@stomp/stompjs
Version:
STOMP client for Javascript and Typescript
268 lines (234 loc) • 7.18 kB
text/typescript
import { IRawFrameType } from './types.js';
/**
* @internal
*/
const NULL = 0;
/**
* @internal
*/
const LF = 10;
/**
* @internal
*/
const CR = 13;
/**
* @internal
*/
const COLON = 58;
/**
* This is an evented, rec descent parser.
* A stream of Octets can be passed and whenever it recognizes
* a complete Frame or an incoming ping it will invoke the registered callbacks.
*
* All incoming Octets are fed into _onByte function.
* Depending on current state the _onByte function keeps changing.
* Depending on the state it keeps accumulating into _token and _results.
* State is indicated by current value of _onByte, all states are named as _collect.
*
* STOMP standards https://stomp.github.io/stomp-specification-1.2.html
* imply that all lengths are considered in bytes (instead of string lengths).
* So, before actual parsing, if the incoming data is String it is converted to Octets.
* This allows faithful implementation of the protocol and allows NULL Octets to be present in the body.
*
* There is no peek function on the incoming data.
* When a state change occurs based on an Octet without consuming the Octet,
* the Octet, after state change, is fed again (_reinjectByte).
* This became possible as the state change can be determined by inspecting just one Octet.
*
* There are two modes to collect the body, if content-length header is there then it by counting Octets
* otherwise it is determined by NULL terminator.
*
* Following the standards, the command and headers are converted to Strings
* and the body is returned as Octets.
* Headers are returned as an array and not as Hash - to allow multiple occurrence of an header.
*
* This parser does not use Regular Expressions as that can only operate on Strings.
*
* It handles if multiple STOMP frames are given as one chunk, a frame is split into multiple chunks, or
* any combination there of. The parser remembers its state (any partial frame) and continues when a new chunk
* is pushed.
*
* Typically the higher level function will convert headers to Hash, handle unescaping of header values
* (which is protocol version specific), and convert body to text.
*
* Check the parser.spec.js to understand cases that this parser is supposed to handle.
*
* Part of `@stomp/stompjs`.
*
* @internal
*/
export class Parser {
private readonly _encoder = new TextEncoder();
private readonly _decoder = new TextDecoder();
// @ts-ignore - it always has a value
private _results: IRawFrameType;
private _token: number[] = [];
private _headerKey: string | undefined;
private _bodyBytesRemaining: number | undefined;
// @ts-ignore - it always has a value
private _onByte: (byte: number) => void;
public constructor(
public onFrame: (rawFrame: IRawFrameType) => void,
public onIncomingPing: () => void
) {
this._initState();
}
public parseChunk(
segment: string | ArrayBuffer,
appendMissingNULLonIncoming: boolean = false
) {
let chunk: Uint8Array;
if (typeof segment === 'string') {
chunk = this._encoder.encode(segment);
} else {
chunk = new Uint8Array(segment);
}
// See https://github.com/stomp-js/stompjs/issues/89
// Remove when underlying issue is fixed.
//
// Send a NULL byte, if the last byte of a Text frame was not NULL.F
if (appendMissingNULLonIncoming && chunk[chunk.length - 1] !== 0) {
const chunkWithNull = new Uint8Array(chunk.length + 1);
chunkWithNull.set(chunk, 0);
chunkWithNull[chunk.length] = 0;
chunk = chunkWithNull;
}
// tslint:disable-next-line:prefer-for-of
for (let i = 0; i < chunk.length; i++) {
const byte = chunk[i];
this._onByte(byte);
}
}
// The following implements a simple Rec Descent Parser.
// The grammar is simple and just one byte tells what should be the next state
private _collectFrame(byte: number): void {
if (byte === NULL) {
// Ignore
return;
}
if (byte === CR) {
// Ignore CR
return;
}
if (byte === LF) {
// Incoming Ping
this.onIncomingPing();
return;
}
this._onByte = this._collectCommand;
this._reinjectByte(byte);
}
private _collectCommand(byte: number): void {
if (byte === CR) {
// Ignore CR
return;
}
if (byte === LF) {
this._results.command = this._consumeTokenAsUTF8();
this._onByte = this._collectHeaders;
return;
}
this._consumeByte(byte);
}
private _collectHeaders(byte: number): void {
if (byte === CR) {
// Ignore CR
return;
}
if (byte === LF) {
this._setupCollectBody();
return;
}
this._onByte = this._collectHeaderKey;
this._reinjectByte(byte);
}
private _reinjectByte(byte: number) {
this._onByte(byte);
}
private _collectHeaderKey(byte: number): void {
if (byte === COLON) {
this._headerKey = this._consumeTokenAsUTF8();
this._onByte = this._collectHeaderValue;
return;
}
this._consumeByte(byte);
}
private _collectHeaderValue(byte: number): void {
if (byte === CR) {
// Ignore CR
return;
}
if (byte === LF) {
this._results.headers.push([
this._headerKey as string,
this._consumeTokenAsUTF8(),
]);
this._headerKey = undefined;
this._onByte = this._collectHeaders;
return;
}
this._consumeByte(byte);
}
private _setupCollectBody() {
const contentLengthHeader = this._results.headers.filter(
(header: [string, string]) => {
return header[0] === 'content-length';
}
)[0];
if (contentLengthHeader) {
this._bodyBytesRemaining = parseInt(contentLengthHeader[1], 10);
this._onByte = this._collectBodyFixedSize;
} else {
this._onByte = this._collectBodyNullTerminated;
}
}
private _collectBodyNullTerminated(byte: number): void {
if (byte === NULL) {
this._retrievedBody();
return;
}
this._consumeByte(byte);
}
private _collectBodyFixedSize(byte: number): void {
// It is post decrement, so that we discard the trailing NULL octet
if ((this._bodyBytesRemaining as number)-- === 0) {
this._retrievedBody();
return;
}
this._consumeByte(byte);
}
private _retrievedBody() {
this._results.binaryBody = this._consumeTokenAsRaw();
try {
this.onFrame(this._results);
} catch (e) {
console.log(
`Ignoring an exception thrown by a frame handler. Original exception: `,
e
);
}
this._initState();
}
// Rec Descent Parser helpers
private _consumeByte(byte: number) {
this._token.push(byte);
}
private _consumeTokenAsUTF8() {
return this._decoder.decode(this._consumeTokenAsRaw());
}
private _consumeTokenAsRaw() {
const rawResult = new Uint8Array(this._token);
this._token = [];
return rawResult;
}
private _initState() {
this._results = {
command: undefined,
headers: [],
binaryBody: undefined,
};
this._token = [];
this._headerKey = undefined;
this._onByte = this._collectFrame;
}
}