diff --git a/src/vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase.ts b/src/vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase.ts
index 9598964eff93fef6ccfca4f32b957c8584ced00a..3c98e8b6b31cae17dc6082bb1c98c0772f4704a0 100644
--- a/src/vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase.ts
+++ b/src/vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase.ts
@@ -8,49 +8,7 @@ import { Position } from 'vs/editor/common/core/position';
 import { CharCode } from 'vs/base/common/charCode';
 import { Range } from 'vs/editor/common/core/range';
 import { ITextSnapshot } from 'vs/platform/files/common/files';
-
-export const enum NodeColor {
-	Black = 0,
-	Red = 1,
-}
-
-export function getNodeColor(node: TreeNode) {
-	return node.color;
-}
-
-function leftest(node: TreeNode): TreeNode {
-	while (node.left !== SENTINEL) {
-		node = node.left;
-	}
-	return node;
-}
-
-function righttest(node: TreeNode): TreeNode {
-	while (node.right !== SENTINEL) {
-		node = node.right;
-	}
-	return node;
-}
-
-function calculateSize(node: TreeNode): number {
-	if (node === SENTINEL) {
-		return 0;
-	}
-
-	return node.size_left + node.piece.length + calculateSize(node.right);
-}
-
-function calculateLF(node: TreeNode): number {
-	if (node === SENTINEL) {
-		return 0;
-	}
-
-	return node.lf_left + node.piece.lineFeedCnt + calculateLF(node.right);
-}
-
-function resetSentinel(): void {
-	SENTINEL.parent = SENTINEL;
-}
+import { leftest, righttest, updateTreeMetadata, rbDelete, fixInsert, NodeColor, SENTINEL, TreeNode } from 'vs/editor/common/model/pieceTreeTextBuffer/rbTreeBase';
 
 // const lfRegex = new RegExp(/\r\n|\r|\n/g);
 
@@ -138,84 +96,6 @@ export function createLineStarts(r: number[], str: string): LineStarts {
 	return result;
 }
 
-export class TreeNode {
-	parent: TreeNode;
-	left: TreeNode;
-	right: TreeNode;
-	color: NodeColor;
-
-	// Piece
-	piece: Piece;
-	size_left: number; // size of the left subtree (not inorder)
-	lf_left: number; // line feeds cnt in the left subtree (not in order)
-
-	constructor(piece: Piece, color: NodeColor) {
-		this.piece = piece;
-		this.color = color;
-		this.size_left = 0;
-		this.lf_left = 0;
-		this.parent = null;
-		this.left = null;
-		this.right = null;
-	}
-
-	public next(): TreeNode {
-		if (this.right !== SENTINEL) {
-			return leftest(this.right);
-		}
-
-		let node: TreeNode = this;
-
-		while (node.parent !== SENTINEL) {
-			if (node.parent.left === node) {
-				break;
-			}
-
-			node = node.parent;
-		}
-
-		if (node.parent === SENTINEL) {
-			return SENTINEL;
-		} else {
-			return node.parent;
-		}
-	}
-
-	public prev(): TreeNode {
-		if (this.left !== SENTINEL) {
-			return righttest(this.left);
-		}
-
-		let node: TreeNode = this;
-
-		while (node.parent !== SENTINEL) {
-			if (node.parent.right === node) {
-				break;
-			}
-
-			node = node.parent;
-		}
-
-		if (node.parent === SENTINEL) {
-			return SENTINEL;
-		} else {
-			return node.parent;
-		}
-	}
-
-	public detach(): void {
-		this.parent = null;
-		this.left = null;
-		this.right = null;
-	}
-}
-
-export const SENTINEL: TreeNode = new TreeNode(null, NodeColor.Black);
-SENTINEL.parent = SENTINEL;
-SENTINEL.left = SENTINEL;
-SENTINEL.right = SENTINEL;
-SENTINEL.color = NodeColor.Black;
-
 export interface NodePosition {
 	/**
 	 * Piece Index
@@ -393,7 +273,6 @@ export class PieceTreeBase {
 		this.create(chunks);
 	}
 
-
 	// #region Buffer API
 	public createSnapshot(BOM: string): ITextSnapshot {
 		return new PieceTreeSnapshot(this, BOM);
@@ -654,7 +533,7 @@ export class PieceTreeBase {
 			if (startPosition.nodeStartOffset === offset) {
 				if (cnt === startNode.piece.length) { // delete node
 					let next = startNode.next();
-					this.rbDelete(startNode);
+					rbDelete(this, startNode);
 					this.validateCRLFWithPrevNode(next);
 					this.computeBufferMetadata();
 					return;
@@ -718,7 +597,7 @@ export class PieceTreeBase {
 			piece.length -= 1;
 
 			value += '\n';
-			this.updateTreeMetadata(node, -1, -1);
+			updateTreeMetadata(this, node, -1, -1);
 
 			if (node.piece.length === 0) {
 				nodesToDel.push(node);
@@ -822,7 +701,7 @@ export class PieceTreeBase {
 
 	deleteNodes(nodes: TreeNode[]): void {
 		for (let i = 0; i < nodes.length; i++) {
-			this.rbDelete(nodes[i]);
+			rbDelete(this, nodes[i]);
 		}
 	}
 
@@ -978,7 +857,7 @@ export class PieceTreeBase {
 		let lf_delta = piece.lineFeedCnt - originalLFCnt;
 		let size_delta = newEndOffset - originalEndOffset;
 		piece.length += size_delta;
-		this.updateTreeMetadata(node, size_delta, lf_delta);
+		updateTreeMetadata(this, node, size_delta, lf_delta);
 	}
 
 	deleteNodeHead(node: TreeNode, pos: BufferCursor) {
@@ -992,7 +871,7 @@ export class PieceTreeBase {
 		let lf_delta = piece.lineFeedCnt - originalLFCnt;
 		let size_delta = originalStartOffset - newStartOffset;
 		piece.length += size_delta;
-		this.updateTreeMetadata(node, size_delta, lf_delta);
+		updateTreeMetadata(this, node, size_delta, lf_delta);
 	}
 
 	shrinkNode(node: TreeNode, start: BufferCursor, end: BufferCursor) {
@@ -1008,7 +887,7 @@ export class PieceTreeBase {
 		let newLength = this.offsetInBuffer(piece.bufferIndex, start) - this.offsetInBuffer(piece.bufferIndex, originalStartPos);
 		let newLFCnt = piece.lineFeedCnt;
 		piece.length = newLength;
-		this.updateTreeMetadata(node, newLength - oldLength, newLFCnt - oldLFCnt);
+		updateTreeMetadata(this, node, newLength - oldLength, newLFCnt - oldLFCnt);
 
 		// new right piece, end, originalEndPos
 		let newPiece = new Piece(
@@ -1052,7 +931,7 @@ export class PieceTreeBase {
 		node.piece.lineFeedCnt = newLineFeedCnt;
 		let lf_delta = newLineFeedCnt - oldLineFeedCnt;
 		this._lastChangeBufferPos = endPos;
-		this.updateTreeMetadata(node, value.length, lf_delta);
+		updateTreeMetadata(this, node, value.length, lf_delta);
 	}
 
 	nodeAt(offset: number): NodePosition {
@@ -1247,7 +1126,7 @@ export class PieceTreeBase {
 		prev.piece.length -= 1;
 		prev.piece.lineFeedCnt -= 1;
 
-		this.updateTreeMetadata(prev, - 1, -1);
+		updateTreeMetadata(this, prev, - 1, -1);
 		if (prev.piece.length === 0) {
 			nodesToDel.push(prev);
 		}
@@ -1259,7 +1138,7 @@ export class PieceTreeBase {
 		next.piece.lineFeedCnt = this.getLineFeedCnt(next.piece.bufferIndex, next.piece.start, next.piece.end); // @todo, we can optimize
 		// }
 
-		this.updateTreeMetadata(next, - 1, -1);
+		updateTreeMetadata(this, next, - 1, -1);
 		if (next.piece.length === 0) {
 			nodesToDel.push(next);
 		}
@@ -1270,7 +1149,7 @@ export class PieceTreeBase {
 		// delete empty nodes
 
 		for (let i = 0; i < nodesToDel.length; i++) {
-			this.rbDelete(nodesToDel[i]);
+			rbDelete(this, nodesToDel[i]);
 		}
 	}
 
@@ -1282,7 +1161,7 @@ export class PieceTreeBase {
 				value += '\n';
 
 				if (nextNode.piece.length === 1) {
-					this.rbDelete(nextNode);
+					rbDelete(this, nextNode);
 				} else {
 
 					let piece = nextNode.piece;
@@ -1290,7 +1169,7 @@ export class PieceTreeBase {
 					piece.start = newStart;
 					piece.length -= 1;
 					piece.lineFeedCnt = this.getLineFeedCnt(piece.bufferIndex, piece.start, piece.end); // @todo, we can optimize
-					this.updateTreeMetadata(nextNode, -1, -1);
+					updateTreeMetadata(this, nextNode, -1, -1);
 				}
 				return true;
 			}
@@ -1303,7 +1182,7 @@ export class PieceTreeBase {
 
 	// #endregion
 
-	// #region Red Black Tree
+	// #region Tree operations
 	iterate(node: TreeNode, callback: (node: TreeNode) => boolean): boolean {
 		if (node === SENTINEL) {
 			return callback(SENTINEL);
@@ -1330,53 +1209,6 @@ export class PieceTreeBase {
 		return currentContent;
 	}
 
-	leftRotate(x: TreeNode) {
-		let y = x.right;
-
-		// fix size_left
-		y.size_left += x.size_left + (x.piece ? x.piece.length : 0);
-		y.lf_left += x.lf_left + (x.piece ? x.piece.lineFeedCnt : 0);
-		x.right = y.left;
-
-		if (y.left !== SENTINEL) {
-			y.left.parent = x;
-		}
-		y.parent = x.parent;
-		if (x.parent === SENTINEL) {
-			this.root = y;
-		} else if (x.parent.left === x) {
-			x.parent.left = y;
-		} else {
-			x.parent.right = y;
-		}
-		y.left = x;
-		x.parent = y;
-	}
-
-	rightRotate(y: TreeNode) {
-		let x = y.left;
-		y.left = x.right;
-		if (x.right !== SENTINEL) {
-			x.right.parent = y;
-		}
-		x.parent = y.parent;
-
-		// fix size_left
-		y.size_left -= x.size_left + (x.piece ? x.piece.length : 0);
-		y.lf_left -= x.lf_left + (x.piece ? x.piece.lineFeedCnt : 0);
-
-		if (y.parent === SENTINEL) {
-			this.root = x;
-		} else if (y === y.parent.right) {
-			y.parent.right = x;
-		} else {
-			y.parent.left = x;
-		}
-
-		x.right = y;
-		y.parent = x;
-	}
-
 	/**
 	 *      node              node
 	 *     /  \              /  \
@@ -1405,7 +1237,7 @@ export class PieceTreeBase {
 			z.parent = nextNode;
 		}
 
-		this.fixInsert(z);
+		fixInsert(this, z);
 		return z;
 	}
 
@@ -1437,266 +1269,10 @@ export class PieceTreeBase {
 			z.parent = prevNode;
 		}
 
-		this.fixInsert(z);
+		fixInsert(this, z);
 		return z;
 	}
 
-	rbDelete(z: TreeNode) {
-		let x: TreeNode;
-		let y: TreeNode;
-
-		if (z.left === SENTINEL) {
-			y = z;
-			x = y.right;
-		} else if (z.right === SENTINEL) {
-			y = z;
-			x = y.left;
-		} else {
-			y = leftest(z.right);
-			x = y.right;
-		}
-
-		if (y === this.root) {
-			this.root = x;
-
-			// if x is null, we are removing the only node
-			x.color = NodeColor.Black;
-			z.detach();
-			resetSentinel();
-			this.root.parent = SENTINEL;
-
-			return;
-		}
-
-		let yWasRed = (y.color === NodeColor.Red);
-
-		if (y === y.parent.left) {
-			y.parent.left = x;
-		} else {
-			y.parent.right = x;
-		}
-
-		if (y === z) {
-			x.parent = y.parent;
-			this.recomputeTreeMetadata(x);
-		} else {
-			if (y.parent === z) {
-				x.parent = y;
-			} else {
-				x.parent = y.parent;
-			}
-
-			// as we make changes to x's hierarchy, update size_left of subtree first
-			this.recomputeTreeMetadata(x);
-
-			y.left = z.left;
-			y.right = z.right;
-			y.parent = z.parent;
-			y.color = z.color;
-
-			if (z === this.root) {
-				this.root = y;
-			} else {
-				if (z === z.parent.left) {
-					z.parent.left = y;
-				} else {
-					z.parent.right = y;
-				}
-			}
-
-			if (y.left !== SENTINEL) {
-				y.left.parent = y;
-			}
-			if (y.right !== SENTINEL) {
-				y.right.parent = y;
-			}
-			// update metadata
-			// we replace z with y, so in this sub tree, the length change is z.item.length
-			y.size_left = z.size_left;
-			y.lf_left = z.lf_left;
-			this.recomputeTreeMetadata(y);
-		}
-
-		z.detach();
-
-		if (x.parent.left === x) {
-			let newSizeLeft = calculateSize(x);
-			let newLFLeft = calculateLF(x);
-			if (newSizeLeft !== x.parent.size_left || newLFLeft !== x.parent.lf_left) {
-				let delta = newSizeLeft - x.parent.size_left;
-				let lf_delta = newLFLeft - x.parent.lf_left;
-				x.parent.size_left = newSizeLeft;
-				x.parent.lf_left = newLFLeft;
-				this.updateTreeMetadata(x.parent, delta, lf_delta);
-			}
-		}
-
-		this.recomputeTreeMetadata(x.parent);
-
-		if (yWasRed) {
-			resetSentinel();
-			return;
-		}
-
-		// RB-DELETE-FIXUP
-		let w: TreeNode;
-		while (x !== this.root && x.color === NodeColor.Black) {
-			if (x === x.parent.left) {
-				w = x.parent.right;
-
-				if (w.color === NodeColor.Red) {
-					w.color = NodeColor.Black;
-					x.parent.color = NodeColor.Red;
-					this.leftRotate(x.parent);
-					w = x.parent.right;
-				}
-
-				if (w.left.color === NodeColor.Black && w.right.color === NodeColor.Black) {
-					w.color = NodeColor.Red;
-					x = x.parent;
-				} else {
-					if (w.right.color === NodeColor.Black) {
-						w.left.color = NodeColor.Black;
-						w.color = NodeColor.Red;
-						this.rightRotate(w);
-						w = x.parent.right;
-					}
-
-					w.color = x.parent.color;
-					x.parent.color = NodeColor.Black;
-					w.right.color = NodeColor.Black;
-					this.leftRotate(x.parent);
-					x = this.root;
-				}
-			} else {
-				w = x.parent.left;
-
-				if (w.color === NodeColor.Red) {
-					w.color = NodeColor.Black;
-					x.parent.color = NodeColor.Red;
-					this.rightRotate(x.parent);
-					w = x.parent.left;
-				}
-
-				if (w.left.color === NodeColor.Black && w.right.color === NodeColor.Black) {
-					w.color = NodeColor.Red;
-					x = x.parent;
-
-				} else {
-					if (w.left.color === NodeColor.Black) {
-						w.right.color = NodeColor.Black;
-						w.color = NodeColor.Red;
-						this.leftRotate(w);
-						w = x.parent.left;
-					}
-
-					w.color = x.parent.color;
-					x.parent.color = NodeColor.Black;
-					w.left.color = NodeColor.Black;
-					this.rightRotate(x.parent);
-					x = this.root;
-				}
-			}
-		}
-		x.color = NodeColor.Black;
-		resetSentinel();
-	}
-
-	fixInsert(x: TreeNode) {
-		this.recomputeTreeMetadata(x);
-
-		while (x !== this.root && x.parent.color === NodeColor.Red) {
-			if (x.parent === x.parent.parent.left) {
-				const y = x.parent.parent.right;
-
-				if (y.color === NodeColor.Red) {
-					x.parent.color = NodeColor.Black;
-					y.color = NodeColor.Black;
-					x.parent.parent.color = NodeColor.Red;
-					x = x.parent.parent;
-				} else {
-					if (x === x.parent.right) {
-						x = x.parent;
-						this.leftRotate(x);
-					}
-
-					x.parent.color = NodeColor.Black;
-					x.parent.parent.color = NodeColor.Red;
-					this.rightRotate(x.parent.parent);
-				}
-			} else {
-				const y = x.parent.parent.left;
-
-				if (y.color === NodeColor.Red) {
-					x.parent.color = NodeColor.Black;
-					y.color = NodeColor.Black;
-					x.parent.parent.color = NodeColor.Red;
-					x = x.parent.parent;
-				} else {
-					if (x === x.parent.left) {
-						x = x.parent;
-						this.rightRotate(x);
-					}
-					x.parent.color = NodeColor.Black;
-					x.parent.parent.color = NodeColor.Red;
-					this.leftRotate(x.parent.parent);
-				}
-			}
-		}
-
-		this.root.color = NodeColor.Black;
-	}
-
-	updateTreeMetadata(x: TreeNode, delta: number, lineFeedCntDelta: number): void {
-		// node length change or line feed count change
-		while (x !== this.root && x !== SENTINEL) {
-			if (x.parent.left === x) {
-				x.parent.size_left += delta;
-				x.parent.lf_left += lineFeedCntDelta;
-			}
-
-			x = x.parent;
-		}
-	}
-
-	recomputeTreeMetadata(x: TreeNode) {
-		let delta = 0;
-		let lf_delta = 0;
-		if (x === this.root) {
-			return;
-		}
-
-		if (delta === 0) {
-			// go upwards till the node whose left subtree is changed.
-			while (x !== this.root && x === x.parent.right) {
-				x = x.parent;
-			}
-
-			if (x === this.root) {
-				// well, it means we add a node to the end (inorder)
-				return;
-			}
-
-			// x is the node whose right subtree is changed.
-			x = x.parent;
-
-			delta = calculateSize(x.left) - x.size_left;
-			lf_delta = calculateLF(x.left) - x.lf_left;
-			x.size_left += delta;
-			x.lf_left += lf_delta;
-		}
-
-		// go upwards till root. O(logN)
-		while (x !== this.root && (delta !== 0 || lf_delta !== 0)) {
-			if (x.parent.left === x) {
-				x.parent.size_left += delta;
-				x.parent.lf_left += lf_delta;
-			}
-
-			x = x.parent;
-		}
-	}
-
 	getContentOfSubTree(node: TreeNode): string {
 		let str = '';
 
diff --git a/src/vs/editor/common/model/pieceTreeTextBuffer/rbTreeBase.ts b/src/vs/editor/common/model/pieceTreeTextBuffer/rbTreeBase.ts
new file mode 100644
index 0000000000000000000000000000000000000000..84417b947cd7b47d1d162eab284b601f1770b359
--- /dev/null
+++ b/src/vs/editor/common/model/pieceTreeTextBuffer/rbTreeBase.ts
@@ -0,0 +1,427 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+'use strict';
+
+import { Piece, PieceTreeBase } from 'vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase';
+
+export class TreeNode {
+	parent: TreeNode;
+	left: TreeNode;
+	right: TreeNode;
+	color: NodeColor;
+
+	// Piece
+	piece: Piece;
+	size_left: number; // size of the left subtree (not inorder)
+	lf_left: number; // line feeds cnt in the left subtree (not in order)
+
+	constructor(piece: Piece, color: NodeColor) {
+		this.piece = piece;
+		this.color = color;
+		this.size_left = 0;
+		this.lf_left = 0;
+		this.parent = null;
+		this.left = null;
+		this.right = null;
+	}
+
+	public next(): TreeNode {
+		if (this.right !== SENTINEL) {
+			return leftest(this.right);
+		}
+
+		let node: TreeNode = this;
+
+		while (node.parent !== SENTINEL) {
+			if (node.parent.left === node) {
+				break;
+			}
+
+			node = node.parent;
+		}
+
+		if (node.parent === SENTINEL) {
+			return SENTINEL;
+		} else {
+			return node.parent;
+		}
+	}
+
+	public prev(): TreeNode {
+		if (this.left !== SENTINEL) {
+			return righttest(this.left);
+		}
+
+		let node: TreeNode = this;
+
+		while (node.parent !== SENTINEL) {
+			if (node.parent.right === node) {
+				break;
+			}
+
+			node = node.parent;
+		}
+
+		if (node.parent === SENTINEL) {
+			return SENTINEL;
+		} else {
+			return node.parent;
+		}
+	}
+
+	public detach(): void {
+		this.parent = null;
+		this.left = null;
+		this.right = null;
+	}
+}
+
+export const SENTINEL: TreeNode = new TreeNode(null, NodeColor.Black);
+SENTINEL.parent = SENTINEL;
+SENTINEL.left = SENTINEL;
+SENTINEL.right = SENTINEL;
+SENTINEL.color = NodeColor.Black;
+
+export const enum NodeColor {
+	Black = 0,
+	Red = 1,
+}
+
+export function leftest(node: TreeNode): TreeNode {
+	while (node.left !== SENTINEL) {
+		node = node.left;
+	}
+	return node;
+}
+
+export function righttest(node: TreeNode): TreeNode {
+	while (node.right !== SENTINEL) {
+		node = node.right;
+	}
+	return node;
+}
+
+export function calculateSize(node: TreeNode): number {
+	if (node === SENTINEL) {
+		return 0;
+	}
+
+	return node.size_left + node.piece.length + calculateSize(node.right);
+}
+
+export function calculateLF(node: TreeNode): number {
+	if (node === SENTINEL) {
+		return 0;
+	}
+
+	return node.lf_left + node.piece.lineFeedCnt + calculateLF(node.right);
+}
+
+export function resetSentinel(): void {
+	SENTINEL.parent = SENTINEL;
+}
+
+export function leftRotate(tree: PieceTreeBase, x: TreeNode) {
+	let y = x.right;
+
+	// fix size_left
+	y.size_left += x.size_left + (x.piece ? x.piece.length : 0);
+	y.lf_left += x.lf_left + (x.piece ? x.piece.lineFeedCnt : 0);
+	x.right = y.left;
+
+	if (y.left !== SENTINEL) {
+		y.left.parent = x;
+	}
+	y.parent = x.parent;
+	if (x.parent === SENTINEL) {
+		tree.root = y;
+	} else if (x.parent.left === x) {
+		x.parent.left = y;
+	} else {
+		x.parent.right = y;
+	}
+	y.left = x;
+	x.parent = y;
+}
+
+export function rightRotate(tree: PieceTreeBase, y: TreeNode) {
+	let x = y.left;
+	y.left = x.right;
+	if (x.right !== SENTINEL) {
+		x.right.parent = y;
+	}
+	x.parent = y.parent;
+
+	// fix size_left
+	y.size_left -= x.size_left + (x.piece ? x.piece.length : 0);
+	y.lf_left -= x.lf_left + (x.piece ? x.piece.lineFeedCnt : 0);
+
+	if (y.parent === SENTINEL) {
+		tree.root = x;
+	} else if (y === y.parent.right) {
+		y.parent.right = x;
+	} else {
+		y.parent.left = x;
+	}
+
+	x.right = y;
+	y.parent = x;
+}
+
+export function rbDelete(tree: PieceTreeBase, z: TreeNode) {
+	let x: TreeNode;
+	let y: TreeNode;
+
+	if (z.left === SENTINEL) {
+		y = z;
+		x = y.right;
+	} else if (z.right === SENTINEL) {
+		y = z;
+		x = y.left;
+	} else {
+		y = leftest(z.right);
+		x = y.right;
+	}
+
+	if (y === tree.root) {
+		tree.root = x;
+
+		// if x is null, we are removing the only node
+		x.color = NodeColor.Black;
+		z.detach();
+		resetSentinel();
+		tree.root.parent = SENTINEL;
+
+		return;
+	}
+
+	let yWasRed = (y.color === NodeColor.Red);
+
+	if (y === y.parent.left) {
+		y.parent.left = x;
+	} else {
+		y.parent.right = x;
+	}
+
+	if (y === z) {
+		x.parent = y.parent;
+		recomputeTreeMetadata(tree, x);
+	} else {
+		if (y.parent === z) {
+			x.parent = y;
+		} else {
+			x.parent = y.parent;
+		}
+
+		// as we make changes to x's hierarchy, update size_left of subtree first
+		recomputeTreeMetadata(tree, x);
+
+		y.left = z.left;
+		y.right = z.right;
+		y.parent = z.parent;
+		y.color = z.color;
+
+		if (z === tree.root) {
+			tree.root = y;
+		} else {
+			if (z === z.parent.left) {
+				z.parent.left = y;
+			} else {
+				z.parent.right = y;
+			}
+		}
+
+		if (y.left !== SENTINEL) {
+			y.left.parent = y;
+		}
+		if (y.right !== SENTINEL) {
+			y.right.parent = y;
+		}
+		// update metadata
+		// we replace z with y, so in this sub tree, the length change is z.item.length
+		y.size_left = z.size_left;
+		y.lf_left = z.lf_left;
+		recomputeTreeMetadata(tree, y);
+	}
+
+	z.detach();
+
+	if (x.parent.left === x) {
+		let newSizeLeft = calculateSize(x);
+		let newLFLeft = calculateLF(x);
+		if (newSizeLeft !== x.parent.size_left || newLFLeft !== x.parent.lf_left) {
+			let delta = newSizeLeft - x.parent.size_left;
+			let lf_delta = newLFLeft - x.parent.lf_left;
+			x.parent.size_left = newSizeLeft;
+			x.parent.lf_left = newLFLeft;
+			updateTreeMetadata(tree, x.parent, delta, lf_delta);
+		}
+	}
+
+	recomputeTreeMetadata(tree, x.parent);
+
+	if (yWasRed) {
+		resetSentinel();
+		return;
+	}
+
+	// RB-DELETE-FIXUP
+	let w: TreeNode;
+	while (x !== tree.root && x.color === NodeColor.Black) {
+		if (x === x.parent.left) {
+			w = x.parent.right;
+
+			if (w.color === NodeColor.Red) {
+				w.color = NodeColor.Black;
+				x.parent.color = NodeColor.Red;
+				leftRotate(tree, x.parent);
+				w = x.parent.right;
+			}
+
+			if (w.left.color === NodeColor.Black && w.right.color === NodeColor.Black) {
+				w.color = NodeColor.Red;
+				x = x.parent;
+			} else {
+				if (w.right.color === NodeColor.Black) {
+					w.left.color = NodeColor.Black;
+					w.color = NodeColor.Red;
+					rightRotate(tree, w);
+					w = x.parent.right;
+				}
+
+				w.color = x.parent.color;
+				x.parent.color = NodeColor.Black;
+				w.right.color = NodeColor.Black;
+				leftRotate(tree, x.parent);
+				x = tree.root;
+			}
+		} else {
+			w = x.parent.left;
+
+			if (w.color === NodeColor.Red) {
+				w.color = NodeColor.Black;
+				x.parent.color = NodeColor.Red;
+				rightRotate(tree, x.parent);
+				w = x.parent.left;
+			}
+
+			if (w.left.color === NodeColor.Black && w.right.color === NodeColor.Black) {
+				w.color = NodeColor.Red;
+				x = x.parent;
+
+			} else {
+				if (w.left.color === NodeColor.Black) {
+					w.right.color = NodeColor.Black;
+					w.color = NodeColor.Red;
+					leftRotate(tree, w);
+					w = x.parent.left;
+				}
+
+				w.color = x.parent.color;
+				x.parent.color = NodeColor.Black;
+				w.left.color = NodeColor.Black;
+				rightRotate(tree, x.parent);
+				x = tree.root;
+			}
+		}
+	}
+	x.color = NodeColor.Black;
+	resetSentinel();
+}
+
+export function fixInsert(tree: PieceTreeBase, x: TreeNode) {
+	recomputeTreeMetadata(tree, x);
+
+	while (x !== tree.root && x.parent.color === NodeColor.Red) {
+		if (x.parent === x.parent.parent.left) {
+			const y = x.parent.parent.right;
+
+			if (y.color === NodeColor.Red) {
+				x.parent.color = NodeColor.Black;
+				y.color = NodeColor.Black;
+				x.parent.parent.color = NodeColor.Red;
+				x = x.parent.parent;
+			} else {
+				if (x === x.parent.right) {
+					x = x.parent;
+					leftRotate(tree, x);
+				}
+
+				x.parent.color = NodeColor.Black;
+				x.parent.parent.color = NodeColor.Red;
+				rightRotate(tree, x.parent.parent);
+			}
+		} else {
+			const y = x.parent.parent.left;
+
+			if (y.color === NodeColor.Red) {
+				x.parent.color = NodeColor.Black;
+				y.color = NodeColor.Black;
+				x.parent.parent.color = NodeColor.Red;
+				x = x.parent.parent;
+			} else {
+				if (x === x.parent.left) {
+					x = x.parent;
+					rightRotate(tree, x);
+				}
+				x.parent.color = NodeColor.Black;
+				x.parent.parent.color = NodeColor.Red;
+				leftRotate(tree, x.parent.parent);
+			}
+		}
+	}
+
+	tree.root.color = NodeColor.Black;
+}
+
+export function updateTreeMetadata(tree: PieceTreeBase, x: TreeNode, delta: number, lineFeedCntDelta: number): void {
+	// node length change or line feed count change
+	while (x !== tree.root && x !== SENTINEL) {
+		if (x.parent.left === x) {
+			x.parent.size_left += delta;
+			x.parent.lf_left += lineFeedCntDelta;
+		}
+
+		x = x.parent;
+	}
+}
+
+export function recomputeTreeMetadata(tree: PieceTreeBase, x: TreeNode) {
+	let delta = 0;
+	let lf_delta = 0;
+	if (x === tree.root) {
+		return;
+	}
+
+	if (delta === 0) {
+		// go upwards till the node whose left subtree is changed.
+		while (x !== tree.root && x === x.parent.right) {
+			x = x.parent;
+		}
+
+		if (x === tree.root) {
+			// well, it means we add a node to the end (inorder)
+			return;
+		}
+
+		// x is the node whose right subtree is changed.
+		x = x.parent;
+
+		delta = calculateSize(x.left) - x.size_left;
+		lf_delta = calculateLF(x.left) - x.lf_left;
+		x.size_left += delta;
+		x.lf_left += lf_delta;
+	}
+
+	// go upwards till root. O(logN)
+	while (x !== tree.root && (delta !== 0 || lf_delta !== 0)) {
+		if (x.parent.left === x) {
+			x.parent.size_left += delta;
+			x.parent.lf_left += lf_delta;
+		}
+
+		x = x.parent;
+	}
+}
diff --git a/src/vs/editor/test/common/model/pieceTreeTextBuffer/pieceTreeTextBuffer.test.ts b/src/vs/editor/test/common/model/pieceTreeTextBuffer/pieceTreeTextBuffer.test.ts
index a04ab200bd61de8e0b52172fc438393172354ba7..a396f91cc406cd4e61668481e8dff10a17675f52 100644
--- a/src/vs/editor/test/common/model/pieceTreeTextBuffer/pieceTreeTextBuffer.test.ts
+++ b/src/vs/editor/test/common/model/pieceTreeTextBuffer/pieceTreeTextBuffer.test.ts
@@ -9,7 +9,8 @@ import { Position } from 'vs/editor/common/core/position';
 import { Range } from 'vs/editor/common/core/range';
 import { PieceTreeTextBufferBuilder } from 'vs/editor/common/model/pieceTreeTextBuffer/pieceTreeTextBufferBuilder';
 import { DefaultEndOfLine } from 'vs/editor/common/model';
-import { PieceTreeBase, SENTINEL, NodeColor, TreeNode } from 'vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase';
+import { PieceTreeBase } from 'vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase';
+import { SENTINEL, NodeColor, TreeNode } from 'vs/editor/common/model/pieceTreeTextBuffer/rbTreeBase';
 import { PieceTreeTextBuffer } from 'vs/editor/common/model/pieceTreeTextBuffer/pieceTreeTextBuffer';
 
 const alphabet = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ\r\n';