Java: Added access object for vector of struct and vector of tables. (#5233)

* Java: Added access object for vector of struct and vector of tables.

* Java: Workarounds removed when accessing the union vector.

java/com/google/flatbuffers/BaseVector.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import java.nio.ByteBuffer;
+
+/// @cond FLATBUFFERS_INTERNAL
+
+/**
+ * All vector access objects derive from this class, and add their own accessors.
+ */
+public class BaseVector {
+  /** Used to hold the vector data position. */
+  private int vector;
+  /** Used to hold the vector size. */
+  private int length;
+  /** Used to hold the vector element size in table. */
+  private int element_size;
+  /** The underlying ByteBuffer to hold the data of the vector. */
+  protected ByteBuffer bb;
+
+  /**
+   * Get the start data of a vector.
+   *
+   * @return Returns the start of the vector data.
+   */
+  protected int __vector() {
+    return vector;
+  }
+
+  /**
+   * Gets the element position in vector's ByteBuffer.
+   *
+   * @param j An `int` index of element into a vector.
+   * @return Returns the position of the vector element in a ByteBuffer.
+   */
+  protected int __element(int j) {
+    return vector + j * element_size;
+  }
+
+  /**
+   * Re-init the internal state with an external buffer {@code ByteBuffer}, an offset within and
+   * element size.
+   *
+   * This method exists primarily to allow recycling vector instances without risking memory leaks
+   * due to {@code ByteBuffer} references.
+   */
+  protected void __reset(int _vector, int _element_size, ByteBuffer _bb) { 
+    bb = _bb;
+    if (bb != null) {
+      vector = _vector;
+      length = bb.getInt(_vector - Constants.SIZEOF_INT);
+      element_size = _element_size;
+    } else {
+      vector = 0;
+      length = 0;
+      element_size = 0;
+    }
+  }
+
+  /**
+   * Resets the internal state with a null {@code ByteBuffer} and a zero position.
+   *
+   * This method exists primarily to allow recycling vector instances without risking memory leaks
+   * due to {@code ByteBuffer} references. The instance will be unusable until it is assigned
+   * again to a {@code ByteBuffer}.
+   */
+  public void reset() {
+    __reset(0, 0, null);
+  }
+
+  /**
+   * Get the length of a vector.
+   *
+   * @return Returns the length of the vector.
+   */
+  public int length() {
+    return length;
+  }
+}
+
+/// @endcond

java/com/google/flatbuffers/BooleanVector.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import static com.google.flatbuffers.Constants.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * Helper type for accessing vector of booleans.
+ */
+public final class BooleanVector extends BaseVector {
+  /**
+   * Assigns vector access object to vector data.
+   *
+   * @param _vector Start data of a vector.
+   * @param _bb Table's ByteBuffer.
+   * @return Returns current vector access object assigned to vector data whose offset is stored at
+   *         `vector`.
+   */
+  public BooleanVector __assign(int _vector, ByteBuffer _bb) {
+    __reset(_vector, Constants.SIZEOF_BYTE, _bb); return this;
+  }
+
+  /**
+   * Reads the boolean at the given index.
+   *
+   * @param j The index from which the boolean will be read.
+   * @return the boolean value at the given index.
+   */
+  public boolean get(int j) { 
+    return 0 != bb.get(__element(j));
+  }
+}

java/com/google/flatbuffers/ByteVector.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import static com.google.flatbuffers.Constants.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * Helper type for accessing vector of signed or unsigned 8-bit values.
+ */
+public final class ByteVector extends BaseVector {
+  /**
+   * Assigns vector access object to vector data.
+   *
+   * @param vector Start data of a vector.
+   * @param bb Table's ByteBuffer.
+   * @return Returns current vector access object assigned to vector data whose offset is stored at
+   *         `vector`.
+   */
+  public ByteVector __assign(int vector, ByteBuffer bb) { 
+    __reset(vector, Constants.SIZEOF_BYTE, bb); return this;
+  }
+
+  /**
+   * Reads the byte at the given index.
+   *
+   * @param j The index from which the byte will be read.
+   * @return the 8-bit value at the given index.
+   */
+  public byte get(int j) {
+     return bb.get(__element(j));
+  }
+
+  /**
+   * Reads the byte at the given index, zero-extends it to type int, and returns the result,
+   * which is therefore in the range 0 through 255.
+   *
+   * @param j The index from which the byte will be read.
+   * @return the unsigned 8-bit at the given index.
+   */
+  public int getAsUnsigned(int j) {
+    return (int) get(j) & 0xFF;
+  }
+}

java/com/google/flatbuffers/DoubleVector.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import static com.google.flatbuffers.Constants.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * Helper type for accessing vector of double values.
+ */
+public final class DoubleVector extends BaseVector {
+  /**
+   * Assigns vector access object to vector data.
+   *
+   * @param _vector Start data of a vector.
+   * @param _bb Table's ByteBuffer.
+   * @return Returns current vector access object assigned to vector data whose offset is stored at
+   *         `vector`.
+   */
+  public DoubleVector __assign(int _vector, ByteBuffer _bb) {
+     __reset(_vector, Constants.SIZEOF_DOUBLE, _bb); return this;
+  }
+
+  /**
+   * Reads the double value at the given index.
+   *
+   * @param j The index from which the double value will be read.
+   * @return the double value at the given index.
+   */
+  public double get(int j) {
+    return bb.getDouble(__element(j));
+  }
+}

java/com/google/flatbuffers/FloatVector.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import static com.google.flatbuffers.Constants.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * Helper type for accessing vector of float values.
+ */
+public final class FloatVector extends BaseVector {
+  /**
+   * Assigns vector access object to vector data.
+   *
+   * @param _vector Start data of a vector.
+   * @param _bb Table's ByteBuffer.
+   * @return Returns current vector access object assigned to vector data whose offset is stored at
+   *         `vector`.
+   */
+  public FloatVector __assign(int _vector, ByteBuffer _bb) {
+    __reset(_vector, Constants.SIZEOF_FLOAT, _bb); return this;
+  }
+
+  /**
+   * Reads the float value at the given index.
+   *
+   * @param j The index from which the float value will be read.
+   * @return the float value at the given index.
+   */
+  public float get(int j) { 
+    return bb.getFloat(__element(j));
+  }
+}

java/com/google/flatbuffers/IntVector.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import static com.google.flatbuffers.Constants.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * Helper type for accessing vector of signed or unsigned 32-bit values.
+ */
+public final class IntVector extends BaseVector {
+  /**
+   * Assigns vector access object to vector data.
+   *
+   * @param _vector Start data of a vector.
+   * @param _bb Table's ByteBuffer.
+   * @return Returns current vector access object assigned to vector data whose offset is stored at
+   *         `vector`.
+   */
+  public IntVector __assign(int _vector, ByteBuffer _bb) {
+    __reset(_vector, Constants.SIZEOF_INT, _bb); return this;
+  }
+
+  /**
+   * Reads the integer at the given index.
+   *
+   * @param j The index from which the integer will be read.
+   * @return the 32-bit value at the given index.
+   */
+  public int get(int j) {
+    return bb.getInt(__element(j));
+  }
+
+  /**
+   * Reads the integer at the given index, zero-extends it to type long, and returns the result,
+   * which is therefore in the range 0 through 4294967295.
+   *
+   * @param j The index from which the integer will be read.
+   * @return the unsigned 32-bit at the given index.
+   */
+  public long getAsUnsigned(int j) {
+    return (long) get(j) & 0xFFFFFFFFL;
+  }
+}

java/com/google/flatbuffers/LongVector.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import static com.google.flatbuffers.Constants.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * Helper type for accessing vector of long values.
+ */
+public final class LongVector extends BaseVector {
+  /**
+   * Assigns vector access object to vector data.
+   *
+   * @param _vector Start data of a vector.
+   * @param _bb Table's ByteBuffer.
+   * @return Returns current vector access object assigned to vector data whose offset is stored at
+   *         `vector`.
+   */
+  public LongVector __assign(int _vector, ByteBuffer _bb) {
+    __reset(_vector, Constants.SIZEOF_LONG, _bb); return this;
+  }
+
+  /**
+   * Reads the long value at the given index.
+   *
+   * @param j The index from which the long value will be read.
+   * @return the signed 64-bit value at the given index.
+   */
+  public long get(int j) {
+    return bb.getLong(__element(j));
+  }
+}

java/com/google/flatbuffers/ShortVector.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import static com.google.flatbuffers.Constants.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * Helper type for accessing vector of signed or unsigned 16-bit values.
+ */
+public final class ShortVector extends BaseVector {
+  /**
+   * Assigns vector access object to vector data.
+   *
+   * @param _vector Start data of a vector.
+   * @param _bb Table's ByteBuffer.
+   * @return Returns current vector access object assigned to vector data whose offset is stored at
+   *         `vector`.
+   */
+  public ShortVector __assign(int _vector, ByteBuffer _bb) {
+    __reset(_vector, Constants.SIZEOF_SHORT, _bb); return this;
+  }
+
+  /**
+   * Reads the short value at the given index.
+   *
+   * @param j The index from which the short value will be read.
+   * @return the 16-bit value at the given index.
+   */
+  public short get(int j) {
+    return bb.getShort(__element(j));
+  }
+
+  /**
+   * Reads the short at the given index, zero-extends it to type int, and returns the result,
+   * which is therefore in the range 0 through 65535.
+   *
+   * @param j The index from which the short value will be read.
+   * @return the unsigned 16-bit at the given index.
+   */
+  public int getAsUnsigned(int j) {
+    return (int) get(j) & 0xFFFF;
+  }
+}

java/com/google/flatbuffers/StringVector.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import static com.google.flatbuffers.Constants.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * Helper type for accessing vector of String.
+ */
+public final class StringVector extends BaseVector {
+  private Utf8 utf8 = Utf8.getDefault();
+
+  /**
+   * Assigns vector access object to vector data.
+   *
+   * @param _vector Start data of a vector.
+   * @param _element_size Size of a vector element.
+   * @param _bb Table's ByteBuffer.
+   * @return Returns current vector access object assigned to vector data whose offset is stored at
+   *         `vector`.
+   */
+  public StringVector __assign(int _vector, int _element_size, ByteBuffer _bb) {
+    __reset(_vector, _element_size, _bb); return this;
+  }
+
+  /**
+   * Reads the String at the given index.
+   *
+   * @param j The index from which the String value will be read.
+   * @return the String at the given index.
+   */
+  public String get(int j) {
+    return Table.__string(__element(j), bb, utf8);
+  }
+}

java/com/google/flatbuffers/Table.java

@@ -75,6 +75,13 @@ public class Table {
     return offset + bb.getInt(offset);
   }
 
+  /**
+   * Retrieve a relative offset.
+   *
+   * @param offset An `int` index into a ByteBuffer containing the relative offset.
+   * @param bb from which the relative offset will be retrieved.
+   * @return Returns the relative offset stored at `offset`.
+   */
   protected static int __indirect(int offset, ByteBuffer bb) {
     return offset + bb.getInt(offset);
   }
@@ -91,6 +98,23 @@ public class Table {
    * @return Returns a `String` from the data stored inside the FlatBuffer at `offset`.
    */
   protected String __string(int offset) {
+    return __string(offset, bb, utf8);
+  }
+
+  /**
+   * Create a Java `String` from UTF-8 data stored inside the FlatBuffer.
+   *
+   * This allocates a new string and converts to wide chars upon each access,
+   * which is not very efficient. Instead, each FlatBuffer string also comes with an
+   * accessor based on __vector_as_bytebuffer below, which is much more efficient,
+   * assuming your Java program can handle UTF-8 data directly.
+   *
+   * @param offset An `int` index into the Table's ByteBuffer.
+   * @param bb Table ByteBuffer used to read a string at given offset.
+   * @param utf8 decoder that creates a Java `String` from UTF-8 characters.
+   * @return Returns a `String` from the data stored inside the FlatBuffer at `offset`.
+   */
+  protected static String __string(int offset, ByteBuffer bb, Utf8 utf8) {
     offset += bb.getInt(offset);
     int length = bb.getInt(offset);
     return utf8.decodeUtf8(bb, offset + SIZEOF_INT, length);
@@ -169,11 +193,19 @@ public class Table {
    * @return Returns the Table that points to the union at `offset`.
    */
   protected Table __union(Table t, int offset) {
-    offset += bb_pos;
-    t.bb_pos = offset + bb.getInt(offset);
-    t.bb = bb;
-    t.vtable_start = t.bb_pos - bb.getInt(t.bb_pos);
-    t.vtable_size = bb.getShort(t.vtable_start);
+    return __union(t, offset, bb);
+  }
+
+  /**
+   * Initialize any Table-derived type to point to the union at the given `offset`.
+   *
+   * @param t A `Table`-derived type that should point to the union at `offset`.
+   * @param offset An `int` index into the Table's ByteBuffer.
+   * @param bb Table ByteBuffer used to initialize the object Table-derived type.
+   * @return Returns the Table that points to the union at `offset`.
+   */
+  protected static Table __union(Table t, int offset, ByteBuffer bb) {
+    t.__reset(__indirect(offset, bb), bb);
     return t;
   }
 

java/com/google/flatbuffers/UnionVector.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import static com.google.flatbuffers.Constants.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * Helper type for accessing vector of unions.
+ */
+public final class UnionVector extends BaseVector {
+  /**
+   * Assigns vector access object to vector data.
+   *
+   * @param _vector Start data of a vector.
+   * @param _element_size Size of a vector element.
+   * @param _bb Table's ByteBuffer.
+   * @return Returns current vector access object assigned to vector data whose offset is stored at
+   *         `vector`.
+   */
+  public UnionVector __assign(int _vector, int _element_size, ByteBuffer _bb) {
+    __reset(_vector, _element_size, _bb); return this;
+  }
+
+
+  /**
+   * Initialize any Table-derived type to point to the union at the given `index`.
+   *
+   * @param obj A `Table`-derived type that should point to the union at `index`.
+   * @param j An `int` index into the union vector.
+   * @return Returns the Table that points to the union at `index`.
+   */
+  public Table get(Table obj, int j) {
+    return Table.__union(obj, __element(j), bb);
+  }
+}