/**
* Copyright 2009 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS-IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
function newSkipList() {
var PROFILER = window.PROFILER;
if (!PROFILER) {
PROFILER = function() { return {start:noop, mark:noop, literal:noop, end:noop, cancel:noop}; };
}
function noop() {}
// if there are N elements in the skiplist, "start" is element -1 and "end" is element N
var start = {key:null, levels: 1, upPtrs:[null], downPtrs:[null], downSkips:[1], downSkipWidths:[0]};
var end = {key:null, levels: 1, upPtrs:[null], downPtrs:[null], downSkips:[null], downSkipWidths:[null]};
var numNodes = 0;
var totalWidth = 0;
var keyToNodeMap = {};
start.downPtrs[0] = end;
end.upPtrs[0] = start;
// a "point" object at location x allows modifications immediately after the first
// x elements of the skiplist, such as multiple inserts or deletes.
// After an insert or delete using point P, the point is still valid and points
// to the same index in the skiplist. Other operations with other points invalidate
// this point.
function _getPoint(targetLoc) {
var numLevels = start.levels;
var lvl = numLevels-1;
var i = -1, ws = 0;
var nodes = new Array(numLevels);
var idxs = new Array(numLevels);
var widthSkips = new Array(numLevels);
nodes[lvl] = start;
idxs[lvl] = -1;
widthSkips[lvl] = 0;
while (lvl >= 0) {
var n = nodes[lvl];
while (n.downPtrs[lvl] &&
(i + n.downSkips[lvl] < targetLoc)) {
i += n.downSkips[lvl];
ws += n.downSkipWidths[lvl];
n = n.downPtrs[lvl];
}
nodes[lvl] = n;
idxs[lvl] = i;
widthSkips[lvl] = ws;
lvl--;
if (lvl >= 0) {
nodes[lvl] = n;
}
}
return {nodes:nodes, idxs:idxs, loc:targetLoc, widthSkips:widthSkips, toString: function() {
return "getPoint("+targetLoc+")"; } };
}
function _getNodeAtOffset(targetOffset) {
var i = 0;
var n = start;
var lvl = start.levels-1;
while (lvl >= 0 && n.downPtrs[lvl]) {
while (n.downPtrs[lvl] && (i + n.downSkipWidths[lvl] <= targetOffset)) {
i += n.downSkipWidths[lvl];
n = n.downPtrs[lvl];
}
lvl--;
}
if (n === start) return (start.downPtrs[0] || null);
else if (n === end) return (targetOffset == totalWidth ? (end.upPtrs[0] || null) : null);
return n;
}
function _entryWidth(e) { return (e && e.width) || 0; }
function _insertKeyAtPoint(point, newKey, entry) {
var p = PROFILER("insertKey", false);
var newNode = {key:newKey, levels: 0, upPtrs:[], downPtrs:[], downSkips:[], downSkipWidths:[]};
p.mark("donealloc");
var pNodes = point.nodes;
var pIdxs = point.idxs;
var pLoc = point.loc;
var widthLoc = point.widthSkips[0] + point.nodes[0].downSkipWidths[0];
var newWidth = _entryWidth(entry);
p.mark("loop1");
while (newNode.levels == 0 || Math.random() < 0.01) {
var lvl = newNode.levels;
newNode.levels++;
if (lvl == pNodes.length) {
// assume we have just passed the end of point.nodes, and reached one level greater
// than the skiplist currently supports
pNodes[lvl] = start;
pIdxs[lvl] = -1;
start.levels++;
end.levels++;
start.downPtrs[lvl] = end;
end.upPtrs[lvl] = start;
start.downSkips[lvl] = numNodes+1;
start.downSkipWidths[lvl] = totalWidth;
point.widthSkips[lvl] = 0;
}
var me = newNode;
var up = pNodes[lvl];
var down = up.downPtrs[lvl];
var skip1 = pLoc - pIdxs[lvl];
var skip2 = up.downSkips[lvl] + 1 - skip1;
up.downSkips[lvl] = skip1;
up.downPtrs[lvl] = me;
me.downSkips[lvl] = skip2;
me.upPtrs[lvl] = up;
me.downPtrs[lvl] = down;
down.upPtrs[lvl] = me;
var widthSkip1 = widthLoc - point.widthSkips[lvl];
var widthSkip2 = up.downSkipWidths[lvl] + newWidth - widthSkip1;
up.downSkipWidths[lvl] = widthSkip1;
me.downSkipWidths[lvl] = widthSkip2;
}
p.mark("loop2");
p.literal(pNodes.length, "PNL");
for(var lvl=newNode.levels; lvl<pNodes.length; lvl++) {
var up = pNodes[lvl];
up.downSkips[lvl]++;
up.downSkipWidths[lvl] += newWidth;
}
p.mark("map");
keyToNodeMap['$KEY$'+newKey] = newNode;
numNodes++;
totalWidth += newWidth;
p.end();
}
function _getNodeAtPoint(point) {
return point.nodes[0].downPtrs[0];
}
function _incrementPoint(point) {
point.loc++;
for(var i=0;i<point.nodes.length;i++) {
if (point.idxs[i] + point.nodes[i].downSkips[i] < point.loc) {
point.idxs[i] += point.nodes[i].downSkips[i];
point.widthSkips[i] += point.nodes[i].downSkipWidths[i];
point.nodes[i] = point.nodes[i].downPtrs[i];
}
}
}
function _deleteKeyAtPoint(point) {
var elem = point.nodes[0].downPtrs[0];
var elemWidth = _entryWidth(elem.entry);
for(var i=0;i<point.nodes.length;i++) {
if (i < elem.levels) {
var up = elem.upPtrs[i];
var down = elem.downPtrs[i];
var totalSkip = up.downSkips[i] + elem.downSkips[i] - 1;
up.downPtrs[i] = down;
down.upPtrs[i] = up;
up.downSkips[i] = totalSkip;
var totalWidthSkip = up.downSkipWidths[i] + elem.downSkipWidths[i] - elemWidth;
up.downSkipWidths[i] = totalWidthSkip;
}
else {
var up = point.nodes[i];
var down = up.downPtrs[i];
up.downSkips[i]--;
up.downSkipWidths[i] -= elemWidth;
}
}
delete keyToNodeMap['$KEY$'+elem.key];
numNodes--;
totalWidth -= elemWidth;
}
function _propagateWidthChange(node) {
var oldWidth = node.downSkipWidths[0];
var newWidth = _entryWidth(node.entry);
var widthChange = newWidth - oldWidth;
var n = node;
var lvl = 0;
while (lvl < n.levels) {
n.downSkipWidths[lvl] += widthChange;
lvl++;
while (lvl >= n.levels && n.upPtrs[lvl-1]) {
n = n.upPtrs[lvl-1];
}
}
totalWidth += widthChange;
}
function _getNodeIndex(node, byWidth) {
var dist = (byWidth ? 0 : -1);
var n = node;
while (n !== start) {
var lvl = n.levels-1;
n = n.upPtrs[lvl];
if (byWidth) dist += n.downSkipWidths[lvl];
else dist += n.downSkips[lvl];
}
return dist;
}
/*function _debugToString() {
var array = [start];
while (array[array.length-1] !== end) {
array[array.length] = array[array.length-1].downPtrs[0];
}
function getIndex(node) {
if (!node) return null;
for(var i=0;i<array.length;i++) {
if (array[i] === node)
return i-1;
}
return false;
}
var processedArray = map(array, function(node) {
var x = {key:node.key, levels: node.levels, downSkips: node.downSkips,
upPtrs: map(node.upPtrs, getIndex), downPtrs: map(node.downPtrs, getIndex),
downSkipWidths: node.downSkipWidths};
return x;
});
return map(processedArray, function (x) { return x.toSource(); }).join("\n");
}*/
function _getNodeByKey(key) {
return keyToNodeMap['$KEY$'+key];
}
// Returns index of first entry such that entryFunc(entry) is truthy,
// or length() if no such entry. Assumes all falsy entries come before
// all truthy entries.
function _search(entryFunc) {
var low = start;
var lvl = start.levels-1;
var lowIndex = -1;
function f(node) {
if (node === start) return false;
else if (node === end) return true;
else return entryFunc(node.entry);
}
while (lvl >= 0) {
var nextLow = low.downPtrs[lvl];
while (!f(nextLow)) {
lowIndex += low.downSkips[lvl];
low = nextLow;
nextLow = low.downPtrs[lvl];
}
lvl--;
}
return lowIndex+1;
}
/*
The skip-list contains "entries", JavaScript objects that each must have a unique "key" property
that is a string.
*/
var self = {
length: function() { return numNodes; },
atIndex: function(i) {
if (i < 0) console.warn("atIndex("+i+")");
if (i >= numNodes) console.warn("atIndex("+i+">="+numNodes+")");
return _getNodeAtPoint(_getPoint(i)).entry;
},
// differs from Array.splice() in that new elements are in an array, not varargs
splice: function(start, deleteCount, newEntryArray) {
if (start < 0) console.warn("splice("+start+", ...)");
if (start + deleteCount > numNodes) {
console.warn("splice("+start+", "+deleteCount+", ...), N="+numNodes);
console.warn("%s %s %s", typeof start, typeof deleteCount, typeof numNodes);
console.trace();
}
if (! newEntryArray) newEntryArray = [];
var pt = _getPoint(start);
for(var i=0;i<deleteCount;i++) {
_deleteKeyAtPoint(pt);
}
for(var i=(newEntryArray.length-1);i>=0;i--) {
var entry = newEntryArray[i];
_insertKeyAtPoint(pt, entry.key, entry);
var node = _getNodeByKey(entry.key);
node.entry = entry;
}
},
next: function (entry) {
return _getNodeByKey(entry.key).downPtrs[0].entry || null;
},
prev: function (entry) {
return _getNodeByKey(entry.key).upPtrs[0].entry || null;
},
push: function(entry) {
self.splice(numNodes, 0, [entry]);
},
slice: function(start, end) {
// act like Array.slice()
if (start === undefined) start = 0;
else if (start < 0) start += numNodes;
if (end === undefined) end = numNodes;
else if (end < 0) end += numNodes;
if (start < 0) start = 0;
if (start > numNodes) start = numNodes;
if (end < 0) end = 0;
if (end > numNodes) end = numNodes;
dmesg(String([start,end,numNodes]));
if (end <= start) return [];
var n = self.atIndex(start);
var array = [n];
for(var i=1;i<(end-start);i++) {
n = self.next(n);
array.push(n);
}
return array;
},
atKey: function(key) { return _getNodeByKey(key).entry; },
indexOfKey: function(key) { return _getNodeIndex(_getNodeByKey(key)); },
indexOfEntry: function (entry) { return self.indexOfKey(entry.key); },
containsKey: function(key) { return !!(_getNodeByKey(key)); },
// gets the last entry starting at or before the offset
atOffset: function(offset) { return _getNodeAtOffset(offset).entry; },
keyAtOffset: function(offset) { return self.atOffset(offset).key; },
offsetOfKey: function(key) { return _getNodeIndex(_getNodeByKey(key), true); },
offsetOfEntry: function(entry) { return self.offsetOfKey(entry.key); },
setEntryWidth: function(entry, width) { entry.width = width; _propagateWidthChange(_getNodeByKey(entry.key)); },
totalWidth: function() { return totalWidth; },
offsetOfIndex: function(i) {
if (i < 0) return 0;
if (i >= numNodes) return totalWidth;
return self.offsetOfEntry(self.atIndex(i));
},
indexOfOffset: function(offset) {
if (offset <= 0) return 0;
if (offset >= totalWidth) return numNodes;
return self.indexOfEntry(self.atOffset(offset));
},
search: function(entryFunc) {
return _search(entryFunc);
},
//debugToString: _debugToString,
debugGetPoint: _getPoint,
debugDepth: function() { return start.levels; }
}
return self;
}
