"Mattias Sjögren" <mattias.dont.want.spam@mvps.org> wrote in message
news:uE6Q1kaDHHA.1220@TK2MSFTNGP04.phx.gbl...
> Olivier,
>
>>Given a StringBuilder, I need to produce a LPTSTR to call unmanaged code,
>>and get back a modified StringBuilder on return.
>
> That sounds like the default marshaling for a StringBuilder. Can't you
> just pass the StringBuilder as is and let the CLR handle the rest?
>
>
> Mattias
>
> --
> Mattias Sjögren [C# MVP]  mattias @ mvps.org
> http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
> Please reply only to the newsgroup.

"Walter Wang [MSFT]" <waw***@online.microsoft.com> wrote in message
news:xUPTXfjDHHA.4808@TK2MSFTNGXA01.phx.gbl...
> Hi Olivier,
>
> Based on my understanding, your scenario is:
> 1) You're writing a wrapper in managed C++ to wrap some unmanaged code
> 2) The input is a StringBuilder, the outout is also a StringBuilder
> 3) You don't want to use DllImport to do the marshaling of StringBuilder
>
> Please correct me if I've misunderstood anything.
>
> I believe you could use PtrToStringChars() to access the internal wchar_t*
> of a managed string. For the reverse part, you could use
> Marshal::PtrToStringAnsi or Uni to convert from ANSI or Unicode to a
> managed string.
>
> #StringConvertor : A convertor class for managed-unmanaged string
> conversions that handles memory de-allocations - The Code Project -
> Managed
> C++
> http://www.codeproject.com/managedcpp/StringConvertor.asp
> A convertor class for managed-unmanaged string conversions that handles
> memory de-allocations. Caller need not worry about freeing unmanaged
> memory
> allocations.
>
> #I Love that New Syntax Smell : Pointer to String chars - Everett style
> http://blogs.msdn.com/arich/archive/2003/12/22/45219.aspx
> Can I get a native pointer to the data in a CLR String?  The short answer
> is yes, so long as you don't mind a wchar_t* - which is native analog of
> the actual backing store type for a CLR String (the CLR type
> System::Char).
>
> #I Love that New Syntax Smell : Pinning Pointers
> http://blogs.msdn.com/arich/archive/2004/08/27/221588.aspx
> Pinning Pointers
>
> #Managed C++ - Learn by Example - Part 1 - The Code Project - Managed C++
> http://www.codeproject.com/managedcpp/cpptomancpp.asp
> VC++ provides a helper function, PtrToStringChars(), defined in "vcclr.h"
> that allows you to access the internal wchar_t* of a managed string.
>
>
>
>
> Sincerely,
> Walter Wang (waw***@online.microsoft.com, remove 'online.')
> Microsoft Online Community Support
>
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"Walter Wang [MSFT]" <waw***@online.microsoft.com> wrote in message
news:lKcrassDHHA.4372@TK2MSFTNGXA01.phx.gbl...
> Hi Olivier,
>
> Thanks for the update.
>
> The DllImport marshalling of StringBuilder internally copies the buffer
> instead of returning the pointer to the internal buffer directly; while
> the
> PtrToStringChars will return the buffer pointer directly (see Pinning
> Pointers for more info). So far I don't know a way how to return the
> buffer
> pointer of StringBuilder directly. I'm afraid for now you might have to
> use
> the DllImport approach as a workaround.
>
> Regards,
> Walter Wang (waw***@online.microsoft.com, remove 'online.')
> Microsoft Online Community Support
>
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