288 lines
8.8 KiB
TypeScript
288 lines
8.8 KiB
TypeScript
import { FILE_IDENTIFIER_LENGTH, SIZEOF_INT } from "./constants.js";
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import { int32, isLittleEndian, float32, float64 } from "./utils.js";
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import { Offset, Table, IGeneratedObject, IUnpackableObject } from "./types.js";
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import { Encoding } from "./encoding.js";
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export class ByteBuffer {
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private position_ = 0;
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private text_decoder_ = new TextDecoder();
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/**
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* Create a new ByteBuffer with a given array of bytes (`Uint8Array`)
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*/
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constructor(private bytes_: Uint8Array) { }
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/**
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* Create and allocate a new ByteBuffer with a given size.
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*/
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static allocate(byte_size: number): ByteBuffer {
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return new ByteBuffer(new Uint8Array(byte_size));
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}
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clear(): void {
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this.position_ = 0;
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}
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/**
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* Get the underlying `Uint8Array`.
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*/
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bytes(): Uint8Array {
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return this.bytes_;
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}
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/**
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* Get the buffer's position.
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*/
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position(): number {
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return this.position_;
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}
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/**
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* Set the buffer's position.
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*/
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setPosition(position: number): void {
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this.position_ = position;
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}
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/**
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* Get the buffer's capacity.
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*/
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capacity(): number {
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return this.bytes_.length;
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}
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readInt8(offset: number): number {
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return this.readUint8(offset) << 24 >> 24;
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}
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readUint8(offset: number): number {
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return this.bytes_[offset];
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}
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readInt16(offset: number): number {
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return this.readUint16(offset) << 16 >> 16;
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}
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readUint16(offset: number): number {
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return this.bytes_[offset] | this.bytes_[offset + 1] << 8;
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}
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readInt32(offset: number): number {
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return this.bytes_[offset] | this.bytes_[offset + 1] << 8 | this.bytes_[offset + 2] << 16 | this.bytes_[offset + 3] << 24;
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}
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readUint32(offset: number): number {
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return this.readInt32(offset) >>> 0;
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}
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readInt64(offset: number): bigint {
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return BigInt.asIntN(64, BigInt(this.readUint32(offset)) + (BigInt(this.readUint32(offset + 4)) << BigInt(32)));
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}
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readUint64(offset: number): bigint {
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return BigInt.asUintN(64, BigInt(this.readUint32(offset)) + (BigInt(this.readUint32(offset + 4)) << BigInt(32)));
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}
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readFloat32(offset: number): number {
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int32[0] = this.readInt32(offset);
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return float32[0];
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}
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readFloat64(offset: number): number {
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int32[isLittleEndian ? 0 : 1] = this.readInt32(offset);
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int32[isLittleEndian ? 1 : 0] = this.readInt32(offset + 4);
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return float64[0];
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}
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writeInt8(offset: number, value: number): void {
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this.bytes_[offset] = value;
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}
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writeUint8(offset: number, value: number): void {
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this.bytes_[offset] = value;
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}
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writeInt16(offset: number, value: number): void {
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this.bytes_[offset] = value;
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this.bytes_[offset + 1] = value >> 8;
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}
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writeUint16(offset: number, value: number): void {
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this.bytes_[offset] = value;
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this.bytes_[offset + 1] = value >> 8;
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}
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writeInt32(offset: number, value: number): void {
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this.bytes_[offset] = value;
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this.bytes_[offset + 1] = value >> 8;
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this.bytes_[offset + 2] = value >> 16;
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this.bytes_[offset + 3] = value >> 24;
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}
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writeUint32(offset: number, value: number): void {
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this.bytes_[offset] = value;
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this.bytes_[offset + 1] = value >> 8;
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this.bytes_[offset + 2] = value >> 16;
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this.bytes_[offset + 3] = value >> 24;
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}
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writeInt64(offset: number, value: bigint): void {
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this.writeInt32(offset, Number(BigInt.asIntN(32, value)));
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this.writeInt32(offset + 4, Number(BigInt.asIntN(32, value >> BigInt(32))));
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}
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writeUint64(offset: number, value: bigint): void {
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this.writeUint32(offset, Number(BigInt.asUintN(32, value)));
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this.writeUint32(offset + 4, Number(BigInt.asUintN(32, value >> BigInt(32))));
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}
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writeFloat32(offset: number, value: number): void {
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float32[0] = value;
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this.writeInt32(offset, int32[0]);
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}
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writeFloat64(offset: number, value: number): void {
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float64[0] = value;
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this.writeInt32(offset, int32[isLittleEndian ? 0 : 1]);
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this.writeInt32(offset + 4, int32[isLittleEndian ? 1 : 0]);
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}
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/**
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* Return the file identifier. Behavior is undefined for FlatBuffers whose
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* schema does not include a file_identifier (likely points at padding or the
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* start of a the root vtable).
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*/
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getBufferIdentifier(): string {
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if (this.bytes_.length < this.position_ + SIZEOF_INT +
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FILE_IDENTIFIER_LENGTH) {
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throw new Error(
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'FlatBuffers: ByteBuffer is too short to contain an identifier.');
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}
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let result = "";
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for (let i = 0; i < FILE_IDENTIFIER_LENGTH; i++) {
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result += String.fromCharCode(
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this.readInt8(this.position_ + SIZEOF_INT + i));
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}
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return result;
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}
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/**
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* Look up a field in the vtable, return an offset into the object, or 0 if the
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* field is not present.
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*/
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__offset(bb_pos: number, vtable_offset: number): Offset {
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const vtable = bb_pos - this.readInt32(bb_pos);
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return vtable_offset < this.readInt16(vtable) ? this.readInt16(vtable + vtable_offset) : 0;
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}
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/**
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* Initialize any Table-derived type to point to the union at the given offset.
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*/
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__union(t: Table, offset: number): Table {
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t.bb_pos = offset + this.readInt32(offset);
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t.bb = this;
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return t;
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}
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/**
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* Create a JavaScript string from UTF-8 data stored inside the FlatBuffer.
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* This allocates a new string and converts to wide chars upon each access.
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*
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* To avoid the conversion to string, pass Encoding.UTF8_BYTES as the
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* "optionalEncoding" argument. This is useful for avoiding conversion when
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* the data will just be packaged back up in another FlatBuffer later on.
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*
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* @param offset
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* @param opt_encoding Defaults to UTF16_STRING
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*/
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__string(offset: number, opt_encoding?: Encoding): string | Uint8Array {
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offset += this.readInt32(offset);
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const length = this.readInt32(offset);
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offset += SIZEOF_INT;
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const utf8bytes = this.bytes_.subarray(offset, offset + length);
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if (opt_encoding === Encoding.UTF8_BYTES)
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return utf8bytes;
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else
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return this.text_decoder_.decode(utf8bytes);
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}
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/**
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* Handle unions that can contain string as its member, if a Table-derived type then initialize it,
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* if a string then return a new one
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*
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* WARNING: strings are immutable in JS so we can't change the string that the user gave us, this
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* makes the behaviour of __union_with_string different compared to __union
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*/
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__union_with_string(o: Table | string, offset: number) : Table | string {
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if(typeof o === 'string') {
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return this.__string(offset) as string;
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}
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return this.__union(o, offset);
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}
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/**
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* Retrieve the relative offset stored at "offset"
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*/
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__indirect(offset: Offset): Offset {
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return offset + this.readInt32(offset);
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}
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/**
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* Get the start of data of a vector whose offset is stored at "offset" in this object.
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*/
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__vector(offset: Offset): Offset {
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return offset + this.readInt32(offset) + SIZEOF_INT; // data starts after the length
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}
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/**
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* Get the length of a vector whose offset is stored at "offset" in this object.
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*/
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__vector_len(offset: Offset): Offset {
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return this.readInt32(offset + this.readInt32(offset));
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}
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__has_identifier(ident: string): boolean {
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if (ident.length != FILE_IDENTIFIER_LENGTH) {
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throw new Error('FlatBuffers: file identifier must be length ' +
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FILE_IDENTIFIER_LENGTH);
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}
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for (let i = 0; i < FILE_IDENTIFIER_LENGTH; i++) {
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if (ident.charCodeAt(i) != this.readInt8(this.position() + SIZEOF_INT + i)) {
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return false;
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}
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}
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return true;
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}
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/**
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* A helper function for generating list for obj api
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*/
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createScalarList<T>(listAccessor: (i: number) => T | null, listLength: number): T[] {
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const ret: T[] = [];
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for(let i = 0; i < listLength; ++i) {
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const val = listAccessor(i);
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if(val !== null) {
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ret.push(val);
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}
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}
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return ret;
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}
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/**
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* A helper function for generating list for obj api
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* @param listAccessor function that accepts an index and return data at that index
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* @param listLength listLength
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* @param res result list
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*/
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createObjList<T1 extends IUnpackableObject<T2>, T2 extends IGeneratedObject>(listAccessor: (i: number) => T1 | null, listLength: number): T2[] {
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const ret: T2[] = [];
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for(let i = 0; i < listLength; ++i) {
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const val = listAccessor(i);
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if(val !== null) {
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ret.push(val.unpack());
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}
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}
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return ret;
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}
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}
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