public static isHighSurrogate(model: ICursorSimpleModel, lineNumber: number, charOffset: number): boolean {
		let lineContent = model.getLineContent(lineNumber);
		if (charOffset < 0 || charOffset >= lineContent.length) {
			return false;
		}
		return strings.isHighSurrogate(lineContent.charCodeAt(charOffset));
	}

/**
 * See https://github.com/Microsoft/vscode/issues/6885.
 * It appears that having very large spans causes very slow reading of character positions.
 * So here we try to avoid that.
 */
function splitLargeTokens(lineContent: string, tokens: LinePart[]): LinePart[] {
	let lastTokenEndIndex = 0;
	let result: LinePart[] = [], resultLen = 0;
	for (let i = 0, len = tokens.length; i < len; i++) {
		const token = tokens[i];
		const tokenEndIndex = token.endIndex;
		let diff = (tokenEndIndex - lastTokenEndIndex);
		if (diff > Constants.LongToken) {
			const tokenType = token.type;
			const piecesCount = Math.ceil(diff / Constants.LongToken);
			for (let j = 1; j < piecesCount; j++) {
				let pieceEndIndex = lastTokenEndIndex + (j * Constants.LongToken);
				let lastCharInPiece = lineContent.charCodeAt(pieceEndIndex - 1);
				if (strings.isHighSurrogate(lastCharInPiece)) {
					// Don't cut in the middle of a surrogate pair
					pieceEndIndex--;
				}
				result[resultLen++] = new LinePart(pieceEndIndex, tokenType);
			}
			result[resultLen++] = new LinePart(tokenEndIndex, tokenType);
		} else {
			result[resultLen++] = token;
		}
		lastTokenEndIndex = tokenEndIndex;
	}

	return result;
}

	private _prepareRender(ctx: RenderingContext): ViewCursorRenderData {
		let textContent = '';
		let textContentClassName = '';

		if (this._cursorStyle === TextEditorCursorStyle.Line || this._cursorStyle === TextEditorCursorStyle.LineThin) {
			const visibleRange = ctx.visibleRangeForPosition(this._position);
			if (!visibleRange) {
				// Outside viewport
				return null;
			}
			let width: number;
			if (this._cursorStyle === TextEditorCursorStyle.Line) {
				width = dom.computeScreenAwareSize(this._lineCursorWidth > 0 ? this._lineCursorWidth : 2);
				if (width > 2) {
					const lineContent = this._context.model.getLineContent(this._position.lineNumber);
					textContent = lineContent.charAt(this._position.column - 1);
				}
			} else {
				width = dom.computeScreenAwareSize(1);
			}
			let left = visibleRange.left;
			if (width >= 2 && left >= 1) {
				// try to center cursor
				left -= 1;
			}
			const top = ctx.getVerticalOffsetForLineNumber(this._position.lineNumber) - ctx.bigNumbersDelta;
			return new ViewCursorRenderData(top, left, width, this._lineHeight, textContent, textContentClassName);
		}

		const visibleRangeForCharacter = ctx.linesVisibleRangesForRange(new Range(this._position.lineNumber, this._position.column, this._position.lineNumber, this._position.column + 1), false);

		if (!visibleRangeForCharacter || visibleRangeForCharacter.length === 0 || visibleRangeForCharacter[0].ranges.length === 0) {
			// Outside viewport
			return null;
		}

		const range = visibleRangeForCharacter[0].ranges[0];
		const width = range.width < 1 ? this._typicalHalfwidthCharacterWidth : range.width;

		if (this._cursorStyle === TextEditorCursorStyle.Block) {
			const lineData = this._context.model.getViewLineData(this._position.lineNumber);
			textContent = lineData.content.charAt(this._position.column - 1);
			if (strings.isHighSurrogate(lineData.content.charCodeAt(this._position.column - 1))) {
				textContent += lineData.content.charAt(this._position.column);
			}
			const tokenIndex = lineData.tokens.findTokenIndexAtOffset(this._position.column - 1);
			textContentClassName = lineData.tokens.getClassName(tokenIndex);
		}

		let top = ctx.getVerticalOffsetForLineNumber(this._position.lineNumber) - ctx.bigNumbersDelta;
		let height = this._lineHeight;

		// Underline might interfere with clicking
		if (this._cursorStyle === TextEditorCursorStyle.Underline || this._cursorStyle === TextEditorCursorStyle.UnderlineThin) {
			top += this._lineHeight - 2;
			height = 2;
		}

		return new ViewCursorRenderData(top, range.left, width, height, textContent, textContentClassName);
	}

	/**
	 * Normalize line decorations. Overlapping decorations will generate multiple segments
	 */
	public static normalize(lineContent: string, lineDecorations: LineDecoration[]): DecorationSegment[] {
		if (lineDecorations.length === 0) {
			return [];
		}

		let result: DecorationSegment[] = [];

		let stack = new Stack();
		let nextStartOffset = 0;

		for (let i = 0, len = lineDecorations.length; i < len; i++) {
			let d = lineDecorations[i];
			let startColumn = d.startColumn;
			let endColumn = d.endColumn;
			let className = d.className;

			// If the position would end up in the middle of a high-low surrogate pair, we move it to before the pair
			if (startColumn > 1) {
				const charCodeBefore = lineContent.charCodeAt(startColumn - 2);
				if (strings.isHighSurrogate(charCodeBefore)) {
					startColumn--;
				}
			}

			if (endColumn > 1) {
				const charCodeBefore = lineContent.charCodeAt(endColumn - 2);
				if (strings.isHighSurrogate(charCodeBefore)) {
					endColumn--;
				}
			}

			let currentStartOffset = startColumn - 1;
			let currentEndOffset = endColumn - 2;

			nextStartOffset = stack.consumeLowerThan(currentStartOffset, nextStartOffset, result);

			if (stack.count === 0) {
				nextStartOffset = currentStartOffset;
			}
			stack.insert(currentEndOffset, className);
		}

		stack.consumeLowerThan(Constants.MAX_SAFE_SMALL_INTEGER, nextStartOffset, result);

		return result;
	}

	public write1(charCode: number): void {
		const remainingSpace = this._capacity - this._bufferLength;

		if (remainingSpace <= 1) {
			if (remainingSpace === 0 || strings.isHighSurrogate(charCode)) {
				this._flushBuffer();
			}
		}

		this._buffer[this._bufferLength++] = charCode;
	}

	private positionRightOf(start: IPosition, model: ITextModel): Position {
		let column = start.column;
		let lineNumber = start.lineNumber;

		if (column < model.getLineMaxColumn(lineNumber)) {
			if (isHighSurrogate(model.getLineContent(lineNumber).charCodeAt(column - 1))) {
				// character after column is a high surrogate
				column = column + 2;
			} else {
				column = column + 1;
			}
		} else if (lineNumber < model.getLineCount()) {
			lineNumber = lineNumber + 1;
			column = 0;
		}

		return new Position(lineNumber, column);
	}

function isHighSurrogate(model: ICursorMoveHelperModel, lineNumber: number, column: number) {
	return strings.isHighSurrogate(model.getLineContent(lineNumber).charCodeAt(column - 1));
}