MLE-22706 Added encode/decode support for vectors

Author: rjrudin

marklogic-client-api/src/main/java/com/marklogic/client/util/VectorUtil.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2010-2025 Progress Software Corporation and/or its subsidiaries or affiliates. All Rights Reserved.
+ */
+package com.marklogic.client.util;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.Base64;
+
+/**
+ * Supports encoding and decoding vectors using the same approach as the vec:base64-encode and vec:base64-decode
+ * functions supported by the MarkLogic server.
+ *
+ * @since 7.2.0
+ */
+public interface VectorUtil {
+
+	static String encode(float... vector) {
+		final int dimensions = vector.length;
+		ByteBuffer buffer = ByteBuffer.allocate(8 + 4 * dimensions);
+		buffer.order(ByteOrder.LITTLE_ENDIAN);
+		buffer.putInt(0); // version
+		buffer.putInt(dimensions);
+		for (float v : vector) {
+			buffer.putFloat(v);
+		}
+		return Base64.getEncoder().encodeToString(buffer.array());
+	}
+
+	static float[] decode(String encodedVector) {
+		ByteBuffer buffer = ByteBuffer.wrap(Base64.getDecoder().decode(encodedVector));
+		buffer.order(ByteOrder.LITTLE_ENDIAN);
+
+		final int version = buffer.getInt();
+		if (version != 0) {
+			throw new IllegalArgumentException("Unsupported vector version: " + version);
+		}
+
+		final int dimensions = buffer.getInt();
+		float[] vector = new float[dimensions];
+		for (int i = 0; i < dimensions; i++) {
+			vector[i] = buffer.getFloat();
+		}
+		return vector;
+	}
+}

marklogic-client-api/src/test/java/com/marklogic/client/util/VectorUtilTest.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2010-2025 Progress Software Corporation and/or its subsidiaries or affiliates. All Rights Reserved.
+ */
+package com.marklogic.client.util;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.marklogic.client.test.Common;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class VectorUtilTest {
+
+	private final float[] VECTOR = new float[]{3.14f, 1.59f, 2.65f};
+	private final double ACCEPTABLE_DELTA = 0.0001;
+
+	@Test
+	void encodeAndDecodeWithJavaClient() {
+		String encoded = VectorUtil.encode(VECTOR);
+		assertEquals("AAAAAAMAAADD9UhAH4XLP5qZKUA=", encoded);
+
+		float[] decoded = VectorUtil.decode(encoded);
+		assertEquals(VECTOR.length, decoded.length);
+		for (int i = 0; i < VECTOR.length; i++) {
+			assertEquals(VECTOR[i], decoded[i], ACCEPTABLE_DELTA);
+		}
+	}
+
+	@Test
+	void encodeAndDecodeWithServer() {
+		String encoded = VectorUtil.encode(VECTOR);
+		assertEquals("AAAAAAMAAADD9UhAH4XLP5qZKUA=", encoded);
+
+		ArrayNode decoded = (ArrayNode) Common.newEvalClient().newServerEval()
+			.xquery("vec:base64-decode('%s')".formatted(encoded))
+			.evalAs(JsonNode.class);
+
+		assertEquals(3, decoded.size());
+		assertEquals(3.14f, decoded.get(0).asDouble(), ACCEPTABLE_DELTA);
+		assertEquals(1.59f, decoded.get(1).asDouble(), ACCEPTABLE_DELTA);
+		assertEquals(2.65f, decoded.get(2).asDouble(), ACCEPTABLE_DELTA);
+	}
+
+	@Test
+	void encodeWithServerAndDecodeWithJavaClient() {
+		String encoded = Common.newEvalClient().newServerEval()
+			.xquery("vec:base64-encode(vec:vector((3.14, 1.59, 2.65)))")
+			.evalAs(String.class);
+		assertEquals("AAAAAAMAAADD9UhAH4XLP5qZKUA=", encoded);
+
+		float[] decoded = VectorUtil.decode(encoded);
+		assertEquals(VECTOR.length, decoded.length);
+		for (int i = 0; i < VECTOR.length; i++) {
+			assertEquals(VECTOR[i], decoded[i], ACCEPTABLE_DELTA);
+		}
+	}
+}