Re: A failing oif C#?

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"Matt" <matttelles@xxxxxxxxxxx> wrote in message
news:1123615773.907470.209150@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> Ken Allen wrote:
>> wackyphill@xxxxxxxxx wrote:
>> > You can infact mark a section of your c# code unsafe and use pointers
>> > just like c++.
>> >
>> How does one mark a section unsafe and have the code before and after
>> that section as safe (managed) code?
>>
>> How does one use pointers at all in C#? Even in unsafe code? If I have a
>> buffer, which is probably defined as a byte array, how do I 'cast' a
>> subset of that array to be treated as a structure with data members? The
>> only way I have seen is to marshal a (cast as IntPtr) specific subset of
>> the array into a structure.
>>
>> -ken
>
> You can do anything in unsafe code, including writing C++ (more or
> less) code:
>
> unsafe
> {
> char s[200];
> int x = 10;
> memcpy(
>

No it's not, you can't call (not directly) unmanaged code like memcpy(...),
calling unmanaged code from C# is only possible through PInvoke and COM
interop.
unsafe doesn't mean "native" it's simply an indication that the block may
contains native C style pointers and can perform pointer arithmetics but
that's it, the code remains managed (compiled to IL) code and the data like
a char array is still GC heap allocated and JIT tracked data.


unsafe {
// allocates a managed array of type char
char[] s = new char[200];
// pin the array object and take the address of the first char in the array
fixed (char* ptr = &s[0])
{
// use ptr f.i as an argument in a call to unmanaged code using
PInvoke interop

}// un-pin the char array!!!
}

Willy.



.

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