"Sylvain Fortin" <Sylvain Fortin@discussions.microsoft.com> wrote in message
news:A8D53990-F8C1-4DAF-BD4C-CB8C96730AEF@microsoft.com...
> Hi everyone,
>
> My application is written in VB.NET and will run on a SmartPhone. My
> problem
> is that my application is making too many string copy
> (String.Substring(...))
> which is slowing my application.
>
> Example of what the application has to do:
>
> oSize = oGraph.MeasureString(strValue.Substring(5, 10), oFont)
>
> Example of what could be done easily in c/c++ (very ugly but works):
>
> cValue = strValue[15];
>
> strValue[15] = '\0'
> oSize = oGraph.MeasureString(&strValue[5], oFont)
> strValue[15] = oChar
>
>
> The first example made a copy when String.Substring(...) was called, which
> used memory that will have to be freed later by the garbage collector. The
> second example is ugly but I wanted to give a good example of what I ment.
> I'm sure you got my point, I haven't used any additionnal memory...
>
> I need a way to do this kind of job in VB.NET cause I can't use the amount
> of memory my application need at the moment and the CPU time is completely
> lost by these String.Substring(...) operation. Also, I need to be able to
> call any .NET function with the string.
>
> Any help will be greatly appreciated!
>
> Regards,
>
> Sylvain Fortin

"Sylvain Fortin" <Sylvain Fortin@discussions.microsoft.com> wrote in message
news:A8D53990-F8C1-4DAF-BD4C-CB8C96730AEF@microsoft.com...
> Hi everyone,
>
> My application is written in VB.NET and will run on a SmartPhone. My
problem
> is that my application is making too many string copy
(String.Substring(...))
> which is slowing my application.
>
> Example of what the application has to do:
>
> oSize = oGraph.MeasureString(strValue.Substring(5, 10), oFont)
>
> Example of what could be done easily in c/c++ (very ugly but works):
>
> cValue = strValue[15];
>
> strValue[15] = '\0'
> oSize = oGraph.MeasureString(&strValue[5], oFont)
> strValue[15] = oChar
>
>
> The first example made a copy when String.Substring(...) was called, which
> used memory that will have to be freed later by the garbage collector. The
> second example is ugly but I wanted to give a good example of what I ment.
> I'm sure you got my point, I haven't used any additionnal memory...
>
> I need a way to do this kind of job in VB.NET cause I can't use the amount
> of memory my application need at the moment and the CPU time is completely
> lost by these String.Substring(...) operation. Also, I need to be able to
> call any .NET function with the string.
>
> Any help will be greatly appreciated!
>
> Regards,
>
> Sylvain Fortin

"Bob Grommes" wrote:

> There is a built-in indexer for any string.
>
> Your MeasureString method could use the indexer to examine the relevant
> characters without creating new strings in the process, or having to pass in
> a substring of the characters to examine:
>
> for (int i = start;i <= end;i++) {
> // evaluate the character strValue[i]
> }
>
> Just pass the start and end points and the string and let MeasureString do
> the work.
>
> Unfortunately the indexer is read-only, so you will still have the overhead
> of a String.Replace() call on strValue when you want to put the size byte
> back in. This will result in a completely new string being created to
> replace the original one.
>
> Two possible solutions:
>
> (1) Instead of a string, use a StringBuilder to build up the string, using
> StringBuilder.Append(string) and/or StringBuilder.Append(char) and creating
> the string all at once with StringBuilder.ToString().
>
> (2) Instead of a string, use a character array, converting it to a string
> all at once when you've finished manipulating it. Or possibly, a byte
> array.
>
> The basic idea is to avoid explicitly or implictly creating lots of strings.
> Strings in C# are immutable so any change at all to a string destroys the
> old one and creates a new one.
>
> I'm assuming of course that you've accurately diagnosed your performance
> bottleneck. While it's true that using StringBuilders and other techniques
> can be much faster than simple string manipulation, it's only a practical
> problem in tight loops, especially on fast hardware.
>
> --Bob
>
> "Sylvain Fortin" <Sylvain Fortin@discussions.microsoft.com> wrote in message
> news:A8D53990-F8C1-4DAF-BD4C-CB8C96730AEF@microsoft.com...
> > Hi everyone,
> >
> > My application is written in VB.NET and will run on a SmartPhone. My
> > problem
> > is that my application is making too many string copy
> > (String.Substring(...))
> > which is slowing my application.
> >
> > Example of what the application has to do:
> >
> > oSize = oGraph.MeasureString(strValue.Substring(5, 10), oFont)
> >
> > Example of what could be done easily in c/c++ (very ugly but works):
> >
> > cValue = strValue[15];
> >
> > strValue[15] = '\0'
> > oSize = oGraph.MeasureString(&strValue[5], oFont)
> > strValue[15] = oChar
> >
> >
> > The first example made a copy when String.Substring(...) was called, which
> > used memory that will have to be freed later by the garbage collector. The
> > second example is ugly but I wanted to give a good example of what I ment.
> > I'm sure you got my point, I haven't used any additionnal memory...
> >
> > I need a way to do this kind of job in VB.NET cause I can't use the amount
> > of memory my application need at the moment and the CPU time is completely
> > lost by these String.Substring(...) operation. Also, I need to be able to
> > call any .NET function with the string.
> >
> > Any help will be greatly appreciated!
> >
> > Regards,
> >
> > Sylvain Fortin
>
>