Deflate caching improvements

Author: Col-E

src/main/java/software/coley/llzip/format/compression/UnsafeDeflateDecompressor.java

@@ -9,68 +9,89 @@
 import java.util.ArrayDeque;
 import java.util.Deque;
 import java.util.zip.DataFormatException;
+import java.util.zip.Inflater;
 import java.util.zip.ZipException;
 
 /**
  * Optimized implementation of {@link DeflateDecompressor} with unsafe resetting for more throughput.
  *
  * @author xDark
  */
+@SuppressWarnings("UnnecessaryLocalVariable")
 public class UnsafeDeflateDecompressor implements Decompressor {
-	private static final Deque<UnsafeInflater> INFLATERS = new ArrayDeque<>();
+	private static final int DEFLATE_CACHE_LIMIT = 64;
+	private static final Deque<DeflateEntry> DEFLATE_ENTRIES = new ArrayDeque<>();
+	private static final byte[] emptyBuf = new byte[0];
+
+	static {
+		Deque<DeflateEntry> entries = DEFLATE_ENTRIES;
+		for (int i = 0; i < DEFLATE_CACHE_LIMIT; i++) {
+			entries.push(new DeflateEntry());
+		}
+	}
 
 	@Override
 	public ByteData decompress(LocalFileHeader header, ByteData data) throws IOException {
 		if (header.getCompressionMethod() != ZipCompressions.DEFLATED)
 			throw new IOException("LocalFileHeader contents not using 'Deflated'!");
 		FastWrapOutputStream out = new FastWrapOutputStream();
-		UnsafeInflater inflater;
-		Deque<UnsafeInflater> inflaters = INFLATERS;
+		DeflateEntry entry;
+		Deque<DeflateEntry> inflaters = DEFLATE_ENTRIES;
 		synchronized (inflaters) {
-			inflater = inflaters.poll();
-			if (inflater == null) {
-				inflater = new UnsafeInflater(true);
-			}
+			entry = inflaters.poll();
+		}
+		if (entry == null) {
+			entry = new DeflateEntry();
+		} else {
+			// Normal 'Inflater' reset() is synchronized and bottlenecks us,
+			// but we're using 'UnsafeInflater' which bypasses that.
+			entry.inflater.reset();
 		}
 		try {
-			byte[] output = new byte[1024];
-			byte[] buffer = new byte[1024];
+			byte[] output = entry.decompress;
+			byte[] buffer = entry.buffer;
+			Inflater inflater = entry.inflater;
 			long position = 0L;
 			long length = data.length();
+			inflater.setInput(emptyBuf);
 			do {
 				if (inflater.needsInput()) {
 					int remaining = (int) Math.min(buffer.length, length);
-					if (remaining == 0) {
-						break;
+					if (remaining != 0) {
+						data.get(position, buffer, 0, remaining);
+						length -= remaining;
+						position += remaining;
+						inflater.setInput(buffer, 0, remaining);
 					}
-					data.get(position, buffer, 0, remaining);
-					length -= remaining;
-					position += remaining;
-					inflater.setInput(buffer, 0, remaining);
 				}
 				int count = inflater.inflate(output);
 				if (count != 0) {
 					out.write(output, 0, count);
 				}
-			} while (!inflater.finished() && !inflater.needsDictionary());
+			} while (!inflater.finished());
 		} catch (DataFormatException e) {
-			String s = e.getMessage();
-			throw (ZipException) new ZipException(s != null ? null : "Invalid ZLIB data format").initCause(e);
+			String msg = e.getMessage();
+			throw (ZipException) new ZipException(msg != null ? null : "Invalid ZLIB data format").initCause(e);
 		} finally {
 			end:
 			{
-				if (inflaters.size() < 32) {
+				if (inflaters.size() < DEFLATE_CACHE_LIMIT) {
 					synchronized (inflaters) {
-						if (inflaters.size() < 32) {
-							inflater.fastReset();
-							inflaters.push(inflater);
+						if (inflaters.size() < DEFLATE_CACHE_LIMIT) {
+							inflaters.addFirst(entry);
 							break end;
 						}
 					}
 				}
-				inflater.end();
+				entry.inflater.end();
 			}
 		}
 		return out.wrap();
 	}
+
+	private static final class DeflateEntry {
+		final Inflater inflater = new UnsafeInflater(true);
+		final byte[] decompress = new byte[1024];
+		final byte[] buffer = new byte[8192];
+	}
 }

src/main/java/software/coley/llzip/util/UnsafeInflater.java

@@ -54,10 +54,8 @@ public UnsafeInflater(boolean nowrap) {
 		super(nowrap);
 	}
 
-	/**
-	 * {@link #reset()} but without synchronization.
-	 */
-	public void fastReset() {
+	@Override
+	public void reset() {
 		try {
 			Object zsRefValue = UNSAFE.getObject(this, off_zsRef);
 			if (mh_address == null) {