Refactored logic in QrTemplate and ReedSolomonGenerator into new Memozier class.

src/io/nayuki/fastqrcodegen/Memoizer.java

@@ -0,0 +1,88 @@
+/* 
+ * Fast QR Code generator library
+ * 
+ * Copyright (c) Project Nayuki. (MIT License)
+ * https://www.nayuki.io/page/fast-qr-code-generator-library
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ * - The above copyright notice and this permission notice shall be included in
+ *   all copies or substantial portions of the Software.
+ * - The Software is provided "as is", without warranty of any kind, express or
+ *   implied, including but not limited to the warranties of merchantability,
+ *   fitness for a particular purpose and noninfringement. In no event shall the
+ *   authors or copyright holders be liable for any claim, damages or other
+ *   liability, whether in an action of contract, tort or otherwise, arising from,
+ *   out of or in connection with the Software or the use or other dealings in the
+ *   Software.
+ */
+
+package io.nayuki.fastqrcodegen;
+
+import java.lang.ref.SoftReference;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.Function;
+
+
+// A thread-safe cache based on soft references.
+final class Memoizer<T,R> {
+	
+	private final Function<T,R> function;
+	private Map<T,SoftReference<R>> cache = new HashMap<>();
+	private Set<T> pending = new HashSet<>();
+	
+	
+	// Creates a memoizer based on the given function that takes one input to compute an output.
+	public Memoizer(Function<T,R> func) {
+		function = func;
+	}
+	
+	
+	// Computes function.apply(arg) or returns a cached copy of a previous call.
+	public R get(T arg) {
+		while (true) {
+			synchronized(this) {
+				if (cache.containsKey(arg)) {
+					SoftReference<R> ref = cache.get(arg);
+					R result = ref.get();
+					if (result != null)
+						return result;
+					cache.remove(arg);
+				}
+				// Now cache.containsKey(arg) == false
+				
+				if (!pending.contains(arg)) {
+					pending.add(arg);
+					break;
+				}
+				
+				try {
+					this.wait();
+				} catch (InterruptedException e) {
+					throw new RuntimeException(e);
+				}
+			}
+		}
+		
+		try {
+			R result = function.apply(arg);
+			synchronized(this) {
+				cache.put(arg, new SoftReference<>(result));
+			}
+			return result;
+		} finally {
+			synchronized(this) {
+				pending.remove(arg);
+				this.notifyAll();
+			}
+		}
+	}
+	
+}

src/io/nayuki/fastqrcodegen/QrCode.java

@@ -248,7 +248,7 @@ public final class QrCode {
 		errorCorrectionLevel = Objects.requireNonNull(ecl);
 		Objects.requireNonNull(dataCodewords);
 		
-		QrTemplate tpl = QrTemplate.getInstance(ver);
+		QrTemplate tpl = QrTemplate.MEMOIZER.get(ver);
 		modules = tpl.template.clone();
 		
 		// Compute ECC, draw modules, do masking
@@ -407,7 +407,7 @@ public final class QrCode {
 		// Split data into blocks, calculate ECC, and interleave
 		// (not concatenate) the bytes into a single sequence
 		byte[] result = new byte[rawCodewords];
-		ReedSolomonGenerator rs = ReedSolomonGenerator.getInstance(blockEccLen);
+		ReedSolomonGenerator rs = ReedSolomonGenerator.MEMOIZER.get(blockEccLen);
 		byte[] ecc = new byte[blockEccLen];  // Temporary storage per iteration
 		for (int i = 0, k = 0; i < numBlocks; i++) {
 			int datLen = shortBlockDataLen + (i < numShortBlocks ? 0 : 1);

src/io/nayuki/fastqrcodegen/QrTemplate.java

@@ -25,59 +25,12 @@ package io.nayuki.fastqrcodegen;
 
 import static io.nayuki.fastqrcodegen.QrCode.MAX_VERSION;
 import static io.nayuki.fastqrcodegen.QrCode.MIN_VERSION;
-import java.lang.ref.SoftReference;
 
 
 final class QrTemplate {
 	
-	/*---- Factory members ----*/
+	public static final Memoizer<Integer,QrTemplate> MEMOIZER
-	
+		= new Memoizer<>(QrTemplate::new);
-	public static QrTemplate getInstance(int version) {
-		if (version < MIN_VERSION || version > MAX_VERSION)
-			throw new IllegalArgumentException("Version out of range");
-		
-		while (true) {
-			synchronized(cache) {
-				SoftReference<QrTemplate> ref = cache[version];
-				if (ref != null) {
-					QrTemplate result = ref.get();
-					if (result != null)
-						return result;
-					cache[version] = null;
-				}
-				
-				if (!isPending[version]) {
-					isPending[version] = true;
-					break;
-				}
-				
-				try {
-					cache.wait();
-				} catch (InterruptedException e) {
-					throw new RuntimeException(e);
-				}
-			}
-		}
-		
-		try {
-			QrTemplate tpl = new QrTemplate(version);
-			synchronized(cache) {
-				cache[version] = new SoftReference<>(tpl);
-			}
-			return tpl;
-		} finally {
-			synchronized(cache) {
-				isPending[version] = false;
-				cache.notifyAll();
-			}
-		}
-	}
-	
-	
-	@SuppressWarnings("unchecked")
-	private static final SoftReference<QrTemplate>[] cache = new SoftReference[MAX_VERSION + 1];
-	
-	private static final boolean[] isPending = new boolean[MAX_VERSION + 1];
 	
 	
 	

src/io/nayuki/fastqrcodegen/ReedSolomonGenerator.java

@@ -23,63 +23,14 @@
 
 package io.nayuki.fastqrcodegen;
 
-import java.lang.ref.SoftReference;
 import java.util.Arrays;
 import java.util.Objects;
 
 
 final class ReedSolomonGenerator {
 	
-	/*---- Factory members ----*/
+	public static final Memoizer<Integer,ReedSolomonGenerator> MEMOIZER
-	
+		= new Memoizer<>(ReedSolomonGenerator::new);
-	public static ReedSolomonGenerator getInstance(int degree) {
-		if (degree < 1 || degree > MAX_DEGREE)
-			throw new IllegalArgumentException("Degree out of range");
-		
-		while (true) {
-			synchronized(cache) {
-				SoftReference<ReedSolomonGenerator> ref = cache[degree];
-				if (ref != null) {
-					ReedSolomonGenerator result = ref.get();
-					if (result != null)
-						return result;
-					cache[degree] = null;
-				}
-				
-				if (!isPending[degree]) {
-					isPending[degree] = true;
-					break;
-				}
-				
-				try {
-					cache.wait();
-				} catch (InterruptedException e) {
-					throw new RuntimeException(e);
-				}
-			}
-		}
-		
-		try {
-			ReedSolomonGenerator rs = new ReedSolomonGenerator(degree);
-			synchronized(cache) {
-				cache[degree] = new SoftReference<>(rs);
-			}
-			return rs;
-		} finally {
-			synchronized(cache) {
-				isPending[degree] = false;
-				cache.notifyAll();
-			}
-		}
-	}
-	
-	
-	private static final int MAX_DEGREE = 30;
-	
-	@SuppressWarnings("unchecked")
-	private static final SoftReference<ReedSolomonGenerator>[] cache = new SoftReference[MAX_DEGREE + 1];
-	
-	private static final boolean[] isPending = new boolean[MAX_DEGREE + 1];