Merge pull request #3992 from akazakov/master

Add byte array and unintialized array creation to FlatBufferBuilder

java/com/google/flatbuffers/FlatBufferBuilder.java

@@ -367,6 +367,28 @@ public class FlatBufferBuilder {
     }
     /// @endcond
 
+    /**
+     * Create a new array/vector and return a ByteBuffer to be filled later.
+     * Call {@link #endVector} after this method to get an offset to the beginning
+     * of vector.
+     *
+     * @param elem_size the size of each element in bytes.
+     * @param num_elems number of elements in the vector.
+     * @param alignment byte alignment.
+     * @return ByteBuffer with position and limit set to the space allocated for the array.
+     */
+    public ByteBuffer createUnintializedVector(int elem_size, int num_elems, int alignment) {
+        int length = elem_size * num_elems;
+        startVector(elem_size, num_elems, alignment);
+
+        bb.position(space -= length);
+
+        // Slice and limit the copy vector to point to the 'array'
+        ByteBuffer copy = bb.slice().order(ByteOrder.LITTLE_ENDIAN);
+        copy.limit(length);
+        return copy;
+    }
+
    /**
     * Encode the string `s` in the buffer using UTF-8.  If {@code s} is
     * already a {@link CharBuffer}, this method is allocation free.
@@ -413,6 +435,20 @@ public class FlatBufferBuilder {
         return endVector();
     }
 
+    /**
+     * Create a byte array in the buffer.
+     *
+     * @param arr A source array with data
+     * @return The offset in the buffer where the encoded array starts.
+     */
+    public int createByteVector(byte[] arr) {
+        int length = arr.length;
+        startVector(1, length, 1);
+        bb.position(space -= length);
+        bb.put(arr);
+        return endVector();
+    }
+
    /// @cond FLATBUFFERS_INTERNAL
    /**
     * Should not be accessing the final buffer before it is finished.

tests/JavaTest.java

@@ -161,6 +161,10 @@ class JavaTest {
 
         TestNestedFlatBuffer();
 
+        TestCreateByteVector();
+
+        TestCreateUninitializedVector();
+
         System.out.println("FlatBuffers test: completed successfully");
     }
 
@@ -281,6 +285,44 @@ class JavaTest {
         TestEq(nestedMonsterName, nestedMonster.name());
     }
 
+    static void TestCreateByteVector() {
+        FlatBufferBuilder fbb = new FlatBufferBuilder(16);
+        int str = fbb.createString("MyMonster");
+        byte[] inventory = new byte[] { 0, 1, 2, 3, 4 };
+        int vec = fbb.createByteVector(inventory);
+        Monster.startMonster(fbb);
+        Monster.addInventory(fbb, vec);
+        Monster.addName(fbb, str);
+        int monster1 = Monster.endMonster(fbb);
+        Monster.finishMonsterBuffer(fbb, monster1);
+        Monster monsterObject = Monster.getRootAsMonster(fbb.dataBuffer());
+
+        TestEq(monsterObject.inventory(1), (int)inventory[1]);
+        TestEq(monsterObject.inventoryLength(), inventory.length);
+        TestEq(ByteBuffer.wrap(inventory), monsterObject.inventoryAsByteBuffer());
+    }
+
+    static void TestCreateUninitializedVector() {
+        FlatBufferBuilder fbb = new FlatBufferBuilder(16);
+        int str = fbb.createString("MyMonster");
+        byte[] inventory = new byte[] { 0, 1, 2, 3, 4 };
+        ByteBuffer bb = fbb.createUnintializedVector(1, inventory.length, 1);
+        for (byte i:inventory) {
+            bb.put(i);
+        }
+        int vec = fbb.endVector();
+        Monster.startMonster(fbb);
+        Monster.addInventory(fbb, vec);
+        Monster.addName(fbb, str);
+        int monster1 = Monster.endMonster(fbb);
+        Monster.finishMonsterBuffer(fbb, monster1);
+        Monster monsterObject = Monster.getRootAsMonster(fbb.dataBuffer());
+
+        TestEq(monsterObject.inventory(1), (int)inventory[1]);
+        TestEq(monsterObject.inventoryLength(), inventory.length);
+        TestEq(ByteBuffer.wrap(inventory), monsterObject.inventoryAsByteBuffer());
+    }
+
     static <T> void TestEq(T a, T b) {
         if (!a.equals(b)) {
             System.out.println("" + a.getClass().getName() + " " + b.getClass().getName());