Re: genalloc

[Laurent Bercot <ska-skaware@skarnet.org>]

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> After having append many items, I didn't find any API in genalloc to remove an item and then collapse all.
> 
> Did I miss something??
> Should I implement it with byte_copy??

 Generally speaking, what you are asking for (to delete a cell in a
genalloc and shift all the following cells to the left) requires a lot
of memory rewriting and is not needed: there's always a way to avoid
shifting.

 Say you have a genalloc g of type T and you want to delete cell number i.

 If you don't care about the order of your cells, just replace the ith
cell with the last one:
  unsigned int n = genalloc_len(T, g) ;
  genalloc_s(T, g)[i] = genalloc_s(T, g)[n-1] ;
  genalloc_setlen(T, g, n-1) ;

 If you care about the order of your cells, a simple genalloc isn't the
best structure. You could use a linked list structure, using the genalloc
for storage purposes only: expand type T with an unsigned int that is
the index of your "next" cell in the genalloc, make 0 the head of your list,
and there you go. No rewriting needed.

 If you really want to shift cells in a genalloc, then yes, I guess you
could implement it with byte_copy(). But it will be suboptimal in all
cases.

-- 
 Laurent