From 008f0db37778f770ccf3492252e899a600f26dbc Mon Sep 17 00:00:00 2001
From: Andreas Huber <bitbucket@lucares.de>
Date: Sun, 4 Nov 2018 10:42:05 +0100
Subject: [PATCH] add generics to PersistencMap

---
 .../org/lucares/pdb/map/PersistentMap.java    | 116 ++++++++++--------
 .../pdb/map/PersistentMapDiskNode.java        |  30 ++---
 .../lucares/pdb/map/PersistentMapTest.java    |  52 ++++----
 3 files changed, 105 insertions(+), 93 deletions(-)

diff --git a/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java b/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java
index 9b2af99..81901b1 100644
--- a/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java
+++ b/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java
@@ -2,10 +2,9 @@ package org.lucares.pdb.map;
 
 import java.io.IOException;
 import java.io.PrintStream;
-import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
 import java.util.Stack;
-import java.util.function.Function;
 
 import org.lucares.pdb.blockstorage.intsequence.VariableByteEncoder;
 import org.lucares.pdb.diskstorage.DiskBlock;
@@ -14,16 +13,16 @@ import org.lucares.utils.Preconditions;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-public class PersistentMap {
+public class PersistentMap<K, V> {
 
 	private static final Logger LOGGER = LoggerFactory.getLogger(PersistentMap.class);
 
 	// the maximum key
-	private static final byte[] MAX_KEY = new byte[] { Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE,
-			Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE,
-			Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE,
-			Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE,
-			Byte.MAX_VALUE, Byte.MAX_VALUE, Byte.MAX_VALUE };
+	private static final byte[] MAX_KEY;
+	static {
+		MAX_KEY = new byte[20];
+		Arrays.fill(MAX_KEY, Byte.MAX_VALUE);
+	}
 
 	interface VisitorCallback {
 		void visit(PersistentMapDiskNode node, PersistentMapDiskNode parentNode, NodeEntry nodeEntry, int depth);
@@ -33,11 +32,41 @@ public class PersistentMap {
 		void visit(PersistentMapDiskNode node, int depth);
 	}
 
-	public static final Function<byte[], String> STRING_DECODER = t -> new String(t, StandardCharsets.UTF_8);
-	public static final Function<byte[], String> LONG_DECODER = t -> String
-			.valueOf(VariableByteEncoder.decodeFirstValue(t));
+	public interface EncoderDecoder<O> {
+		public byte[] encode(O object);
+
+		public O decode(byte[] bytes);
+	}
+
+	private static final class StringCoder implements EncoderDecoder<String> {
+
+		@Override
+		public byte[] encode(final String object) {
+			return object.getBytes(StandardCharsets.UTF_8);
+		}
+
+		@Override
+		public String decode(final byte[] bytes) {
+			return bytes == null ? null : new String(bytes, StandardCharsets.UTF_8);
+		}
+	}
+
+	private static final class LongCoder implements EncoderDecoder<Long> {
+
+		@Override
+		public byte[] encode(final Long object) {
+			return VariableByteEncoder.encode(object);
+		}
+
+		@Override
+		public Long decode(final byte[] bytes) {
+			return bytes == null ? null : VariableByteEncoder.decodeFirstValue(bytes);
+		}
+	}
+
+	public static final EncoderDecoder<Long> LONG_CODER = new LongCoder();
+	public static final EncoderDecoder<String> STRING_CODER = new StringCoder();
 
-	private static final Charset UTF8 = StandardCharsets.UTF_8;
 	static final int BLOCK_SIZE = 4096;
 	static final long NODE_OFFSET_TO_ROOT_NODE = 8;
 
@@ -45,8 +74,15 @@ public class PersistentMap {
 
 	private int maxEntriesInNode = Integer.MAX_VALUE;
 
-	public PersistentMap(final DiskStorage diskStore) throws IOException {
+	private final EncoderDecoder<K> keyEncoder;
+
+	private final EncoderDecoder<V> valueEncoder;
+
+	public PersistentMap(final DiskStorage diskStore, final EncoderDecoder<K> keyEncoder,
+			final EncoderDecoder<V> valueEncoder) throws IOException {
 		this.diskStore = diskStore;
+		this.keyEncoder = keyEncoder;
+		this.valueEncoder = valueEncoder;
 		initIfNew();
 	}
 
@@ -77,51 +113,26 @@ public class PersistentMap {
 		}
 	}
 
-	public Long putValue(final String key, final long value) throws IOException {
-		final byte[] oldValue = putValue(key.getBytes(UTF8), VariableByteEncoder.encode(value));
-		return oldValue == null ? null : VariableByteEncoder.decodeFirstValue(oldValue);
+	public V putValue(final K key, final V value) throws IOException {
+		final byte[] encodedKey = keyEncoder.encode(key);
+		final byte[] encodedValue = valueEncoder.encode(value);
+		final byte[] oldValue = putValue(encodedKey, encodedValue);
+		return valueEncoder.decode(oldValue);
 	}
 
-	public String putValue(final long key, final String value) throws IOException {
-		final byte[] oldValue = putValue(VariableByteEncoder.encode(key), value.getBytes(UTF8));
-		return oldValue == null ? null : new String(oldValue, UTF8);
+	public V getValue(final K key) throws IOException {
+		final byte[] encodedKey = keyEncoder.encode(key);
+		final byte[] foundValue = getValue(encodedKey);
+		return valueEncoder.decode(foundValue);
 	}
 
-	public Long putValue(final long key, final long value) throws IOException {
-		final byte[] oldValue = putValue(VariableByteEncoder.encode(key), VariableByteEncoder.encode(value));
-		return oldValue == null ? null : VariableByteEncoder.decodeFirstValue(oldValue);
-	}
-
-	public Long getAsLong(final String key) throws IOException {
-		final byte[] buffer = get(key.getBytes(UTF8));
-		return buffer == null ? null : VariableByteEncoder.decodeFirstValue(buffer);
-	}
-
-	public Long getAsLong(final long key) throws IOException {
-		final byte[] buffer = get(VariableByteEncoder.encode(key));
-		return buffer == null ? null : VariableByteEncoder.decodeFirstValue(buffer);
-	}
-
-	public String putValue(final String key, final String value) throws IOException {
-		final byte[] keyBytes = key.getBytes(UTF8);
-		final byte[] valueBytes = value.getBytes(UTF8);
-		final byte[] oldValue = putValue(keyBytes, valueBytes);
-		return oldValue == null ? null : new String(oldValue, UTF8);
-	}
-
-	public String getAsString(final String key) throws IOException {
-		final byte[] value = get(key.getBytes(UTF8));
-
-		return value == null ? null : new String(value, UTF8);
-	}
-
-	public byte[] putValue(final byte[] key, final byte[] value) throws IOException {
+	private byte[] putValue(final byte[] key, final byte[] value) throws IOException {
 		final long rootNodeOffset = readNodeOffsetOfRootNode();
 		final Stack<PersistentMapDiskNode> parents = new Stack<>();
 		return insert(parents, rootNodeOffset, key, value);
 	}
 
-	public byte[] get(final byte[] key) throws IOException {
+	private byte[] getValue(final byte[] key) throws IOException {
 		final long rootNodeOffset = readNodeOffsetOfRootNode();
 		final NodeEntry entry = findNodeEntry(rootNodeOffset, key);
 
@@ -266,8 +277,7 @@ public class PersistentMap {
 		diskBlock.force();
 	}
 
-	public void print(final Function<byte[], String> keyDecoder, final Function<byte[], String> valueDecoder)
-			throws IOException {
+	public void print() throws IOException {
 
 		visitNodeEntriesPreOrder((node, parentNode, nodeEntry, depth) -> {
 
@@ -275,8 +285,8 @@ public class PersistentMap {
 
 			final String children = "#" + node.getEntries().size();
 
-			writer.println("    ".repeat(depth) + "@" + node.getNodeOffset() + " " + children + " "
-					+ nodeEntry.toString(keyDecoder, valueDecoder));
+			writer.println("    ".repeat(depth) + "@" + node.getNodeOffset() + " " + children + " " + nodeEntry
+					.toString(b -> String.valueOf(keyEncoder.decode(b)), b -> String.valueOf(valueEncoder.decode(b))));
 		});
 	}
 
diff --git a/block-storage/src/main/java/org/lucares/pdb/map/PersistentMapDiskNode.java b/block-storage/src/main/java/org/lucares/pdb/map/PersistentMapDiskNode.java
index 8c1d38c..460b7b7 100644
--- a/block-storage/src/main/java/org/lucares/pdb/map/PersistentMapDiskNode.java
+++ b/block-storage/src/main/java/org/lucares/pdb/map/PersistentMapDiskNode.java
@@ -15,26 +15,23 @@ import org.lucares.utils.Preconditions;
  * <pre>
  * Node layout:
  *
- *  ◀──────────   Prefix ──────────▶         ◀───────────────── Suffix ──────────────────▶
- * ┏━━━━━┳━━━┳━━━━━┳━━━━━┳━━━━━┳━━━┳╸╺╸╺╸╺╸╺┳━━━━━━━━━━━┳━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━┓
- * ┃ 456 ┃ 6 ┃ 5,6 ┃ 3,6 ┃ 3,2 ┃ ∅ ┃        ┃"ba"->"147"┃"foobar"->"467"┃"foobaz"->"value"┃
- * ┗━━━━━┻━━━┻━━━━━┻━━━━━┻━━━━━┻━━━┻╸╺╸╺╸╺╸╺┻━━━━━━━━━━━┻━━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━┛
- *    │    │   │ │   │ │   │ │   └▶  null byte that serves as a separator for the prefix.
- *    │    │   │ │   │ │   │ └▶ size of the third last key ("ba" in this example)
- *    │    │   │ │   │ │   └▶ size of the third last value ("147" in this example)
- *    │    │   │ │   │ └▶ size of the second last key ("foobar" in this example)
- *    │    │   │ │   └▶ size of the second last value ("467" in this example)
- *    │    │   │ └▶ size of the last key ("foobaz" in this example)
- *    │    │   └▶ size of the last value (the string "value" in this example)
- *    │    └▶ number of entries * 2
- *    └▶ node offset of the parent node (-1 if there is no parent node)
+ *  ◀───────   Prefix ──────▶          ◀───────────────── Suffix ──────────────────▶
+ * ┏━━━┳━━━━━┳━━━━━┳━━━━━┳━━━┳╸╺╸╺╸╺╸╺┳━━━━━━━━━━━┳━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━┓
+ * ┃ 6 ┃ 5,6 ┃ 3,6 ┃ 3,2 ┃ ∅ ┃        ┃"ba"->"147"┃"foobar"->"467"┃"foobaz"->"value"┃
+ * ┗━━━┻━━━━━┻━━━━━┻━━━━━┻━━━┻╸╺╸╺╸╺╸╺┻━━━━━━━━━━━┻━━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━┛
+ *   │   │ │   │ │   │ │   └▶  null byte that serves as a separator for the prefix.
+ *   │   │ │   │ │   │ └▶ size of the third last key ("ba" in this example)
+ *   │   │ │   │ │   └▶ size of the third last value ("147" in this example)
+ *   │   │ │   │ └▶ size of the second last key ("foobar" in this example)
+ *   │   │ │   └▶ size of the second last value ("467" in this example)
+ *   │   │ └▶ size of the last key ("foobaz" in this example)
+ *   │   └▶ size of the last value (the string "value" in this example)
+ *   └▶ number of entries * 2
  *
  * </pre>
  */
 public class PersistentMapDiskNode {
 
-	public static final long NO_NODE_OFFSET = -1;
-
 	private final List<NodeEntry> entries;
 	private final long nodeOffset;
 
@@ -53,9 +50,6 @@ public class PersistentMapDiskNode {
 					"block size must be " + PersistentMap.BLOCK_SIZE + " but was " + data.length);
 		}
 		final LongList longs = VariableByteEncoder.decode(data);
-		if (longs.size() == 0) {
-			System.out.println();
-		}
 
 		final List<NodeEntry> entries = deserialize(longs, data);
 		return new PersistentMapDiskNode(nodeOffset, entries);
diff --git a/block-storage/src/test/java/org/lucares/pdb/map/PersistentMapTest.java b/block-storage/src/test/java/org/lucares/pdb/map/PersistentMapTest.java
index ec40348..d3f4f0f 100644
--- a/block-storage/src/test/java/org/lucares/pdb/map/PersistentMapTest.java
+++ b/block-storage/src/test/java/org/lucares/pdb/map/PersistentMapTest.java
@@ -41,18 +41,20 @@ public class PersistentMapTest {
 		final String key = "key1";
 
 		try (final DiskStorage ds = new DiskStorage(file)) {
-			final PersistentMap map = new PersistentMap(ds);
+			final PersistentMap<String, String> map = new PersistentMap<>(ds, PersistentMap.STRING_CODER,
+					PersistentMap.STRING_CODER);
 
-			Assert.assertNull(map.getAsString(key));
+			Assert.assertNull(map.getValue(key));
 
 			Assert.assertNull(map.putValue(key, value));
 
-			Assert.assertEquals(map.getAsString(key), value);
+			Assert.assertEquals(map.getValue(key), value);
 		}
 		try (final DiskStorage ds = new DiskStorage(file)) {
-			final PersistentMap map = new PersistentMap(ds);
+			final PersistentMap<String, String> map = new PersistentMap<>(ds, PersistentMap.STRING_CODER,
+					PersistentMap.STRING_CODER);
 
-			Assert.assertEquals(map.getAsString(key), value);
+			Assert.assertEquals(map.getValue(key), value);
 		}
 	}
 
@@ -63,7 +65,8 @@ public class PersistentMapTest {
 		final Random rnd = new Random(1);
 
 		try (final DiskStorage ds = new DiskStorage(file)) {
-			final PersistentMap map = new PersistentMap(ds);
+			final PersistentMap<String, String> map = new PersistentMap<>(ds, PersistentMap.STRING_CODER,
+					PersistentMap.STRING_CODER);
 			map.setMaxEntriesInNode(2);
 
 			for (int i = 0; i < 100; i++) {
@@ -72,7 +75,7 @@ public class PersistentMapTest {
 				final String key = nextUUID.toString() + "__" + i;
 				final String value = "long value to waste some bytes " + i + "__"
 						+ UUID.randomUUID().toString().repeat(1);
-				Assert.assertNull(map.getAsString(key));
+				Assert.assertNull(map.getValue(key));
 
 				Assert.assertNull(map.putValue(key, value));
 
@@ -83,10 +86,10 @@ public class PersistentMapTest {
 				final boolean failEarly = false;
 				if (failEarly) {
 					for (final var entry : insertedValues.entrySet()) {
-						final String actualValue = map.getAsString(entry.getKey());
+						final String actualValue = map.getValue(entry.getKey());
 
 						if (!Objects.equals(actualValue, entry.getValue())) {
-							map.print(PersistentMap.STRING_DECODER, PersistentMap.STRING_DECODER);
+							map.print();
 						}
 
 						Assert.assertEquals(actualValue, entry.getValue(),
@@ -97,7 +100,8 @@ public class PersistentMapTest {
 		}
 
 		try (final DiskStorage ds = new DiskStorage(file)) {
-			final PersistentMap map = new PersistentMap(ds);
+			final PersistentMap<String, String> map = new PersistentMap<>(ds, PersistentMap.STRING_CODER,
+					PersistentMap.STRING_CODER);
 			// map.print(PersistentMap.STRING_DECODER, PersistentMap.STRING_DECODER);
 			final AtomicInteger maxDepth = new AtomicInteger();
 			map.visitNodeEntriesPreOrder(
@@ -109,7 +113,7 @@ public class PersistentMapTest {
 							+ maxDepth.get());
 
 			for (final var entry : insertedValues.entrySet()) {
-				final String actualValue = map.getAsString(entry.getKey());
+				final String actualValue = map.getValue(entry.getKey());
 				Assert.assertEquals(actualValue, entry.getValue(),
 						"value for key " + entry.getKey() + " after all iterations");
 			}
@@ -126,14 +130,15 @@ public class PersistentMapTest {
 		rnd.setSeed(1);
 
 		try (final DiskStorage ds = new DiskStorage(file)) {
-			final PersistentMap map = new PersistentMap(ds);
+			final PersistentMap<Long, Long> map = new PersistentMap<>(ds, PersistentMap.LONG_CODER,
+					PersistentMap.LONG_CODER);
 
 			for (int i = 0; i < 1000; i++) {
 				// System.out.println("\n\ninserting: " + i);
 
 				final Long key = (long) (rnd.nextGaussian() * Integer.MAX_VALUE);
 				final Long value = (long) (rnd.nextGaussian() * Integer.MAX_VALUE);
-				Assert.assertNull(map.getAsLong(key));
+				Assert.assertNull(map.getValue(key));
 
 				Assert.assertNull(map.putValue(key, value));
 
@@ -144,10 +149,10 @@ public class PersistentMapTest {
 				final boolean failEarly = false;
 				if (failEarly) {
 					for (final var entry : insertedValues.entrySet()) {
-						final Long actualValue = map.getAsLong(entry.getKey());
+						final Long actualValue = map.getValue(entry.getKey());
 
 						if (!Objects.equals(actualValue, entry.getValue())) {
-							map.print(PersistentMap.LONG_DECODER, PersistentMap.LONG_DECODER);
+							map.print();
 						}
 
 						Assert.assertEquals(actualValue, entry.getValue(),
@@ -158,7 +163,8 @@ public class PersistentMapTest {
 		}
 
 		try (final DiskStorage ds = new DiskStorage(file)) {
-			final PersistentMap map = new PersistentMap(ds);
+			final PersistentMap<Long, Long> map = new PersistentMap<>(ds, PersistentMap.LONG_CODER,
+					PersistentMap.LONG_CODER);
 			// map.print(PersistentMap.LONG_DECODER, PersistentMap.LONG_DECODER);
 			final AtomicInteger counter = new AtomicInteger();
 			map.visitNodeEntriesPreOrder(
@@ -170,7 +176,7 @@ public class PersistentMapTest {
 							+ "nodes could hold the values");
 
 			for (final var entry : insertedValues.entrySet()) {
-				final Long actualValue = map.getAsLong(entry.getKey());
+				final Long actualValue = map.getValue(entry.getKey());
 				Assert.assertEquals(actualValue, entry.getValue(),
 						"value for key " + entry.getKey() + " after all iterations");
 			}
@@ -186,7 +192,8 @@ public class PersistentMapTest {
 		final Queue<Integer> numbers = new LinkedList<>(Arrays.asList(1, 15, 11, 4, 16, 3, 13));
 
 		try (final DiskStorage ds = new DiskStorage(file)) {
-			final PersistentMap map = new PersistentMap(ds);
+			final PersistentMap<String, String> map = new PersistentMap<>(ds, PersistentMap.STRING_CODER,
+					PersistentMap.STRING_CODER);
 
 			final int numbersSize = numbers.size();
 			for (int i = 0; i < numbersSize; i++) {
@@ -196,7 +203,7 @@ public class PersistentMapTest {
 
 				final String key = "" + keyNumber;
 				final String value = "value";
-				Assert.assertNull(map.getAsString(key));
+				Assert.assertNull(map.getValue(key));
 
 				Assert.assertNull(map.putValue(key, value));
 
@@ -205,7 +212,7 @@ public class PersistentMapTest {
 				// map.print(PersistentMap.STRING_DECODER, PersistentMap.STRING_DECODER);
 
 				for (final var entry : insertedValues.entrySet()) {
-					final String actualValue = map.getAsString(entry.getKey());
+					final String actualValue = map.getValue(entry.getKey());
 
 					Assert.assertEquals(actualValue, entry.getValue(),
 							"value for key " + entry.getKey() + " in the " + i + "th iteration");
@@ -214,7 +221,8 @@ public class PersistentMapTest {
 		}
 
 		try (final DiskStorage ds = new DiskStorage(file)) {
-			final PersistentMap map = new PersistentMap(ds);
+			final PersistentMap<String, String> map = new PersistentMap<>(ds, PersistentMap.STRING_CODER,
+					PersistentMap.STRING_CODER);
 			// map.print(PersistentMap.STRING_DECODER, PersistentMap.STRING_DECODER);
 
 			final AtomicInteger counter = new AtomicInteger();
@@ -222,7 +230,7 @@ public class PersistentMapTest {
 					(node, parentNode, nodeEntry, depth) -> counter.addAndGet(nodeEntry.isInnerNode() ? 1 : 0));
 
 			for (final var entry : insertedValues.entrySet()) {
-				final String actualValue = map.getAsString(entry.getKey());
+				final String actualValue = map.getValue(entry.getKey());
 				Assert.assertEquals(actualValue, entry.getValue(),
 						"value for key " + entry.getKey() + " after all iterations");
 			}