 | Program It |
| A programmer's random thoughts. Copyright © Kenneth Xu 2006 - 2013 |
Here is an interface level class diagram to show the relationship between Java Collection Framework (1.5) interfaces.
More detail class level diagrams can be found in links below
http://www.falkhausen.de/en/diagram/spec/java.util.Collections.html
http://www.jroller.com/VelkaVrana/entry/java_1_6_collections_class
I was playing with my kids during the long weekend and we were trying to solve a puzzle, 36 piece Tropical Fish, made by Outset Media. I have to admit that it was indeed “extremely difficult”, which are the words printed on the box. We gave up in the end. But in order to turn this activity into some positive result, I decided to show my kids how one can write a problem and get the computer to do the job for us. And here we start…
Working with my kids we quickly identified that we need express each piece by its face and four sides. So let’s start with the definition of a piece and its face and sides.
With extremely limited knowledge of tropical marine fish. We worked together to came up with below names.
1: public enum Face
2: {
3: Puffer,
4: Tang,
5: Rainbow,
6: Clown,
7: Zebra,
8: Stars,
9: }
These names are even more farcical. But our goal was to have something that easy to remember, and each has a different first character so only one letter is needed in the printed out.
1: public enum Side
2: {
3: Red,
4: Angel,
5: WhiteHorse,
6: GreenHorse,
7: Strips
8: }
1: public class Piece
2: {
3: public int Id { get; set; } // we assign a unique sequential id to search piece
4: public Face Face { get; set; }
5: public Side Top { get; set; }
6: public Side Bottom { get; set; }
7: public Side Left { get; set; }
8: public Side Right { get; set; }
9:
10: public override string ToString()
11: {
12: return Face + "-" + Id;
13: }
14: }
Just like when we were doing the puzzle manually, we need a place to store and organize the pieces before they gets put into the puzzle. We let the Box do this job, and we also define all the pieces in the box just as what we got when the box was opened.
1: public class Box
2: {
3: readonly int _count;
4: readonly List<Piece> _pieces =
5: new List<Piece>
6: {
7: new Piece {Face = Face.Clown, Top = Side.GreenHorse, Right = Side.Red, Bottom = Side.Angel, Left = Side.WhiteHorse,}, //0
8: new Piece {Face = Face.Clown, Top = Side.Strips, Right = Side.GreenHorse, Bottom = Side.WhiteHorse, Left = Side.Red,},
9: new Piece {Face = Face.Clown, Top = Side.Angel, Right = Side.Strips, Bottom = Side.GreenHorse, Left = Side.Red,},
10: new Piece {Face = Face.Clown, Top = Side.WhiteHorse, Right = Side.Red, Bottom = Side.Angel, Left = Side.GreenHorse,},
11: new Piece {Face = Face.Clown, Top = Side.GreenHorse, Right = Side.Angel, Bottom = Side.WhiteHorse, Left = Side.Red,},
12: new Piece {Face = Face.Clown, Top = Side.Strips, Right = Side.GreenHorse, Bottom = Side.Angel, Left = Side.WhiteHorse,},
13:
14: new Piece {Face = Face.Puffer, Top = Side.GreenHorse, Right = Side.Red, Bottom = Side.Strips, Left = Side.WhiteHorse,}, //6
15: new Piece {Face = Face.Puffer, Top = Side.Angel, Right = Side.Red, Bottom = Side.GreenHorse, Left = Side.WhiteHorse,},
16: new Piece {Face = Face.Puffer, Top = Side.Angel, Right = Side.Strips, Bottom = Side.GreenHorse, Left = Side.WhiteHorse,},
17: new Piece {Face = Face.Puffer, Top = Side.GreenHorse, Right = Side.Strips, Bottom = Side.Angel, Left = Side.WhiteHorse,},
18: new Piece {Face = Face.Puffer, Top = Side.GreenHorse, Right = Side.Angel, Bottom = Side.Red, Left = Side.Strips,},
19: new Piece {Face = Face.Puffer, Top = Side.Angel, Right = Side.GreenHorse, Bottom = Side.Strips, Left = Side.WhiteHorse,},
20:
21: new Piece {Face = Face.Tang, Top = Side.WhiteHorse, Right = Side.Angel, Bottom = Side.Red, Left = Side.GreenHorse,}, //12
22: new Piece {Face = Face.Tang, Top = Side.GreenHorse, Right = Side.Red, Bottom = Side.Strips, Left = Side.WhiteHorse,},
23: new Piece {Face = Face.Tang, Top = Side.Angel, Right = Side.WhiteHorse, Bottom = Side.GreenHorse, Left = Side.Red,},
24: new Piece {Face = Face.Tang, Top = Side.Angel, Right = Side.GreenHorse, Bottom = Side.WhiteHorse, Left = Side.Red,},
25: new Piece {Face = Face.Tang, Top = Side.Strips, Right = Side.WhiteHorse, Bottom = Side.Angel, Left = Side.GreenHorse,},
26: new Piece {Face = Face.Tang, Top = Side.GreenHorse, Right = Side.Red, Bottom = Side.Strips, Left = Side.Angel,},
27:
28: new Piece {Face = Face.Stars, Top = Side.Angel, Right = Side.GreenHorse, Bottom = Side.Red, Left = Side.Strips,}, //18
29: new Piece {Face = Face.Stars, Top = Side.Red, Right = Side.WhiteHorse, Bottom = Side.Angel, Left = Side.GreenHorse,},
30: new Piece {Face = Face.Stars, Top = Side.Strips, Right = Side.WhiteHorse, Bottom = Side.GreenHorse, Left = Side.Angel,},
31: new Piece {Face = Face.Stars, Top = Side.Angel, Right = Side.WhiteHorse, Bottom = Side.GreenHorse, Left = Side.Strips,},
32: new Piece {Face = Face.Stars, Top = Side.Strips, Right = Side.Red, Bottom = Side.WhiteHorse, Left = Side.GreenHorse,},
33: new Piece {Face = Face.Stars, Top = Side.GreenHorse, Right = Side.Red, Bottom = Side.WhiteHorse, Left = Side.Strips,},
34:
35: new Piece {Face = Face.Zebra, Top = Side.WhiteHorse, Right = Side.Strips, Bottom = Side.Red, Left = Side.GreenHorse,}, //24
36: new Piece {Face = Face.Zebra, Top = Side.Angel, Right = Side.Red, Bottom = Side.GreenHorse, Left = Side.Strips,},
37: new Piece {Face = Face.Zebra, Top = Side.GreenHorse, Right = Side.Strips, Bottom = Side.WhiteHorse, Left = Side.Red,},
38: new Piece {Face = Face.Zebra, Top = Side.GreenHorse, Right = Side.Angel, Bottom = Side.Strips, Left = Side.Red,},
39: new Piece {Face = Face.Zebra, Top = Side.Red, Right = Side.Angel, Bottom = Side.Strips, Left = Side.GreenHorse,},
40: new Piece {Face = Face.Zebra, Top = Side.Red, Right = Side.WhiteHorse, Bottom = Side.GreenHorse, Left = Side.Angel,},
41:
42: new Piece {Face = Face.Rainbow, Top = Side.WhiteHorse, Right = Side.GreenHorse, Bottom = Side.Angel, Left = Side.Strips,}, //30
43: new Piece {Face = Face.Rainbow, Top = Side.WhiteHorse, Right = Side.Strips, Bottom = Side.GreenHorse, Left = Side.Angel,},
44: new Piece {Face = Face.Rainbow, Top = Side.WhiteHorse, Right = Side.Strips, Bottom = Side.Angel, Left = Side.GreenHorse,},
45: new Piece {Face = Face.Rainbow, Top = Side.Angel, Right = Side.GreenHorse, Bottom = Side.Strips, Left = Side.Red,},
46: new Piece {Face = Face.Rainbow, Top = Side.Strips, Right = Side.GreenHorse, Bottom = Side.Angel, Left = Side.Red,},
47: new Piece {Face = Face.Rainbow, Top = Side.GreenHorse, Right = Side.Strips, Bottom = Side.WhiteHorse, Left = Side.Angel,},
48: };
49:
50:
51: public Box()
52: {
53: _count = _pieces.Count;
54:
55: for (int i = 0; i < _count; i++)
56: {
57: _pieces[i].Id = i;
58: }
59: }
60:
61: public Piece Take(int index, Predicate<Piece> condition)
62: {
63: for (int i = index; i < _count; i++)
64: {
65: var piece = _pieces[i];
66: if (piece == null) continue;
67: if (condition(piece))
68: {
69: _pieces[i] = null;
70: return piece;
71: }
72: }
73: return null;
74: }
75:
76: public void Return(Piece piece)
77: {
78: _pieces[piece.Id] = piece;
79: }
80: }
In the Box class, we first defined all 36 pieces in a list. Then in the constructor Box(), we gave each piece a unique ID, which is same as its position in the list. We then defined two methods to control the taking and returning of the pieces.
When a piece is taken from the box by using the Take() method, we need to specify a starting index and the condition to search for a matching piece. The starting index is important so that we don’t retry pieces that we already did. The condition is passed in according to the rules of the puzzle and the pieces already put on the puzzle.
When we are stuck, we need to be able to return the piece back and try next. The Box’s Return() method does this job by putting the piece back to its original position in the list.
The solver has a box and a table to solve the puzzle, they are defined and initialized in line 4 and 5. The Main method is the C#’s entry point. It simply calls FindSolution() method to find the solutions, when no solution is found, it displays an error message.
The core logic resides in two methods, FindSolution() and CheckPiece().
CheckPiece verifies if a new piece fits with pieces were already put on the puzzle. It checks:
FindSolution goes through each spot of the puzzle from left to right and top to bottom. It tires each piece one by one until the last spot is filled. When it is stuck, it returns the last piece back to the box and try next one.
When a solution is found, PrintSolution() method is called to print out the layout of the pieces in the solved puzzle.
1: public class Solver
2: {
3: private const int _size = 6;
4: static Piece[,] _puzzle = new Piece[_size,_size];
5: static Box _box = new Box();
6:
7: public static void Main()
8: {
9: if (FindSoution() == 0)
10: {
11: Console.WriteLine("No Answer :(");
12: }
13: }
14:
15: private static int FindSoution()
16: {
17: var count = 0;
18: var i = 0;
19: for (; ; )
20: {
21: var col = i % _size;
22: var row = i / _size;
23:
24: var index = 0;
25: var piece = _puzzle[row, col];
26: if (piece != null) // if we already tried one or more pieces
27: {
28: _puzzle[row, col] = null; // clear
29: _box.Return(piece); // return it back to box
30: index = piece.Id + 1; // and start search for one after it.
31: }
32:
33: piece = _box.Take(index, x => CheckPiece(row, col, x));
34: if (piece == null)
35: {
36: if (i == 0) return count;
37: i--;
38: continue;
39: }
40: _puzzle[row, col] = piece;
41: if (i != _size * _size - 1)
42: {
43: i++;
44: continue;
45: }
46: ++count;
47: Console.WriteLine("Answer " + count);
48: PrintSolution(Console.Out, _puzzle);
49: }
50: }
51:
52: private static bool CheckPiece(int row, int col, Piece x)
53: {
54: if (row != 0 && _puzzle[row - 1, col].Bottom != x.Top ||
55: col != 0 && _puzzle[row, col - 1].Right != x.Left)
56: {
57: return false;
58: }
59: // comment below two for loop to find all non-sudoku answers
60: for (int i = 0; i < row; i++)
61: {
62: if (_puzzle[i, col].Face == x.Face) return false;
63: }
64: for (int i = 0; i < col; i++)
65: {
66: if (_puzzle[row, i].Face == x.Face) return false;
67: }
68: return true;
69: }
70:
71: private static void PrintSolution(TextWriter writer, Piece[,] pieces)
72: {
73: var rows = pieces.GetLength(0);
74: var cols = pieces.GetLength(1);
75: for (var row = 0; row < rows; row++)
76: {
77: for (var col = 0; col < cols; col++)
78: {
79: writer.Write(string.Format(" {0} ",
80: pieces[row, col].Top.ToString()[0]));
81: }
82: writer.WriteLine();
83: for (var col = 0; col < cols; col++)
84: {
85: var piece = pieces[row, col];
86: writer.Write(string.Format("{0} {1} {2} ",
87: piece.Left.ToString()[0],
88: piece.Face.ToString().Substring(0, 4),
89: piece.Right.ToString()[0]));
90: }
91: writer.WriteLine();
92: for (var col = 0; col < cols; col++)
93: {
94: writer.Write(string.Format(" {0} ",
95: pieces[row, col].Bottom.ToString()[0]));
96: }
97: writer.WriteLine();
98: }
99: }
100: }
There is only one solution if the Sudoku rules is considered. The program quickly finds the solution below:
R G A W A G G Zebr A A Rain S S Star G G Clow R R Tang W W Puff S S W R A G A S W R A G A W Clow G G Tang A A Zebr W W Puff S S Star R R Rain G A R G G W S A R G G W S W Puff G G Star W W Clow R R Zebr S S Rain G G Tang W S A A W A A S A A W A A A Star W W Puff R R Tang G G Rain S S Zebr R R Clow S G G W A G G G G W A G G W Tang R R Clow A A Rain S S Star W W Puff R R Zebr A S W G G S S S W G G S S R Rain G G Zebr S S Puff A A Tang R R Clow G G Star R A R R S W W
If the Sudoku rules is not considered, there are total 608 solutions. It took the program a few hours to find all of those.
Some additional interesting facts are:
I encountered a number of custom rules written for FxCop 1.35 in a project. They need to be upgraded to FxCop 1.36. Those custom rules make extensive use of TypeNode.GetTypeNode() method, which does no longer exist in the FxCop 1.36 and above (including Visual Studio build-in Code Analysis).
As Google returned no useful result, I started to explore the new SDK API for an alternative. I found two ways to get a TypeNode instance.
Get an instance of ModuleNode is easy by a location string that I can obtain from a type object, so this sounds like a viable solution:
1: return AssemblyNode.GetAssembly(type.Module.Assembly.Location)
2: .GetType(Identifier.For(type.Namespace), Identifier.For(type.Name));
Code above works great until I encountered nested types. In the case of nested types, the code above just return null. I have used all different combinations of the name, say for a nested type NestedType in MyNamespace.MyType, in below. None of those worked.
| Namespace parameter | Name parameter |
| Namespace | MyType+NestedType |
| Namespace | MyType.NestedType |
| Namespace.MyType | NestedType |
Further investigation found me the method TypeNode.GetNestedType. It turned out that you must get the parent type first, then call that method to get the TypeNode for the nested type. Once this is resolved, I have perfectly working alternative to the missing GetTypeNode in FxCop 1.36. Below are the extension methods to achieve this:
1: public static TypeNode GetType(this ModuleNode @this, Type type)
2: {
3: if (@this == null) { throw new ArgumentNullException("this"); }
4: if (type == null) { throw new ArgumentNullException("type"); }
5: return GetType(@this, type.DeclaringType, type, Identifier.For(type.Namespace));
6: }
7:
8: private static TypeNode GetType(this ModuleNode @this, Type parent, Type type, Identifier @namespace)
9: {
10: if (parent == null) return @this.GetType(@namespace,Identifier.For(type.Name));
11: var parentType = GetType(@this, parent.DeclaringType, parent, @namespace);
12: return parentType.GetNestedType(Identifier.For(type.Name));
13: }
14:
15: public static AssemblyNode GetAssemblyNode(this Type @this)
16: {
17: if (@this == null) throw new ArgumentNullException("this");
18:
19: return AssemblyNode.GetAssembly(@this.Module.Assembly.Location);
20: }
21:
22: public static TypeNode GetTypeNode(this Type @this)
23: {
24: if (@this == null) throw new ArgumentNullException("this");
25: return @this.GetAssemblyNode().GetType(@this);
26: }
As a side note, if you found yourself calling GetTypeNode with a known type, you should define a static field to improve the performance. Just like what was in the FrameworkTypes class. For example, I have below in my project:
1: public static readonly TypeNode CompilerGeneratedAttribute = typeof(CompilerGeneratedAttribute).GetTypeNode();
2: public static readonly TypeNode DebuggerNonUserCodeAttribute = typeof(DebuggerNonUserCodeAttribute).GetTypeNode();
3: public static readonly TypeNode GeneratedCodeAttribute = typeof(GeneratedCodeAttribute).GetTypeNode();
4: public static readonly TypeNode IComponent = typeof(IComponent).GetTypeNode();
5: public static readonly TypeNode FrameworkElement = typeof(FrameworkElement).GetTypeNode();
Today, I received an email from parents of a six years old primary school girl. I shocked on what a school administration did to the little soul. Adding further concerns to the worrying education system in America. Below is the full letter.
A Terrible Thing Happened at the Dutch Neck School
A terrible thing happened to our daughter few weeks ago. She is six and a half years old and a first grader at the Dutch Neck School in West Windsor. We send this email to you because we don't want the same thing to happen to your kids as well.
On Tuesday, March 29, our daughter took two bottles of water (Poland Spring 8oz) to school. She had been taken water to school since the first day she joined the Dutch Neck school. She used to take a large bottle (16oz). On that Tuesday, we asked her to take two small bottles. One is for snack time at classroom, and one is for lunch time because we did not want her to always drink juice or cold milk during lunch time. On that day, our daughter went into the school cafeteria with one bottle of water, and put it under her arm while holding a tray to pick up her lunch. The cafeteria manager stopped her before she checked out and said she stole the water from school. Our daughter explained that she brought the water from home, but the cafeteria staff did not believe her and insisted that she was lying. As a result, our daughter was brought down to crying and pressured to admit that she was stealing. This is not the end: she was then taken to the Principal’s office and forced to write a confession/I am sorry letter and draw a picture to show the stealing process! When my daughter met the Principal and the Assistant of the Principal, she told them again that she did not steal the water and the water was brought from home, but neither believed her.
They made the decision without any further investigation. They did not check with the parents, and they did not check with our daughter's classmates to see if anyone had seen my daughter with the water bottle on her way from the classroom to the cafeteria. The assistant principal called us two hours later and left a message saying that our daughter stole the water from the school cafeteria and they wanted to talk to us about the consequences.
We found the message at about 9:00pm in the evening. Our daughter was so shocked and scared by the whole experience that she didn’t mention anything after school. We sent two emails to the school immediately and explained that we did ask our daughter to take the water to school since we did not want her drink juice or cold milk during lunch. The next morning (Wednesday), we visited the Principal’s office, explained everything in detail, and requested that the principal check with my daughter's classmates. The principal refused to do so, and insisted that cafeteria manager saw my daughter taking the water from the cafeteria shelf. What the Principal told us was totally different as the cafeteria manager told the superintendent in the following investigation. The cafe manager only saw my daughter putting the water bottle under her arm when she was holding a tray to pick up her lunch. What was more, the Principal told us that they would let my daughter write another sorry letter and there was no recess time for her after lunch at that day.
We left the school with determination to prove our daughter's innocent by ourselves. We emailed to the superintendent and called the Mayor of West Windsor. We checked with the parents of our daughter’s classmates and easily found an eye witness: one of the classmates SAW our daughter taking a water bottle from the classroom to the cafeteria on that day.
On that Thursday afternoon, after the superintendent investigated the issue, we received an email from the principal simply letting us know that this incident was dismissed and the stealing record was withdrawn from our daughter's school report. There is no any word of apology in the email.
We cannot accept this email as the end of the issue. The Principal did not admit to any mistake in the way they had handled the whole thing. They even educated us that our daughter should learn to protect herself at the school! How would we expect a six-year-old girl to clearly articulate her own defense when confronted by the principal and the other figures of authority? Isn’t it fearful to know that the “stealing” report would have followed our daughter’s school record everywhere if we had done nothing? Somebody should say sorry for the wrong-doing.
On the first day of this event, the Principal did not check with either the student’s parents or the classmates, two things that were quite easy to do to find out the truth. On the contrary, they forced a six-year-old girl to admit a false accusation in words, in writing and even in drawing!
On the second day, the Principal took no heed of the parents’ explanation and refused even to do a simple investigation among the students. What was worse, they lied that cafeteria manager saw our daughter taking the water from cafeteria shelf. As mentioned above, the cafeteria manager only saw our daughter putting the water bottle under her arm.
In the whole process of the issue, we did not see the vital responsibility from the Principal to students and parents, we only saw negligence, by which a student’s innocence and future could be easily smeared. It is so easy for them to punish their students, but it is so hard for them to acknowledge their mistakes.
After this event, our daughter kept saying she did not want go to the Dutch Neck School anymore, so we had to transfer her to another school. Isn’t it sad that we cannot even trust the school we are paying tax money for to do the right thing to the kids?
All the parents in our daughter's class feel that the school needs to apologize for what it did to our daughter. We write this email to you and wish to get your support. We did this for our daughter, and for all the Dutch Neck students. Please forward this email to any other parents you know. We truly appreciate all the participation in the attached poll. http://www.surveymonkey.com/s/VPR8BGV
It is common that when you have moved your site from one host to another and you want to redirect all the traffic going to old host to be redirect to the new host before the old host is completely unavailable.
This can be easily done with any major web server. For IIS, Microsoft has a page about this and all you need to do is follow the instruction in the section of “to redirect requests to another Web site or directory”.
Sweet, now you type in a URL going to your old site and you automatically landed to the correct page on your new site. But wait, what’s going to happen if one day you have to shutdown the old site completely. Your user’s bookmark and external link from other site will still be pointing to your old site because the redirect was so transparent that they would have never notice the need to correct their bookmark. When the day comes, they’ll suddenly end up with a broken error page.
Yes, we want to put up a page to let our user know about it so they can update their bookmark during the transition period when both old and new site are up and running. Fine, let’s use the method mentioned in the section “to redirect all requests to a single file”. Now our user can see the nicely written notice that the site was moved to a new home. But wait again, what should use do next after reading our notice, they want to go to that particular page on your site! Where should they click?
Well, according to Microsoft, we still have last option. That is redirecting to a program that is smart enough to tell user about the move and then send the user to the right page!? This sounds like what we wanted but does it really justify to write a binary executable for such a simple task? No, there got to be a simpler and better way!
The solution is not difficult. We’re going to tweak the “redirect to program” method by creating an html page with Javascript instead of an binary executable. Let’s call the page “move.html”, you can host the move at anywhere, a virtual dir under old site, anywhere in new site, or a third site.
First, configure you old site’s properties to redirect the site to exactly “http://server/move.html?$P&URI=” without quotes. Make sure none of the checkbox options in the redirect to is checked. See the screenshot below:
Then create the move.html page with below content:
<html>
<script type="text/javascript">
var hu = window.location.search;
var position = hu.lastIndexOf('&URI=');
var query = hu.substring(0, position);
var path = hu.substring(position+5);
if (query == '?') query = '';
var url = 'http://thenewcoolsite' + path + query;
linkstring = '<a href="' + url + '">' + url + '</a>';
</script>
<title>The Cool Site Moved</title>
<body>
<h1>The Cool Site Moved</h1>
Please always use the <a href="http://thenewcoolsite/">http://thenewcoolsite/</a>
to access the the cool site.
<p>
You just landed on the old host of the cool site. This host will be taken offline
soon and you will get an error instead of this page when it happens. Please take
one of the actions below:
<ul>
<li>
If you access from your web browswer's bookmark or faviorate, please update it
now with the new link below.
<li>
If you clicked on a link from an email, please notify the sender to correct the link.
<li>
If you are brought to this page by an application or another web site, please notiffy
the owner of the application ASAP.
</ul>
<p>
The new link to your request is in below. Please click on the link, it will take you
to the page that you are looking for.
<p>
<script type="text/javascript">document.write(linkstring);</script>
</body>
</html>
Now if user access http://oldcoolsite/somedeeplylinked/pagewithparameter.aspx?p1=abc&p2=789, you should get the page below with messages that you want to give to user, as well as a link to the new site that that the user attempted to access.
For this to work, your user’s browser must support Javascript. This is the only limitation but can be a serious limitation for some web sites. But the logic in the Javascript can easily moved to server side with an ASP or JSP.
There are a few good articles explaining how to install Mac OS X on VirtualBox and a lot of people had reported success:
http://www.taranfx.com/install-snow-leopard-virtualbox
http://www.sysprobs.com/mac-os-guest-virtualbox-326-snow-leopard-1064-windows-7-32-bit
http://www.sysprobs.com/install-mac-snow-leopard-1063-oracle-virtualbox-32-apple-intel-pc
But unfortunately, when I try to install on my Lenovo ThinkPad X201 with Core i5 M520 CPU, none of those guide worked. I couldn’t boot up the Mac Installer DVD from the virtual machine. After a number of hours try and error, I finally got to the conclusion that all my failures were because, the boot loader and OS X version combinations that I tried, none of them supports my Core i5 CPU.
I then searched up and down for the support of Core i5 boot loaders. With help from my friend, I found this page. It has no mention of VirtualBox but the tools and instructions worked for me. When I was about to write a full blog of the detail steps, I came to know from Dinesh that he actually had a post about using iBoot with VirtualBox, which was pretty much what I did.
Now you have two options to go. a) Use a pre-built VirtualBox disk image (.vdi) that has both Snow Leopard 10.6.4 and boot loader pre-installed; b) install manually step by step yourself.
This is an easiest option to go,
Snow Leopard 10.6.4 pre-installed bootable VirtualBox disk image download links from fileserve:
Somebody may prefer this option because it allows you customize the installer where you can select if you would install the additional languages and print drivers. I’ll save my time by introducing you to that post for most of it and just noting down things that you need to watch out here.
Lenovo ThinkPad X201, Core i5 M520 CPU, 4GB RAM, Integrated Graphics, Windows 7 Ultimate 32bit, VirtualBox 3.2.8
I have Snow Leopard 10.6.3 Install DVD iso image on hand and so that’s what I used. I believe 10.6.4 will sure work and 10.6.2 is the first version supports Core i series CPU so it “should” work too. Anything older than that won’t work, don’t bother trying.
It is very important that you must update to 10.6.4 before installing the boot loader from MultiBeast package. Otherwise, your Mac won’t boot at all, not even from the iBoot boot loader iso. Always take a snapshot of your VM before you do this.
There are three methods described on this page. I tried first one, doesn’t work, than I tried 2nd one, I cannot start VM. So eventually, that’s how I made it work.
The final xml should look something like below:
... ...
<ExtraData>
<ExtraDataItem name="CustomVideoMode1" value="1280x800x32"/>
<ExtraDataItem name="GUI/LastCloseAction" value="powerOff"/>
... ...
Good luck and your mileage may vary.
Glad to know that the patch I provided near two years ago are now finally applied to the source control. http://trac-hacks.org/ticket/3566