extensions/emmet/src/bufferStream.ts/DocumentStreamReader/constructor
class DocumentStreamReader:	constructor(document: TextDocument, pos?: number, limit?: [number, number]) {
		this.document = document;
		this.start = this.pos = pos ? pos : 0;
		this._sof = limit ? limit[0] : 0;
		this._eof = limit ? limit[1] : document.getText().length;
	}