Documentation/technical/api-allocation-growing.txt

   1 allocation growing API
   2 ======================
   3
   4 Dynamically growing an array using realloc() is error prone and boring.
   5
   6 Define your array with:
   7
   8 * a pointer (`item`) that points at the array, initialized to `NULL`
   9   (although please name the variable based on its contents, not on its
  10   type);
  11
  12 * an integer variable (`alloc`) that keeps track of how big the current
  13   allocation is, initialized to `0`;
  14
  15 * another integer variable (`nr`) to keep track of how many elements the
  16   array currently has, initialized to `0`.
  17
  18 Then before adding `n`th element to the item, call `ALLOC_GROW(item, n,
  19 alloc)`.  This ensures that the array can hold at least `n` elements by
  20 calling `realloc(3)` and adjusting `alloc` variable.
  21
  22 ------------
  23 sometype *item;
  24 size_t nr;
  25 size_t alloc
  26
  27 for (i = 0; i < nr; i++)
  28         if (we like item[i] already)
  29                 return;
  30
  31 /* we did not like any existing one, so add one */
  32 ALLOC_GROW(item, nr + 1, alloc);
  33 item[nr++] = value you like;
  34 ------------
  35
  36 You are responsible for updating the `nr` variable.
  37
  38 If you need to specify the number of elements to allocate explicitly
  39 then use the macro `REALLOC_ARRAY(item, alloc)` instead of `ALLOC_GROW`.