I'm stuck.  What is the best way to convert a struct to a void[]?  I'm using the socket library in phobos and I want to send an aligned struct over the network. Here's the best solution I've come up with so far...

#template Yuck(T)
#{
#    void[] toVoid(inout T src)
#	{
#		ubyte* data = cast(ubyte*)&src;
#		ubyte[] copy = new ubyte[src.sizeof];
#
#		foreach(ubyte b; copy)
#			b = *(data++);
#
#		return cast(void[])copy;
#	}
#}

To convert a struct to void[], I use the following...

#struct Foo { ... }
#
#Foo f;
#void[] fv = Yuck!(Foo).toVoid(f);

Please tell me there is a better way to do this...

On Fri, 10 Sep 2004 01:44:51 +0000 (UTC), mcl <mcl_member@pathlink.com> wrote:

> I'm stuck.  What is the best way to convert a struct to a void[]?  I'm using the
> socket library in phobos and I want to send an aligned struct over the network.
> Here's the best solution I've come up with so far...
>
> #template Yuck(T)
> #{
> #    void[] toVoid(inout T src)
> #	{
> #		ubyte* data = cast(ubyte*)&src;
> #		ubyte[] copy = new ubyte[src.sizeof];
> #		
> #		foreach(ubyte b; copy)
> #			b = *(data++);
> #		
> #		return cast(void[])copy;
> #	}
> #}
>
> To convert a struct to void[], I use the following...
>
> #struct Foo { ... }
> #
> #Foo f;
> #void[] fv = Yuck!(Foo).toVoid(f);
>
> Please tell me there is a better way to do this...

It's a little known fact that you can slice a pointer giving you an array. Slicing a void* will give you a void[]. You can also cast any memory address to a void*, So...

template toVoid(Struct)
{
  void[] toVoid(inout Struct s)
  {
    return (cast(void*)&s)[0..s.sizeof];
  }
}

should do it.

Regan

-- 
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

On Fri, 10 Sep 2004 14:22:56 +1200, Regan Heath wrote:

> On Fri, 10 Sep 2004 01:44:51 +0000 (UTC), mcl <mcl_member@pathlink.com> wrote:
> 
>> I'm stuck.  What is the best way to convert a struct to a void[]?  I'm
>> using the
>> socket library in phobos and I want to send an aligned struct over the
>> network.
>> Here's the best solution I've come up with so far...
>>
>> #template Yuck(T)
>> #{
>> #    void[] toVoid(inout T src)
>> #	{
>> #		ubyte* data = cast(ubyte*)&src;
>> #		ubyte[] copy = new ubyte[src.sizeof];
>> #
>> #		foreach(ubyte b; copy)
>> #			b = *(data++);
>> #
>> #		return cast(void[])copy;
>> #	}
>> #}
>>
>> To convert a struct to void[], I use the following...
>>
>> #struct Foo { ... }
>> #
>> #Foo f;
>> #void[] fv = Yuck!(Foo).toVoid(f);
>>
>> Please tell me there is a better way to do this...
> 
> It's a little known fact that you can slice a pointer giving you an array. Slicing a void* will give you a void[]. You can also cast any memory address to a void*, So...
> 
> template toVoid(Struct)
> {
>    void[] toVoid(inout Struct s)
>    {
>      return (cast(void*)&s)[0..s.sizeof];
>    }
> }
> 
> should do it.
> 
> Regan

It does! And you don't need a template either.

Foo f;
void[] fv = (cast(void*)&f)[0..f.sizeof];

writefln("%d", fv.length);
writefln("%X", cast(uint)&fv[0]);
writefln("%X", cast(uint)&f);

-- 
Derek
Melbourne, Australia
10/Sep/04 12:45:22 PM

On Fri, 10 Sep 2004 12:49:47 +1000, Derek Parnell <derek@psych.ward> wrote:
> On Fri, 10 Sep 2004 14:22:56 +1200, Regan Heath wrote:
>
>> On Fri, 10 Sep 2004 01:44:51 +0000 (UTC), mcl <mcl_member@pathlink.com>
>> wrote:
>>
>>> I'm stuck.  What is the best way to convert a struct to a void[]?  I'm
>>> using the
>>> socket library in phobos and I want to send an aligned struct over the
>>> network.
>>> Here's the best solution I've come up with so far...
>>>
>>> #template Yuck(T)
>>> #{
>>> #    void[] toVoid(inout T src)
>>> #	{
>>> #		ubyte* data = cast(ubyte*)&src;
>>> #		ubyte[] copy = new ubyte[src.sizeof];
>>> #		
>>> #		foreach(ubyte b; copy)
>>> #			b = *(data++);
>>> #		
>>> #		return cast(void[])copy;
>>> #	}
>>> #}
>>>
>>> To convert a struct to void[], I use the following..
>>>
>>> #struct Foo { ... }
>>> #
>>> #Foo f;
>>> #void[] fv = Yuck!(Foo).toVoid(f);
>>>
>>> Please tell me there is a better way to do this...
>>
>> It's a little known fact that you can slice a pointer giving you an array.
>> Slicing a void* will give you a void[]. You can also cast any memory
>> address to a void*, So...
>>
>> template toVoid(Struct)
>> {
>>    void[] toVoid(inout Struct s)
>>    {
>>      return (cast(void*)&s)[0..s.sizeof];
>>    }
>> }
>>
>> should do it.
>>
>> Regan
>
> It does! And you don't need a template either.
>
> Foo f;
> void[] fv = (cast(void*)&f)[0..f.sizeof];
>
> writefln("%d", fv.length);
> writefln("%X", cast(uint)&fv[0]);
> writefln("%X", cast(uint)&f);

Yeah. I assumed there was a reason for using a template.

Regan

-- 
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

"mcl" <mcl_member@pathlink.com> wrote in message news:chr0uj$rvk$1@digitaldaemon.com...
> I'm stuck.  What is the best way to convert a struct to a void[]?  I'm
using the
> socket library in phobos and I want to send an aligned struct over the
network.
> Here's the best solution I've come up with so far...
>

(&f)[0 .. 1]  works just fine. Any array implicitly converts to void[].

On Fri, 10 Sep 2004 01:15:15 -0400, Vathix <vathixSpamFix@dprogramming.com> wrote:
> "mcl" <mcl_member@pathlink.com> wrote in message
> news:chr0uj$rvk$1@digitaldaemon.com...
>> I'm stuck.  What is the best way to convert a struct to a void[]?  I'm
> using the
>> socket library in phobos and I want to send an aligned struct over the
> network.
>> Here's the best solution I've come up with so far...
>>
>
> (&f)[0 .. 1]  works just fine. Any array implicitly converts to void[].

Duh.. (/me smacks my head) of course.

Regan

-- 
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

Vathix wrote:
> 
> "mcl" <mcl_member@pathlink.com> wrote in message news:chr0uj$rvk$1@digitaldaemon.com...
> > I'm stuck.  What is the best way to convert a struct to a void[]?  I'm
> using the
> > socket library in phobos and I want to send an aligned struct over the
> network.
> > Here's the best solution I've come up with so far...
> >
> 
> (&f)[0 .. 1]  works just fine. Any array implicitly converts to void[].

Makes a nice FAQ entry:
   <http://www.wikiservice.at/wiki4d/wiki.cgi?FaqRoadmap#Howtoconverttovoid>

-- 
Helmut Leitner    leitner@hls.via.at
Graz, Austria   www.hls-software.com

In article <opsd3hv4o15a2sq9@digitalmars.com>, Regan Heath says...
>
>On Fri, 10 Sep 2004 12:49:47 +1000, Derek Parnell <derek@psych.ward> wrote:
>> On Fri, 10 Sep 2004 14:22:56 +1200, Regan Heath wrote:
>>
>>> On Fri, 10 Sep 2004 01:44:51 +0000 (UTC), mcl <mcl_member@pathlink.com>
>>> wrote:
>>>
>>>> I'm stuck.  What is the best way to convert a struct to a void[]?  I'm
>>>> using the
>>>> socket library in phobos and I want to send an aligned struct over the
>>>> network.
>>>> Here's the best solution I've come up with so far...
>>>>
>>>> #template Yuck(T)
>>>> #{
>>>> #    void[] toVoid(inout T src)
>>>> #	{
>>>> #		ubyte* data = cast(ubyte*)&src;
>>>> #		ubyte[] copy = new ubyte[src.sizeof];
>>>> #
>>>> #		foreach(ubyte b; copy)
>>>> #			b = *(data++);
>>>> #
>>>> #		return cast(void[])copy;
>>>> #	}
>>>> #}
>>>>
>>>> To convert a struct to void[], I use the following..
>>>>
>>>> #struct Foo { ... }
>>>> #
>>>> #Foo f;
>>>> #void[] fv = Yuck!(Foo).toVoid(f);
>>>>
>>>> Please tell me there is a better way to do this...
>>>
>>> It's a little known fact that you can slice a pointer giving you an
>>> array.
>>> Slicing a void* will give you a void[]. You can also cast any memory
>>> address to a void*, So...
>>>
>>> template toVoid(Struct)
>>> {
>>>    void[] toVoid(inout Struct s)
>>>    {
>>>      return (cast(void*)&s)[0..s.sizeof];
>>>    }
>>> }
>>>
>>> should do it.
>>>
>>> Regan
>>
>> It does! And you don't need a template either.
>>
>> Foo f;
>> void[] fv = (cast(void*)&f)[0..f.sizeof];
>>
>> writefln("%d", fv.length);
>> writefln("%X", cast(uint)&fv[0]);
>> writefln("%X", cast(uint)&f);
>
>Yeah. I assumed there was a reason for using a template.


The reason for the template was to abstract the code for use with different structs since it's a bit complicated. The slice trick is far more elegant, since it's a one-liner.  My only concern: Is the pointer slice in place?   I could see this being a problem with stack allocated structs/classes...

mcl wrote:
>>>Foo f;
>>>void[] fv = (cast(void*)&f)[0..f.sizeof];
>>>
>>>writefln("%d", fv.length);
>>>writefln("%X", cast(uint)&fv[0]);
>>>writefln("%X", cast(uint)&f);
> 
> The reason for the template was to abstract the code for use with different
> structs since it's a bit complicated. The slice trick is far more elegant, since
> it's a one-liner.  My only concern: Is the pointer slice in place?   I could see
> this being a problem with stack allocated structs/classes...   

Yes.  If you want to copy it, then just append .dup:

void[] fv = (&f)[0..f.sizeof].dup;

In article <cht6ve$1vma$1@digitaldaemon.com>, Russ Lewis says...
>
>void[] fv = (&f)[0..f.sizeof].dup;
>

By the way, it's (&f)[0..1], not (&f)[0..f.sizeof]. If f is a Foo then (&f) is
of type (Foo*), so a slice of one element will include one entire struct. I have
corrected this in the wiki as well.

Nick