src/vs/workbench/api/common/extHostDocumentData.ts/ExtHostDocumentData/_positionAt
class ExtHostDocumentData:	private _positionAt(offset: number): vscode.Position {
		offset = Math.floor(offset);
		offset = Math.max(0, offset);

		this._ensureLineStarts();
		const out = this._lineStarts!.getIndexOf(offset);

		const lineLength = this._lines[out.index].length;

		// Ensure we return a valid position
		return new Position(out.index, Math.min(out.remainder, lineLength));
	}