fusl/src/stdio/ftrylockfile.c

#include "stdio_impl.h"
#include "pthread_impl.h"
#include <limits.h>

void __do_orphaned_stdio_locks() {
  FILE* f;
  for (f = __pthread_self()->stdio_locks; f; f = f->next_locked)
    a_store(&f->lock, 0x40000000);
}

void __unlist_locked_file(FILE* f) {
  if (f->lockcount) {
    if (f->next_locked)
      f->next_locked->prev_locked = f->prev_locked;
    if (f->prev_locked)
      f->prev_locked->next_locked = f->next_locked;
    else
      __pthread_self()->stdio_locks = f->next_locked;
  }
}

int ftrylockfile(FILE* f) {
  pthread_t self = __pthread_self();
  int tid = self->tid;
  if (f->lock == tid) {
    if (f->lockcount == LONG_MAX)
      return -1;
    f->lockcount++;
    return 0;
  }
  if (f->lock < 0)
    f->lock = 0;
  if (f->lock || a_cas(&f->lock, 0, tid))
    return -1;
  f->lockcount = 1;
  f->prev_locked = 0;
  f->next_locked = self->stdio_locks;
  if (f->next_locked)
    f->next_locked->prev_locked = f;
  self->stdio_locks = f;
  return 0;
}