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• Developing Schema Compare for Oracle (Part 3): Ghost Objects

  - by Simon Cooper

  In the previous blog post, I covered how we solved the problem of dependencies between objects and between schemas. However, that isn’t the end of the issue. The dependencies algorithm I described works when you’re querying live databases and you can get dependencies for a particular schema direct from the server, and that’s all well and good. To throw a (rather large) spanner in the works, Schema Compare also has the concept of a snapshot, which is a read-only compressed XML representation of a selection of schemas that can be compared in the same way as a live database. This can be useful for keeping historical records or a baseline of a database schema, or comparing a schema on a computer that doesn’t have direct access to the database. So, how do snapshots interact with dependencies? Inter-database dependencies don't pose an issue as we store the dependencies in the snapshot. However, comparing a snapshot to a live database with cross-schema dependencies does cause a problem; what if the live database has a dependency to an object that does not exist in the snapshot? Take a basic example schema, where you’re only populating SchemaA: SOURCE   TARGET (using snapshot) CREATE TABLE SchemaA.Table1 ( Col1 NUMBER REFERENCES SchemaB.Table1(col1));   CREATE TABLE SchemaA.Table1 ( Col1 VARCHAR2(100)); CREATE TABLE SchemaB.Table1 ( Col1 NUMBER PRIMARY KEY);   CREATE TABLE SchemaB.Table1 ( Col1 VARCHAR2(100)); In this case, we want to generate a sync script to synchronize SchemaA.Table1 on the database represented by the snapshot. When taking a snapshot, database dependencies are followed, but because you’re not comparing it to anything at the time, the comparison dependencies algorithm described in my last post cannot be used. So, as you only take a snapshot of SchemaA on the target database, SchemaB.Table1 will not be in the snapshot. If this snapshot is then used to compare against the above source schema, SchemaB.Table1 will be included in the source, but the object will not be found in the target snapshot. This is the same problem that was solved with comparison dependencies, but here we cannot use the comparison dependencies algorithm as the snapshot has not got any information on SchemaB! We've now hit quite a big problem - we’re trying to include SchemaB.Table1 in the target, but we simply do not know the status of this object on the database the snapshot was taken from; whether it exists in the database at all, whether it’s the same as the target, whether it’s different... What can we do about this sorry state of affairs? Well, not a lot, it would seem. We can’t query the original database, as it may not be accessible, and we cannot assume any default state as it could be wrong and break the script (and we currently do not have a roll-back mechanism for failed synchronizes). The only way to fix this properly is for the user to go right back to the start and re-create the snapshot, explicitly including the schemas of these 'ghost' objects. So, the only thing we can do is flag up dependent ghost objects in the UI, and ask the user what we should do with it – assume it doesn’t exist, assume it’s the same as the target, or specify a definition for it. Unfortunately, such functionality didn’t make the cut for v1 of Schema Compare (as this is very much an edge case for a non-critical piece of functionality), so we simply flag the ghost objects up in the sync wizard as unsyncable, and let the user sort out what’s going on and edit the sync script as appropriate. There are some things that we do do to alleviate somewhat this rather unhappy situation; if a user creates a snapshot from the source or target of a database comparison, we include all the objects registered from the database, not just the ones in the schemas originally selected for comparison. This includes any extra dependent objects registered through the comparison dependencies algorithm. If the user then compares the resulting snapshot against the same database they were comparing against when it was created, the extra dependencies will be included in the snapshot as required and everything will be good. Fortunately, this problem will come up quite rarely, and only when the user uses snapshots and tries to sync objects with unknown cross-schema dependencies. However, the solution is not an easy one, and lead to some difficult architecture and design decisions within the product. And all this pain follows from the simple decision to allow schema pre-filtering! Next: why adding a column to a table isn't as easy as you would think...

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• Inside Red Gate - Be Reasonable!

  - by Simon Cooper

  As I discussed in my previous posts, divisions and project teams within Red Gate are allowed a lot of autonomy to manage themselves. It's not just the teams though, there's an awful lot of freedom given to individual employees within the company as well. Reasonableness How Red Gate treats it's employees is embodied in the phrase 'You will be reasonable with us, and we will be reasonable with you'. As an employee, you are trusted to do your job to the best of you ability. There's no one looking over your shoulder, no one clocking you in and out each day. Everyone is working at the company because they want to, and one of the core ideas of Red Gate is that the company exists to 'let people do the best work of their lives'. Everything is geared towards that. To help you do your job, office services and the IT department are there. If you need something to help you work better (a third or fourth monitor, footrests, or a new keyboard) then ask people in Information Systems (IS) or Office Services and you will be given it, no questions asked. Everyone has administrator access to their own machines, and you can install whatever you want on it. If there's a particular bit of software you need, then ask IS and they will buy it. As an example, last year I wanted to replace my main hard drive with an SSD; I had a summer job at school working in a computer repair shop, so knew what to do. I went to IS and asked for 'an SSD, a SATA cable, and a screwdriver'. And I got it there and then, even the screwdriver. Awesome. I screwed it in myself, copied all my main drive files across, and I was good to go. Of course, if you're not happy doing that yourself, then IS will sort it all out for you, no problems. If you need something that the company doesn't have (say, a book off Amazon, or you need some specifications printing off & bound), then everyone has a expense limit of £100 that you can use without any sign-off needed from your managers. If you need a company credit card for whatever reason, then you can get it. This freedom extends to working hours and holiday; you're expected to be in the office 11am-3pm each day, but outside those times you can work whenever you want. If you need a half-day holiday on a days notice, or even the same day, then you'll get it, unless there's a good reason you're needed that day. If you need to work from home for a day or so for whatever reason, then you can. If it's reasonable, then it's allowed. Trust issues? A lot of trust, and a lot of leeway, is given to all the people in Red Gate. Everyone is expected to work hard, do their jobs to the best of their ability, and there will be a minimum of bureaucratic obstacles that stop you doing your work. What happens if you abuse this trust? Well, an example is company trip expenses. You're free to expense what you like; food, drink, transport, etc, but if you expenses are not reasonable, then you will never travel with the company again. Simple as that. Everyone knows when they're abusing the system, so simply don't do it. Along with reasonableness, another phrase used is 'Don't be a ***'. If you act like a ***, and abuse any of the trust placed in you, even if you're the best tester, salesperson, dev, or manager in the company, then you won't be a part of the company any more. From what I know about other companies, employee trust is highly variable between companies, all the way up to CCTV trained on employee's monitors. As a dev, I want to produce well-written & useful code that solves people's problems. Being able to get whatever I need - install whatever tools I need, get time off when I need to, obtain reference books within a day - all let me do my job, and so let Red Gate help other people do their own jobs through the tools we produce. Plus, I don't think I would like working for a company that doesn't allow admin access to your own machine and blocks Facebook!

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• Exporting the frames in a Flash CS5.5 animation and possibly creating the spritesheet

  - by Adam Smith

  Some time ago, I asked a question here to know what would be the best way to create animations when making an Android game and I got great answers. I did what people told me there by exporting each frame from a Flash animation manually and creating the spritesheet also manually and it was very tedious. Now, I changed project and this one is going to contain a lot more animations and I feel like there has to be a better way to to export each frame individually and possibly create my spritesheets in an automated manner. My designer is using Flash CS5.5 and I was wondering if all of this was possible, as I can't find an option or code examples on how to save each frame individually. If this is not possible using Flash, please recommend me another program that can be used to create animations without having to create each frame on its own. I'd rather keep Flash as my designer knows how to use it and it's giving great results.

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• SortedDictionary and SortedList

  - by Simon Cooper

  Apart from Dictionary<TKey, TValue>, there's two other dictionaries in the BCL - SortedDictionary<TKey, TValue> and SortedList<TKey, TValue>. On the face of it, these two classes do the same thing - provide an IDictionary<TKey, TValue> interface where the iterator returns the items sorted by the key. So what's the difference between them, and when should you use one rather than the other? (as in my previous post, I'll assume you have some basic algorithm & datastructure knowledge) SortedDictionary We'll first cover SortedDictionary. This is implemented as a special sort of binary tree called a red-black tree. Essentially, it's a binary tree that uses various constraints on how the nodes of the tree can be arranged to ensure the tree is always roughly balanced (for more gory algorithmical details, see the wikipedia link above). What I'm concerned about in this post is how the .NET SortedDictionary is actually implemented. In .NET 4, behind the scenes, the actual implementation of the tree is delegated to a SortedSet<KeyValuePair<TKey, TValue>>. One example tree might look like this: Each node in the above tree is stored as a separate SortedSet<T>.Node object (remember, in a SortedDictionary, T is instantiated to KeyValuePair<TKey, TValue>): class Node { public bool IsRed; public T Item; public SortedSet<T>.Node Left; public SortedSet<T>.Node Right; } The SortedSet only stores a reference to the root node; all the data in the tree is accessed by traversing the Left and Right node references until you reach the node you're looking for. Each individual node can be physically stored anywhere in memory; what's important is the relationship between the nodes. This is also why there is no constructor to SortedDictionary or SortedSet that takes an integer representing the capacity; there are no internal arrays that need to be created and resized. This may seen trivial, but it's an important distinction between SortedDictionary and SortedList that I'll cover later on. And that's pretty much it; it's a standard red-black tree. Plenty of webpages and datastructure books cover the algorithms behind the tree itself far better than I could. What's interesting is the comparions between SortedDictionary and SortedList, which I'll cover at the end. As a side point, SortedDictionary has existed in the BCL ever since .NET 2. That means that, all through .NET 2, 3, and 3.5, there has been a bona-fide sorted set class in the BCL (called TreeSet). However, it was internal, so it couldn't be used outside System.dll. Only in .NET 4 was this class exposed as SortedSet. SortedList Whereas SortedDictionary didn't use any backing arrays, SortedList does. It is implemented just as the name suggests; two arrays, one containing the keys, and one the values (I've just used random letters for the values): The items in the keys array are always guarenteed to be stored in sorted order, and the value corresponding to each key is stored in the same index as the key in the values array. In this example, the value for key item 5 is 'z', and for key item 8 is 'm'. Whenever an item is inserted or removed from the SortedList, a binary search is run on the keys array to find the correct index, then all the items in the arrays are shifted to accomodate the new or removed item. For example, if the key 3 was removed, a binary search would be run to find the array index the item was at, then everything above that index would be moved down by one: and then if the key/value pair {7, 'f'} was added, a binary search would be run on the keys to find the index to insert the new item, and everything above that index would be moved up to accomodate the new item: If another item was then added, both arrays would be resized (to a length of 10) before the new item was added to the arrays. As you can see, any insertions or removals in the middle of the list require a proportion of the array contents to be moved; an O(n) operation. However, if the insertion or removal is at the end of the array (ie the largest key), then it's only O(log n); the cost of the binary search to determine it does actually need to be added to the end (excluding the occasional O(n) cost of resizing the arrays to fit more items). As a side effect of using backing arrays, SortedList offers IList Keys and Values views that simply use the backing keys or values arrays, as well as various methods utilising the array index of stored items, which SortedDictionary does not (and cannot) offer. The Comparison So, when should you use one and not the other? Well, here's the important differences: Memory usage SortedDictionary and SortedList have got very different memory profiles. SortedDictionary... has a memory overhead of one object instance, a bool, and two references per item. On 64-bit systems, this adds up to ~40 bytes, not including the stored item and the reference to it from the Node object. stores the items in separate objects that can be spread all over the heap. This helps to keep memory fragmentation low, as the individual node objects can be allocated wherever there's a spare 60 bytes. In contrast, SortedList... has no additional overhead per item (only the reference to it in the array entries), however the backing arrays can be significantly larger than you need; every time the arrays are resized they double in size. That means that if you add 513 items to a SortedList, the backing arrays will each have a length of 1024. To conteract this, the TrimExcess method resizes the arrays back down to the actual size needed, or you can simply assign list.Capacity = list.Count. stores its items in a continuous block in memory. If the list stores thousands of items, this can cause significant problems with Large Object Heap memory fragmentation as the array resizes, which SortedDictionary doesn't have. Performance Operations on a SortedDictionary always have O(log n) performance, regardless of where in the collection you're adding or removing items. In contrast, SortedList has O(n) performance when you're altering the middle of the collection. If you're adding or removing from the end (ie the largest item), then performance is O(log n), same as SortedDictionary (in practice, it will likely be slightly faster, due to the array items all being in the same area in memory, also called locality of reference). So, when should you use one and not the other? As always with these sort of things, there are no hard-and-fast rules. But generally, if you: need to access items using their index within the collection are populating the dictionary all at once from sorted data aren't adding or removing keys once it's populated then use a SortedList. But if you: don't know how many items are going to be in the dictionary are populating the dictionary from random, unsorted data are adding & removing items randomly then use a SortedDictionary. The default (again, there's no definite rules on these sort of things!) should be to use SortedDictionary, unless there's a good reason to use SortedList, due to the bad performance of SortedList when altering the middle of the collection.

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• Anatomy of a .NET Assembly - Custom attribute encoding

  - by Simon Cooper

  In my previous post, I covered how field, method, and other types of signatures are encoded in a .NET assembly. Custom attribute signatures differ quite a bit from these, which consequently affects attribute specifications in C#. Custom attribute specifications In C#, you can apply a custom attribute to a type or type member, specifying a constructor as well as the values of fields or properties on the attribute type: public class ExampleAttribute : Attribute { public ExampleAttribute(int ctorArg1, string ctorArg2) { ... } public Type ExampleType { get; set; } } [Example(5, "6", ExampleType = typeof(string))] public class C { ... } How does this specification actually get encoded and stored in an assembly? Specification blob values Custom attribute specification signatures use the same building blocks as other types of signatures; the ELEMENT_TYPE structure. However, they significantly differ from other types of signatures, in that the actual parameter values need to be stored along with type information. There are two types of specification arguments in a signature blob; fixed args and named args. Fixed args are the arguments to the attribute type constructor, named arguments are specified after the constructor arguments to provide a value to a field or property on the constructed attribute type (PropertyName = propValue) Values in an attribute blob are limited to one of the basic types (one of the number types, character, or boolean), a reference to a type, an enum (which, in .NET, has to use one of the integer types as a base representation), or arrays of any of those. Enums and the basic types are easy to store in a blob - you simply store the binary representation. Strings are stored starting with a compressed integer indicating the length of the string, followed by the UTF8 characters. Array values start with an integer indicating the number of elements in the array, then the item values concatentated together. Rather than using a coded token, Type values are stored using a string representing the type name and fully qualified assembly name (for example, MyNs.MyType, MyAssembly, Version=1.0.0.0, Culture=neutral, PublicKeyToken=0123456789abcdef). If the type is in the current assembly or mscorlib then just the type name can be used. This is probably done to prevent direct references between assemblies solely because of attribute specification arguments; assemblies can be loaded in the reflection-only context and attribute arguments still processed, without loading the entire assembly. Fixed and named arguments Each entry in the CustomAttribute metadata table contains a reference to the object the attribute is applied to, the attribute constructor, and the specification blob. The number and type of arguments to the constructor (the fixed args) can be worked out by the method signature referenced by the attribute constructor, and so the fixed args can simply be concatenated together in the blob without any extra type information. Named args are different. These specify the value to assign to a field or property once the attribute type has been constructed. In the CLR, fields and properties can be overloaded just on their type; different fields and properties can have the same name. Therefore, to uniquely identify a field or property you need: Whether it's a field or property (indicated using byte values 0x53 and 0x54, respectively) The field or property type The field or property name After the fixed arg values is a 2-byte number specifying the number of named args in the blob. Each named argument has the above information concatenated together, mostly using the basic ELEMENT_TYPE values, in the same way as a method or field signature. A Type argument is represented using the byte 0x50, and an enum argument is represented using the byte 0x55 followed by a string specifying the name and assembly of the enum type. The named argument property information is followed by the argument value, using the same encoding as fixed args. Boxed objects This would be all very well, were it not for object and object[]. Arguments and properties of type object allow a value of any allowed argument type to be specified. As a result, more information needs to be specified in the blob to interpret the argument bytes as the correct type. So, the argument value is simple prepended with the type of the value by specifying the ELEMENT_TYPE or name of the enum the value represents. For named arguments, a field or property of type object is represented using the byte 0x51, with the actual type specified in the argument value. Some examples... All property signatures start with the 2-byte value 0x0001. Similar to my previous post in the series, names in capitals correspond to a particular byte value in the ELEMENT_TYPE structure. For strings, I'll simply give the string value, rather than the length and UTF8 encoding in the actual blob. I'll be using the following enum and attribute types to demonstrate specification encodings: class AttrAttribute : Attribute { public AttrAttribute() {} public AttrAttribute(Type[] tArray) {} public AttrAttribute(object o) {} public AttrAttribute(MyEnum e) {} public AttrAttribute(ushort x, int y) {} public AttrAttribute(string str, Type type1, Type type2) {} public int Prop1 { get; set; } public object Prop2 { get; set; } public object[] ObjectArray; } enum MyEnum : int { Val1 = 1, Val2 = 2 } Now, some examples: Here, the the specification binds to the (ushort, int) attribute constructor, with fixed args only. The specification blob starts off with a prolog, followed by the two constructor arguments, then the number of named arguments (zero): [Attr(42, 84)] 0x0001 0x002a 0x00000054 0x0000 An example of string and type encoding: [Attr("MyString", typeof(Array), typeof(System.Windows.Forms.Form))] 0x0001 "MyString" "System.Array" "System.Windows.Forms.Form, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" 0x0000 As you can see, the full assembly specification of a type is only needed if the type isn't in the current assembly or mscorlib. Note, however, that the C# compiler currently chooses to fully-qualify mscorlib types anyway. An object argument (this binds to the object attribute constructor), and two named arguments (a null string is represented by 0xff and the empty string by 0x00) [Attr((ushort)40, Prop1 = 12, Prop2 = "")] 0x0001 U2 0x0028 0x0002 0x54 I4 "Prop1" 0x0000000c 0x54 0x51 "Prop2" STRING 0x00 Right, more complicated now. A type array as a fixed argument: [Attr(new[] { typeof(string), typeof(object) })] 0x0001 0x00000002 // the number of elements "System.String" "System.Object" 0x0000 An enum value, which is simply represented using the underlying value. The CLR works out that it's an enum using information in the attribute constructor signature: [Attr(MyEnum.Val1)] 0x0001 0x00000001 0x0000 And finally, a null array, and an object array as a named argument: [Attr((Type[])null, ObjectArray = new object[] { (byte)2, typeof(decimal), null, MyEnum.Val2 })] 0x0001 0xffffffff 0x0001 0x53 SZARRAY 0x51 "ObjectArray" 0x00000004 U1 0x02 0x50 "System.Decimal" STRING 0xff 0x55 "MyEnum" 0x00000002 As you'll notice, a null object is encoded as a null string value, and a null array is represented using a length of -1 (0xffffffff). How does this affect C#? So, we can now explain why the limits on attribute arguments are so strict in C#. Attribute specification blobs are limited to basic numbers, enums, types, and arrays. As you can see, this is because the raw CLR encoding can only accommodate those types. Special byte patterns have to be used to indicate object, string, Type, or enum values in named arguments; you can't specify an arbitary object type, as there isn't a generalised way of encoding the resulting value in the specification blob. In particular, decimal values can't be encoded, as it isn't a 'built-in' CLR type that has a native representation (you'll notice that decimal constants in C# programs are compiled as several integer arguments to DecimalConstantAttribute). Jagged arrays also aren't natively supported, although you can get around it by using an array as a value to an object argument: [Attr(new object[] { new object[] { new Type[] { typeof(string) } }, 42 })] Finally... Phew! That was a bit longer than I thought it would be. Custom attribute encodings are complicated! Hopefully this series has been an informative look at what exactly goes on inside a .NET assembly. In the next blog posts, I'll be carrying on with the 'Inside Red Gate' series.

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• Project structure: where to put business logic

  - by Mister Smith

  First of all, I'm not asking where does business logic belong. This has been asked before and most answers I've read agree in that it belongs in the model: Where to put business logic in MVC design? How much business logic should be allowed to exist in the controller layer? How accurate is "Business logic should be in a service, not in a model"? Why put the business logic in the model? What happens when I have multiple types of storage? However people disagree in the way this logic should be distributed across classes. There seem to exist three major currents of thought: Fat model with business logic inside entity classes. Anemic model and business logic in "Service" classes. It depends. I find all of them problematic. The first option is what most Fowlerites stick to. The problem with a fat model is that sometimes a business logic funtion is not only related to a class, and instead uses a bunch of other classes. If, for example, we are developing a web store, there should be a function that calcs an order's total. We could think of putting this function inside the Order class, but what actually happens is that the logic needs to use different classes, not only data contained in the Order class, but also in the User class, the Session class, and maybe the Tax class, Country class, or Giftcard, Payment, etc. Some of these classes could be composed inside the Order class, but some others not. Sorry if the example is not very good, but I hope you understand what I mean. Putting such a function inside the Order class would break the single responsibility principle, adding unnecesary dependences. The business logic would be scattered across entity classes, making it hard to find. The second option is the one I usually follow, but after many projects I'm still in doubt about how to name the class or classes holding the business logic. In my company we usually develop apps with offline capabilities. The user is able to perform entire transactions offline, so all validation and business rules should be implemented in the client, and then there's usually a background thread that syncs with the server. So we usually have the following classes/packages in every project: Data model (DTOs) Data Access Layer (Persistence) Web Services layer (Usually one class per WS, and one method per WS method). Now for the business logic, what is the standard approach? A single class holding all the logic? Multiple classes? (if so, what criteria is used to distribute the logic across them?). And how should we name them? FooManager? FooService? (I know the last one is common, but in our case it is bad naming because the WS layer usually has classes named FooWebService). The third option is probably the right one, but it is also devoid of any useful info. To sum up: I don't like the first approach, but I accept that I might have been unable to fully understand the Zen of it. So if you advocate for fat models as the only and universal solution you are welcome to post links explaining how to do it the right way. I'd like to know what is the standard design and naming conventions for the second approach in OO languages. Class names and package structure, in particular. It would also be helpful too if you could include links to Open Source projects showing how it is done. Thanks in advance.

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• How to become an expert web-developer?

  - by John Smith

  I am currently a Junior PHP developer and I really LOVE it, I love internet from first time I got into it, I always loved smartly-created websites, always was wondering how it all works, always admired websites with good design and rich functionality, and finally I am creating web-sites on my own and it feels really great. My goals are to become expert web-developer (aiming for creating websites for small and medium business, not enterprise-sized systems), to have a great full-time job, to do freelance and to create my own startup in future. General question: What do I do to be an expert, professional and demanded web-programmer? More concrete questions: 1). How do I choose languages and technologies needed? I know that every web-developer must know HTML+CSS+JS+AJAX+JQuery, I am doing some design aswell cause I like it and I need it for freelance also. But what about backend languages? Currently I picked PHP cause it's most demanded in my area and most of web uses it, but what would happen in future? Say, in 3 years, I am good at PHP and PHP frameworks by than, but what if some other languages get most popular? Do I switch to them? I know that good programmer is not about languages and frameworks but about ability to learn and to aim the goals, but still I think that learning frameworks for some language can take quite some time. Am I wrong? 2). In general, what are basic guidelines to be expert web-developer? What are most important things I should focus on? Thank you!

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• setting globals in html or body [migrated]

  - by paul smith

  I have some questions regarding the following css that I found: html, body { height:100%; min-width:100%; position:absolute; } html { background: none repeat scroll 0 0 #fff; color:#fff; font-family:arial,helvetica,sans-serif; font-size:15px; } is it necessary to have height and min-width to 100% on the html and body? What's the benefit? what is the reason for using position absolute? why did they set the background/color/font on the html and not the body? Is there a difference? Or is it just preference?

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• 256 Worker Role 3D Rendering Demo is now a Lab on my Azure Course

  - by Alan Smith

  Ever since I came up with the crazy idea of creating an Azure application that would spin up 256 worker roles (please vote if you like it ) to render a 3D animation created using the Kinect depth camera I have been trying to think of something useful to do with it. I have also been busy working on developing training materials for a Windows Azure course that I will be delivering through a training partner in Stockholm, and for customers wanting to learn Windows Azure. I hit on the idea of combining the render demo and a course lab and creating a lab where the students would create and deploy their own mini render farms, which would participate in a single render job, consisting of 2,000 frames. The architecture of the solution is shown below. As students would be creating and deploying their own applications, I thought it would be fun to introduce some competitiveness into the lab. In the 256 worker role demo I capture the rendering statistics for each role, so it was fairly simple to include the students name in these statistics. This allowed the process monitor application to capture the number of frames each student had rendered and display a high-score table. When I demoed the application I deployed one instance that started rendering a frame every few minutes, and the challenge for the students was to deploy and scale their applications, and then overtake my single role instance by the end of the lab time. I had the process monitor running on the projector during the lab so the class could see the progress of their deployments, and how they were performing against my implementation and their classmates. When I tested the lab for the first time in Oslo last week it was a great success, the students were keen to be the first to build and deploy their solution and then watch the frames appear. As the students mostly had MSDN suspicions they were able to scale to the full 20 worker role instances and before long we had over 100 worker roles working on the animation. There were, however, a few issues who the couple of issues caused by the competitive nature of the lab. The first student to scale the application to 20 instances would render the most frames and win; there was no way for others to catch up. Also, as they were competing against each other, there was no incentive to help others on the course get their application up and running. I have now re-written the lab to divide the student into teams that will compete to render the most frames. This means that if one developer on the team can deploy and scale quickly, the other team still has a chance to catch up. It also means that if a student finishes quickly and puts their team in the lead they will have an incentive to help the other developers on their team get up and running. As I was using “Sharks with Lasers” for a lot of my demos, and reserved the sharkswithfreakinlasers namespaces for some of the Azure services (well somebody had to do it), the students came up with some creative alternatives, like “Camels with Cannons” and “Honey Badgers with Homing Missiles”. That gave me the idea for the teams having to choose a creative name involving animals and weapons. The team rendering architecture diagram is shown below.   Render Challenge Rules In order to ensure fair play a number of rules are imposed on the lab. ·         The class will be divided into teams, each team choses a name. ·         The team name must consist of a ferocious animal combined with a hazardous weapon. ·         Teams can allocate as many worker roles as they can muster to the render job. ·         Frame processing statistics and rendered frames will be vigilantly monitored; any cheating, tampering, and other foul play will result in penalties. The screenshot below shows an example of the team render farm in action, Badgers with Bombs have taken a lead over Camels with Cannons, and both are  leaving the Sharks with Lasers standing. If you are interested in attending a scheduled delivery of my Windows Azure or Windows Azure Service bus courses, or would like on-site training, more details are here.

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• Pulseaudio no sound card detected. Dummy output only

  - by Zach Smith

  I'm using 12.10 Quantal with Openbox and a .xinitrc script at login instead of a display manager. Its a relatively fresh install and I noticed when I opened pavucontrol the only output was a dummy one. I check around and it appears that my soundcard is physically installed but Pulseaudio isn't detecting it. I'm really unsure what I should do but any help getting my audio back would be appreciated. Edit: further info if its at all useful: dante@dante-ubuntu:~$ uname -a && aplay -l && cat /proc/asound/version && head -n 1 /proc/asound/card*/codec#* Linux dante-ubuntu 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux aplay: device_list:252: no soundcards found... Advanced Linux Sound Architecture Driver Version 1.0.25. == /proc/asound/card0/codec#0 <== Codec: ATI R6xx HDMI == /proc/asound/card1/codec#0 <== Codec: IDT 92HD81B1X5

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• Anatomy of a .NET Assembly - CLR metadata 1

  - by Simon Cooper

  Before we look at the bytes comprising the CLR-specific data inside an assembly, we first need to understand the logical format of the metadata (For this post I only be looking at simple pure-IL assemblies; mixed-mode assemblies & other things complicates things quite a bit). Metadata streams Most of the CLR-specific data inside an assembly is inside one of 5 streams, which are analogous to the sections in a PE file. The name of each section in a PE file starts with a ., and the name of each stream in the CLR metadata starts with a #. All but one of the streams are heaps, which store unstructured binary data. The predefined streams are: #~ Also called the metadata stream, this stream stores all the information on the types, methods, fields, properties and events in the assembly. Unlike the other streams, the metadata stream has predefined contents & structure. #Strings This heap is where all the namespace, type & member names are stored. It is referenced extensively from the #~ stream, as we'll be looking at later. #US Also known as the user string heap, this stream stores all the strings used in code directly. All the strings you embed in your source code end up in here. This stream is only referenced from method bodies. #GUID This heap exclusively stores GUIDs used throughout the assembly. #Blob This heap is for storing pure binary data - method signatures, generic instantiations, that sort of thing. Items inside the heaps (#Strings, #US, #GUID and #Blob) are indexed using a simple binary offset from the start of the heap. At that offset is a coded integer giving the length of that item, then the item's bytes immediately follow. The #GUID stream is slightly different, in that GUIDs are all 16 bytes long, so a length isn't required. Metadata tables The #~ stream contains all the assembly metadata. The metadata is organised into 45 tables, which are binary arrays of predefined structures containing information on various aspects of the metadata. Each entry in a table is called a row, and the rows are simply concatentated together in the file on disk. For example, each row in the TypeRef table contains: A reference to where the type is defined (most of the time, a row in the AssemblyRef table). An offset into the #Strings heap with the name of the type An offset into the #Strings heap with the namespace of the type. in that order. The important tables are (with their table number in hex): 0x2: TypeDef 0x4: FieldDef 0x6: MethodDef 0x14: EventDef 0x17: PropertyDef Contains basic information on all the types, fields, methods, events and properties defined in the assembly. 0x1: TypeRef The details of all the referenced types defined in other assemblies. 0xa: MemberRef The details of all the referenced members of types defined in other assemblies. 0x9: InterfaceImpl Links the types defined in the assembly with the interfaces that type implements. 0xc: CustomAttribute Contains information on all the attributes applied to elements in this assembly, from method parameters to the assembly itself. 0x18: MethodSemantics Links properties and events with the methods that comprise the get/set or add/remove methods of the property or method. 0x1b: TypeSpec 0x2b: MethodSpec These tables provide instantiations of generic types and methods for each usage within the assembly. There are several ways to reference a single row within a table. The simplest is to simply specify the 1-based row index (RID). The indexes are 1-based so a value of 0 can represent 'null'. In this case, which table the row index refers to is inferred from the context. If the table can't be determined from the context, then a particular row is specified using a token. This is a 4-byte value with the most significant byte specifying the table, and the other 3 specifying the 1-based RID within that table. This is generally how a metadata table row is referenced from the instruction stream in method bodies. The third way is to use a coded token, which we will look at in the next post. So, back to the bytes Now we've got a rough idea of how the metadata is logically arranged, we can now look at the bytes comprising the start of the CLR data within an assembly: The first 8 bytes of the .text section are used by the CLR loader stub. After that, the CLR-specific data starts with the CLI header. I've highlighted the important bytes in the diagram. In order, they are: The size of the header. As the header is a fixed size, this is always 0x48. The CLR major version. This is always 2, even for .NET 4 assemblies. The CLR minor version. This is always 5, even for .NET 4 assemblies, and seems to be ignored by the runtime. The RVA and size of the metadata header. In the diagram, the RVA 0x20e4 corresponds to the file offset 0x2e4 Various flags specifying if this assembly is pure-IL, whether it is strong name signed, and whether it should be run as 32-bit (this is how the CLR differentiates between x86 and AnyCPU assemblies). A token pointing to the entrypoint of the assembly. In this case, 06 (the last byte) refers to the MethodDef table, and 01 00 00 refers to to the first row in that table. (after a gap) RVA of the strong name signature hash, which comes straight after the CLI header. The RVA 0x2050 corresponds to file offset 0x250. The rest of the CLI header is mainly used in mixed-mode assemblies, and so is zeroed in this pure-IL assembly. After the CLI header comes the strong name hash, which is a SHA-1 hash of the assembly using the strong name key. After that comes the bodies of all the methods in the assembly concatentated together. Each method body starts off with a header, which I'll be looking at later. As you can see, this is a very small assembly with only 2 methods (an instance constructor and a Main method). After that, near the end of the .text section, comes the metadata, containing a metadata header and the 5 streams discussed above. We'll be looking at this in the next post. Conclusion The CLI header data doesn't have much to it, but we've covered some concepts that will be important in later posts - the logical structure of the CLR metadata and the overall layout of CLR data within the .text section. Next, I'll have a look at the contents of the #~ stream, and how the table data is arranged on disk.

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• Gnome-terminal doesn't close at end of SSH session

  - by Simón

  I have defined in gnome-terminal that it closes at end of shell. When I press Control-D or I execute exit, the terminal closes. But if I open the SSH session with gnome-terminal -x ssh server and I execute reboot in the SSH session (to reboot the remote server), it hangs and it doesn't close. What's happening? This worked to me before but I have to reinstall my Ubuntu (in local) and now gnome-terminal doesn't close itself when SSH session ends.

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• Inside Red Gate - Project teams

  - by Simon Cooper

  Within each division in Red Gate, development effort is structured around one or more project teams; currently, each division contains 2-3 separate teams. These are self contained units responsible for a particular development project. Project team structure The typical size of a development team varies, but is normally around 4-7 people - one project manager, two developers, one or two testers, a technical author (who is responsible for the text within the application, website content, and help documentation) and a user experience designer (who designs and prototypes the UIs) . However, team sizes can vary from 3 up to 12, depending on the division and project. As an rule, all the team sits together in the same area of the office. (Again, this is my experience of what happens. I haven't worked in the DBA division, and SQL Tools might have changed completely since I moved to .NET. As I mentioned in my previous post, each division is free to structure itself as it sees fit.) Depending on the project, and the other needs in the division, the tech author and UX designer may be shared between several projects. Generally, developers and testers work on one project at a time. If the project is a simple point release, then it might not need a UX designer at all. However, if it's a brand new product, then a UX designer and tech author will be involved right from the start. Developers, testers, and the project manager will normally stay together in the same team as they work on different projects, unless there's a good reason to split or merge teams for a particular project. Technical authors and UX designers will normally go wherever they are needed in the division, depending on what each project needs at the time. In my case, I was working with more or less the same people for over 2 years, all the way through SQL Compare 7, 8, and Schema Compare for Oracle. This helped to build a great sense of camaraderie wihin the team, and helped to form and maintain a team identity. This, in turn, meant we worked very well together, and so the final result was that much better (as well as making the work more fun). How is a project started and run? The product manager within each division collates user feedback and ideas, does lots of research, throws in a few ideas from people within the company, and then comes up with a list of what the division should work on in the next few years. This is split up into projects, and after each project is greenlit (I'll be discussing this later on) it is then assigned to a project team, as and when they become available (I'm sure there's lots of discussions and meetings at this point that I'm not aware of!). From that point, it's entirely up to the project team. Just as divisions are autonomous, project teams are also given a high degree of autonomy. All the teams in Red Gate use some sort of vaguely agile methodology; most use some variations on SCRUM, some have experimented with Kanban. Some store the project progress on a whiteboard, some use our bug tracker, others use different methods. It all depends on what the team members think will work best for them to get the best result at the end. From that point, the project proceeds as you would expect; code gets written, tests pass and fail, discussions about how to resolve various problems are had and decided upon, and out pops a new product, new point release, new internal tool, or whatever the project's goal was. The project manager ensures that everyone works together without too much bloodshed and that thrown missiles are constrained to Nerf bullets, the developers write the code, the testers ensure it actually works, and the tech author and UX designer ensure that people will be able to use the final product to solve their problem (after all, developers make lousy UI designers and technical authors). Projects in Red Gate last a relatively short amount of time; most projects are less than 6 months. The longest was 18 months. This has evolved as the company has grown, and I suspect is a side effect of the type of software Red Gate produces. As an ISV, we sell packaged software; we only get revenue when customers purchase the ready-made tools. As a result, we only get a sellable piece of software right at the end of a project. Therefore, the longer the project lasts, the more time and money has to be invested by the company before we get any revenue from it, and the riskier the project becomes. This drives the average project time down. Small project teams are the core of how Red Gate produces software, and are what the whole development effort of the company is built around. In my next post, I'll be looking at the office itself, and how all 200 of us manage to fit on two floors of a small office building.

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• The SmartAssembly Rearchitecture

  - by Simon Cooper

  You may have noticed that not a lot has happened to SmartAssembly in the past few months. However, the team has been very busy behind the scenes working on an entirely new version of SmartAssembly. SmartAssembly 6.5 Over the past few releases of SmartAssembly, the team had come to the realisation that the current 'architecture' - grown organically, way before RedGate bought it, from a simple name obfuscator over the years into a full-featured obfuscator and assembly instrumentation tool - was simply not up to the task. Not for what we wanted to do with it at the time, and not what we have planned for the future. Not only was it not up to what we wanted it to do, but it was severely limiting our development capabilities; long-standing bugs in the root architecture that couldn't be fixed, some rather...interesting...design decisions, and convoluted logic that increased the complexity of any bugfix or new feature tenfold. So, we set out to fix this. Earlier this year, a new engine was written on which SmartAssembly would be based. Over the following few months, each feature was ported over to the new engine and extensively tested by our existing unit and integration tests. The engine was linked into the existing UI (no easy task, due to the tight coupling between the UI and old engine), and existing RedGate products were tested on the new SmartAssembly to ensure the new engine acted in the same way. The result is SmartAssembly 6.5. The risks of a rearchitecture Are there risks to rearchitecting a product like SmartAssembly? Of course. There was a lot of undocumented behaviour in the old engine, and as part of the rearchitecture we had to find this behaviour, define it, and document it. In the process we found some behaviour of the old engine that simply did not make sense; hence the changes in pruning & obfuscation behaviour in the release notes. All the special edge cases we had to find, document, and re-implement. There was a chance that these special cases would not be found until near the end of the project, when everything is functionally complete and interacting together. By that stage, it would be hard to go back and change anything without a whole lot of extra work, delaying the release by months. We always knew this was a possibility; our initial estimate of the time required was '4 months, ± 4 months'. And that was including various mitigation strategies to reduce the likelihood of these issues being found right at the end. Fortunately, this worst-case did not happen. However, the rearchitecture did produce some benefits. As well as numerous bug fixes that we could not fix any other way, we've also added logging that lets you find out exactly why a particular field or property wasn't pruned or obfuscated. There's a new command line interface, we've tested it with WP7.1 and Silverlight 5, and we've added a new option to error reporting to improve the performance of instrumented apps by ~10%, at the cost of inaccurate line numbers in reports. So? What differences will I see? Largely none. SmartAssembly 6.5 produces the same output as SmartAssembly 6.2. The performance of 6.5 will be much faster for some users, and generally the same as 6.2 for the remaining. If you've encountered a bug with previous versions of SmartAssembly, I encourage you to try 6.5, as it has most likely been fixed in the rearchitecture. If you encounter a bug with 6.5, please do tell us; we'll be doing another release quite soon, so we'll aim to fix any issues caused by 6.5 in that release. Most importantly, the new architecture finally allows us to implement some Big Things with SmartAssembly we've been planning for many months; these will fundamentally change how you build, release and monitor your application. Stay tuned for further updates!

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• Given an XML which contains a representation of a graph, how to apply it DFS algorithm? [on hold]

  - by winston smith

  Given the followin XML which is a directed graph: <?xml version="1.0" encoding="iso-8859-1" ?> <!DOCTYPE graph PUBLIC "-//FC//DTD red//EN" "../dtd/graph.dtd"> <graph direct="1"> <vertex label="V0"/> <vertex label="V1"/> <vertex label="V2"/> <vertex label="V3"/> <vertex label="V4"/> <vertex label="V5"/> <edge source="V0" target="V1" weight="1"/> <edge source="V0" target="V4" weight="1"/> <edge source="V5" target="V2" weight="1"/> <edge source="V5" target="V4" weight="1"/> <edge source="V1" target="V2" weight="1"/> <edge source="V1" target="V3" weight="1"/> <edge source="V1" target="V4" weight="1"/> <edge source="V2" target="V3" weight="1"/> </graph> With this classes i parsed the graph and give it an adjacency list representation: import java.io.IOException; import java.util.HashSet; import java.util.LinkedList; import java.util.Collection; import java.util.Iterator; import java.util.logging.Level; import java.util.logging.Logger; import practica3.util.Disc; public class ParsingXML { public static void main(String[] args) { try { // TODO code application logic here Collection<Vertex> sources = new HashSet<Vertex>(); LinkedList<String> lines = Disc.readFile("xml/directed.xml"); for (String lin : lines) { int i = Disc.find(lin, "source=\""); String data = ""; if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } Vertex v = new Vertex(); v.setName(data); v.setAdy(new HashSet<Vertex>()); sources.add(v); } } Iterator it = sources.iterator(); while (it.hasNext()) { Vertex ver = (Vertex) it.next(); Collection<Vertex> adyacencias = ver.getAdy(); LinkedList<String> ls = Disc.readFile("xml/graphs.xml"); for (String lin : ls) { int i = Disc.find(lin, "target=\""); String data = ""; if (lin.contains("source=\""+ver.getName())) { Vertex v = new Vertex(); if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } v.setName(data); } i = Disc.find(lin, "weight=\""); data = ""; if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } v.setWeight(Integer.parseInt(data)); } if (v.getName() != null) { adyacencias.add(v); } } } } for (Vertex vert : sources) { System.out.println(vert); System.out.println("adyacencias: " + vert.getAdy()); } } catch (IOException ex) { Logger.getLogger(ParsingXML.class.getName()).log(Level.SEVERE, null, ex); } } } This is another class: import java.util.Collection; import java.util.Objects; public class Vertex { private String name; private int weight; private Collection ady; public Collection getAdy() { return ady; } public void setAdy(Collection adyacencias) { this.ady = adyacencias; } public String getName() { return name; } public void setName(String nombre) { this.name = nombre; } public int getWeight() { return weight; } public void setWeight(int weight) { this.weight = weight; } @Override public int hashCode() { int hash = 7; hash = 43 * hash + Objects.hashCode(this.name); hash = 43 * hash + this.weight; return hash; } @Override public boolean equals(Object obj) { if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } final Vertex other = (Vertex) obj; if (!Objects.equals(this.name, other.name)) { return false; } if (this.weight != other.weight) { return false; } return true; } @Override public String toString() { return "Vertice{" + "name=" + name + ", weight=" + weight + '}'; } } And finally: /** * * @author user */ /* -*-jde-*- */ /* <Disc.java> Contains the main argument*/ import java.io.*; import java.util.LinkedList; /** * Lectura y escritura de archivos en listas de cadenas * Ideal para el uso de las clases para gráficas. * * @author Peralta Santa Anna Victor Miguel * @since Julio 2011 */ public class Disc { /** * Metodo para lectura de un archivo * * @param fileName archivo que se va a leer * @return El archivo en representacion de lista de cadenas */ public static LinkedList<String> readFile(String fileName) throws IOException { BufferedReader file = new BufferedReader(new FileReader(fileName)); LinkedList<String> textlist = new LinkedList<String>(); while (file.ready()) { textlist.add(file.readLine().trim()); } file.close(); /* for(String linea:textlist){ if(linea.contains("source")){ //String generado = linea.replaceAll("<\\w+\\s+\"", ""); //System.out.println(generado); } }*/ return textlist; }//readFile public static int find(String linea,String palabra){ int i,j; boolean found = false; for(i=0,j=0;i<linea.length();i++){ if(linea.charAt(i)==palabra.charAt(j)){ j++; if(j==palabra.length()){ found = true; return i; } }else{ continue; } } if(!found){ i= -1; } return i; } /** * Metodo para la escritura de un archivo * * @param fileName archivo que se va a escribir * @param tofile la lista de cadenas que quedaran en el archivo * @param append el bit que dira si se anexa el contenido o se empieza de cero */ public static void writeFile(String fileName, LinkedList<String> tofile, boolean append) throws IOException { FileWriter file = new FileWriter(fileName, append); for (int i = 0; i < tofile.size(); i++) { file.write(tofile.get(i) + "\n"); } file.close(); }//writeFile /** * Metodo para escritura de un archivo * @param msg archivo que se va a escribir * @param tofile la cadena que quedaran en el archivo * @param append el bit que dira si se anexa el contenido o se empieza de cero */ public static void writeFile(String msg, String tofile, boolean append) throws IOException { FileWriter file = new FileWriter(msg, append); file.write(tofile); file.close(); }//writeFile }// I'm stuck on what can be the best way to given an adjacency list representation of the graph how to apply it Depth-first search algorithm. Any idea of how to aproach to complete the task?

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• Inside Red Gate - Experimenting In Public

  - by Simon Cooper

  Over the next few weeks, we'll be performing experiments on SmartAssembly to confirm or refute various hypotheses we have about how people use the product, what is stopping them from using it to its full extent, and what we can change to make it more useful and easier to use. Some of these experiments can be done within the team, some within Red Gate, and some need to be done on external users. External testing Some external testing can be done by standard usability tests and surveys, however, there are some hypotheses that can only be tested by building a version of SmartAssembly with some things in the UI or implementation changed. We'll then be able to look at how the experimental build is used compared to the 'mainline' build, which forms our baseline or control group, and use this data to confirm or refute the relevant hypotheses. However, there are several issues we need to consider before running experiments using separate builds: Ideally, the user wouldn't know they're running an experimental SmartAssembly. We don't want users to use the experimental build like it's an experimental build, we want them to use it like it's the real mainline build. Only then will we get valid, useful, and informative data concerning our hypotheses. There's no point running the experiments if we can't find out what happens after the download. To confirm or refute some of our hypotheses, we need to find out how the tool is used once it is installed. Fortunately, we've applied feature usage reporting to the SmartAssembly codebase itself to provide us with that information. Of course, this then makes the experimental data conditional on the user agreeing to send that data back to us in the first place. Unfortunately, even though this does limit the amount of useful data we'll be getting back, and possibly skew the data, there's not much we can do about this; we don't collect feature usage data without the user's consent. Looks like we'll simply have to live with this. What if the user tries to buy the experiment? This is something that isn't really covered by the Lean Startup book; how do you support users who give you money for an experiment? If the experiment is a new feature, and the user buys a license for SmartAssembly based on that feature, then what do we do if we later decide to pivot & scrap that feature? We've either got to spend time and money bringing that feature up to production quality and into the mainline anyway, or we've got disgruntled customers. Either way is bad. Again, there's not really any good solution to this. Similarly, what if we've removed some features for an experiment and a potential new user downloads the experimental build? (As I said above, there's no indication the build is an experimental build, as we want to see what users really do with it). The crucial feature they need is missing, causing a bad trial experience, a lost potential customer, and a lost chance to help the customer with their problem. Again, this is something not really covered by the Lean Startup book, and something that doesn't have a good solution. So, some tricky issues there, not all of them with nice easy answers. Turns out the practicalities of running Lean Startup experiments are more complicated than they first seem!

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• How to prevent a hacked-server from spoofing a master server?

  - by Cody Smith

  I wish to setup a room-based multilayer game model where players may host matches and serve as host (IE the server with authoritative power). I wish to host a master server which tracks player's items, rank, cash, exp, etc. In such a model, how can I prevent someone that is hosting a game (with a modified server) from spoofing the master server with invalid match results, thus gaining exp, money or rankings. Thanks. -Cody

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• What encoding is used by javax.xml.transform.Transformer?

  - by Simon Reeves

  Please can you answer a couple of questions based on the code below (excludes the try/catch blocks), which transforms input XML and XSL files into an output XSL-FO file: File xslFile = new File("inXslFile.xsl"); File xmlFile = new File("sourceXmlFile.xml"); TransformerFactory tFactory = TransformerFactory.newInstance(); Transformer transformer = tFactory.newTransformer(new StreamSource(xslFile)); FileOutputStream fos = new FileOutputStream(new File("outFoFile.fo"); transformer.transform(new StreamSource(xmlFile), new StreamResult(fos)); inXslFile is encoded using UTF-8 - however there are no tags in file which states this. sourceXmlFile is UTF-8 encoded and there may be a metatag at start of file indicating this. am currently using Java 6 with intention of upgrading in the future. What encoding is used when reading the xslFile? What encoding is used when reading the xmlFile? What encoding will be applied to the FO outfile? How can I obtain the info (properties) for 1 - 3? Is there a method call? How can the properties in 4 be altered - using configuration and dynamically? if known - Where is there info (web site) on this that I can read - I have looked without much success.

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• Can unit tests verify software requirements?

  - by Peter Smith

  I have often heard unit tests help programmers build confidence in their software. But is it enough for verifying that software requirements are met? I am losing confidence that software is working just because the unit tests pass. We have experienced some failures in production deployment due to an untested\unverified execution path. These failures are sometimes quite large, impact business operations and often requires an immediate fix. The failure is very rarely traced back to a failing unit test. We have large unit test bodies that have reasonable line coverage but almost all of these focus on individual classes and not on their interactions. Manual testing seems to be ineffective because the software being worked on is typically large with many execution paths and many integration points with other software. It is very painful to manually test all of the functionality and it never seems to flush out all the bugs. Are we doing unit testing wrong when it seems we still are failing to verify the software correctly before deployment? Or do most shops have another layer of automated testing in addition to unit tests?

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• CQRS without using others patterns

  - by John Smith

  I would like to explain CQRS to my team of developers. I just can't figure out how to explain it in the simplest way so they can implement the pattern rapidly without any others frameworks. I've read a lot of resources including video and articles but I don't find how to implement CQRS without using others patterns like a service Bus, event sourcing pattern, domain driven design. I know the purpose of these pattern but for the first step, I don't want them to think CQRS and theses patterns must be tied together. My first idea is to say that CQRS is about separating the read part and the write part. The read part is composed only of the UI project, and DAL project. Then the write part is composed of a typical multilayer architecture: UI/BLL/DAL. Then, does CQRS say we must also have two datastore ? What about the notion of commands which reveal the user's intention, is it also something part of CQRS or DDD ? Basically, how to implement CQRS without using others patterns. I concede it's also not that clear in my mind because I've used to work with NCQRS/DDD/Event Sourcing/ServiceBus in my personal project. Thanks

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• PostSharp, Obfuscation, and IL

  - by Simon Cooper

  Aspect-oriented programming (AOP) is a relatively new programming paradigm. Originating at Xerox PARC in 1994, the paradigm was first made available for general-purpose development as an extension to Java in 2001. From there, it has quickly been adapted for use in all the common languages used today. In the .NET world, one of the primary AOP toolkits is PostSharp. Attributes and AOP Normally, attributes in .NET are entirely a metadata construct. Apart from a few special attributes in the .NET framework, they have no effect whatsoever on how a class or method executes within the CLR. Only by using reflection at runtime can you access any attributes declared on a type or type member. PostSharp changes this. By declaring a custom attribute that derives from PostSharp.Aspects.Aspect, applying it to types and type members, and running the resulting assembly through the PostSharp postprocessor, you can essentially declare 'clever' attributes that change the behaviour of whatever the aspect has been applied to at runtime. A simple example of this is logging. By declaring a TraceAttribute that derives from OnMethodBoundaryAspect, you can automatically log when a method has been executed: public class TraceAttribute : PostSharp.Aspects.OnMethodBoundaryAspect { public override void OnEntry(MethodExecutionArgs args) { MethodBase method = args.Method; System.Diagnostics.Trace.WriteLine( String.Format( "Entering {0}.{1}.", method.DeclaringType.FullName, method.Name)); } public override void OnExit(MethodExecutionArgs args) { MethodBase method = args.Method; System.Diagnostics.Trace.WriteLine( String.Format( "Leaving {0}.{1}.", method.DeclaringType.FullName, method.Name)); } } [Trace] public void MethodToLog() { ... } Now, whenever MethodToLog is executed, the aspect will automatically log entry and exit, without having to add the logging code to MethodToLog itself. PostSharp Performance Now this does introduce a performance overhead - as you can see, the aspect allows access to the MethodBase of the method the aspect has been applied to. If you were limited to C#, you would be forced to retrieve each MethodBase instance using Type.GetMethod(), matching on the method name and signature. This is slow. Fortunately, PostSharp is not limited to C#. It can use any instruction available in IL. And in IL, you can do some very neat things. Ldtoken C# allows you to get the Type object corresponding to a specific type name using the typeof operator: Type t = typeof(Random); The C# compiler compiles this operator to the following IL: ldtoken [mscorlib]System.Random call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle( valuetype [mscorlib]System.RuntimeTypeHandle) The ldtoken instruction obtains a special handle to a type called a RuntimeTypeHandle, and from that, the Type object can be obtained using GetTypeFromHandle. These are both relatively fast operations - no string lookup is required, only direct assembly and CLR constructs are used. However, a little-known feature is that ldtoken is not just limited to types; it can also get information on methods and fields, encapsulated in a RuntimeMethodHandle or RuntimeFieldHandle: // get a MethodBase for String.EndsWith(string) ldtoken method instance bool [mscorlib]System.String::EndsWith(string) call class [mscorlib]System.Reflection.MethodBase [mscorlib]System.Reflection.MethodBase::GetMethodFromHandle( valuetype [mscorlib]System.RuntimeMethodHandle) // get a FieldInfo for the String.Empty field ldtoken field string [mscorlib]System.String::Empty call class [mscorlib]System.Reflection.FieldInfo [mscorlib]System.Reflection.FieldInfo::GetFieldFromHandle( valuetype [mscorlib]System.RuntimeFieldHandle) These usages of ldtoken aren't usable from C# or VB, and aren't likely to be added anytime soon (Eric Lippert's done a blog post on the possibility of adding infoof, methodof or fieldof operators to C#). However, PostSharp deals directly with IL, and so can use ldtoken to get MethodBase objects quickly and cheaply, without having to resort to string lookups. The kicker However, there are problems. Because ldtoken for methods or fields isn't accessible from C# or VB, it hasn't been as well-tested as ldtoken for types. This has resulted in various obscure bugs in most versions of the CLR when dealing with ldtoken and methods, and specifically, generic methods and methods of generic types. This means that PostSharp was behaving incorrectly, or just plain crashing, when aspects were applied to methods that were generic in some way. So, PostSharp has to work around this. Without using the metadata tokens directly, the only way to get the MethodBase of generic methods is to use reflection: Type.GetMethod(), passing in the method name as a string along with information on the signature. Now, this works fine. It's slower than using ldtoken directly, but it works, and this only has to be done for generic methods. Unfortunately, this poses problems when the assembly is obfuscated. PostSharp and Obfuscation When using ldtoken, obfuscators don't affect how PostSharp operates. Because the ldtoken instruction directly references the type, method or field within the assembly, it is unaffected if the name of the object is changed by an obfuscator. However, the indirect loading used for generic methods was breaking, because that uses the name of the method when the assembly is put through the PostSharp postprocessor to lookup the MethodBase at runtime. If the name then changes, PostSharp can't find it anymore, and the assembly breaks. So, PostSharp needs to know about any changes an obfuscator does to an assembly. The way PostSharp does this is by adding another layer of indirection. When PostSharp obfuscation support is enabled, it includes an extra 'name table' resource in the assembly, consisting of a series of method & type names. When PostSharp needs to lookup a method using reflection, instead of encoding the method name directly, it looks up the method name at a fixed offset inside that name table: MethodBase genericMethod = typeof(ContainingClass).GetMethod(GetNameAtIndex(22)); PostSharp.NameTable resource: ... 20: get_Prop1 21: set_Prop1 22: DoFoo 23: GetWibble When the assembly is later processed by an obfuscator, the obfuscator can replace all the method and type names within the name table with their new name. That way, the reflection lookups performed by PostSharp will now use the new names, and everything will work as expected: MethodBase genericMethod = typeof(#kGy).GetMethod(GetNameAtIndex(22)); PostSharp.NameTable resource: ... 20: #kkA 21: #zAb 22: #EF5a 23: #2tg As you can see, this requires direct support by an obfuscator in order to perform these rewrites. Dotfuscator supports it, and now, starting with SmartAssembly 6.6.4, SmartAssembly does too. So, a relatively simple solution to a tricky problem, with some CLR bugs thrown in for good measure. You don't see those every day!

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• Separate shaders from HTML file in WebGL

  - by Chris Smith

  I'm ramping up on WebGL and was wondering what is the best way to specify my vertex and fragment shaders. Looking at some tutorials, the shaders are embedded directly in the HTML. (And referenced via an ID.) For example: <script id="shader_1-fs" type="x-shader/x-fragment"> precision highp float; void main(void) { // ... } </script> <script id="shader_1-vs" type="x-shader/x-vertex"> attribute vec3 aVertexPosition; uniform mat4 uMVMatrix; // ... My question is, is it possible to have my shaders referenced in a separate file? (Ideally as plain text.) I presume this is straight forward in JavaScript. Is there essentially a way to do this: var shaderText = LoadRemoteFileOnSever('/shaders/shader_1.txt');

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• Can an agile shop really score 12 on the Joel Test?

  - by Simon

  I really like the Joel test, use it myself, and encourage my staff and interviewees to consider it carefully. However I don't think I can ever score more than 9 because a few points seem to contradict the Agile Manifesto, XP and TDD, which are the bedrocks of my world. Specifically: the questions about schedule, specs, testers and quiet working conditions run counter to what we are trying to create and the values that we have adopted in being genuinely agile. So my question is: is it possible for a true Agile shop to score 12?

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• what is best book to learn optimized programming in java [closed]

  - by Abhishek Simon

  Possible Duplicate: Is there a canonical book for learning Java as an experienced developer? Let me elaborate a little: I used to be a C/C++ programmer where I used data structure concept like trees, queues stack etc and tried to optimize as much as possible, minimum no. of loops, variables and tried to make it efficient. It's been a couple of years that I started writing java codes, but it is simply not that efficient in terms of performance, memory intensive etc. To the point: I want to enter programming challenges using java so I need to improve my approach at things I program. So please suggest me some books that can help me learn to program better and have a chance in solving challenges in programming.

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• Subterranean IL: Custom modifiers

  - by Simon Cooper

  In IL, volatile is an instruction prefix used to set a memory barrier at that instruction. However, in C#, volatile is applied to a field to indicate that all accesses on that field should be prefixed with volatile. As I mentioned in my previous post, this means that the field definition needs to store this information somehow, as such a field could be accessed from another assembly. However, IL does not have a concept of a 'volatile field'. How is this information stored? Attributes The standard way of solving this is to apply a VolatileAttribute or similar to the field; this extra metadata notifies the C# compiler that all loads and stores to that field should use the volatile prefix. However, there is a problem with this approach, namely, the .NET C++ compiler. C++ allows methods to be overloaded using properties, like volatile or const, on the parameters; this is perfectly legal C++: public ref class VolatileMethods { void Method(int *i) {} void Method(volatile int *i) {} } If volatile was specified using a custom attribute, then the VolatileMethods class wouldn't be compilable to IL, as there is nothing to differentiate the two methods from each other. This is where custom modifiers come in. Custom modifiers Custom modifiers are similar to custom attributes, but instead of being applied to an IL element separately to its declaration, they are embedded within the field or parameter's type signature itself. The VolatileMethods class would be compiled to the following IL: .class public VolatileMethods { .method public instance void Method(int32* i) {} .method public instance void Method( int32 modreq( [mscorlib]System.Runtime.CompilerServices.IsVolatile)* i) {} } The modreq([mscorlib]System.Runtime.CompilerServices.IsVolatile) is the custom modifier. This adds a TypeDef or TypeRef token to the signature of the field or parameter, and even though they are mostly ignored by the CLR when it's executing the program, this allows methods and fields to be overloaded in ways that wouldn't be allowed using attributes. Because the modifiers are part of the signature, they need to be fully specified when calling such a method in IL: call instance void Method( int32 modreq([mscorlib]System.Runtime.CompilerServices.IsVolatile)*) There are two ways of applying modifiers; modreq specifies required modifiers (like IsVolatile), and modopt specifies optional modifiers that can be ignored by compilers (like IsLong or IsConst). The type specified as the modifier argument are simple placeholders; if you have a look at the definitions of IsVolatile and IsLong they are completely empty. They exist solely to be referenced by a modifier. Custom modifiers are used extensively by the C++ compiler to specify concepts that aren't expressible in IL, but still need to be taken into account when calling method overloads. C++ and C# That's all very well and good, but how does this affect C#? Well, the C++ compiler uses modreq(IsVolatile) to specify volatility on both method parameters and fields, as it would be slightly odd to have the same concept represented using a modifier or attribute depending on what it was applied to. Once you've compiled your C++ project, it can then be referenced and used from C#, so the C# compiler has to recognise the modreq(IsVolatile) custom modifier applied to fields, and vice versa. So, even though you can't overload fields or parameters with volatile using C#, volatile needs to be expressed using a custom modifier rather than an attribute to guarentee correct interoperability and behaviour with any C++ dlls that happen to come along. Next up: a closer look at attributes, and how certain attributes compile in unexpected ways.

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