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Delphi WideString and Delphi 2009+

Asked 2010-11-04T12:34:07.530
13

I am writing a class that will save wide strings to a binary file. I'm using Delphi 2005 for this but the app will later be ported to Delphi 2010. I'm feeling very unsure here, can someone confirm that:

  1. A Delphi 2005 WideString is exactly the same type as a Delphi 2010 String

  2. A Delphi 2005 WideString char as well as a Delphi 2010 String char is guaranteed to always be 2 bytes in size.

With all the Unicode formats out there I don't want to be hit with one of the chars in my string suddenly being 3 bytes wide or something like that.

Edit: Found this: "I indeed said UnicodeString, not WideString. WideString still exists, and is unchanged. WideString is allocated by the Windows memory manager, and should be used for interacting with COM objects. WideString maps directly to the BSTR type in COM." at http://www.micro-isv.asia/2008/08/get-ready-for-delphi-2009-and-unicode/

Now I'm even more confused. So a Delphi 2010 WideString is not the same as a Delphi 2005 WideString? Should I use UnicodeString instead?

Edit 2: There's no UnicodeString type in Delphi 2005. FML.

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For your first question: WideString is not exactly the same type as D2010's string. WideString is the same COM BSTR type that it has always been. It's managed by Windows, with no reference counting, so it makes a copy of the whole BSTR every time you pass it somewhere.

UnicodeString, which is the default string type in D2009 and on, is basically a UTF-16 version of the AnsiString we all know and love. It's got a reference count and is managed by the Delphi compiler.

For the second, the default char type is now WideChar, which are the same chars that have always been used in WideString. It's a UTF-16 encoding, 2 bytes per char. If you save WideString data to a file, you can load it into a UnicodeString without trouble. The difference between the two types has to do with memory management, not the data format.

answered 2010-11-04T12:46:48.603

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