PooledFactory();
+
     /**
      * Constructor.
      * @param reader the {@link ReaderAdapter} from which to read {@link Expression}s.
@@ -270,6 +272,7 @@ private void collectEExpressionArgs() {
     public void beginEvaluatingMacroInvocation(MacroEvaluator macroEvaluator) {
         expressions.clear();
         expressionPool.clear();
+        presenceBitmapPool.clear();
         // TODO performance: avoid fully materializing all expressions up-front.
         if (reader.isInStruct()) {
             expressions.add(expressionPool.createFieldName(reader.getFieldNameSymbol()));