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WIP re-engineer for more robust operation, less chaining, and biggest-stack-possible chains
jonroach 5 Jun 2026 16:14
1 contributor
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{line.log.rev}
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9 months ago
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 #include "future.h"
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 #include "coroutine.h"
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 #include "task.h"
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 #include <assert.h>
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 #include <stdio.h>
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 #include <stdlib.h>
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 #include <time.h>
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 #include <errno.h>
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 #include <math.h>
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 #include <string.h>
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 #include "timespec_utils.h"
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 Future_vfptrs_t Future_vfptrs = {
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 &Future_dtor,
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 &_Future_Await,
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 &_Future_SetResult
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 };
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 typedef struct Future_WatcherSpec {
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 Future_Watcher watcher;
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 void *me;
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 } Future_WatcherSpec;
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Last week
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 void Future_ctor
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 (
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 Future *fut
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 ){
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 fut->vfptrs = &Future_vfptrs;
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 _Cor_Mutex_ctor(&fut->mutex);
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 fut->state = Future_State_Waiting;
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 fut->value = NULL;
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 fut->canceled = false;
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 fut->watchers = NULL;
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 fut->nwatchers = 0;
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 fut->maxwatchers = 0;
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 }
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 Future *
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 Future_New(
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 void
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 ){
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 Future *fut = malloc(sizeof(Future));
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 Future_ctor(fut);
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 return fut;
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 }
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 void
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 Future_dtor(
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 Future *fut
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 ){
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 _Cor_Mutex_Lock(&fut->mutex);
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 assert(fut->nwatchers == 0);
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 free(fut->watchers);
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 _Cor_Mutex_Unlock(&fut->mutex);
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 _Cor_Mutex_dtor(&fut->mutex);
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 }
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 void
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 Future_Delete(
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 Future *fut
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 ){
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 fut->vfptrs->dtor(fut);
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 free(fut);
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 }
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 void
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 Future_AddWatcher(
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 Future *fut,
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 Future_Watcher watcher,
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 void *watcher_me
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 ){
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 _Cor_Mutex_Lock(&fut->mutex);
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 if (fut->state == Future_State_Done) {
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 _Cor_Mutex_Unlock(&fut->mutex);
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 watcher(watcher_me, fut);
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 } else {
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 if (fut->nwatchers >= fut->maxwatchers) {
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 fut->maxwatchers = (fut->maxwatchers == 0) ? 4 : fut->maxwatchers * 2;
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 fut->watchers = realloc(fut->watchers, fut->maxwatchers * sizeof(Future_WatcherSpec));
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 assert(fut->watchers);
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 }
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 fut->watchers[fut->nwatchers].watcher = watcher;
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 fut->watchers[fut->nwatchers].me = watcher_me;
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 fut->nwatchers++;
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 _Cor_Mutex_Unlock(&fut->mutex);
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 }
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 }
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 void
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 Future_RemoveWatcher(
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 Future *fut,
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 Future_Watcher watcher,
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 void *watcher_me
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 ){
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 _Cor_Mutex_Lock(&fut->mutex);
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 for (int i = 0; i < fut->nwatchers; i++) {
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 if (fut->watchers[i].watcher == watcher && fut->watchers[i].me == watcher_me) {
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 fut->nwatchers--;
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 if (i < fut->nwatchers) {
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 fut->watchers[i] = fut->watchers[fut->nwatchers];
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 }
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 break;
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 }
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 }
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 _Cor_Mutex_Unlock(&fut->mutex);
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 }
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 static void
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 _Future_Ready(
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 Future *fut
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 ){
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 fut->state = Future_State_Done;
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 // Take note of watchers list, and reset it
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 Future_WatcherSpec *watchers = fut->watchers;
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 int nwatchers = fut->nwatchers;
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 fut->watchers = NULL;
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 fut->nwatchers = 0;
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 _Cor_Mutex_Unlock(&fut->mutex);
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 // notify those watchers
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 for (int i = 0; i < nwatchers; i++) {
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 watchers[i].watcher(watchers[i].me, fut);
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 }
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 free(watchers);
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 }
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 void
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 Future_SetResult(
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 Future *fut,
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 bool canceled,
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 void *value
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 ){
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 fut->vfptrs->set_result(fut, canceled, value);
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 }
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 Coroutine_Err
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 Future_GetResult(
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 Future *fut,
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 void **res
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 ){
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 if(fut->state != Future_State_Done){
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 return Coroutine_Err_WrongState;
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 }
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 if (res){
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 *res = fut->value;
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 }
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 return fut->canceled ? Coroutine_Err_Canceled : Coroutine_OK;
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 }
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 typedef struct future_bits {
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 Future *fut;
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 Coroutine *cor;
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 } future_bits;
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 static void
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 future_complete(
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 void *me,
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 Future *fut
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 ){
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 (void)fut;
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 Coroutine *cor = (Coroutine *)me;
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 Coroutine_NS(Continue)(cor, NULL, false);
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 }
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 static void
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 on_yield_for_future(
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 void *me
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 ){
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 future_bits *bits = (future_bits *)me;
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 Future_AddWatcher(bits->fut, future_complete, bits->cor);
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 }
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 void
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 _Future_Await(
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 Future *fut
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 ){
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 future_bits bits;
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 bits.fut = fut;
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 bits.cor = Coroutine_NS(GetActive)();
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 Task *my_task = current_task;
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 current_task = NULL;
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 my_task->awaiting_future = fut;
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 if (my_task->canceled){
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 Future_SetResult(fut, true, my_task->cancel_value);
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 }
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 Coroutine_NS(Yield)(NULL, on_yield_for_future, &bits);
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 my_task->awaiting_future = NULL;
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 current_task = my_task;
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 }
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 void
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 _Future_SetResult(
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 Future *fut,
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 bool canceled,
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 void *res
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 ){
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 _Cor_Mutex_Lock(&fut->mutex);
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 if(fut->state == Future_State_Waiting){
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 fut->canceled = canceled;
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 fut->value = res;
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 _Future_Ready(fut);
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 } else {
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 _Cor_Mutex_Unlock(&fut->mutex);
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 }
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 }
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 Coroutine_Err
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 Future_Await(
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 Future *fut,
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 void **res
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 ){
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 fut->vfptrs->await(fut);
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 if (res){
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 *res = fut->value;
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 }
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 return fut->canceled ? Coroutine_Err_Canceled : Coroutine_OK;
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 }
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