/*

* Copyright 2014 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.CharBuffer;

import java.nio.charset.CharacterCodingException;

import java.nio.charset.Charset;

import java.nio.charset.CharsetDecoder;

import java.nio.charset.CoderResult;

/// @cond FLATBUFFERS_INTERNAL

/**

* All tables in the generated code derive from this class, and add their own accessors.

*/

public class Table {

private final static ThreadLocal<CharsetDecoder> UTF8_DECODER = new ThreadLocal<CharsetDecoder>() {

@Override

protected CharsetDecoder initialValue() {

return Charset.forName("UTF-8").newDecoder();

}

};

private final static ThreadLocal<CharBuffer> CHAR_BUFFER = new ThreadLocal<CharBuffer>();

/** Used to hold the position of the `bb` buffer. */

protected int bb_pos;

/** The underlying ByteBuffer to hold the data of the Table. */

protected ByteBuffer bb;

/**

* Get the underlying ByteBuffer.

*

* @return Returns the Table's ByteBuffer.

*/

public ByteBuffer getByteBuffer() { return bb; }

/**

* Look up a field in the vtable.

*

* @param vtable_offset An `int` offset to the vtable in the Table's ByteBuffer.

* @return Returns an offset into the object, or `0` if the field is not present.

*/

protected int __offset(int vtable_offset) {

int vtable = bb_pos - bb.getInt(bb_pos);

return vtable_offset < bb.getShort(vtable) ? bb.getShort(vtable + vtable_offset) : 0;

}

/**

* Retrieve a relative offset.

*

* @param offset An `int` index into the Table's ByteBuffer containing the relative offset.

* @return Returns the relative offset stored at `offset`.

*/

protected int __indirect(int offset) {

return offset + bb.getInt(offset);

}

/**

* 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.

* @return Returns a `String` from the data stored inside the FlatBuffer at `offset`.

*/

protected String __string(int offset) {

CharsetDecoder decoder = UTF8_DECODER.get();

decoder.reset();

offset += bb.getInt(offset);

ByteBuffer src = bb.duplicate().order(ByteOrder.LITTLE_ENDIAN);

int length = src.getInt(offset);

src.position(offset + SIZEOF_INT);

src.limit(offset + SIZEOF_INT + length);

int required = (int)((float)length * decoder.maxCharsPerByte());

CharBuffer dst = CHAR_BUFFER.get();

if (dst == null || dst.capacity() < required) {

dst = CharBuffer.allocate(required);

CHAR_BUFFER.set(dst);

}

dst.clear();

try {

CoderResult cr = decoder.decode(src, dst, true);

if (!cr.isUnderflow()) {

cr.throwException();

}

} catch (CharacterCodingException x) {

throw new Error(x);

}

return dst.flip().toString();

}

/**

* Get the length of a vector.

*

* @param offset An `int` index into the Table's ByteBuffer.

* @return Returns the length of the vector whose offset is stored at `offset`.

*/

protected int __vector_len(int offset) {

offset += bb_pos;

offset += bb.getInt(offset);

return bb.getInt(offset);

}

/**

* Get the start data of a vector.

*

* @param offset An `int` index into the Table's ByteBuffer.

* @return Returns the start of the vector data whose offset is stored at `offset`.

*/

protected int __vector(int offset) {

offset += bb_pos;

return offset + bb.getInt(offset) + SIZEOF_INT; // data starts after the length

}

/**

* Get a whole vector as a ByteBuffer.

*

* This is efficient, since it only allocates a new {@link ByteBuffer} object,

* but does not actually copy the data, it still refers to the same bytes

* as the original ByteBuffer. Also useful with nested FlatBuffers, etc.

*

* @param vector_offset The position of the vector in the byte buffer

* @param elem_size The size of each element in the array

* @return The {@link ByteBuffer} for the array

*/

protected ByteBuffer __vector_as_bytebuffer(int vector_offset, int elem_size) {

int o = __offset(vector_offset);

if (o == 0) return null;

ByteBuffer bb = this.bb.duplicate().order(ByteOrder.LITTLE_ENDIAN);

int vectorstart = __vector(o);

bb.position(vectorstart);

bb.limit(vectorstart + __vector_len(o) * elem_size);

return 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.

* @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;

return t;

}

/**

* Check if a {@link ByteBuffer} contains a file identifier.

*

* @param bb A {@code ByteBuffer} to check if it contains the identifier

* `ident`.

* @param ident A `String` identifier of the FlatBuffer file.

* @return True if the buffer contains the file identifier

*/

protected static boolean __has_identifier(ByteBuffer bb, String ident) {

if (ident.length() != FILE_IDENTIFIER_LENGTH)

throw new AssertionError("FlatBuffers: file identifier must be length " +

FILE_IDENTIFIER_LENGTH);

for (int i = 0; i < FILE_IDENTIFIER_LENGTH; i++) {

if (ident.charAt(i) != (char)bb.get(bb.position() + SIZEOF_INT + i)) return false;

}

return true;

}

}

/// @endcond