zircon/third_party/ulib/musl/src/stdio/ftrylockfile.c

#include <limits.h>

#include "atomic.h"
#include "stdio_impl.h"
#include "threads_impl.h"

int ftrylockfile(FILE* f) {
  int tid = __thread_get_tid_for_filelock();
  if (f->lock == tid) {
    if (f->lockcount == LONG_MAX)
      return -1;
    f->lockcount++;
    return 0;
  }
  if (atomic_load(&f->lock) < 0)
    atomic_store(&f->lock, 0);
  if (atomic_load(&f->lock) || a_cas_shim(&f->lock, 0, tid))
    return -1;
  f->lockcount = 1;
  return 0;
}