VarInt

src/main/java/ru/vk/itmo/plyasovklimentii/ByteArraySegment.java

@@ -0,0 +1,48 @@
+package ru.vk.itmo.plyasovklimentii;
+
+import java.io.IOException;
+import java.lang.foreign.MemorySegment;
+import java.nio.ByteBuffer;
+
+/**
+ * Growable buffer with {@link ByteBuffer} and {@link MemorySegment} interface.
+ *
+ * @author incubos
+ */
+final class ByteArraySegment {
+    private byte[] array;
+    private MemorySegment segment;
+
+    ByteArraySegment(final int capacity) {
+        this.array = new byte[capacity];
+        this.segment = MemorySegment.ofArray(array);
+    }
+
+    void withArray(final ArrayConsumer consumer) throws IOException {
+        consumer.process(array);
+    }
+
+    MemorySegment segment() {
+        return segment;
+    }
+
+    void ensureCapacity(final long size) {
+        if (size > Integer.MAX_VALUE) {
+            throw new IllegalArgumentException("Too big!");
+        }
+
+        final int capacity = (int) size;
+        if (array.length >= capacity) {
+            return;
+        }
+
+        // Grow to the nearest bigger power of 2
+        final int newSize = Integer.highestOneBit(capacity) << 1;
+        array = new byte[newSize];
+        segment = MemorySegment.ofArray(array);
+    }
+
+    interface ArrayConsumer {
+        void process(byte[] array) throws IOException;
+    }
+}

src/main/java/ru/vk/itmo/plyasovklimentii/LiveFilteringIterator.java

@@ -0,0 +1,52 @@
+package ru.vk.itmo.plyasovklimentii;
+
+import ru.vk.itmo.Entry;
+
+import java.lang.foreign.MemorySegment;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * Filters non tombstone {@link Entry}s.
+ *
+ * @author incubos
+ */
+final class LiveFilteringIterator implements Iterator<Entry<MemorySegment>> {
+    private final Iterator<Entry<MemorySegment>> delegate;
+    private Entry<MemorySegment> next;
+
+    LiveFilteringIterator(final Iterator<Entry<MemorySegment>> delegate) {
+        this.delegate = delegate;
+        skipTombstones();
+    }
+
+    private void skipTombstones() {
+        while (delegate.hasNext()) {
+            final Entry<MemorySegment> entry = delegate.next();
+            if (entry.value() != null) {
+                this.next = entry;
+                break;
+            }
+        }
+    }
+
+    @Override
+    public boolean hasNext() {
+        return next != null;
+    }
+
+    @Override
+    public Entry<MemorySegment> next() {
+        if (!hasNext()) {
+            throw new NoSuchElementException();
+        }
+
+        // Consume
+        final Entry<MemorySegment> result = next;
+        next = null;
+
+        skipTombstones();
+
+        return result;
+    }
+}