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callback.c
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callback.c
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/*
* Facility for queueing callback functions to be run from the
* top-level event loop after the current top-level activity finishes.
*/
#include <stddef.h>
#include "putty.h"
struct callback {
struct callback *next;
toplevel_callback_fn_t fn;
void *ctx;
};
struct callback *cbhead = NULL, *cbtail = NULL;
toplevel_callback_notify_fn_t notify_frontend = NULL;
void *frontend = NULL;
void request_callback_notifications(toplevel_callback_notify_fn_t fn,
void *fr)
{
notify_frontend = fn;
frontend = fr;
}
void queue_toplevel_callback(toplevel_callback_fn_t fn, void *ctx)
{
struct callback *cb;
cb = snew(struct callback);
cb->fn = fn;
cb->ctx = ctx;
/* If the front end has requested notification of pending
* callbacks, and we didn't already have one queued, let it know
* we do have one now. */
if (notify_frontend && !cbhead)
notify_frontend(frontend);
if (cbtail)
cbtail->next = cb;
else
cbhead = cb;
cbtail = cb;
cb->next = NULL;
}
void run_toplevel_callbacks(void)
{
if (cbhead) {
struct callback *cb = cbhead;
/*
* Careful ordering here. We call the function _before_
* advancing cbhead (though, of course, we must free cb
* _after_ advancing it). This means that if the very last
* callback schedules another callback, cbhead does not become
* NULL at any point, and so the frontend notification
* function won't be needlessly pestered.
*/
cb->fn(cb->ctx);
cbhead = cb->next;
sfree(cb);
if (!cbhead)
cbtail = NULL;
}
}
int toplevel_callback_pending(void)
{
return cbhead != NULL;
}