digitalmars.D.learn - struct Unique(T)
- ChrisG (52/52) Nov 06 2013 Hi, I've been following the D language off and on for several
- Chris Cain (13/27) Nov 06 2013 I'm pretty sure things like Unique have been neglected for
- ChrisG (4/36) Nov 07 2013 Ok, thanks. That does make some sense to me. I read some of the
- Namespace (10/62) Nov 07 2013 Dgame use the SDL also and needed therefore (as you do) shared
Hi, I've been following the D language off and on for several
years, have read Andrei's D book, but haven't ever posted here
was playing with D using the derelict bindings for the SDL
library.
The SDL library uses handles in the form of struct pointers for
resource management. In C++ I like using unique and shared
pointers to manage C handles. Additionally, I like being able to
specify custom clean up functions for specific resources. For
example:
typedef std::unique_ptr<HandleType, HandleDeleter> handle_ptr;
My question is: what's the status of D's struct Unique? It looks
like struct RefCounted is current, but I can't tell with Unique.
There's several comments in the source that say: doesn't work
yet. It seems like some of it could be made to work as intended.
For example, the commented out code to disallow construction via
an lvalue:
// this(U)(ref Unique!(U) u) = null; // commented out
// this(this) = null;
Couldn't this be written:
disable this(U)(ref Unique!(U) u);
disable this(this);
Seems to work when I try it. It stopped the copy from working,
but I can still do a move. Like this:
Unique!(int) i1 = new int;
Unique!(int) i2 = move(i1); // works!
Next, I'd like to be able to use a custom deleter. For example, a
naive implementation I could write would be something like:
struct Unique2(T, string D = "delete")
{
...
~this()
{
debug(Unique2) writeln("Unique destructor of ", (_p is
null)? null: _p);
if (_p !is null)
{
mixin(""~D~" (_p);"); // delete _p;
_p = null;
}
}
...
So, I could do things like:
Unique2!(int, "free") i1 = cast(int*)malloc(int.sizeof); // lame
example
A real implementation would allow more interesting deleters in
the form of delegates, but I'm already stretching my D skillz.
Anyway, am I missing something here? Is there a better D language
feature I'm not thinking about that provides the same
functionality as C++'s std::unique_ptr<> with custom deleters;
besides putting scope (exit) everywhere?
-Chris
Nov 06 2013
On Thursday, 7 November 2013 at 00:07:25 UTC, ChrisG wrote:My question is: what's the status of D's struct Unique? It looks like struct RefCounted is current, but I can't tell with Unique. There's several comments in the source that say: doesn't work yet. It seems like some of it could be made to work as intended. For example, the commented out code to disallow construction via an lvalue:I'm pretty sure things like Unique have been neglected for awhile. Probably for a decent reason, but a lot of language features have been landing that could help polish it up a bit more.Next, I'd like to be able to use a custom deleter. For example, a naive implementation I could write would be something like: ... snip ... So, I could do things like: Unique2!(int, "free") i1 = cast(int*)malloc(int.sizeof); // lame example A real implementation would allow more interesting deleters in the form of delegates, but I'm already stretching my D skillz.I think Unique will probably be getting something along those lines reasonably shortly, but std.allocator will have to be fully completed first. http://forum.dlang.org/thread/l4btsk$5u8$1 digitalmars.com Once that's done we'll see some memory management schemes like what you're suggesting be implemented. But it's probably not a good idea to add that stuff before we figure out a good way to use it with the new std.allocator effectively.
Nov 06 2013
"ChrisG" <christopher.gassib gmail.com> On Thursday, 7 November 2013 at 01:09:45 UTC, Chris Cain wrote:On Thursday, 7 November 2013 at 00:07:25 UTC, ChrisG wrote:Ok, thanks. That does make some sense to me. I read some of the std.allocator thread. I'll take a look at that code and see what I can make of it.My question is: what's the status of D's struct Unique? It looks like struct RefCounted is current, but I can't tell with Unique. There's several comments in the source that say: doesn't work yet. It seems like some of it could be made to work as intended. For example, the commented out code to disallow construction via an lvalue:I'm pretty sure things like Unique have been neglected for awhile. Probably for a decent reason, but a lot of language features have been landing that could help polish it up a bit more.Next, I'd like to be able to use a custom deleter. For example, a naive implementation I could write would be something like: ... snip ... So, I could do things like: Unique2!(int, "free") i1 = cast(int*)malloc(int.sizeof); // lame example A real implementation would allow more interesting deleters in the form of delegates, but I'm already stretching my D skillz.I think Unique will probably be getting something along those lines reasonably shortly, but std.allocator will have to be fully completed first. http://forum.dlang.org/thread/l4btsk$5u8$1 digitalmars.com Once that's done we'll see some memory management schemes like what you're suggesting be implemented. But it's probably not a good idea to add that stuff before we figure out a good way to use it with the new std.allocator effectively.
Nov 07 2013
On Thursday, 7 November 2013 at 00:07:25 UTC, ChrisG wrote:
Hi, I've been following the D language off and on for several
years, have read Andrei's D book, but haven't ever posted here
I was playing with D using the derelict bindings for the SDL
library.
The SDL library uses handles in the form of struct pointers for
resource management. In C++ I like using unique and shared
pointers to manage C handles. Additionally, I like being able
to specify custom clean up functions for specific resources.
For example:
typedef std::unique_ptr<HandleType, HandleDeleter> handle_ptr;
My question is: what's the status of D's struct Unique? It
looks like struct RefCounted is current, but I can't tell with
Unique. There's several comments in the source that say:
doesn't work yet. It seems like some of it could be made to
work as intended. For example, the commented out code to
disallow construction via an lvalue:
// this(U)(ref Unique!(U) u) = null; // commented out
// this(this) = null;
Couldn't this be written:
disable this(U)(ref Unique!(U) u);
disable this(this);
Seems to work when I try it. It stopped the copy from working,
but I can still do a move. Like this:
Unique!(int) i1 = new int;
Unique!(int) i2 = move(i1); // works!
Next, I'd like to be able to use a custom deleter. For example,
a naive implementation I could write would be something like:
struct Unique2(T, string D = "delete")
{
...
~this()
{
debug(Unique2) writeln("Unique destructor of ", (_p is
null)? null: _p);
if (_p !is null)
{
mixin(""~D~" (_p);"); // delete _p;
_p = null;
}
}
...
So, I could do things like:
Unique2!(int, "free") i1 = cast(int*)malloc(int.sizeof); //
lame example
A real implementation would allow more interesting deleters in
the form of delegates, but I'm already stretching my D skillz.
Anyway, am I missing something here? Is there a better D
language feature I'm not thinking about that provides the same
functionality as C++'s std::unique_ptr<> with custom deleters;
besides putting scope (exit) everywhere?
-Chris
Dgame use the SDL also and needed therefore (as you do) shared
and unique pointers (mostly shared). So I wrote my own versions
and like to share them with you, maybe it helps you.
Surface with shared SDL_Surface:
https://github.com/Dgame/Dgame/blob/master/Graphics/Surface.d#L67
Creation of the shared_ptr:
https://github.com/Dgame/Dgame/blob/master/Graphics/Surface.d#L100
And the shared_ptr struct:
https://github.com/Dgame/Dgame/blob/master/Internal/Shared.d
Nov 07 2013
On Thursday, 7 November 2013 at 09:51:38 UTC, Namespace wrote:Dgame use the SDL also and needed therefore (as you do) shared and unique pointers (mostly shared). So I wrote my own versions and like to share them with you, maybe it helps you. Surface with shared SDL_Surface: https://github.com/Dgame/Dgame/blob/master/Graphics/Surface.d#L67 Creation of the shared_ptr: https://github.com/Dgame/Dgame/blob/master/Graphics/Surface.d#L100 And the shared_ptr struct: https://github.com/Dgame/Dgame/blob/master/Internal/Shared.dThanks. I've been looking through your website and github. Very cool stuff. What license is your code released under?
Nov 07 2013
On Thursday, 7 November 2013 at 18:19:35 UTC, ChrisG wrote:On Thursday, 7 November 2013 at 09:51:38 UTC, Namespace wrote:Under zlib/png. I should add this on my site and in my code. Thanks for remembering. :)Dgame use the SDL also and needed therefore (as you do) shared and unique pointers (mostly shared). So I wrote my own versions and like to share them with you, maybe it helps you. Surface with shared SDL_Surface: https://github.com/Dgame/Dgame/blob/master/Graphics/Surface.d#L67 Creation of the shared_ptr: https://github.com/Dgame/Dgame/blob/master/Graphics/Surface.d#L100 And the shared_ptr struct: https://github.com/Dgame/Dgame/blob/master/Internal/Shared.dThanks. I've been looking through your website and github. Very cool stuff. What license is your code released under?
Nov 07 2013