Then that would mean the "fixed" keyword works differently when used with buffers, which I would find strange. See http://msdn2.microsoft.com/en-us/library/f58wzh21.aspx.
I admit I have not done actual tests on this, so you may be right. Sébastien > -----Original Message----- > From: Discussion of advanced .NET topics. [mailto:ADVANCED- > [EMAIL PROTECTED] On Behalf Of gregory young > Sent: Tuesday, November 14, 2006 2:31 PM > To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM > Subject: Re: [ADVANCED-DOTNET] Data Structures in .Net? > > Sebastien I am 90% sure you are incorrect about fixed buffers in terms > of those being included a struct as "fighting" the garbage collector .. > > It should be able to get by without pinning (unlike normal usage of the > fixed keyword) ... remember it defines the memory directly within the > struct so you can just keep the managed reference to the struct and > offset from it. > > ex: > unsafe struct test > { > public fixed char foo[255]; > public int bar; > public fixed bool foo2[128]; > } > static void Main(string[] args) > { > test t; > t.foo[22] = 'c'; > } > > on the access ... there is no need to pin anything in order to access > the variable (it is t + something (he fixed keyword here is actually > putting the array allocations directly in the struct) .. because of > this I would assume no pinning .. no pinning would seem to disagree > with your fragmentation statement and not playing nicely with the GC ... > > Cheers, > > Greg > > On 11/14/06, Sebastien Lorion <[EMAIL PROTECTED]> wrote: > > A solution like this is actually fighting against the way .NET was > designed. > > Strings are immutable and so you cannot modify a string in-place, you > > need a string builder. Looking on the net you will see that there are > > many benefits to immutability and actually, not only for strings. > > > > The problem with the suggested code is that it is very inefficient. > > The net result is that you will be creating a new string object every > > single time you read one of the properties. That might put a lot of > > stress on the garbage collector and triggers many Gen0 collections > and > > thus promote prematurely other objects to an older generation. > > > > On the other hand, by using fixed buffers, you are effectively > working > > against the garbage collector which tries to defragment memory. If > you > > have many of these objects in memory, it will be next to impossible > to > > defragment it. One of the consequences of that is losing locality of > > reference, one of the most important factor in performance. On top of > > that, using unsafe code requires special permissions on the client. > > > > Both solutions also suffer from the fact that you will use 60 chars > > arrays no matter the actual required memory is. "John Smith" is 9 > > chars, why waste > > 51 ? > > > > I think one of the point of using such kind of memory layout (ala > > COBOL) was to maximize memory and simplify code. As you can, we are > > far from doing that now. A better and much simpler solution would be > > to have 3 fields (first, last, middle) and concatenate them only when > > FullName is required. Using a method "GetFullName()" would further > > clearly indicate to developers that a new object is created and so, > > they might want to put in a temporary variable and avoid calling that > method too many times. > > > > Sébastien > > > > > -----Original Message----- > > > From: Discussion of advanced .NET topics. [mailto:ADVANCED- > > > [EMAIL PROTECTED] On Behalf Of Jon Rothlander > > > Sent: Tuesday, November 14, 2006 1:23 PM > > > To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM > > > Subject: Re: [ADVANCED-DOTNET] Data Structures in .Net? > > > > > > Thanks for your response. I like your approach this to. This is > > > the kind of thing that I have done in the past to support this sort > > > of issue. Can you tell me why you are not sure this is a good > idea? > > > I want to under the issues people have with this because I am > > > working on a client's code and I want to be aware of any issues > with > > > this approach, as it's similar to what I have been doing. > > > > > > Your solution is very similar to what I have done in the past to > > > work around this issue when supporting legacy applications in .Net. > > > There's allot of work in translating the code when using these > > > approach, which is what I am trying to avoid by looking at another > > > option. However, the other options seem to be unsafe, and I'm not > > > sure I want to take that leap just yet. > > > That's what I'm currently looking at. > > > > > > -----Original Message----- > > > From: Discussion of advanced .NET topics. > > > [mailto:[EMAIL PROTECTED] On Behalf Of Bob > > > Provencher > > > Sent: Monday, November 13, 2006 9:24 PM > > > To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM > > > Subject: Re: [ADVANCED-DOTNET] Data Structures in .Net? > > > > > > Something like this would work the way you want... > > > > > > public class Line > > > { > > > const int LineLength = 60; > > > const int FirstNameOffset = 0; > > > const int FirstNameLength = 20; > > > StringBuilder sb = new StringBuilder( LineLength ); > > > > > > public string FirstName > > > { > > > get > > > { > > > return sb.ToString( FirstNameOffset, > > > FirstNameLength ); > > > } > > > set > > > { > > > char[] inchars; > > > inchars = value.ToCharArray( 0, > value.Length ); > > > for ( int i = 0; i < sb.Length; i++ ) > > > { > > > if ( i < value.Length ) > > > { > > > sb.Chars[ i ] = > inchars[ i ]; > > > } > > > else > > > { > > > sb.Chars[ i ] = ' '; > > > } > > > } > > > } > > > } > > > > > > } > > > > > > But I'm not sure doing this is a good idea... > > > > =================================== > > This list is hosted by DevelopMentor(r) http://www.develop.com > > > > View archives and manage your subscription(s) at > > http://discuss.develop.com > > > > > -- > If knowledge can create problems, it is not through ignorance that we > can solve them. > > Isaac Asimov > > =================================== > This list is hosted by DevelopMentor® http://www.develop.com > > View archives and manage your subscription(s) at > http://discuss.develop.com =================================== This list is hosted by DevelopMentor® http://www.develop.com View archives and manage your subscription(s) at http://discuss.develop.com
