src/TortoisePlink/callback.c

   1 /*
   2  * Facility for queueing callback functions to be run from the
   3  * top-level event loop after the current top-level activity finishes.
   4  */
   5
   6 #include <stddef.h>
   7
   8 #include "putty.h"
   9
  10 struct callback {
  11     struct callback *next;
  12
  13     toplevel_callback_fn_t fn;
  14     void *ctx;
  15 };
  16
  17 struct callback *cbhead = NULL, *cbtail = NULL;
  18
  19 toplevel_callback_notify_fn_t notify_frontend = NULL;
  20 void *frontend = NULL;
  21
  22 void request_callback_notifications(toplevel_callback_notify_fn_t fn,
  23                                     void *fr)
  24 {
  25     notify_frontend = fn;
  26     frontend = fr;
  27 }
  28
  29 void queue_toplevel_callback(toplevel_callback_fn_t fn, void *ctx)
  30 {
  31     struct callback *cb;
  32
  33     cb = snew(struct callback);
  34     cb->fn = fn;
  35     cb->ctx = ctx;
  36
  37     /* If the front end has requested notification of pending
  38      * callbacks, and we didn't already have one queued, let it know
  39      * we do have one now. */
  40     if (notify_frontend && !cbhead)
  41         notify_frontend(frontend);
  42
  43     if (cbtail)
  44         cbtail->next = cb;
  45     else
  46         cbhead = cb;
  47     cbtail = cb;
  48     cb->next = NULL;
  49 }
  50
  51 void run_toplevel_callbacks(void)
  52 {
  53     if (cbhead) {
  54         struct callback *cb = cbhead;
  55         /*
  56          * Careful ordering here. We call the function _before_
  57          * advancing cbhead (though, of course, we must free cb
  58          * _after_ advancing it). This means that if the very last
  59          * callback schedules another callback, cbhead does not become
  60          * NULL at any point, and so the frontend notification
  61          * function won't be needlessly pestered.
  62          */
  63         cb->fn(cb->ctx);
  64         cbhead = cb->next;
  65         sfree(cb);
  66         if (!cbhead)
  67             cbtail = NULL;
  68     }
  69 }
  70
  71 int toplevel_callback_pending(void)
  72 {
  73     return cbhead != NULL;
  74 }