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 ‘Conference Topics’ Category

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.NET/C#: UnitPrefixes class that facilitates distinguishing decimal and binary file/drive/memory size (mega versus mibi, etc)

Posted by jpluimers on 2013/08/14

Everyone knows there is a size difference between a gigabyte of memory, and a gigabyte of disk space.

The former is 102410241024, the latter is 100010001000.

To facilitate this, I’ve created a C# class UnitPrefixes containing quite a few constants and readonly values.

The class is below, but a few interesting facts first:

  • Most values are const, but a few are readonly static variables because they cannot calculated at compile time (the C# compiler by design does very limited calculations at compile time; it is complex enough as it already is).
    As Jon Skeet explains, there are some other differences between const and readonly static, which is why I favour const.
  • Though all consts are positive, I could have used UInt32 and UInt64, but the .NET framework favours signed Int32 and Int64 types for parameters, so to avoid casting, I used the signed ones.
  • There is no Int128 or UInt128, but there is System.Numerics.BigInteger which I use for values too large for 64-bit integers.
    Note that BigInteger is relatively new, so this code will only work in C# 4 or higher, and requires .NET 4 or higher.
    This is also the place where I use the public readonly static fields, as I need to call the BigInteger constructor to initialize it.
  • I used the Decimal type, as the mantissa holds up to 28 digits of accuracy.

I used the Wikipedia pages Binary Prefix and Metric Prefix (I could also have used File Size) for the unit names and abbreviations.

Note that BitsPerByte is a const I needed too, and I will probably add constants for 512 and 4096, as you see those often in computing as well.

The below sample code is also available as a changeset on BeSharp.CodePlex.com. Read the rest of this entry »

Posted in .NET, .NET 4.0, .NET 4.5, C#, C# 4.0, C# 5.0, Conference Topics, Conferences, Development, Event, Jon Skeet, Software Development | Tagged: , | Leave a Comment »

Reminiscence of the past: Delphi I/O error 131

Posted by jpluimers on 2013/08/06

I was called by a client that didn’t want to do maintenance on an old Delphi application, but wanted to get dir of an I/O Error 131:

I/O Error 131: ERROR_NEGATIVE_SEEK

MessageText: An attempt was made to move the file pointer before the beginning of the file.

Tough luck: psychic powers told me someone is using an unsigned 32-bit integer to access a file using traditional style Assign/Reset/Seek/Read/Close patterns that Delphi kept as intrinsic routines for Turbo Pascal backward compatibility, and that file has grown over 2 gigabyte in size.

I quickly found an import file had grown over the 2 gigabyte, so this was indeed the case.

The original developers didn’t do the file access using the 64-bit Seek/Position of the TStream descendant TFileStream.

Too bad, as now someone has to dig through the mothballs to find the sources (if they survived 3 different version control system switches), create a working development environment, and fix the bug.

Another instance where technical debt in IT raises its ugly head and the compound interest is really expensive.

–jeroen

via: erikmartin.com – IO Errors in Delphi.

Posted in Conference Topics, Conferences, Delphi, Delphi 5, Development, Event, Software Development, Technical Debt | 14 Comments »

A few notes on Delphi, WSDL and SOAP: passing nil values, Document/Literal versus RPC Encoded

Posted by jpluimers on 2013/05/14

I had some notes on Delphi WSDL and SOAP peculiarities somewhere, but I misplaced them.

Luckily, I found some links that explain most of my notes well:

–jeroen

Posted in Conference Topics, Conferences, Delphi, Delphi 2007, Delphi 2009, Delphi 2010, Delphi XE, Delphi XE2, Delphi XE3, Development, Event, SOAP/WebServices, Software Development | Leave a Comment »

Delphi: you should avoid the `with` statement as it makes your code less future proof

Posted by jpluimers on 2013/03/27

As I wrote before, I’m with the [WayBack] Delphi with haters camp, and this is why:

Using the [WayBack] with statement in Delphi makes your code less future proof.

Originally, the with statement in Pascal was argumented in part of allowing compiler optimisations:

PASCAL User Manual and Report – Kathleen Jensen, Niklaus Wirth – Google Books

The with clause effectively opens the scope containing field identifiers of the specified record variable, so that the field identifiers may occur as variable identifiers. (Thereby providing an opportunity for the compiler to optimize the qualified statement.)

Screenshots of this 1975 book are below the fold.

The Delphi (actually even before that Turbo Pascal compiler) has no measurable difference between with and non-with code.

The debugger however, still does not support with, and there are other drawbacks of which one is below.

The below code example is just one of many. I show it because I recently bumped into doing some long overdue code porting to Delphi XE3.

Since I’ve been bitten by using with a couple of times before, it didn’t take me long to find the cause.

Example code where FIConData is of type NOTIFYICONDATAW that used to compile fine:

    with FIconData do
    begin
      cbSize := SizeOf(FIconData);
      Wnd := Self.Handle;
      uID := $DEDB;
      uFlags := NIF_MESSAGE or NIF_ICON or NIF_TIP;
      hIcon := Application.Icon.Handle;
      uCallbackMessage := WM_CAS400NTIcon;
      StrCopy(szTip, PChar(Caption));
    end;

Well, as of Compiler Version 20, it doesn’t compile any more. Read the rest of this entry »

Posted in Borland Pascal, Conference Topics, Conferences, Delphi, Delphi 1, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi XE, Delphi XE2, Delphi XE3, Development, Event, Pascal, Software Development, Turbo Pascal, With statement | 32 Comments »

ntfs – How do you find what process is holding a file open in Windows? – Server Fault

Posted by jpluimers on 2013/03/15

First a warning: when you have found the process holding open a file, and you want to forcibly close the handle, read this post why you should not: Windows Confidential: Forcing Handles Closed.

In fact:

if you forcibly need to close a handle to salvage something, you should reboot shortly afterwards.

Back to the question at hand:

How do you find what process is holding a file open in Windows?

One thing that annoys me no end about Windows is the old “sharing violation” error. Often you can’t identify what’s holding it open. Usually it’s just an editor or explorer just pointing to a relevant directory but sometimes I’ve had to resort to rebooting my machine.

Any suggestions on how to find the culprit?

All of the below solutions require you to run with Administrative privileges.

On current Windows versions, if you run them without UAC elevation, they will miss a lot of processes. And still: under some secured environments you won’t see all processes anyway.

My preferred answer is not on the list:

Quit the application that holds the handle

All the tools that show you the handles will indicate which process holds the handle.

Often, you can just quit that process, do your job on the affected file, then relaunch that process.

When the process is Explorer, there is a neat little trick that works for Windows Vista and up:

For explorer, btw, hold ctrl-shift and right-click a blank area of the start menu, and you’ll get “Exit Explorer” – ps, not quite Jeff’s answer.. – Mark Sowul

Another answer I like is to use Handle, as it is both a command-line tool, and allows for wildcard searching: Read the rest of this entry »

Posted in Conference Topics, Conferences, Event, Power User, Windows, Windows 7, Windows 8, Windows Server 2000, Windows Server 2003, Windows Server 2003 R2, Windows Server 2008, Windows Server 2008 R2, Windows Vista, Windows XP | Leave a Comment »

Delphi “Variant Records”, a few notes

Posted by jpluimers on 2013/03/14

Variant Records are a feature that has been in the Pascal language since Standard Pascal.

A cool page for historic perspective is R3R: Pascal Features in Popular Compilers, hopefully someone will update it to more modern versions of the mentioned compilers.

There is not much official documentation on the Delphi side on this, so below some parts of a case I used for a project that started in 1997 and is still in use to day. Read the rest of this entry »

Posted in APPC, AS/400 / iSeries / System i, ASCII, COBOL, Communications Development, Conference Topics, Conferences, CPI-C, Delphi, Delphi 1, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi 8, Delphi XE, Delphi XE2, Delphi XE3, Development, Encoding, Event, HIS Host Integration Services, Internet protocol suite, MQ Message Queueing/Queuing, SNA, Software Development, TCP, Unicode, UTF-8, WebSphere MQ | 9 Comments »

If you think CSV is easy; think again!

Posted by jpluimers on 2012/12/05

Lots of people think CSV is easy: it’s just a bunch of values separated with commas. But in practice it is not. Various reasons can make CSV very hard, especially since “CSV” is not a single, well-defined format. As always importing is always harder than exporting. A few reasons that make it hard:

A few links that helped me a lot getting input and output of CSV right in C#:

Thanks to Jabulaza:

–jeroen

via: Comma-separated values – Wikipedia, the free encyclopedia.

Posted in Conference Topics, Conferences, CSV, Development, EBCDIC, Encoding, Event, Software Development | 4 Comments »

Dear fellow programmer. If you aren’t experienced doing multi-threading, please don’t!

Posted by jpluimers on 2012/07/05

Recently I was asked to investigate a performance problem with a certain .NET application.

The first error I got when getting the app to build in Visual Studio 2010, and then run it was like this:

System.ComponentModel.InvalidAsynchronousStateException was caught
  Message=An error occurred invoking the method.  The destination thread no longer exists.
  Source=System.Windows.Forms
  StackTrace:
       at System.Windows.Forms.Control.WaitForWaitHandle(WaitHandle waitHandle)
       at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
       at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
       at UI.Splash.SetStatus(String status) in C:\...\Splash.cs:line 395
       at UI.Menu.Main() in C:\...\Menu.cs:line 4275
  InnerException:

Someone built their own splash logic with multi-threading.

Funny that today, this got answered on StackOverflow by [WayBack] mgie: [WayBack] multithreading – TMonitor synchronization / Application.ProcessMessages – Stack Overflow.

Though that is a Delphi link (and points to the nice libraries [Archive.is] AsynCalls and [WayBack] OmniThreadLibrary), the most important link it contains is to  [WayBack] Borland Newsgroup Archive :: borland.public.delphi.internet.winsock :: Re: Disconnect TIdHttp in thread.

That sounds like a Delphi link too, but the subtitle “‘Ways to get into avoidable trouble with threads, V1.2′” hints the essence: it is a post that describes in an environment-agnostic way how to avoid multi-threading problems.

Recommended reading!

Anyway: Building multi-threaded code is hard. Even harder fleshing out all the corner cases and potential error conditions.

No matter what kind of programming environment: If you have not done lots of multi-threaded programming, then please don’t do it yourself: go ask someone that does know how to do it. Or better, try to avoid it.

I try to let libraries to the handling of multi-threading for me, if I use multi-threading at all, as others are far better at this than I am.

–jeroen

Posted in .NET, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, C# 5.0, Conference Topics, Conferences, Delphi, Development, Event, Java, Software Development, VB.NET, VBS, Visual Studio 2010, Visual Studio and tools, WinForms | 6 Comments »

ISO 8601 Date, Time and DateTime in Delphi (was: Simple example to show DateTime.Now in ISO 8601 format on ideone.com | Online C# Compiler & Debugging Tool)

Posted by jpluimers on 2011/08/18

In the past I wrote about a Simple example to show DateTime.Now in ISO 8601 format on ideone.com | Online C# Compiler & Debugging Tool , using ISO 8601 in batch-files, and how ISO 8601 is used in Google Calendar URLs.

Time to write something about ISO 8601 Date, Time and DateTime and Delphi.

First of all the DateUtils unit contains a bunch of routines (for instance DecodeDateWeek) that understand ISO 8601 week numbers, where:

  • Weeks start at Monday
  • The first week of a year contains (these are equivalent):
    • The first thursday in that year
    • Has at least 4 days in that year
    • Contains the 4th of January

Otherwise the week containing January 1st is week 52 or 53 of the previous year

ISO 8601 also specifies how to format Dates, Times,  DateTimes and durations according to some basic principles.

XML uses ISO 8601 to format Date, Time and DateTime and some other formats as text too.

So it is no wonder that since Delphi 6, it contains a XSBuiltIns unit covering (among other things) ISO 8601 formatting.

Given the many Delphi ISO 8601 relates questions on StackOverflow of which I answered two, and my need for ISO 8601 DateTime conversion for exporting Excel XML, here is are some samples to get started in the unit below (and in this codeplex changeset).

The unit covers Date, Time and DateTime.
You can write similar code for Duration.

Oops, I covered it already in ISO 8601: Delphi way to convert XML date and time to TDateTime and back (via: Stack Overflow)

Read the rest of this entry »

Posted in Conference Topics, Conferences, Delphi, Development, Event, ISO 8601, Power User, Software Development | 4 Comments »

ISO 8601: Delphi way to convert XML date and time to TDateTime and back (via: Stack Overflow)

Posted by jpluimers on 2011/07/19

Recently I needed a way of concerting back and forth ISO 8601 DateTime values used in XML from Delphi.

Thoug the Delphi DateUtils unit has some ISO 8601 features for calculating week numbers, you actually need to the XSBuiltIns unit for converting back and forth to ISO 8601 text representation of a DateTime.

I remembered answering the related In Delphi is there a function to convert XML date and time to TDateTime question on StackOverflow a while ago (and forgot that this was back in 2009 <g>).

ISO 8601 dates can either include a time-zone, or be in UTC, which is not part of that answer. So lets elaborate on that answer a bit now:

UTC times in ISO 8601 format end in a Z time zone designator like this:

    <Created>2011-06-29T17:01:45.505Z</Created>

The Z UTC indicator is basically a shortcut for a timezone offset of +00:00 or -00:00, effectively being a zero (or zulu) timezone.

Nonzero timezones start with an optional + or -, followed by the hours and minutes offset from UTC, for instance +01:00 for the Central European Time zone.

    <Created>2011-06-29T17:01:45.505+01:00</Created>

When you want historical time zones, then you need the Delphi TZDB interface to the historical TZ database.

To do the timezone calculations, I used the TimeZoneBias function from Indy, which is either in the IdGlobal unit (Indy <= version 9) or the IdGlobalProtocols unit (Indy 10 and up).

Conversion is done by using the TXSDateTime (that like all the XS conversion classes descends from TRemotableXS in the InvokeRegistry unit).

Most of the classes descending from TRemotableXS contain two methods: NativeToXS and XSToNative doing the underlying conversions.

Since I didn’t need the historical reference in the TZDB, this is the code that I came up with:

unit Iso8601Unit;

interface

type
  TIso8601 = class(TObject)
  public
    class function DateTimeFromIso8601(const Value: string): TDateTime; static;
    class function UtcDateTimeToIso8601(const Value: TDateTime): string; static;
    class function DateTimeToIso8601(const Value: TDateTime): string; static;
    class function UtcNow: TDateTime; static;
    class function ToUtc(const Value: TDateTime): TDateTime; static;
    class function FromUtc(const Value: TDateTime): TDateTime; static;
  end;

implementation

uses
  IdGlobalProtocols, {IdGlobal for Index   SysUtils,
  XSBuiltIns;

class function TIso8601.DateTimeFromIso8601(const Value: string): TDateTime;
begin
  with TXSDateTime.Create() do
  try
    XSToNative(value); // convert from WideString
    Result := AsDateTime; // convert to TDateTime  finally
  finally
    Free();
  end;
end;

class function TIso8601.UtcDateTimeToIso8601(const Value: TDateTime): string;
begin
  with TXSDateTime.Create() do
  try
    AsUTCDateTime := Value;
    Result := NativeToXS; // convert to WideString
  finally
    Free();
  end;
end;

class function TIso8601.DateTimeToIso8601(const Value: TDateTime): string;
begin
  with TXSDateTime.Create() do
  try
    AsDateTime := Value; // convert from TDateTime
    Result := NativeToXS; // convert to WideString
  finally
    Free();
  end;
end;

class function TIso8601.UtcNow: TDateTime;
begin
  Result := ToUtc(Now);
end;

class function TIso8601.ToUtc(const Value: TDateTime): TDateTime;
var
  Bias: TDateTime;
begin
  Bias := TimeZoneBias;
  Result := Value + TimeZoneBias;
end;

class function TIso8601.FromUtc(const Value: TDateTime): TDateTime;
var
  Bias: TDateTime;
begin
  Bias := TimeZoneBias;
  Result := Value - TimeZoneBias;
end;

end.

–jeroen

via In Delphi is there a function to convert XML date and time to TDateTime – Stack Overflow.

Posted in Conference Topics, Conferences, Delphi, Development, Event, Software Development | 7 Comments »

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