src/vs/editor/common/model/textModel.ts/TextModel/getOffsetAt
class TextModel:	public getOffsetAt(rawPosition: IPosition): number {
		this._assertNotDisposed();
		const position = this._validatePosition(rawPosition.lineNumber, rawPosition.column, StringOffsetValidationType.Relaxed);
		return this._buffer.getOffsetAt(position.lineNumber, position.column);
	}