Resource Management... Howto?

[Samuel Winchenbach]

Jarrett Billingsley wrote:
> "Samuel Winchenbach" <swinchen at eece.maine.edu> wrote in message 
> news:f6o2k2$2gu6$1 at digitalmars.com...
> 
>> class TextureHandle
>> {
>>     private Texture mTexture;
>>     private char[]  mName;
>>     this(texture aTexture, char[] aName)
>>     {
>>         mTexture = aTexture;
>>         mName = aName;
>>
>>     }
>>     ~this()
>>     {
>>         mTexture.mRef--;
>>         if (mTexture.mRef == 0)
>>         {
>>             mTexture.freeGPUtexture();
>>             textureList.remove(aName);
>>             delete mTexture;
>>         }
>>     }
>>
>> }
> 
> The only issue with this is that _technically_ what you're doing in the 
> destructor is illegal.  Destructors of non-scope classes aren't guaranteed 
> to be called (i.e. on program exit, they might not be, but the GC will 
> definitely call them).  Furthermore, the order of destruction is undefined, 
> meaning that on program exit, mTexture might be destroyed before this, 
> causing a nasty access violation when you try to do "mTexture.ref--".
> 
> However, you can avoid this ugly nondeterministic-ness by always using scope 
> references to TextureHandle (you can have scope references to non-scope 
> classes, too), or by keeping all instances of TextureHandle in a 
> static/global list which you clean up in a "static ~this()" -- when static 
> dtors are called, the GC has not yet cleaned up, so it's still legal to 
> access reference members in class dtors. 
> 
> 

Ok...  How do you learn these things?  I have been referencing the 
digitalmars docs and well.. it sort of seems incomplete.


Anyways here is my next attempt.  I have to change it around and get rid 
of the "loadTexture" function because that can not return scope classes, 
which makes sense I suppose.

btw, thanks for the help!  This is certainly and educational experience.



module texture;

import std.stdio;

scope class TextureHandle
{
     private Texture mTexture;
     private char[]  mName;

     this(char[] aName)
     {	
         mName = aName;

         if (auto t = (aName in textureList))
         {
             mTexture = *t;
         }
         else
         {
             mTexture = new Texture();
             textureList[aName] = mTexture;
         }

         mTexture.mRef++;

     }

     ~this()
     {
         mTexture.mRef--;
         if (mTexture.mRef == 0)
         {
             mTexture.freeGPUtexture();
             textureList.remove(mName);
             delete mTexture;
         }
     }
}

private
{
     Texture[char[]] textureList;

     class Texture
     {
         private uint mRef = 0;
         this()
         {
         }

         ~this()
         {
         }
         void freeGPUtexture()
         {
         }
     }
}