593 lines
18 KiB
TypeScript
593 lines
18 KiB
TypeScript
import { ByteBuffer } from "./byte-buffer.js"
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import { SIZEOF_SHORT, SIZE_PREFIX_LENGTH, SIZEOF_INT, FILE_IDENTIFIER_LENGTH } from "./constants.js"
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import { Offset, IGeneratedObject } from "./types.js"
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export class Builder {
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private bb: ByteBuffer
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/** Remaining space in the ByteBuffer. */
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private space: number
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/** Minimum alignment encountered so far. */
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private minalign = 1
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/** The vtable for the current table. */
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private vtable: number[] | null = null
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/** The amount of fields we're actually using. */
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private vtable_in_use = 0
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/** Whether we are currently serializing a table. */
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private isNested = false;
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/** Starting offset of the current struct/table. */
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private object_start = 0
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/** List of offsets of all vtables. */
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private vtables: number[] = []
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/** For the current vector being built. */
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private vector_num_elems = 0
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/** False omits default values from the serialized data */
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private force_defaults = false;
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private string_maps: Map<string | Uint8Array, number> | null = null;
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private text_encoder = new TextEncoder();
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/**
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* Create a FlatBufferBuilder.
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*/
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constructor(opt_initial_size?: number) {
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let initial_size: number;
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if (!opt_initial_size) {
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initial_size = 1024;
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} else {
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initial_size = opt_initial_size;
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}
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/**
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* @type {ByteBuffer}
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* @private
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*/
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this.bb = ByteBuffer.allocate(initial_size);
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this.space = initial_size;
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}
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clear(): void {
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this.bb.clear();
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this.space = this.bb.capacity();
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this.minalign = 1;
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this.vtable = null;
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this.vtable_in_use = 0;
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this.isNested = false;
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this.object_start = 0;
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this.vtables = [];
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this.vector_num_elems = 0;
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this.force_defaults = false;
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this.string_maps = null;
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}
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/**
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* In order to save space, fields that are set to their default value
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* don't get serialized into the buffer. Forcing defaults provides a
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* way to manually disable this optimization.
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*
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* @param forceDefaults true always serializes default values
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*/
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forceDefaults(forceDefaults: boolean): void {
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this.force_defaults = forceDefaults;
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}
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/**
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* Get the ByteBuffer representing the FlatBuffer. Only call this after you've
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* called finish(). The actual data starts at the ByteBuffer's current position,
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* not necessarily at 0.
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*/
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dataBuffer(): ByteBuffer {
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return this.bb;
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}
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/**
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* Get the bytes representing the FlatBuffer. Only call this after you've
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* called finish().
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*/
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asUint8Array(): Uint8Array {
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return this.bb.bytes().subarray(this.bb.position(), this.bb.position() + this.offset());
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}
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/**
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* Prepare to write an element of `size` after `additional_bytes` have been
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* written, e.g. if you write a string, you need to align such the int length
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* field is aligned to 4 bytes, and the string data follows it directly. If all
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* you need to do is alignment, `additional_bytes` will be 0.
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*
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* @param size This is the of the new element to write
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* @param additional_bytes The padding size
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*/
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prep(size: number, additional_bytes: number): void {
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// Track the biggest thing we've ever aligned to.
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if (size > this.minalign) {
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this.minalign = size;
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}
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// Find the amount of alignment needed such that `size` is properly
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// aligned after `additional_bytes`
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const align_size = ((~(this.bb.capacity() - this.space + additional_bytes)) + 1) & (size - 1);
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// Reallocate the buffer if needed.
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while (this.space < align_size + size + additional_bytes) {
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const old_buf_size = this.bb.capacity();
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this.bb = Builder.growByteBuffer(this.bb);
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this.space += this.bb.capacity() - old_buf_size;
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}
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this.pad(align_size);
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}
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pad(byte_size: number): void {
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for (let i = 0; i < byte_size; i++) {
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this.bb.writeInt8(--this.space, 0);
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}
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}
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writeInt8(value: number): void {
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this.bb.writeInt8(this.space -= 1, value);
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}
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writeInt16(value: number): void {
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this.bb.writeInt16(this.space -= 2, value);
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}
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writeInt32(value: number): void {
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this.bb.writeInt32(this.space -= 4, value);
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}
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writeInt64(value: bigint): void {
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this.bb.writeInt64(this.space -= 8, value);
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}
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writeFloat32(value: number): void {
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this.bb.writeFloat32(this.space -= 4, value);
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}
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writeFloat64(value: number): void {
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this.bb.writeFloat64(this.space -= 8, value);
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}
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/**
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* Add an `int8` to the buffer, properly aligned, and grows the buffer (if necessary).
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* @param value The `int8` to add the buffer.
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*/
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addInt8(value: number): void {
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this.prep(1, 0);
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this.writeInt8(value);
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}
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/**
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* Add an `int16` to the buffer, properly aligned, and grows the buffer (if necessary).
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* @param value The `int16` to add the buffer.
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*/
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addInt16(value: number): void {
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this.prep(2, 0);
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this.writeInt16(value);
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}
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/**
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* Add an `int32` to the buffer, properly aligned, and grows the buffer (if necessary).
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* @param value The `int32` to add the buffer.
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*/
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addInt32(value: number): void {
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this.prep(4, 0);
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this.writeInt32(value);
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}
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/**
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* Add an `int64` to the buffer, properly aligned, and grows the buffer (if necessary).
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* @param value The `int64` to add the buffer.
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*/
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addInt64(value: bigint): void {
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this.prep(8, 0);
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this.writeInt64(value);
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}
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/**
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* Add a `float32` to the buffer, properly aligned, and grows the buffer (if necessary).
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* @param value The `float32` to add the buffer.
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*/
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addFloat32(value: number): void {
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this.prep(4, 0);
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this.writeFloat32(value);
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}
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/**
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* Add a `float64` to the buffer, properly aligned, and grows the buffer (if necessary).
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* @param value The `float64` to add the buffer.
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*/
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addFloat64(value: number): void {
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this.prep(8, 0);
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this.writeFloat64(value);
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}
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addFieldInt8(voffset: number, value: number, defaultValue: number): void {
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if (this.force_defaults || value != defaultValue) {
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this.addInt8(value);
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this.slot(voffset);
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}
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}
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addFieldInt16(voffset: number, value: number, defaultValue: number): void {
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if (this.force_defaults || value != defaultValue) {
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this.addInt16(value);
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this.slot(voffset);
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}
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}
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addFieldInt32(voffset: number, value: number, defaultValue: number): void {
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if (this.force_defaults || value != defaultValue) {
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this.addInt32(value);
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this.slot(voffset);
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}
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}
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addFieldInt64(voffset: number, value: bigint, defaultValue: bigint): void {
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if (this.force_defaults || value !== defaultValue) {
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this.addInt64(value);
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this.slot(voffset);
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}
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}
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addFieldFloat32(voffset: number, value: number, defaultValue: number): void {
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if (this.force_defaults || value != defaultValue) {
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this.addFloat32(value);
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this.slot(voffset);
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}
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}
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addFieldFloat64(voffset: number, value: number, defaultValue: number): void {
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if (this.force_defaults || value != defaultValue) {
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this.addFloat64(value);
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this.slot(voffset);
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}
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}
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addFieldOffset(voffset: number, value: Offset, defaultValue: Offset): void {
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if (this.force_defaults || value != defaultValue) {
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this.addOffset(value);
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this.slot(voffset);
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}
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}
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/**
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* Structs are stored inline, so nothing additional is being added. `d` is always 0.
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*/
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addFieldStruct(voffset: number, value: Offset, defaultValue: Offset): void {
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if (value != defaultValue) {
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this.nested(value);
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this.slot(voffset);
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}
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}
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/**
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* Structures are always stored inline, they need to be created right
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* where they're used. You'll get this assertion failure if you
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* created it elsewhere.
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*/
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nested(obj: Offset): void {
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if (obj != this.offset()) {
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throw new TypeError('FlatBuffers: struct must be serialized inline.');
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}
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}
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/**
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* Should not be creating any other object, string or vector
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* while an object is being constructed
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*/
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notNested(): void {
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if (this.isNested) {
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throw new TypeError('FlatBuffers: object serialization must not be nested.');
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}
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}
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/**
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* Set the current vtable at `voffset` to the current location in the buffer.
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*/
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slot(voffset: number): void {
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if (this.vtable !== null)
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this.vtable[voffset] = this.offset();
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}
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/**
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* @returns Offset relative to the end of the buffer.
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*/
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offset(): Offset {
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return this.bb.capacity() - this.space;
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}
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/**
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* Doubles the size of the backing ByteBuffer and copies the old data towards
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* the end of the new buffer (since we build the buffer backwards).
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*
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* @param bb The current buffer with the existing data
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* @returns A new byte buffer with the old data copied
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* to it. The data is located at the end of the buffer.
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*
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* uint8Array.set() formally takes {Array<number>|ArrayBufferView}, so to pass
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* it a uint8Array we need to suppress the type check:
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* @suppress {checkTypes}
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*/
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static growByteBuffer(bb: ByteBuffer): ByteBuffer {
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const old_buf_size = bb.capacity();
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// Ensure we don't grow beyond what fits in an int.
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if (old_buf_size & 0xC0000000) {
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throw new Error('FlatBuffers: cannot grow buffer beyond 2 gigabytes.');
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}
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const new_buf_size = old_buf_size << 1;
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const nbb = ByteBuffer.allocate(new_buf_size);
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nbb.setPosition(new_buf_size - old_buf_size);
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nbb.bytes().set(bb.bytes(), new_buf_size - old_buf_size);
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return nbb;
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}
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/**
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* Adds on offset, relative to where it will be written.
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*
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* @param offset The offset to add.
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*/
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addOffset(offset: Offset): void {
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this.prep(SIZEOF_INT, 0); // Ensure alignment is already done.
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this.writeInt32(this.offset() - offset + SIZEOF_INT);
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}
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/**
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* Start encoding a new object in the buffer. Users will not usually need to
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* call this directly. The FlatBuffers compiler will generate helper methods
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* that call this method internally.
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*/
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startObject(numfields: number): void {
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this.notNested();
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if (this.vtable == null) {
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this.vtable = [];
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}
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this.vtable_in_use = numfields;
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for (let i = 0; i < numfields; i++) {
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this.vtable[i] = 0; // This will push additional elements as needed
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}
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this.isNested = true;
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this.object_start = this.offset();
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}
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/**
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* Finish off writing the object that is under construction.
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*
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* @returns The offset to the object inside `dataBuffer`
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*/
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endObject(): Offset {
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if (this.vtable == null || !this.isNested) {
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throw new Error('FlatBuffers: endObject called without startObject');
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}
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this.addInt32(0);
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const vtableloc = this.offset();
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// Trim trailing zeroes.
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let i = this.vtable_in_use - 1;
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// eslint-disable-next-line no-empty
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for (; i >= 0 && this.vtable[i] == 0; i--) {}
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const trimmed_size = i + 1;
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// Write out the current vtable.
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for (; i >= 0; i--) {
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// Offset relative to the start of the table.
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this.addInt16(this.vtable[i] != 0 ? vtableloc - this.vtable[i] : 0);
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}
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const standard_fields = 2; // The fields below:
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this.addInt16(vtableloc - this.object_start);
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const len = (trimmed_size + standard_fields) * SIZEOF_SHORT;
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this.addInt16(len);
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// Search for an existing vtable that matches the current one.
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let existing_vtable = 0;
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const vt1 = this.space;
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outer_loop:
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for (i = 0; i < this.vtables.length; i++) {
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const vt2 = this.bb.capacity() - this.vtables[i];
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if (len == this.bb.readInt16(vt2)) {
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for (let j = SIZEOF_SHORT; j < len; j += SIZEOF_SHORT) {
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if (this.bb.readInt16(vt1 + j) != this.bb.readInt16(vt2 + j)) {
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continue outer_loop;
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}
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}
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existing_vtable = this.vtables[i];
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break;
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}
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}
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if (existing_vtable) {
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// Found a match:
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// Remove the current vtable.
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this.space = this.bb.capacity() - vtableloc;
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// Point table to existing vtable.
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this.bb.writeInt32(this.space, existing_vtable - vtableloc);
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} else {
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// No match:
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// Add the location of the current vtable to the list of vtables.
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this.vtables.push(this.offset());
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// Point table to current vtable.
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this.bb.writeInt32(this.bb.capacity() - vtableloc, this.offset() - vtableloc);
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}
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this.isNested = false;
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return vtableloc as Offset;
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}
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/**
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* Finalize a buffer, poiting to the given `root_table`.
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*/
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finish(root_table: Offset, opt_file_identifier?: string, opt_size_prefix?: boolean): void {
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const size_prefix = opt_size_prefix ? SIZE_PREFIX_LENGTH : 0;
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if (opt_file_identifier) {
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const file_identifier = opt_file_identifier;
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this.prep(this.minalign, SIZEOF_INT +
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FILE_IDENTIFIER_LENGTH + size_prefix);
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if (file_identifier.length != FILE_IDENTIFIER_LENGTH) {
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throw new TypeError('FlatBuffers: file identifier must be length ' +
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FILE_IDENTIFIER_LENGTH);
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}
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for (let i = FILE_IDENTIFIER_LENGTH - 1; i >= 0; i--) {
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this.writeInt8(file_identifier.charCodeAt(i));
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}
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}
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this.prep(this.minalign, SIZEOF_INT + size_prefix);
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this.addOffset(root_table);
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if (size_prefix) {
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this.addInt32(this.bb.capacity() - this.space);
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}
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this.bb.setPosition(this.space);
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}
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/**
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* Finalize a size prefixed buffer, pointing to the given `root_table`.
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*/
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finishSizePrefixed(this: Builder, root_table: Offset, opt_file_identifier?: string): void {
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this.finish(root_table, opt_file_identifier, true);
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}
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/**
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* This checks a required field has been set in a given table that has
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* just been constructed.
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*/
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requiredField(table: Offset, field: number): void {
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const table_start = this.bb.capacity() - table;
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const vtable_start = table_start - this.bb.readInt32(table_start);
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const ok = field < this.bb.readInt16(vtable_start) &&
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this.bb.readInt16(vtable_start + field) != 0;
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// If this fails, the caller will show what field needs to be set.
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if (!ok) {
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throw new TypeError('FlatBuffers: field ' + field + ' must be set');
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}
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}
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/**
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* Start a new array/vector of objects. Users usually will not call
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* this directly. The FlatBuffers compiler will create a start/end
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* method for vector types in generated code.
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*
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* @param elem_size The size of each element in the array
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* @param num_elems The number of elements in the array
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* @param alignment The alignment of the array
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*/
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startVector(elem_size: number, num_elems: number, alignment: number): void {
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this.notNested();
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this.vector_num_elems = num_elems;
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this.prep(SIZEOF_INT, elem_size * num_elems);
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this.prep(alignment, elem_size * num_elems); // Just in case alignment > int.
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}
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/**
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* Finish off the creation of an array and all its elements. The array must be
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* created with `startVector`.
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*
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* @returns The offset at which the newly created array
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* starts.
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*/
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endVector(): Offset {
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this.writeInt32(this.vector_num_elems);
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return this.offset();
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}
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/**
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* Encode the string `s` in the buffer using UTF-8. If the string passed has
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* already been seen, we return the offset of the already written string
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*
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* @param s The string to encode
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* @return The offset in the buffer where the encoded string starts
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*/
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createSharedString(s: string | Uint8Array): Offset {
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if (!s) { return 0 }
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if (!this.string_maps) {
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this.string_maps = new Map();
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}
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if (this.string_maps.has(s)) {
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return this.string_maps.get(s) as Offset
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}
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const offset = this.createString(s)
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this.string_maps.set(s, offset)
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return offset
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}
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/**
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* Encode the string `s` in the buffer using UTF-8. If a Uint8Array is passed
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* instead of a string, it is assumed to contain valid UTF-8 encoded data.
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*
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* @param s The string to encode
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* @return The offset in the buffer where the encoded string starts
|
|
*/
|
|
createString(s: string | Uint8Array | null | undefined): Offset {
|
|
if (s === null || s === undefined) {
|
|
return 0;
|
|
}
|
|
|
|
let utf8: string | Uint8Array | number[];
|
|
if (s instanceof Uint8Array) {
|
|
utf8 = s;
|
|
} else {
|
|
utf8 = this.text_encoder.encode(s);
|
|
}
|
|
|
|
this.addInt8(0);
|
|
this.startVector(1, utf8.length, 1);
|
|
this.bb.setPosition(this.space -= utf8.length);
|
|
for (let i = 0, offset = this.space, bytes = this.bb.bytes(); i < utf8.length; i++) {
|
|
bytes[offset++] = utf8[i];
|
|
}
|
|
return this.endVector();
|
|
}
|
|
|
|
/**
|
|
* A helper function to pack an object
|
|
*
|
|
* @returns offset of obj
|
|
*/
|
|
createObjectOffset(obj: string | IGeneratedObject | null): Offset {
|
|
if(obj === null) {
|
|
return 0
|
|
}
|
|
|
|
if(typeof obj === 'string') {
|
|
return this.createString(obj);
|
|
} else {
|
|
return obj.pack(this);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* A helper function to pack a list of object
|
|
*
|
|
* @returns list of offsets of each non null object
|
|
*/
|
|
createObjectOffsetList(list: (string | IGeneratedObject)[]): Offset[] {
|
|
const ret: number[] = [];
|
|
|
|
for(let i = 0; i < list.length; ++i) {
|
|
const val = list[i];
|
|
|
|
if(val !== null) {
|
|
ret.push(this.createObjectOffset(val));
|
|
} else {
|
|
throw new TypeError(
|
|
'FlatBuffers: Argument for createObjectOffsetList cannot contain null.');
|
|
}
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
createStructOffsetList(list: (string | IGeneratedObject)[], startFunc: (builder: Builder, length: number) => void): Offset {
|
|
startFunc(this, list.length);
|
|
this.createObjectOffsetList(list.slice().reverse());
|
|
return this.endVector();
|
|
}
|
|
}
|