add visitor that find all values by a prefix of the key

block-storage/src/test/java/org/lucares/pdb/map/NodeEntryTest.java

@@ -1,7 +1,37 @@
 package org.lucares.pdb.map;
 
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.lucares.pdb.map.NodeEntry.ValueType;
+import org.testng.Assert;
+import org.testng.annotations.DataProvider;
 import org.testng.annotations.Test;
 
 @Test
 public class NodeEntryTest {
+	@DataProvider
+	public Object[][] providerPrefixCompare() {
+		final List<Object[]> result = new ArrayList<>();
+
+		result.add(new Object[] { "ab", "abc", -1 });
+		result.add(new Object[] { "abb", "abc", -1 });
+		result.add(new Object[] { "abc", "abc", 0 });
+		result.add(new Object[] { "abcd", "abc", 0 });
+		result.add(new Object[] { "abd", "abc", 1 });
+		result.add(new Object[] { "abz", "abc", 23 });
+
+		return result.toArray(Object[][]::new);
+	}
+
+	@Test(dataProvider = "providerPrefixCompare")
+	public void testPrefixCompare(final String key, final String prefix, final int expected) {
+
+		final NodeEntry nodeEntry = new NodeEntry(ValueType.NODE_POINTER, key.getBytes(StandardCharsets.UTF_8),
+				new byte[0]);
+
+		final int actual = nodeEntry.compareKeyPrefix(prefix.getBytes(StandardCharsets.UTF_8));
+		Assert.assertEquals(actual, expected, key + " ? " + prefix);
+	}
 }

block-storage/src/test/java/org/lucares/pdb/map/PersistentMapTest.java

@@ -6,7 +6,9 @@ import java.nio.file.Path;
 import java.security.SecureRandom;
 import java.util.Arrays;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.LinkedList;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Queue;
 import java.util.Random;
@@ -14,6 +16,7 @@ import java.util.UUID;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import org.lucares.pdb.diskstorage.DiskStorage;
+import org.lucares.pdb.map.PersistentMap.Visitor;
 import org.lucares.utils.file.FileUtils;
 import org.testng.Assert;
 import org.testng.annotations.AfterMethod;
@@ -238,4 +241,42 @@ public class PersistentMapTest {
 		}
 	}
 
+	@Test
+	public void testFindAllByPrefix() throws Exception {
+		final Path file = dataDirectory.resolve("map.db");
+
+		final Map<String, String> expectedBar = new HashMap<>();
+		for (int i = 0; i < 100; i++) {
+			// the value is a little bit longer to make sure that the values don't fit into
+			// a single leaf node
+			expectedBar.put("bar:" + i, "bar:" + i + "__##################################");
+		}
+
+		final Map<String, String> input = new HashMap<>();
+		input.putAll(expectedBar);
+		for (int i = 0; i < 500; i++) {
+			input.put(UUID.randomUUID().toString(), UUID.randomUUID().toString());
+		}
+
+		try (final DiskStorage ds = new DiskStorage(file)) {
+			final PersistentMap<String, String> map = new PersistentMap<>(ds, PersistentMap.STRING_CODER,
+					PersistentMap.STRING_CODER);
+
+			map.putAllValues(input);
+		}
+
+		try (final DiskStorage ds = new DiskStorage(file)) {
+			final PersistentMap<String, String> map = new PersistentMap<>(ds, PersistentMap.STRING_CODER,
+					PersistentMap.STRING_CODER);
+
+			{
+				final LinkedHashMap<String, String> actualBar = new LinkedHashMap<>();
+				final Visitor<String, String> visitor = (key, value) -> actualBar.put(key, value);
+				map.visitValues("bar:", visitor);
+
+				Assert.assertEquals(actualBar, expectedBar);
+			}
+		}
+	}
+
 }