ltt/branches/poly/doc/developer/hook_prio.txt

   1 Linux Trace Toolkit
   2
   3 Mathieu Desnoyers 18-05-2004
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   6 Seeing that a very precise hook call ordering is needed when processing events
   7 (especially the order for calling state update hooks and event delivery hooks),
   8 this document defines a new type and interface that permits to merge all kind of
   9 hooks, eventually sorted by the priority associated to them.
  10
  11 As the LttvHooksById has never been used up to this point in the project, I
  12 doubt that any real need for it exists. If we still want to implement it, it
  13 would require to create temporary by_id hook lists, add all the specific by_id
  14 hooks and the main hooks to it, and sort it before the traceset reading starts.
  15
  16 - Type LttvHooksPrio
  17
  18 This is a new type containing hooks associated with a priority. It has its own
  19 interface which pretty much looks like the one found in hook.h, plus the fact
  20 that a priority is associated with each hook. (lttv_hooks_prio_add,
  21 lttv_hooks_prio_call, lttv_hooks_prio_remove are sample names of functions
  22 offered by this interface) The container for this type would be a garray, just
  23 like hook.c, but a lttv_hooks_prio_sort would be required in order to sort the
  24 array before using lttv_hooks_prio_call.
  25
  26 The viewers will just have to pass hooks to the main window through this type,
  27 using the hookprio.h interface to manipulate it. Then, the main window will add
  28 them and remove them from the context to deliver exactly the events requested by
  29 each viewer through process traceset.
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  31 If we want to make this data type more encapsulated, we could call
  32 lttv_hooks_prio_sort upon each modification to the structure. Then, a simple
  33 lttv_hooks_prio_call would be assured to call the hooks in the right order.
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