DelphiDabbler's Blog

In my blog " Initialising Dynamic Arrays " I mentioned I have been writing some unit tests that needed numerous repetative array initialisation operations. Well, one of the other common operations I found myself writing was the deletion of items from dynamic arrays. So I decided to find a generic way of doing this. Assuming we know the index of the item to be deleted we need the equivalent of Delphi's built-in Delete procedure for strings. If you read the previous post you won't be surprised to learn that I decided to further extend the Generics.Collections.TArray class by adding to the TArrayEx class I introduced there. My first attempt emulates Delphi's Delete procedure by deleting the array element in-place: i.e. it updates the array passed as a parameter. Unsurprisingly the method is called DeleteInPlace . Here's how it goes: type TArrayEx = class ( TArray ) public .. . class procedure DeleteInPlace < T > ( var A : ...

When writing some unit tests a while ago I found myself needing to initialise some dynamic arrays with test data. It would be nice if we could do something like this: var A : array of Integer ; begin A := ( 1 , 2 , 3 , 4 ) ; // !! WRONG end ; but we can't. So I decided to write some functions to initialise dynamic arrays to the contents of another array, be it a constant, a literal or another dynamic array. The result was a set of overloaded routines, one for each data type I needed to handle, for example for Integer and string arrays I had: function CloneArray ( const A : array of Integer ) : TIntegerDynArray ; overload ; var Idx : Integer ; begin SetLength ( Result , Length ( A ) ) ; for Idx := Low ( A ) to High ( A ) do Result [ Idx - Low ( A ) ] := A [ Idx ] ; end ; function CloneArray ( const A : array of string ) : TStringDynArray ; overload ; var Idx : Integer ; begin SetLength ( Result , Len...

The other day I was writing some unit tests and needed some helper functions to look up some array elements of in arrays of different base types. I had several overloaded functions to do the job, like this: function IndexOf ( const Item : string ; const A : array of string ) : Integer ; overload ; function IndexOf ( const Item : Integer ; const A : array of Integer ) : Integer ; overload ; Oh, I thought, generics are a way round this, so I replaced the overloaded functions with something like function IndexOf < T > ( const Item : T ; const A : array of T ) : Integer ; only to be get compiler error 2530: Type parameters not allowed on global procedure or function . Now, I didn't know that and I'm sharing it in case some of you didn't either. And the solution? I sorted it by using a static class to hold the code, i.e. type TSomeClass = class ( TObject ) public class function IndexOf < T > ( const Ite...

One of my favourite additions to Delphi over the past years has been the for..in construct and the associated enumerators. I just love the way we can do var Ch : Char ; S : string ; begin S := 'Some text' ; for Ch in S do // Do something with Ch end ; So how come I missed that enumerators work on sets and arrays? I'm mentioning this here just in case it's slipped past anyone else, and in case you can tell me about any other enumerators I might have missed! Since forever I've being having to do stuff like this for arrays and sets: const cMyArray : array [ 1 .. 4 ] of Byte = ( 51 , 60 , 80 , 81 ) ; cMySet : set of Byte = [ 50 , 51 , 80 , 81 , 40 , 30 , 32 ] ; var I : Integer ; B : Byte ; begin for B := Low ( Byte ) to High ( Byte ) do if B in cMySet then // Do stuff with B for I := Low ( cMyArray ) to High ( cMyArray ) do // Do stuff my cMyArray[I] end ; ...

For about three months now I've had some code that tests and exercises some of the snippets in the Code Snippets Database . But, if you don't get the Code Snippets newsletter, you won't know about it because I forgot to tell anyone else! Anyhow, the code is stored in my Delphi Doodlings Subversion repository on Assembla in the CodeSnippets sub-directory of the trunk. There are currently three test projects: TestDriveCat.dpr in the Src/Cat-Drive sub-directory. This is a demo program that exercises all the routines in the Code Snippets database's Drive Management category. This project was updated today to bring up to date with a new addition to the category. TestHexCat.dpr in the Src/Cat-Hex sub-directory This is a set of DUnit tests for all the routines in the Hex Utilities category. TestWinSysCat.dpr in the Src/Cat-WynSys sub-directory. This new demo program was added today and exercises all the routines in the Windows System category. I'm only u...

A while ago someone asked me how to go about decoding Base 64 encoded code in a single routine. Here's what I came up with. It uses the Indy internet component suite to do the grunt work and simply wraps the various Indy calls into a function. uses Classes , IdCoderMIME .. . function Base64Decode ( const EncodedText : string ) : TBytes ; var DecodedStm : TBytesStream ; Decoder : TIdDecoderMIME ; begin Decoder := TIdDecoderMIME . Create ( nil ) ; try DecodedStm := TBytesStream . Create ; try Decoder . DecodeBegin ( DecodedStm ) ; Decoder . Decode ( EncodedText ) ; Decoder . DecodeEnd ; Result := DecodedStm . Bytes ; finally DecodedStm . Free ; end ; finally Decoder . Free ; end ; end ; This function decodes the encoded text passed in EncodedText , which must contain only valid Base 64 encoding characters, and returns the resulting raw data as an array of bytes. We use I...

There have been a few reports of a possible virus in the third party Delphi Tips Editor published on DelphiDabbler.com . Just to let everyone know that this is likely (but not guaranteed) to have been a false positive due to the exe compressor used by the author. However, to be on the safe side the offending code has been replaced by a recompiled version that passes all the tests at http://www.virustotal.com/ . If you're using the program please make sure you download the latest version here .