com.google.flatbuffers.Table Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of flatbuffers-java Show documentation
Show all versions of flatbuffers-java Show documentation
Memory Efficient Serialization Library
/*
* 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;
/// @cond FLATBUFFERS_INTERNAL
/**
* All tables in the generated code derive from this class, and add their own accessors.
*/
public class Table {
/** 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;
/** Used to hold the vtable position. */
private int vtable_start;
/** Used to hold the vtable size. */
private int vtable_size;
Utf8 utf8 = Utf8.getDefault();
/**
* 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) {
return vtable_offset < vtable_size ? bb.getShort(vtable_start + vtable_offset) : 0;
}
protected static int __offset(int vtable_offset, int offset, ByteBuffer bb) {
int vtable = bb.capacity() - offset;
return bb.getShort(vtable + vtable_offset - bb.getInt(vtable)) + vtable;
}
/**
* 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);
}
/**
* 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);
}
/**
* 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) {
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);
}
/**
* 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 vector as a ByteBuffer.
*
* This is more efficient than using duplicate, since it doesn't copy the data
* nor allocattes a new {@link ByteBuffer}, creating no garbage to be collected.
*
* @param bb The {@link ByteBuffer} for the array
* @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_in_bytebuffer(ByteBuffer bb, int vector_offset, int elem_size) {
int o = this.__offset(vector_offset);
if (o == 0) return null;
int vectorstart = __vector(o);
bb.rewind();
bb.limit(vectorstart + __vector_len(o) * elem_size);
bb.position(vectorstart);
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) {
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;
}
/**
* 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;
}
/**
* Sort tables by the key.
*
* @param offsets An 'int' indexes of the tables into the bb.
* @param bb A {@code ByteBuffer} to get the tables.
*/
protected void sortTables(int[] offsets, final ByteBuffer bb) {
Integer[] off = new Integer[offsets.length];
for (int i = 0; i < offsets.length; i++) off[i] = offsets[i];
java.util.Arrays.sort(off, new java.util.Comparator() {
public int compare(Integer o1, Integer o2) {
return keysCompare(o1, o2, bb);
}
});
for (int i = 0; i < offsets.length; i++) offsets[i] = off[i];
}
/**
* Compare two tables by the key.
*
* @param o1 An 'Integer' index of the first key into the bb.
* @param o2 An 'Integer' index of the second key into the bb.
* @param bb A {@code ByteBuffer} to get the keys.
*/
protected int keysCompare(Integer o1, Integer o2, ByteBuffer bb) { return 0; }
/**
* Compare two strings in the buffer.
*
* @param offset_1 An 'int' index of the first string into the bb.
* @param offset_2 An 'int' index of the second string into the bb.
* @param bb A {@code ByteBuffer} to get the strings.
*/
protected static int compareStrings(int offset_1, int offset_2, ByteBuffer bb) {
offset_1 += bb.getInt(offset_1);
offset_2 += bb.getInt(offset_2);
int len_1 = bb.getInt(offset_1);
int len_2 = bb.getInt(offset_2);
int startPos_1 = offset_1 + SIZEOF_INT;
int startPos_2 = offset_2 + SIZEOF_INT;
int len = Math.min(len_1, len_2);
for(int i = 0; i < len; i++) {
if (bb.get(i + startPos_1) != bb.get(i + startPos_2))
return bb.get(i + startPos_1) - bb.get(i + startPos_2);
}
return len_1 - len_2;
}
/**
* Compare string from the buffer with the 'String' object.
*
* @param offset_1 An 'int' index of the first string into the bb.
* @param key Second string as a byte array.
* @param bb A {@code ByteBuffer} to get the first string.
*/
protected static int compareStrings(int offset_1, byte[] key, ByteBuffer bb) {
offset_1 += bb.getInt(offset_1);
int len_1 = bb.getInt(offset_1);
int len_2 = key.length;
int startPos_1 = offset_1 + Constants.SIZEOF_INT;
int len = Math.min(len_1, len_2);
for (int i = 0; i < len; i++) {
if (bb.get(i + startPos_1) != key[i])
return bb.get(i + startPos_1) - key[i];
}
return len_1 - len_2;
}
/**
* Re-init the internal state with an external buffer {@code ByteBuffer} and an offset within.
*
* This method exists primarily to allow recycling Table instances without risking memory leaks
* due to {@code ByteBuffer} references.
*/
protected void __reset(int _i, ByteBuffer _bb) {
bb = _bb;
if (bb != null) {
bb_pos = _i;
vtable_start = bb_pos - bb.getInt(bb_pos);
vtable_size = bb.getShort(vtable_start);
} else {
bb_pos = 0;
vtable_start = 0;
vtable_size = 0;
}
}
/**
* Resets the internal state with a null {@code ByteBuffer} and a zero position.
*
* This method exists primarily to allow recycling Table 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, null);
}
}
/// @endcond
© 2015 - 2024 Weber Informatics LLC | Privacy Policy