CodeSnip problems, problems, problems

Arrgh!

I've been having a lot of problems with the CodeSnip program's database update code - it's been working for some and not for others. All this has happened since I converted the program to Unicode and compiled with Delphi 2010.

I'm posting this for two reasons:

  1. To try to explain to long suffering users what has been going on with program lately - it's not usually this flaky.
  2. To forewarn anyone about to fall down the same hole as I have.

The problem never raised its head on my system, but did on some that don't use the Windows-1252 code page. The problem was caused by a checksum failure, which in turn was caused by the downloaded data being converted to the wrong code page before the checksum got calculated: result - bang - bad checksum.

My code relies on Indy components to translate downloaded content into text - and Indy and I make different assumptions about how this should be done. And I'm not sure either of us was correct, but they are a much more experienced bunch than I am so I'm prepared to take the blame!

The upshot of all this is that a proper fix insn't going to be trivial. I produced a temporary fix in v3.5.4 by the simple expedient of not checking the checksum. Then I went and commented out a crucial piece of code that meant that downloaded failed for everyone. At least that's fair I suppose because it screwed up UK and USA users just as much as those in the rest of the world!

Next up is a total rewrite of the web service management code - I'm going to handle the raw data myself and perform my own translations rather than let Indy do it. And I'm going to do the checksum properly using HTTP headers rather than my own custom approach.

I may write some of this up here once I've worked it all out.

And the moral of this story - be damn careful about character encoding when interacting with web services, and be sure you understand what your components are up to.

Some news for CodeSnip users: I've hacked the update web service to recognise v3.5.4 and feed it data that doesn't make it fall over. And I've released v3.5.5 that does the temporary fix that v3.5.4 was supposed to do. Please update. Again!

Comments

Post a Comment

Comments are very welcome, but please don't comment here if:

1) You have a query about, or a bug report for, one of my programs or libraries. Most of my posts contain a link to the relevant repository where there will be an issue tracker you can use.

2) You have a query about any 3rd party programs I feature, please address them to the developer(s) - there will be a link in the post.

3) You're one of the tiny, tiny minority who are aggressive or abusive - in the bin you go and reported you will be!

Thanks

Popular posts from this blog

Initialising dynamic arrays

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...
Read more

Deleting elements from a dynamic array

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 : ...
Read more

New String Property Editor Planned For RAD Studio 12 Yukon 🤞

Image
This blog post is based on a pre-release version of the RAD Studio software and it has been written with specific permission by Embarcadero. No feature is committed until the product GA release. It seems I'm getting very excited about multi-line strings of late. My previous post was about multi-line string literals for Delphi  and this time I'm talking about the new multi-line string property editor being slated for the RAD Studio 12 IDE. For more years than I care to remember, I've been frustrated by the inability to enter multi-line strings in the Delphi IDE object inspector. That meant having to resort to code to initialise some multi-line labels. So frustrated was I that I wrote a little property editor of my own ( stringpe ), way back in 2004. It's still around and on GitHub. Here's what it (sometimes) looks like: Yeah, I know this is Vista - I used an old screenshot Sometimes? Well it looked like that until it got installed on DPI aware Delphis, and then it sh...
Read more