Added support for binary format for halfvec

src/main/java/com/pgvector/PGhalfvec.java

@@ -7,13 +7,15 @@
 import java.util.List;
 import java.util.Objects;
 import org.postgresql.PGConnection;
+import org.postgresql.util.ByteConverter;
+import org.postgresql.util.PGBinaryObject;
 import org.postgresql.util.PGobject;
 
 /**
  * PGhalfvec class
  */
-public class PGhalfvec extends PGobject implements Serializable, Cloneable {
-    private float[] vec;
+public class PGhalfvec extends PGobject implements PGBinaryObject, Serializable, Cloneable {
+    private short[] vec;
 
     /**
      * Constructor
@@ -29,7 +31,14 @@ public PGhalfvec() {
      */
     public PGhalfvec(float[] v) {
         this();
-        vec = v;
+        if (v == null) {
+            vec = null;
+        } else {
+            vec = new short[v.length];
+            for (int i = 0; i < v.length; i++) {
+                vec[i] = Float.floatToFloat16(v[i]);
+            }
+        }
     }
 
     /**
@@ -43,10 +52,10 @@ public <T extends Number> PGhalfvec(List<T> v) {
         if (Objects.isNull(v)) {
             vec = null;
         } else {
-            vec = new float[v.size()];
+            vec = new short[v.size()];
             int i = 0;
             for (T f : v) {
-                vec[i++] = f.floatValue();
+                vec[i++] = Float.floatToFloat16(f.floatValue());
             }
         }
     }
@@ -70,9 +79,9 @@ public void setValue(String s) throws SQLException {
             vec = null;
         } else {
             String[] sp = s.substring(1, s.length() - 1).split(",");
-            vec = new float[sp.length];
+            vec = new short[sp.length];
             for (int i = 0; i < sp.length; i++) {
-                vec[i] = Float.parseFloat(sp[i]);
+                vec[i] = Float.floatToFloat16(Float.parseFloat(sp[i]));
             }
         }
     }
@@ -84,7 +93,52 @@ public String getValue() {
         if (vec == null) {
             return null;
         } else {
-            return Arrays.toString(vec).replace(" ", "");
+            float[] fvec = new float[vec.length];
+            for (int i = 0; i < vec.length; i++) {
+                fvec[i] = Float.float16ToFloat(vec[i]);
+            }
+            return Arrays.toString(fvec).replace(" ", "");
+        }
+    }
+
+    /**
+     * Returns the number of bytes for the binary representation
+     */
+    public int lengthInBytes() {
+        return vec == null ? 0 : 4 + vec.length * 2;
+    }
+
+    /**
+     * Sets the value from a binary representation of a half vector
+     */
+    public void setByteValue(byte[] value, int offset) throws SQLException {
+        int dim = ByteConverter.int2(value, offset);
+
+        int unused = ByteConverter.int2(value, offset + 2);
+        if (unused != 0) {
+            throw new SQLException("expected unused to be 0");
+        }
+
+        vec = new short[dim];
+        for (int i = 0; i < dim; i++) {
+            vec[i] = ByteConverter.int2(value, offset + 4 + i * 2);
+        }
+    }
+
+    /**
+     * Writes the binary representation of a half vector
+     */
+    public void toBytes(byte[] bytes, int offset) {
+        if (vec == null) {
+            return;
+        }
+
+        // server will error on overflow due to unconsumed buffer
+        // could set to Short.MAX_VALUE for friendlier error message
+        ByteConverter.int2(bytes, offset, vec.length);
+        ByteConverter.int2(bytes, offset + 2, 0);
+        for (int i = 0; i < vec.length; i++) {
+            ByteConverter.int2(bytes, offset + 4 + i * 2, vec[i]);
         }
     }
 
@@ -94,7 +148,11 @@ public String getValue() {
      * @return an array
      */
     public float[] toArray() {
-        return vec;
+        float[] v = new float[vec.length];
+        for (int i = 0; i < vec.length; i++) {
+            v[i] = Float.float16ToFloat(vec[i]);
+        }
+        return v;
     }
 
     /**