Re: From ILGenerator and emit to fixed? - C# Discussion Boards

10-Dec-08 4:12

Hi,
Recently I'm working on small compiler for fun (or actually still thinking about it's main features and implementing basic syntax) and I've ran into strange problem. Something that I thought would be easy seem not to be that easy Smile | :)

. What is troubling my mind, is that construction:

int[] b = new int [100];
fixed (int* p = b)
{
   int* z = p;
   for (int i = 0; i < 100; ++i)
   {
     *z = i;
     z++;
   }
}

Such code when compiled and disassembled produces such code:

.locals init ([0] int32[] b,
             [1] int32 i,
             [2] int32& pinned p,
             [3] int32* z,
             [4] bool CS$4$0000,
             [5] int32[] CS$0$0001)
[...].IL_0031:  ldloc.s    CS$0$0001
IL_0033:  ldc.i4.0
IL_0034:  ldelema    [mscorlib]System.Int32
IL_0039:  stloc.2

This code, from what I understand after searching information in MSDN and few other articles, pins table b (table [5] is the same as b) by pointing to it's first element with p pointer.
I've tried to produce such code using ILGenerator, but I have no idea how to declare local variable of type int& (managed pointer), I guess I can declare only int* pointers, now the main question is, will above code work if I change [2] int32& pinned p to [2] int* pinned p. If yes, why compiler uses this type, not just int* pointers, if no - how I can generate such code using code emit?
I've made small test, disassembled code compiled with csc, changed pointer from int& to int* and yes, it works, but I can't prove anything with that, because GC had no reason to move the table in memory and I can't force him to try that, so that answered nothing except that I know such construction would be legal.

[Solution]

For future use hehe, I'll post solution I've come by accident, and it does seem to work:
ilGen.DeclareLocal(Type.GetType("System.Int32&"), true);

Although it's impossible to "do" anything with this type in code, it seems that it is possible to emit it to assembly (after all Smile | :)

modified on Wednesday, December 10, 2008 12:23 PM

Luc Pattyn10-Dec-08 5:07

Luc Pattyn

10-Dec-08 5:07

Hi,

could it be the "int32& pinned p" line is actually a mistake in the disassembly process, and
"int32* pinned p" is what is meant from the start? What does the disassembly show for your own code?

IMO you can force the GC to move things using a scenario like this one:
- create a class A that takes a lot of memory, say 50KB, but well below the "huge object" threshold (which is around 75KB IIRC).
- create a second class B that takes slightly more memory.
- instantiate a lot of objects A, keeping their references somewhere, say in a List, until allocating a few more would make you run out of memory.
- remove half (i.e.every second) of those objects
- now start instantiating the same number of objects from class B.

Such scenario is bound to call the GC, which will have to compact (i.e. move most of the A objects) to fill the order. You can fix your class A objects, or alternatively you can replace class A by an array of appropriate size.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

Fixturized forever. Confused | :confused:

Ravadre10-Dec-08 5:49

10-Dec-08 5:49

Hi,

I'm afraid it's not a mistake of a compiler. Based on this article for example:
http://www.codeproject.com/KB/msil/ilassembly.aspx
It looks like it's just a type, now the question is, does it has some special meaning, especially when pinning objects in memory. Your method looks like it should work, I'll try it and do some tests as soon as I have few free minutes, which means now Smile | :)

Simon P Stevens10-Dec-08 5:11

Simon P Stevens

10-Dec-08 5:11

Sorry, I can't answer your question. That's the kind of question that you are only likely to get a proper answer from someone who worked at MS, and wrote portions of the CLR/C# compiler. (Do you have an MSDN license, try the MS managed forums)

All I can do is point out a reflector plugin I came across the other day: http://www.codeplex.com/reflectoraddins/Wiki/View.aspx?title=ReflectionEmitLanguage&referringTitle=Home[^]

Basically, it displays the C# code that you would need to write to output the same IL for the method.

Maybe it will help you figure out how to do what you are trying.

Good luck. Smile | :)

Simon

Ravadre10-Dec-08 5:47

10-Dec-08 5:47

Well, I was hoping someone had similiar problem, that's why I asked here in first place Smile | :)

. I've tried this plugin that you've recommened, but unfortunately without any success. This plugin just copy&paste type from exe, which produces line like that:

LocalBuilder p = gen.DeclareLocal(typeof(Int32&));

This isn't even proper c# statement hehe Smile | :)

. So I guess, this path leads to the dead end.

Simon P Stevens10-Dec-08 5:55

Simon P Stevens

10-Dec-08 5:55

Ravadre wrote:
This isn't even proper c# statement hehe Smile. So I guess, this path leads to the dead end.

Oh well. I've not used it myself, I just remember seeing it and thinking it looked interesting while looking for a different plug-in. Sorry.

Good luck. Wink | ;)

Simon

Ravadre10-Dec-08 6:01

Re: Widows helper and CHM

10-Dec-08 6:01

The bright side is that I didn't know that such plugin exists, and it is cool, it will be handy, that's for sure. So thanks for showing me it Smile | :)

Widows helper and CHM

half-life10-Dec-08 4:01

half-life

10-Dec-08 4:01

hi,

i'm would like to write a help to an application i've built
how can integrat the windows help in my app, and use a CHM file with it Smile | :)

THANKS

Have Fun
Never forget it

EliottA10-Dec-08 4:28

EliottA

10-Dec-08 4:28

Not really a C# question but ok, a quick search Here[^] brought up some promising results, but google isn't your friend.

1[^]
2[^]
3[^]
4[^]

Just to name a few from googles first page result.

Re: Widows helper and CHM

half-life10-Dec-08 6:55

half-life

10-Dec-08 6:55

THANKS

the question remaining is do i call system.process()
with what? in order to show the windows helper

Smile | :)

Have Fun
Never forget it

Re: Widows helper and CHM

EliottA10-Dec-08 6:57

EliottA

10-Dec-08 6:57

Maybe any one of These?[^]

Google this stuff, none of it is related to this forum.

Edit: Doesn't windows have a default player? Just run the CHM and see if it opens up, try things first.

Using google example #1[^]
using google example 2[^]
using google example 3[^]

Format of decimal numbers [modified]

Diving Flo10-Dec-08 2:00

Diving Flo

10-Dec-08 2:00

Hi there,

actually this is a very common problem, but I do not see the solution. The situation is as follows. I have a decimal number. I want to convert it to a string without trailing zeroes, a dot as a decimal separator and a maximum of 17 digits.

Examples:
0.1234100 -> 0.12341
0.0 -> 0
0.00000196525616047 -> 0.00000196525616047 (not 1.96525616047E-06)
12123.12432 -> 12123.12432

DecimalValue.ToString("G17", nfi)

gives me an exponential output.

DecimalValue.ToString("G", nfi)

gives me trailing zeroes and more than 17 digits.

thanks,
Albi

modified on Wednesday, December 10, 2008 8:20 AM

Re: Format of decimal numbers

Mirko198010-Dec-08 2:24

Mirko1980

10-Dec-08 2:24

Use DecimalValue.ToString("#.#################"); (reference here[^])

Re: Format of decimal numbers

Diving Flo10-Dec-08 2:35

Diving Flo

10-Dec-08 2:35

Oh boy, sometimes the solution is that easy and you just do not see it. Blush | :O

Thanks!
Albi

any API to make flash file conversion?

George_George10-Dec-08 1:52

George_George

10-Dec-08 1:52

Hello everyone,

Are there API provided by Microsoft to convert video file of other types to Flash video file? If no such API provided by Microsoft, any API provided by other parties?

thanks in advance,
George

Lev Danielyan10-Dec-08 2:20

Lev Danielyan

10-Dec-08 2:20

I'm pretty much sure that Microsoft won't have that kind of API, since Flash is Adobe's (ex-Macromedia's) proprietary file format (at least it was, I'm not sure if Adobe opened the specs)

You can check the NetFFMpeg[^] project, which is a .Net wrapper to ffmpeg[^]

Regards,
Lev

George_George10-Dec-08 2:23

George_George

10-Dec-08 2:23

Thanks Lev!

I have tried the following code to embed a flash media player and embed a movie to play, which is bush.wmv. But the page is empty, do you know what is wrong please?

<html>
<body>
<OBJECT classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"
codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,40,0"
WIDTH="550" HEIGHT="400" id="myMovieName"><PARAM NAME=movie VALUE="D:\Bush.wmv"><PARAM NAME=quality VALUE=high><PARAM NAME=bgcolor VALUE=#FFFFFF><EMBED src="/support/flash/ts/documents/myFlashMovie.swf" quality=high bgcolor=#FFFFFF WIDTH="550" HEIGHT="400"
NAME="Bush" ALIGN="" TYPE="application/x-shockwave-flash"
PLUGINSPAGE="http://www.macromedia.com/go/getflashplayer"></EMBED></OBJECT>
</body>
</html>

regards,
George

Lev Danielyan10-Dec-08 2:28

Lev Danielyan

10-Dec-08 2:28

Well, I think this is not the right forum for this question Wink | ;)

But anyway, I think the problem is that you are trying to play Windows Media file (wmv) with Adobe's flash player.
I think you should first convert the wmv to flv.

Regards,
Lev