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/*
* 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.io.IOException;
import java.io.InputStream;
import java.nio.*;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.lang.Integer;
/// @file
/// @addtogroup flatbuffers_java_api
/// @{
/**
* Class that helps you build a FlatBuffer. See the section
* "Use in Java/C#" in the main FlatBuffers documentation.
*/
public class FlatBufferBuilder {
/// @cond FLATBUFFERS_INTERNAL
ByteBuffer bb; // Where we construct the FlatBuffer.
int space; // Remaining space in the ByteBuffer.
int minalign = 1; // Minimum alignment encountered so far.
int[] vtable = null; // The vtable for the current table.
int vtable_in_use = 0; // The amount of fields we're actually using.
boolean nested = false; // Whether we are currently serializing a table.
boolean finished = false; // Whether the buffer is finished.
int object_start; // Starting offset of the current struct/table.
int[] vtables = new int[16]; // List of offsets of all vtables.
int num_vtables = 0; // Number of entries in `vtables` in use.
int vector_num_elems = 0; // For the current vector being built.
boolean force_defaults = false; // False omits default values from the serialized data.
ByteBufferFactory bb_factory; // Factory for allocating the internal buffer
final Utf8 utf8; // UTF-8 encoder to use
Map string_pool; // map used to cache shared strings.
/// @endcond
/**
* Maximum size of buffer to allocate. If we're allocating arrays on the heap,
* the header size of the array counts towards its maximum size.
*/
private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
/**
* Default buffer size that is allocated if an initial size is not given, or is
* non positive.
*/
private static final int DEFAULT_BUFFER_SIZE = 1024;
/**
* Start with a buffer of size `initial_size`, then grow as required.
*
* @param initial_size The initial size of the internal buffer to use.
* @param bb_factory The factory to be used for allocating the internal buffer
*/
public FlatBufferBuilder(int initial_size, ByteBufferFactory bb_factory) {
this(initial_size, bb_factory, null, Utf8.getDefault());
}
/**
* Start with a buffer of size `initial_size`, then grow as required.
*
* @param initial_size The initial size of the internal buffer to use.
* @param bb_factory The factory to be used for allocating the internal buffer
* @param existing_bb The byte buffer to reuse.
* @param utf8 The Utf8 codec
*/
public FlatBufferBuilder(int initial_size, ByteBufferFactory bb_factory,
ByteBuffer existing_bb, Utf8 utf8) {
if (initial_size <= 0) {
initial_size = DEFAULT_BUFFER_SIZE;
}
this.bb_factory = bb_factory;
if (existing_bb != null) {
bb = existing_bb;
bb.clear();
bb.order(ByteOrder.LITTLE_ENDIAN);
} else {
bb = bb_factory.newByteBuffer(initial_size);
}
this.utf8 = utf8;
space = bb.capacity();
}
/**
* Start with a buffer of size `initial_size`, then grow as required.
*
* @param initial_size The initial size of the internal buffer to use.
*/
public FlatBufferBuilder(int initial_size) {
this(initial_size, HeapByteBufferFactory.INSTANCE, null, Utf8.getDefault());
}
/**
* Start with a buffer of 1KiB, then grow as required.
*/
public FlatBufferBuilder() {
this(DEFAULT_BUFFER_SIZE);
}
/**
* Alternative constructor allowing reuse of {@link ByteBuffer}s. The builder
* can still grow the buffer as necessary. User classes should make sure
* to call {@link #dataBuffer()} to obtain the resulting encoded message.
*
* @param existing_bb The byte buffer to reuse.
* @param bb_factory The factory to be used for allocating a new internal buffer if
* the existing buffer needs to grow
*/
public FlatBufferBuilder(ByteBuffer existing_bb, ByteBufferFactory bb_factory) {
this(existing_bb.capacity(), bb_factory, existing_bb, Utf8.getDefault());
}
/**
* Alternative constructor allowing reuse of {@link ByteBuffer}s. The builder
* can still grow the buffer as necessary. User classes should make sure
* to call {@link #dataBuffer()} to obtain the resulting encoded message.
*
* @param existing_bb The byte buffer to reuse.
*/
public FlatBufferBuilder(ByteBuffer existing_bb) {
this(existing_bb, new HeapByteBufferFactory());
}
/**
* Alternative initializer that allows reusing this object on an existing
* `ByteBuffer`. This method resets the builder's internal state, but keeps
* objects that have been allocated for temporary storage.
*
* @param existing_bb The byte buffer to reuse.
* @param bb_factory The factory to be used for allocating a new internal buffer if
* the existing buffer needs to grow
* @return Returns `this`.
*/
public FlatBufferBuilder init(ByteBuffer existing_bb, ByteBufferFactory bb_factory){
this.bb_factory = bb_factory;
bb = existing_bb;
bb.clear();
bb.order(ByteOrder.LITTLE_ENDIAN);
minalign = 1;
space = bb.capacity();
vtable_in_use = 0;
nested = false;
finished = false;
object_start = 0;
num_vtables = 0;
vector_num_elems = 0;
if (string_pool != null) {
string_pool.clear();
}
return this;
}
/**
* An interface that provides a user of the FlatBufferBuilder class the ability to specify
* the method in which the internal buffer gets allocated. This allows for alternatives
* to the default behavior, which is to allocate memory for a new byte-array
* backed `ByteBuffer` array inside the JVM.
*
* The FlatBufferBuilder class contains the HeapByteBufferFactory class to
* preserve the default behavior in the event that the user does not provide
* their own implementation of this interface.
*/
public static abstract class ByteBufferFactory {
/**
* Create a `ByteBuffer` with a given capacity.
* The returned ByteBuf must have a ByteOrder.LITTLE_ENDIAN ByteOrder.
*
* @param capacity The size of the `ByteBuffer` to allocate.
* @return Returns the new `ByteBuffer` that was allocated.
*/
public abstract ByteBuffer newByteBuffer(int capacity);
/**
* Release a ByteBuffer. Current {@link FlatBufferBuilder}
* released any reference to it, so it is safe to dispose the buffer
* or return it to a pool.
* It is not guaranteed that the buffer has been created
* with {@link #newByteBuffer(int) }.
*
* @param bb the buffer to release
*/
public void releaseByteBuffer(ByteBuffer bb) {
}
}
/**
* An implementation of the ByteBufferFactory interface that is used when
* one is not provided by the user.
*
* Allocate memory for a new byte-array backed `ByteBuffer` array inside the JVM.
*/
public static final class HeapByteBufferFactory extends ByteBufferFactory {
public static final HeapByteBufferFactory INSTANCE = new HeapByteBufferFactory();
@Override
public ByteBuffer newByteBuffer(int capacity) {
return ByteBuffer.allocate(capacity).order(ByteOrder.LITTLE_ENDIAN);
}
}
/**
* Helper function to test if a field is present in the table
*
* @param table Flatbuffer table
* @param offset virtual table offset
* @return true if the filed is present
*/
public static boolean isFieldPresent(Table table, int offset) {
return table.__offset(offset) != 0;
}
/**
* Reset the FlatBufferBuilder by purging all data that it holds.
*/
public void clear(){
space = bb.capacity();
bb.clear();
minalign = 1;
while(vtable_in_use > 0) vtable[--vtable_in_use] = 0;
vtable_in_use = 0;
nested = false;
finished = false;
object_start = 0;
num_vtables = 0;
vector_num_elems = 0;
if (string_pool != null) {
string_pool.clear();
}
}
/**
* Doubles the size of the backing {@link ByteBuffer} and copies the old data towards the
* end of the new buffer (since we build the buffer backwards).
*
* @param bb The current buffer with the existing data.
* @param bb_factory The factory to be used for allocating the new internal buffer
* @return A new byte buffer with the old data copied copied to it. The data is
* located at the end of the buffer.
*/
static ByteBuffer growByteBuffer(ByteBuffer bb, ByteBufferFactory bb_factory) {
int old_buf_size = bb.capacity();
int new_buf_size;
if (old_buf_size == 0) {
new_buf_size = DEFAULT_BUFFER_SIZE;
}
else {
if (old_buf_size == MAX_BUFFER_SIZE) { // Ensure we don't grow beyond what fits in an int.
throw new AssertionError("FlatBuffers: cannot grow buffer beyond 2 gigabytes.");
}
new_buf_size = (old_buf_size & 0xC0000000) != 0 ? MAX_BUFFER_SIZE : old_buf_size << 1;
}
bb.position(0);
ByteBuffer nbb = bb_factory.newByteBuffer(new_buf_size);
new_buf_size = nbb.clear().capacity(); // Ensure the returned buffer is treated as empty
nbb.position(new_buf_size - old_buf_size);
nbb.put(bb);
return nbb;
}
/**
* Offset relative to the end of the buffer.
*
* @return Offset relative to the end of the buffer.
*/
public int offset() {
return bb.capacity() - space;
}
/**
* Add zero valued bytes to prepare a new entry to be added.
*
* @param byte_size Number of bytes to add.
*/
public void pad(int byte_size) {
for (int i = 0; i < byte_size; i++) bb.put(--space, (byte)0);
}
/**
* Prepare to write an element of `size` after `additional_bytes`
* have been written, e.g. if you write a string, you need to align such
* the int length field is aligned to {@link com.google.flatbuffers.Constants#SIZEOF_INT}, and
* the string data follows it directly. If all you need to do is alignment, `additional_bytes`
* will be 0.
*
* @param size This is the of the new element to write.
* @param additional_bytes The padding size.
*/
public void prep(int size, int additional_bytes) {
// Track the biggest thing we've ever aligned to.
if (size > minalign) minalign = size;
// Find the amount of alignment needed such that `size` is properly
// aligned after `additional_bytes`
int align_size = ((~(bb.capacity() - space + additional_bytes)) + 1) & (size - 1);
// Reallocate the buffer if needed.
while (space < align_size + size + additional_bytes) {
int old_buf_size = bb.capacity();
ByteBuffer old = bb;
bb = growByteBuffer(old, bb_factory);
if (old != bb) {
bb_factory.releaseByteBuffer(old);
}
space += bb.capacity() - old_buf_size;
}
pad(align_size);
}
/**
* Add a `boolean` to the buffer, backwards from the current location. Doesn't align nor
* check for space.
*
* @param x A `boolean` to put into the buffer.
*/
public void putBoolean(boolean x) { bb.put (space -= Constants.SIZEOF_BYTE, (byte)(x ? 1 : 0)); }
/**
* Add a `byte` to the buffer, backwards from the current location. Doesn't align nor
* check for space.
*
* @param x A `byte` to put into the buffer.
*/
public void putByte (byte x) { bb.put (space -= Constants.SIZEOF_BYTE, x); }
/**
* Add a `short` to the buffer, backwards from the current location. Doesn't align nor
* check for space.
*
* @param x A `short` to put into the buffer.
*/
public void putShort (short x) { bb.putShort (space -= Constants.SIZEOF_SHORT, x); }
/**
* Add an `int` to the buffer, backwards from the current location. Doesn't align nor
* check for space.
*
* @param x An `int` to put into the buffer.
*/
public void putInt (int x) { bb.putInt (space -= Constants.SIZEOF_INT, x); }
/**
* Add a `long` to the buffer, backwards from the current location. Doesn't align nor
* check for space.
*
* @param x A `long` to put into the buffer.
*/
public void putLong (long x) { bb.putLong (space -= Constants.SIZEOF_LONG, x); }
/**
* Add a `float` to the buffer, backwards from the current location. Doesn't align nor
* check for space.
*
* @param x A `float` to put into the buffer.
*/
public void putFloat (float x) { bb.putFloat (space -= Constants.SIZEOF_FLOAT, x); }
/**
* Add a `double` to the buffer, backwards from the current location. Doesn't align nor
* check for space.
*
* @param x A `double` to put into the buffer.
*/
public void putDouble (double x) { bb.putDouble(space -= Constants.SIZEOF_DOUBLE, x); }
/// @endcond
/**
* Add a `boolean` to the buffer, properly aligned, and grows the buffer (if necessary).
*
* @param x A `boolean` to put into the buffer.
*/
public void addBoolean(boolean x) { prep(Constants.SIZEOF_BYTE, 0); putBoolean(x); }
/**
* Add a `byte` to the buffer, properly aligned, and grows the buffer (if necessary).
*
* @param x A `byte` to put into the buffer.
*/
public void addByte (byte x) { prep(Constants.SIZEOF_BYTE, 0); putByte (x); }
/**
* Add a `short` to the buffer, properly aligned, and grows the buffer (if necessary).
*
* @param x A `short` to put into the buffer.
*/
public void addShort (short x) { prep(Constants.SIZEOF_SHORT, 0); putShort (x); }
/**
* Add an `int` to the buffer, properly aligned, and grows the buffer (if necessary).
*
* @param x An `int` to put into the buffer.
*/
public void addInt (int x) { prep(Constants.SIZEOF_INT, 0); putInt (x); }
/**
* Add a `long` to the buffer, properly aligned, and grows the buffer (if necessary).
*
* @param x A `long` to put into the buffer.
*/
public void addLong (long x) { prep(Constants.SIZEOF_LONG, 0); putLong (x); }
/**
* Add a `float` to the buffer, properly aligned, and grows the buffer (if necessary).
*
* @param x A `float` to put into the buffer.
*/
public void addFloat (float x) { prep(Constants.SIZEOF_FLOAT, 0); putFloat (x); }
/**
* Add a `double` to the buffer, properly aligned, and grows the buffer (if necessary).
*
* @param x A `double` to put into the buffer.
*/
public void addDouble (double x) { prep(Constants.SIZEOF_DOUBLE, 0); putDouble (x); }
/**
* Adds on offset, relative to where it will be written.
*
* @param off The offset to add.
*/
public void addOffset(int off) {
prep(SIZEOF_INT, 0); // Ensure alignment is already done.
assert off <= offset();
off = offset() - off + SIZEOF_INT;
putInt(off);
}
/// @cond FLATBUFFERS_INTERNAL
/**
* Start a new array/vector of objects. Users usually will not call
* this directly. The `FlatBuffers` compiler will create a start/end
* method for vector types in generated code.
*
* The expected sequence of calls is:
*
* - Start the array using this method.
* - Call {@link #addOffset(int)} `num_elems` number of times to set
* the offset of each element in the array.
* - Call {@link #endVector()} to retrieve the offset of the array.
*
*
* For example, to create an array of strings, do:
*
{@code
* // Need 10 strings
* FlatBufferBuilder builder = new FlatBufferBuilder(existingBuffer);
* int[] offsets = new int[10];
*
* for (int i = 0; i < 10; i++) {
* offsets[i] = fbb.createString(" " + i);
* }
*
* // Have the strings in the buffer, but don't have a vector.
* // Add a vector that references the newly created strings:
* builder.startVector(4, offsets.length, 4);
*
* // Add each string to the newly created vector
* // The strings are added in reverse order since the buffer
* // is filled in back to front
* for (int i = offsets.length - 1; i >= 0; i--) {
* builder.addOffset(offsets[i]);
* }
*
* // Finish off the vector
* int offsetOfTheVector = fbb.endVector();
* }
*
* @param elem_size The size of each element in the array.
* @param num_elems The number of elements in the array.
* @param alignment The alignment of the array.
*/
public void startVector(int elem_size, int num_elems, int alignment) {
notNested();
vector_num_elems = num_elems;
prep(SIZEOF_INT, elem_size * num_elems);
prep(alignment, elem_size * num_elems); // Just in case alignment > int.
nested = true;
}
/**
* Finish off the creation of an array and all its elements. The array
* must be created with {@link #startVector(int, int, int)}.
*
* @return The offset at which the newly created array starts.
* @see #startVector(int, int, int)
*/
public int endVector() {
if (!nested)
throw new AssertionError("FlatBuffers: endVector called without startVector");
nested = false;
putInt(vector_num_elems);
return offset();
}
/// @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;
}
/**
* Create a vector of tables.
*
* @param offsets Offsets of the tables.
* @return Returns offset of the vector.
*/
public int createVectorOfTables(int[] offsets) {
notNested();
startVector(Constants.SIZEOF_INT, offsets.length, Constants.SIZEOF_INT);
for(int i = offsets.length - 1; i >= 0; i--) addOffset(offsets[i]);
return endVector();
}
/**
* Create a vector of sorted by the key tables.
*
* @param obj Instance of the table subclass.
* @param offsets Offsets of the tables.
* @return Returns offset of the sorted vector.
*/
public int createSortedVectorOfTables(T obj, int[] offsets) {
obj.sortTables(offsets, bb);
return createVectorOfTables(offsets);
}
/**
* Encode the String `s` in the buffer using UTF-8. If a String with
* this exact contents has already been serialized using this method,
* instead simply returns the offset of the existing String.
*
* Usage of the method will incur into additional allocations,
* so it is advisable to use it only when it is known upfront that
* your message will have several repeated strings.
*
* @param s The String to encode.
* @return The offset in the buffer where the encoded String starts.
*/
public int createSharedString(String s) {
if (string_pool == null) {
string_pool = new HashMap<>();
int offset = createString(s);
string_pool.put(s, offset);
return offset;
}
Integer offset = string_pool.get(s);
if(offset == null) {
offset = createString(s);
string_pool.put(s, offset);
}
return offset;
}
/**
* Encode the string `s` in the buffer using UTF-8. If {@code s} is
* already a {@link CharBuffer}, this method is allocation free.
*
* @param s The string to encode.
* @return The offset in the buffer where the encoded string starts.
*/
public int createString(CharSequence s) {
int length = utf8.encodedLength(s);
addByte((byte)0);
startVector(1, length, 1);
bb.position(space -= length);
utf8.encodeUtf8(s, bb);
return endVector();
}
/**
* Create a string in the buffer from an already encoded UTF-8 string in a ByteBuffer.
*
* @param s An already encoded UTF-8 string as a `ByteBuffer`.
* @return The offset in the buffer where the encoded string starts.
*/
public int createString(ByteBuffer s) {
int length = s.remaining();
addByte((byte)0);
startVector(1, length, 1);
bb.position(space -= length);
bb.put(s);
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();
}
/**
* Create a byte array in the buffer.
*
* @param arr a source array with data.
* @param offset the offset in the source array to start copying from.
* @param length the number of bytes to copy from the source array.
* @return The offset in the buffer where the encoded array starts.
*/
public int createByteVector(byte[] arr, int offset, int length) {
startVector(1, length, 1);
bb.position(space -= length);
bb.put(arr, offset, length);
return endVector();
}
/**
* Create a byte array in the buffer.
*
* The source {@link ByteBuffer} position is advanced by {@link ByteBuffer#remaining()} places
* after this call.
*
* @param byteBuffer A source {@link ByteBuffer} with data.
* @return The offset in the buffer where the encoded array starts.
*/
public int createByteVector(ByteBuffer byteBuffer) {
int length = byteBuffer.remaining();
startVector(1, length, 1);
bb.position(space -= length);
bb.put(byteBuffer);
return endVector();
}
/// @cond FLATBUFFERS_INTERNAL
/**
* Should not be accessing the final buffer before it is finished.
*/
public void finished() {
if (!finished)
throw new AssertionError(
"FlatBuffers: you can only access the serialized buffer after it has been" +
" finished by FlatBufferBuilder.finish().");
}
/**
* Should not be creating any other object, string or vector
* while an object is being constructed.
*/
public void notNested() {
if (nested)
throw new AssertionError("FlatBuffers: object serialization must not be nested.");
}
/**
* Structures are always stored inline, they need to be created right
* where they're used. You'll get this assertion failure if you
* created it elsewhere.
*
* @param obj The offset of the created object.
*/
public void Nested(int obj) {
if (obj != offset())
throw new AssertionError("FlatBuffers: struct must be serialized inline.");
}
/**
* Start encoding a new object in the buffer. Users will not usually need to
* call this directly. The `FlatBuffers` compiler will generate helper methods
* that call this method internally.
*
* For example, using the "Monster" code found on the "landing page". An
* object of type `Monster` can be created using the following code:
*
*
{@code
* int testArrayOfString = Monster.createTestarrayofstringVector(fbb, new int[] {
* fbb.createString("test1"),
* fbb.createString("test2")
* });
*
* Monster.startMonster(fbb);
* Monster.addPos(fbb, Vec3.createVec3(fbb, 1.0f, 2.0f, 3.0f, 3.0,
* Color.Green, (short)5, (byte)6));
* Monster.addHp(fbb, (short)80);
* Monster.addName(fbb, str);
* Monster.addInventory(fbb, inv);
* Monster.addTestType(fbb, (byte)Any.Monster);
* Monster.addTest(fbb, mon2);
* Monster.addTest4(fbb, test4);
* Monster.addTestarrayofstring(fbb, testArrayOfString);
* int mon = Monster.endMonster(fbb);
* }
*
* Here:
*
* - The call to `Monster#startMonster(FlatBufferBuilder)` will call this
* method with the right number of fields set.
* - `Monster#endMonster(FlatBufferBuilder)` will ensure {@link #endObject()} is called.
*
*
* It's not recommended to call this method directly. If it's called manually, you must ensure
* to audit all calls to it whenever fields are added or removed from your schema. This is
* automatically done by the code generated by the `FlatBuffers` compiler.
*
* @param numfields The number of fields found in this object.
*/
public void startTable(int numfields) {
notNested();
if (vtable == null || vtable.length < numfields) vtable = new int[numfields];
vtable_in_use = numfields;
Arrays.fill(vtable, 0, vtable_in_use, 0);
nested = true;
object_start = offset();
}
/**
* Add a `boolean` to a table at `o` into its vtable, with value `x` and default `d`.
*
* @param o The index into the vtable.
* @param x A `boolean` to put into the buffer, depending on how defaults are handled. If
* `force_defaults` is `false`, compare `x` against the default value `d`. If `x` contains the
* default value, it can be skipped.
* @param d A `boolean` default value to compare against when `force_defaults` is `false`.
*/
public void addBoolean(int o, boolean x, boolean d) { if(force_defaults || x != d) { addBoolean(x); slot(o); } }
/**
* Add a `byte` to a table at `o` into its vtable, with value `x` and default `d`.
*
* @param o The index into the vtable.
* @param x A `byte` to put into the buffer, depending on how defaults are handled. If
* `force_defaults` is `false`, compare `x` against the default value `d`. If `x` contains the
* default value, it can be skipped.
* @param d A `byte` default value to compare against when `force_defaults` is `false`.
*/
public void addByte (int o, byte x, int d) { if(force_defaults || x != d) { addByte (x); slot(o); } }
/**
* Add a `short` to a table at `o` into its vtable, with value `x` and default `d`.
*
* @param o The index into the vtable.
* @param x A `short` to put into the buffer, depending on how defaults are handled. If
* `force_defaults` is `false`, compare `x` against the default value `d`. If `x` contains the
* default value, it can be skipped.
* @param d A `short` default value to compare against when `force_defaults` is `false`.
*/
public void addShort (int o, short x, int d) { if(force_defaults || x != d) { addShort (x); slot(o); } }
/**
* Add an `int` to a table at `o` into its vtable, with value `x` and default `d`.
*
* @param o The index into the vtable.
* @param x An `int` to put into the buffer, depending on how defaults are handled. If
* `force_defaults` is `false`, compare `x` against the default value `d`. If `x` contains the
* default value, it can be skipped.
* @param d An `int` default value to compare against when `force_defaults` is `false`.
*/
public void addInt (int o, int x, int d) { if(force_defaults || x != d) { addInt (x); slot(o); } }
/**
* Add a `long` to a table at `o` into its vtable, with value `x` and default `d`.
*
* @param o The index into the vtable.
* @param x A `long` to put into the buffer, depending on how defaults are handled. If
* `force_defaults` is `false`, compare `x` against the default value `d`. If `x` contains the
* default value, it can be skipped.
* @param d A `long` default value to compare against when `force_defaults` is `false`.
*/
public void addLong (int o, long x, long d) { if(force_defaults || x != d) { addLong (x); slot(o); } }
/**
* Add a `float` to a table at `o` into its vtable, with value `x` and default `d`.
*
* @param o The index into the vtable.
* @param x A `float` to put into the buffer, depending on how defaults are handled. If
* `force_defaults` is `false`, compare `x` against the default value `d`. If `x` contains the
* default value, it can be skipped.
* @param d A `float` default value to compare against when `force_defaults` is `false`.
*/
public void addFloat (int o, float x, double d) { if(force_defaults || x != d) { addFloat (x); slot(o); } }
/**
* Add a `double` to a table at `o` into its vtable, with value `x` and default `d`.
*
* @param o The index into the vtable.
* @param x A `double` to put into the buffer, depending on how defaults are handled. If
* `force_defaults` is `false`, compare `x` against the default value `d`. If `x` contains the
* default value, it can be skipped.
* @param d A `double` default value to compare against when `force_defaults` is `false`.
*/
public void addDouble (int o, double x, double d) { if(force_defaults || x != d) { addDouble (x); slot(o); } }
/**
* Add an `offset` to a table at `o` into its vtable, with value `x` and default `d`.
*
* @param o The index into the vtable.
* @param x An `offset` to put into the buffer, depending on how defaults are handled. If
* `force_defaults` is `false`, compare `x` against the default value `d`. If `x` contains the
* default value, it can be skipped.
* @param d An `offset` default value to compare against when `force_defaults` is `false`.
*/
public void addOffset (int o, int x, int d) { if(force_defaults || x != d) { addOffset (x); slot(o); } }
/**
* Add a struct to the table. Structs are stored inline, so nothing additional is being added.
*
* @param voffset The index into the vtable.
* @param x The offset of the created struct.
* @param d The default value is always `0`.
*/
public void addStruct(int voffset, int x, int d) {
if(x != d) {
Nested(x);
slot(voffset);
}
}
/**
* Set the current vtable at `voffset` to the current location in the buffer.
*
* @param voffset The index into the vtable to store the offset relative to the end of the
* buffer.
*/
public void slot(int voffset) {
vtable[voffset] = offset();
}
/**
* Finish off writing the object that is under construction.
*
* @return The offset to the object inside {@link #dataBuffer()}.
* @see #startTable(int)
*/
public int endTable() {
if (vtable == null || !nested)
throw new AssertionError("FlatBuffers: endTable called without startTable");
addInt(0);
int vtableloc = offset();
// Write out the current vtable.
int i = vtable_in_use - 1;
// Trim trailing zeroes.
for (; i >= 0 && vtable[i] == 0; i--) {}
int trimmed_size = i + 1;
for (; i >= 0 ; i--) {
// Offset relative to the start of the table.
short off = (short)(vtable[i] != 0 ? vtableloc - vtable[i] : 0);
addShort(off);
}
final int standard_fields = 2; // The fields below:
addShort((short)(vtableloc - object_start));
addShort((short)((trimmed_size + standard_fields) * SIZEOF_SHORT));
// Search for an existing vtable that matches the current one.
int existing_vtable = 0;
outer_loop:
for (i = 0; i < num_vtables; i++) {
int vt1 = bb.capacity() - vtables[i];
int vt2 = space;
short len = bb.getShort(vt1);
if (len == bb.getShort(vt2)) {
for (int j = SIZEOF_SHORT; j < len; j += SIZEOF_SHORT) {
if (bb.getShort(vt1 + j) != bb.getShort(vt2 + j)) {
continue outer_loop;
}
}
existing_vtable = vtables[i];
break outer_loop;
}
}
if (existing_vtable != 0) {
// Found a match:
// Remove the current vtable.
space = bb.capacity() - vtableloc;
// Point table to existing vtable.
bb.putInt(space, existing_vtable - vtableloc);
} else {
// No match:
// Add the location of the current vtable to the list of vtables.
if (num_vtables == vtables.length) vtables = Arrays.copyOf(vtables, num_vtables * 2);
vtables[num_vtables++] = offset();
// Point table to current vtable.
bb.putInt(bb.capacity() - vtableloc, offset() - vtableloc);
}
nested = false;
return vtableloc;
}
/**
* Checks that a required field has been set in a given table that has
* just been constructed.
*
* @param table The offset to the start of the table from the `ByteBuffer` capacity.
* @param field The offset to the field in the vtable.
*/
public void required(int table, int field) {
int table_start = bb.capacity() - table;
int vtable_start = table_start - bb.getInt(table_start);
boolean ok = bb.getShort(vtable_start + field) != 0;
// If this fails, the caller will show what field needs to be set.
if (!ok)
throw new AssertionError("FlatBuffers: field " + field + " must be set");
}
/// @endcond
/**
* Finalize a buffer, pointing to the given `root_table`.
*
* @param root_table An offset to be added to the buffer.
* @param size_prefix Whether to prefix the size to the buffer.
*/
protected void finish(int root_table, boolean size_prefix) {
prep(minalign, SIZEOF_INT + (size_prefix ? SIZEOF_INT : 0));
addOffset(root_table);
if (size_prefix) {
addInt(bb.capacity() - space);
}
bb.position(space);
finished = true;
}
/**
* Finalize a buffer, pointing to the given `root_table`.
*
* @param root_table An offset to be added to the buffer.
*/
public void finish(int root_table) {
finish(root_table, false);
}
/**
* Finalize a buffer, pointing to the given `root_table`, with the size prefixed.
*
* @param root_table An offset to be added to the buffer.
*/
public void finishSizePrefixed(int root_table) {
finish(root_table, true);
}
/**
* Finalize a buffer, pointing to the given `root_table`.
*
* @param root_table An offset to be added to the buffer.
* @param file_identifier A FlatBuffer file identifier to be added to the buffer before
* `root_table`.
* @param size_prefix Whether to prefix the size to the buffer.
*/
protected void finish(int root_table, String file_identifier, boolean size_prefix) {
prep(minalign, SIZEOF_INT + FILE_IDENTIFIER_LENGTH + (size_prefix ? SIZEOF_INT : 0));
if (file_identifier.length() != FILE_IDENTIFIER_LENGTH)
throw new AssertionError("FlatBuffers: file identifier must be length " +
FILE_IDENTIFIER_LENGTH);
for (int i = FILE_IDENTIFIER_LENGTH - 1; i >= 0; i--) {
addByte((byte)file_identifier.charAt(i));
}
finish(root_table, size_prefix);
}
/**
* Finalize a buffer, pointing to the given `root_table`.
*
* @param root_table An offset to be added to the buffer.
* @param file_identifier A FlatBuffer file identifier to be added to the buffer before
* `root_table`.
*/
public void finish(int root_table, String file_identifier) {
finish(root_table, file_identifier, false);
}
/**
* Finalize a buffer, pointing to the given `root_table`, with the size prefixed.
*
* @param root_table An offset to be added to the buffer.
* @param file_identifier A FlatBuffer file identifier to be added to the buffer before
* `root_table`.
*/
public void finishSizePrefixed(int root_table, String file_identifier) {
finish(root_table, file_identifier, true);
}
/**
* In order to save space, fields that are set to their default value
* don't get serialized into the buffer. Forcing defaults provides a
* way to manually disable this optimization.
*
* @param forceDefaults When set to `true`, always serializes default values.
* @return Returns `this`.
*/
public FlatBufferBuilder forceDefaults(boolean forceDefaults){
this.force_defaults = forceDefaults;
return this;
}
/**
* Get the ByteBuffer representing the FlatBuffer. Only call this after you've
* called `finish()`. The actual data starts at the ByteBuffer's current position,
* not necessarily at `0`.
*
* @return The {@link ByteBuffer} representing the FlatBuffer
*/
public ByteBuffer dataBuffer() {
finished();
return bb;
}
/**
* The FlatBuffer data doesn't start at offset 0 in the {@link ByteBuffer}, but
* now the {@code ByteBuffer}'s position is set to that location upon {@link #finish(int)}.
*
* @return The {@link ByteBuffer#position() position} the data starts in {@link #dataBuffer()}
* @deprecated This method should not be needed anymore, but is left
* here for the moment to document this API change. It will be removed in the future.
*/
@Deprecated
private int dataStart() {
finished();
return space;
}
/**
* A utility function to copy and return the ByteBuffer data from `start` to
* `start` + `length` as a `byte[]`.
*
* @param start Start copying at this offset.
* @param length How many bytes to copy.
* @return A range copy of the {@link #dataBuffer() data buffer}.
* @throws IndexOutOfBoundsException If the range of bytes is ouf of bound.
*/
public byte[] sizedByteArray(int start, int length){
finished();
byte[] array = new byte[length];
bb.position(start);
bb.get(array);
return array;
}
/**
* A utility function to copy and return the ByteBuffer data as a `byte[]`.
*
* @return A full copy of the {@link #dataBuffer() data buffer}.
*/
public byte[] sizedByteArray() {
return sizedByteArray(space, bb.capacity() - space);
}
/**
* A utility function to return an InputStream to the ByteBuffer data
*
* @return An InputStream that starts at the beginning of the ByteBuffer data
* and can read to the end of it.
*/
public InputStream sizedInputStream() {
finished();
ByteBuffer duplicate = bb.duplicate();
duplicate.position(space);
duplicate.limit(bb.capacity());
return new ByteBufferBackedInputStream(duplicate);
}
/**
* A class that allows a user to create an InputStream from a ByteBuffer.
*/
static class ByteBufferBackedInputStream extends InputStream {
ByteBuffer buf;
public ByteBufferBackedInputStream(ByteBuffer buf) {
this.buf = buf;
}
public int read() throws IOException {
try {
return buf.get() & 0xFF;
} catch(BufferUnderflowException e) {
return -1;
}
}
}
}
/// @}