@stomp/stompjs
Version:
STOMP client for Javascript and Typescript
222 lines • 7.17 kB
JavaScript
/**
* @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 {
constructor(onFrame, onIncomingPing) {
this.onFrame = onFrame;
this.onIncomingPing = onIncomingPing;
this._encoder = new TextEncoder();
this._decoder = new TextDecoder();
this._token = [];
this._initState();
}
parseChunk(segment, appendMissingNULLonIncoming = false) {
let chunk;
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
_collectFrame(byte) {
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);
}
_collectCommand(byte) {
if (byte === CR) {
// Ignore CR
return;
}
if (byte === LF) {
this._results.command = this._consumeTokenAsUTF8();
this._onByte = this._collectHeaders;
return;
}
this._consumeByte(byte);
}
_collectHeaders(byte) {
if (byte === CR) {
// Ignore CR
return;
}
if (byte === LF) {
this._setupCollectBody();
return;
}
this._onByte = this._collectHeaderKey;
this._reinjectByte(byte);
}
_reinjectByte(byte) {
this._onByte(byte);
}
_collectHeaderKey(byte) {
if (byte === COLON) {
this._headerKey = this._consumeTokenAsUTF8();
this._onByte = this._collectHeaderValue;
return;
}
this._consumeByte(byte);
}
_collectHeaderValue(byte) {
if (byte === CR) {
// Ignore CR
return;
}
if (byte === LF) {
this._results.headers.push([
this._headerKey,
this._consumeTokenAsUTF8(),
]);
this._headerKey = undefined;
this._onByte = this._collectHeaders;
return;
}
this._consumeByte(byte);
}
_setupCollectBody() {
const contentLengthHeader = this._results.headers.filter((header) => {
return header[0] === 'content-length';
})[0];
if (contentLengthHeader) {
this._bodyBytesRemaining = parseInt(contentLengthHeader[1], 10);
this._onByte = this._collectBodyFixedSize;
}
else {
this._onByte = this._collectBodyNullTerminated;
}
}
_collectBodyNullTerminated(byte) {
if (byte === NULL) {
this._retrievedBody();
return;
}
this._consumeByte(byte);
}
_collectBodyFixedSize(byte) {
// It is post decrement, so that we discard the trailing NULL octet
if (this._bodyBytesRemaining-- === 0) {
this._retrievedBody();
return;
}
this._consumeByte(byte);
}
_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
_consumeByte(byte) {
this._token.push(byte);
}
_consumeTokenAsUTF8() {
return this._decoder.decode(this._consumeTokenAsRaw());
}
_consumeTokenAsRaw() {
const rawResult = new Uint8Array(this._token);
this._token = [];
return rawResult;
}
_initState() {
this._results = {
command: undefined,
headers: [],
binaryBody: undefined,
};
this._token = [];
this._headerKey = undefined;
this._onByte = this._collectFrame;
}
}
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