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

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Archive for December 7th, 2021

Kristian Köhntopp on Twitter: “Playing with a Ceph Storage Volume in a VM: The new openstack backend provisions an all-flash Ceph volume, which after tuning delivers a commit latency of around 1.1ms or so”

Posted by jpluimers on 2021/12/07

Not on an average VM (8 threads and 16gb memory) or network (100gbit), but ceph isn’t average solution.

For my link archive this long Twitter thread:

Archive.is Kristian Köhntopp on Twitter: “Playing with a Ceph Storage Volume in a VM: The new openstack backend provisions an all-flash Ceph volume, which after tuning delivers a commit latency of around 1.1ms or so. My dev VM has 8 Threads and 16 GB of memory, and mounts the Ceph Volume with XFS in /a.”

Hopefully this one day makes into a blog post at [Wayback] Die wunderbare Welt von Isotopp | Something old, something new, something borrowed, something blue.

–jeroen

Posted in *nix, *nix-tools, Linux, Power User, Storage | Leave a Comment »

How to build a CD ISO image file from the windows command line? – Stack Overflow

Posted by jpluimers on 2021/12/07

As I might need this in the future, some highlights from [Wayback] How to build a CD ISO image file from the windows command line? – Stack Overflow:

–jeroen

 

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

On TStrings (and TStringList) sorting: what the default Sort behaviour is and how to change sorting order

Posted by jpluimers on 2021/12/07

Because I need this eventually, here the full quote of my answer in [Wayback] sorting – How can I get TStringList to sort differently in Delphi – Stack Overflow (The default Sort behaviour is to accommodate i18n sorting in natural order):

i18n sorting totally depends on your locale.
So I totally agree with PA that this is not a bug: the default Sort behaviour works as designed to allow i18n to work properly.

Like Gerry mentions, TStringList.Sort uses AnsiCompareStr and AnsiCompareText (I’ll explain in a few lines how it does that).

But: TStringList is flexible, it contains SortCustomSort and CompareStrings, which all are virtual (so you can override them in a descendant class)
Furthermore, when you call CustomSort, you can plug in your own Compare function.

At the of this answer is a Compare function that does what you want:

  • Case Sensitive
  • Not using any locale
  • Just compare the ordinal value of the characters of the strings

CustomSort is defined as this:

procedure TStringList.CustomSort(Compare: TStringListSortCompare);
begin
  if not Sorted and (FCount > 1) then
  begin
    Changing;
    QuickSort(0, FCount - 1, Compare);
    Changed;
  end;
end;

By default, the Sort method has a very simple implementation, passing a default Compare function called StringListCompareStrings:

procedure TStringList.Sort;
begin
  CustomSort(StringListCompareStrings);
end;

So, if you define your own TStringListSortCompare compatible Compare method, then you can define your own sorting.
TStringListSortCompare is defined as a global function taking the TStringList and two indexes referring the items you want to compare:

type
  TStringListSortCompare = function(List: TStringList; Index1, Index2: Integer): Integer;

You can use the StringListCompareStrings as a guideline for implementing your own:

function StringListCompareStrings(List: TStringList; Index1, Index2: Integer): Integer;
begin
  Result := List.CompareStrings(List.FList^[Index1].FString,
                                List.FList^[Index2].FString);
end;

So, by default TStringList.Sort defers to TList.CompareStrings:

function TStringList.CompareStrings(const S1, S2: string): Integer;
begin
  if CaseSensitive then
    Result := AnsiCompareStr(S1, S2)
  else
    Result := AnsiCompareText(S1, S2);
end;

Which then use the under lying Windows API function CompareString with the default user locale LOCALE_USER_DEFAULT:

function AnsiCompareStr(const S1, S2: string): Integer;
begin
  Result := CompareString(LOCALE_USER_DEFAULT, 0, PChar(S1), Length(S1),
    PChar(S2), Length(S2)) - 2;
end;

function AnsiCompareText(const S1, S2: string): Integer;
begin
  Result := CompareString(LOCALE_USER_DEFAULT, NORM_IGNORECASE, PChar(S1),
    Length(S1), PChar(S2), Length(S2)) - 2;
end;

Finally the Compare function you need. Again the limitations:

  • Case Sensitive
  • Not using any locale
  • Just compare the ordinal value of the characters of the strings

This is the code:

function StringListCompareStringsByOrdinalCharacterValue(List: TStringList; Index1, Index2: Integer): Integer;
var
  First: string;
  Second: string;
begin
  First := List[Index1];
  Second := List[Index2];
  if List.CaseSensitive then
    Result := CompareStr(First, Second)
  else
    Result := CompareText(First, Second);
end;

Delphi ain’t closed, quite the opposite: often it is a really flexible architecture.
It is often just a bit of digging to see where you can hook into the that flexibility.

–jeroen

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

 
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