The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘Development’ Category

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Delphi: getting the name of the current unit

Posted by jpluimers on 2021/01/28

If you have a class (like TMyClass) in the current unit, you can get the unit name as follows:

  • inside a method of the class (either instance or class method): call UnitName or UnitScope to get the unit name
  • outside a method of the class: call TMyClass.UnitName or TMyClass.UnitScope

Delphi added UnitName [WayBack] and  Delphi XE2 added UnitScope [Archive.is]. Their implementations are different, but I have not seen classes where the outcome is different.

The code below shows that when the underlying RTTI UnitName field inside a PTypeData referred by a PTypeInfo contains an @ sign, then UnitName takes the part before the @, and UnitScope the part after the @, but I have not yet seen units where the underlying field contains an @ sign.

If you have seen that, please let me know.

I needed this in order to research some unit initialisation order issues.

A post helpful with that was [WayBack] windows – Can I determine the order in which my units have been initialized? – Stack Overflow for which this comment by Ritsaert Hornstra is the most important bit:

Related: If you use a unit in the interface section you know that that unit will be initialized BEFORE the unit that uses that unit. When using units in the implementation section this is not the case. So usually when you are using a unit with a singleton in it, created in it’s initialization section, you should use that unit in the interface section to make sure that it is initialized before use.

There is also an answer [WayBack] by Remko Weijnen that shows how to hack the current initialisation order if you know the address of InitContext inside the System.InitUnits method.

Back to UnitName versus UnitScope, the code:

class function TObject.UnitName: string;
var
  LClassInfo: Pointer;
  S: _PShortStr;
begin
  LClassInfo := ClassInfo;
  if LClassInfo <> nil then
  begin
    S := @PClassData(PByte(LClassInfo) + 2 + PByte(PByte(LClassInfo) + 1)^).UnitName;
    if S^[1] <> '@' then
      Result := UTF8ToString(S^)
    else
      Result := UTF8ToString(Copy(S^, Pos(_ShortStr(':'), S^) + 1, MaxInt));
  end else
    Result := '';
end;

class function TObject.UnitScope: string;
var
  LClassInfo: Pointer;
  S: _PShortStr;
begin
  LClassInfo := ClassInfo;
  if LClassInfo <> nil then
  begin
    S := @PClassData(PByte(LClassInfo) + 2 + PByte(PByte(LClassInfo) + 1)^).UnitName;
    if S^[1] <> '@' then
      Result := UTF8ToString(S^)
    else
      Result := UTF8ToString(Copy(S^, 2, Pos(_ShortStr(':'), S^) - 2));
  end else
    Result := '';
end;

Related:

–jeroen

Posted in Delphi, Development, Software Development | 1 Comment »

NDC 2019 Keynote: Welcome to the Machine – Hadi Hariri – YouTube

Posted by jpluimers on 2021/01/27

I am really glad this keynote got recorded. Still very relevant, it is as much about software development as it is about society.

Go watch it, as it gives you reason to think about your role in the software development process, and in the information fire hose at large.

Back in the days, David Intersimone was right when he created the regular blog post “Sip from the Firehose” (for early materials, see [WayBack] GetPublished – Author Information: Firehose).

The talk main thread is about current and ever growing overload of information which basically makes it disinformation, combined with the abundance of “AI” recording devices around you that basically make you the product.

Basically we reached all the tick marks of these books:

The session is not just about “how bad is the situation” (it is very), but also provides directions on how to get out of it for both people in the development process, as well as consumers, producers and sharers of information.

via:

–jeroen

Read the rest of this entry »

Posted in .NET, Development, Opinions, Power User, Security, Software Development | Leave a Comment »

Few remember the ancestry of programming languages

Posted by jpluimers on 2021/01/27

A while ago, I saw this tweet:

It mentions LISP (nowadays mostly called Lisp), likely because their derivatives like Scheme and Clojure still actively mention their ancestry.

ALGOL is not in the list, but has had so much influence on modern programming. So here the thread that followed:

–jeroen

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Posted in ALGOL, Delphi, Development, LISP, Software Development | Leave a Comment »

On my research list: Delphi “Package Cache” subtree

Posted by jpluimers on 2021/01/27

On one of the sites, when having some Delphi package registration issues, the standard measure was to delete the complete Package Cache subtree (like HKEY_CURRENT_USER\Software\Embarcadero\BDS\17.0\Package Cache).

Since there is so little information about it, it is on my list of things to eventually research.

Some links I already found, but had no time for to fully read:

Unrelated: You should not delete the folder C:\ProgramData\Package Cache\? – Super User, but matched my initial delphi registry “Package Cache” – Google Search.

Yup, I did it: I added an “Undocumented Delphi” category.

–jeroen

Posted in Delphi, Development, Software Development, Undocumented Delphi | Leave a Comment »

Run your unit tests in parallel with NUnit

Posted by jpluimers on 2021/01/26

TL;DR

The examples in this post are specific for NUnit but, you can apply this pattern for safely running unit tests in parallel to any unit test framework that supports parallel execution.

To safely run tests in parallel, do the following:

  1. Mark your test fixtures with the Parallelizable attribute and set the parallel scope to ParallelScope.All.
  2. Create a private class called TestScope and implement IDisposable.
  3. Put all startup and clean-up logic inside the TestScope constructor and .Dispose() method respectively.
  4. Wrap your test code in a using (var scope = new TestScope) { ... } block

From [WayBack] Run your unit tests in parallel with NUnit, which also covers:

  • Background (on why you might want this)
  • How to safely run tests in parallel
  • Maximizing parallel execution with Visual Studio
  • Maximizing parallel execution with Azure DevOps

Via: [WayBack] Sander Aernouts on Twitter: “Run unit tests in parallel with NUnit without having one test interfere with another test. https://t.co/FC0fNocGov”

–jeroen

Posted in .NET, Development, Software Development | Leave a Comment »

datetime – Determine Whether Two Date Ranges Overlap – Stack Overflow

Posted by jpluimers on 2021/01/26

[WayBack] datetime – Determine Whether Two Date Ranges Overlap – Stack Overflow answer by Charles Bretana with input from Baodad and tomosius.

TL;DR (proof is in the post)

(StartA <= EndB) and (EndA >= StartB)

Alternative (also from the post):

DateRangesOverlap = max(StartA,StartB) < min(EndA,EndB)

It gets complicated when the date boundaries for A and B can be out of order.

The post also covers that.

Related:

–jeroen

Posted in Development, Software Development | Leave a Comment »

Delphi debugging tip: keep an eye on a object field of an object that will go out of scope eventually

Posted by jpluimers on 2021/01/26

Every once in a while you want to have a Delphi Watch of a field inside an object (say an object of type TContext), except that the field has no value yet, but eventually will point to another object (say an object of type TUser).

However, the original object will go out of scope, so you need to employ a few tricks.

First of all, you get the address of that field:

@(Context().FCurrentUser) = $7EF6F624

Then you watch the content of that field:

TUser(PPointer($7EF6F624)^),r = nil

To get to this trick, you have to remember:

  1. The contents of address $7EF6F624 is pointer (at first nil) to a TUser.
  2. You get to the contents of the address $7EF6F624 by using PPointer($7EF6F624)^.
  3. Then you cast it to the object you want with the TUser(...) cast.

–jeroen

Posted in Delphi, Development, Software Development | Leave a Comment »

Thought experiments can help you solve a problem early

Posted by jpluimers on 2021/01/21

Important logical principle to take away from [WayBack] The dialog manager, part 2: Creating the frame window – The Old New Thing:

If you’re not sure whether something is true, ask yourself, “What would the world be like if it were true?” If you find a logical consequence that is obviously wrong, then you have just proven [by contradiction] that the thing you’re considering is indeed not true.

Thought experiments like these can really help you get a feel for parts of a problem before you completely resolve the full problem.

Related: Thought experiment – Wikipedia

–jeroen

Posted in Development, LifeHacker, Power User, science, Software Development | Leave a Comment »

Default XML encoding is UTF-8 (or better: utf-8). If it contains other byte sequences, this is an error.

Posted by jpluimers on 2021/01/21

I should have had the below answer when writing about StUF – receiving data from a provider where UTF-8 is in fact ISO-8859.

A while ago, a co-worker did not believe when I told that default XML encoding really is UTF-8 (and tried to force it to utf-8), and that if the content had byte sequences different from the (either specified or default) encoding, it was a problem.

I though I blogged about the default, and where to find it, but apparently, I did not.

My blog had (and has <g>) a truckload of articles mentioning UTF-8, less articles containing UTF-8, encoding and xml, but the ones having UTF-8, default, encoding and xml did not actually tell about a standard that really defines XML uses UTF-8 as default encoding when there is no other encoding information – like BOM (byte order mark), HTTP, or MIME encoding) available.

W3C indeed specifies it. [WayBack] utf 8 – How default is the default encoding (UTF-8) in the XML Declaration? – Stack Overflow has a summary (thanks James Holderness!):

The Short Answer

Under the very specific circumstances of a UTF-8 encoded document with no external encoding information (which I understand from the comments is what you’re interested in), there is no difference between the two declarations.

The long answer is far more interesting though.

and an elaboration:

Read the rest of this entry »

Posted in Development, Encoding, Software Development, UTF-8, UTF8, XML, XML/XSD | Leave a Comment »

If you use an implementation of TNonRefCountInterfacedObject, then document in the descendants how lifetime management is arranged for

Posted by jpluimers on 2021/01/21

There are a few TNonRefCountInterfacedObject (or maybe better named TNonReferenceCountedInterfacedObject) implementations around (see list of links below).

They can be used to expose interfaces, but do not provide interface reference counting. This means you have to do your own lifetime management, which can bring quite a few headaches.

So each class you descend from it must have proper motivation on why, and how lifetime management is performed.

One thing you can do is mark the class with a hint directive like [WayBack] library.

In addition, [Archive.is] TNonRefCountInterfacedObject / [Archive.is] TNonReferenceCountedInterfacedObject implementations should at least implement [WayBack] IInterface (or [WayBack] IUnknown in really old Delphi versions); I have seen implementations that don’t but just provide almost empty [WayBack] QueryInterface, [WayBack] _AddRef and [WayBack] _Release methods).

Some examples via  “TNonRefCountInterfacedObject” – Google Search:

Delphi RTL/VLC/FMX

I used this GExperts Grep Search expression to find the entries below: (_AddRef|_Release|QueryInterface)

Delphi itself has a few implementations of non-standard interface management that have good documentation on their use cases. So take a look at at least these before doing something odd with interface implementations yourself:

  • [WayBack] TAggregatedObject in System
    • This redirects all IInterface implementations to a controller
    • It does not implement IInterface itself, so a descendent must add the interface reference
    • Descendants are TContainedObject and TPropertyPageImpl (the latter used by TActiveXPropertyPage)
  • [WayBack] TContainedObject in System
    • This redirects all IInterface implementations except QueryInterface to a controller
    • Descendants are for instance TSOAPHeaders (via TSOAPHeadersBase) used by TSoapPascalInvoker, TInvokableClass and TRIO, and TConnectionPoint used by TConnectionPoints
  • [WayBack] TInterfacedPersistent in System.Classes
    • This supports the notion of (potentially) being owned by another TPersistent. Classes like TCollectionItem, TFieldOptions and TEditButton implement this ownership behaviour.
    • When owned, then redirect reference counting to the owner (if that owner implements IInterface), but not QueryInterface
    • When not owned, then it is effectively non-reference counted
  • [WayBack] TComponent in System.Classes
    • This supports the notion of (potentially) being owned by another TComponent. Classes like TComponent and TCollectionItem implement this ownership behaviour.
    • When owned, then redirects all IInterface calls to the owner (including QueryInterface).
  • [Archive.is] TXPEditReaderStream in DUnit XP_OTAEditorUtils. It is largely undocumented.
  • TXPInterfacedObject in DUnit XPInterfacedObject. It is largely undocumented too.

Not so good examples:

  • [WayBack] TCustomVariantType in System.Variants (which is basically TSingletonImplementation with a lot of extra methods)
  • [WayBack] TSingletonImplementation in System.Generics.Defaults(which is basically what most TNonRefCountInterfacedObject implementations do; this is sort of OK as it is meant to be used only in [WayBack] TCustomComparer<T> and descendants that are supposed to be singletons).
  • IUnknown in Winapi.Ole2 (this whole unit is undocumented; the class only has virtual abstract methods; the unit – together with Winapi.OleCtl – seems to be only meant to support the depcrecated Vcl.OleAuto unit.)

And of course there is the standard implementation with proper multi-threading support:

There are quite a few classes that implement reference counting while descending from things like TComponent, usually without the proper multi-threading support that TInferfacedObject has:

Read the rest of this entry »

Posted in Conference Topics, Conferences, Delphi, Development, Event, Software Development | Leave a Comment »

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