Re: Pointers and offsets

[ketmar via Digitalmars-d-learn]

On Wed, 14 Jan 2015 01:16:52 +
Bauss via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote:

 Is it possible to access a pointer by its offsets.
 Ex. write a 32bit integer to a byte pointer at ex. offset 4.
yes, it is. it's same as in c/c++, except that you have to add one
magic word: `cast`. D specs has it all.


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Re: Pointers and offsets

[Mike Parker via Digitalmars-d-learn]

On 1/14/2015 10:17 AM, Bauss wrote:

On Wednesday, 14 January 2015 at 01:16:54 UTC, Bauss wrote:

Is it possible to access a pointer by its offsets.
Ex. write a 32bit integer to a byte pointer at ex. offset 4.

To give an example in C# you can do this:
fixed (byte* Packet = Buffer) // Buffer would be a byte array

And then to set the value of a specific offset
*((TYPE*)(Packet + OFFSET))

Where TYPE could be replaced by ex. uint and OFFSET by 4

I tried to look here:
http://dlang.org/arrays.html

But couldn't seem to find anything like it.


Can't seem to edit OP so at:


The forum is a web interface to a newsgroup, which also has a mailing 
list interface. So no, no editing.



*((TYPE*)(Packet + OFFSET))

It should be:
*((TYPE*)(Packet + OFFSET)) = VALUE;

VALUE has to be of the same type as TYPE of course.


void main()
{
ubyte[16] bytes;
for( int i=0; i4; ++i )
{
*(cast( int* )( bytes.ptr + (i*4))) = i;
}

import std.stdio : writeln;
writeln( cast( int[] )bytes );
}

Re: Pointers and offsets

[Bauss via Digitalmars-d-learn]

On Wednesday, 14 January 2015 at 01:16:54 UTC, Bauss wrote:

Is it possible to access a pointer by its offsets.
Ex. write a 32bit integer to a byte pointer at ex. offset 4.

To give an example in C# you can do this:
fixed (byte* Packet = Buffer) // Buffer would be a byte array

And then to set the value of a specific offset
*((TYPE*)(Packet + OFFSET))

Where TYPE could be replaced by ex. uint and OFFSET by 4

I tried to look here:
http://dlang.org/arrays.html

But couldn't seem to find anything like it.


Can't seem to edit OP so at:
*((TYPE*)(Packet + OFFSET))

It should be:
*((TYPE*)(Packet + OFFSET)) = VALUE;

VALUE has to be of the same type as TYPE of course.