src/vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase.ts/PieceTreeBase/nodeCharCodeAt
class PieceTreeBase:	private nodeCharCodeAt(node: TreeNode, offset: number): number {
		if (node.piece.lineFeedCnt < 1) {
			return -1;
		}
		const buffer = this._buffers[node.piece.bufferIndex];
		const newOffset = this.offsetInBuffer(node.piece.bufferIndex, node.piece.start) + offset;
		return buffer.buffer.charCodeAt(newOffset);
	}