src/vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase.ts/PieceTreeSnapshot/read
class PieceTreeSnapshot:	read(): string | null {
		if (this._pieces.length === 0) {
			if (this._index === 0) {
				this._index++;
				return this._BOM;
			} else {
				return null;
			}
		}

		if (this._index > this._pieces.length - 1) {
			return null;
		}

		if (this._index === 0) {
			return this._BOM + this._tree.getPieceContent(this._pieces[this._index++]);
		}
		return this._tree.getPieceContent(this._pieces[this._index++]);
	}