opaq/cas.cpp at master · anmaped/opaq · GitHub

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#include "cas.h"

bool __atomic_compare_exchange_1(volatile bool *mem, bool *expected,
                                 bool desired, bool weak, int success,
                                 int failure) {
  bool status = true;

  // noInterrupts();

  if (*mem == *expected)
    *mem = desired;
  else
    status = false;

  // interrupts();

  return status;
}

static inline unsigned long arch_local_irq_save(void) {
  unsigned long flags;
  asm volatile("rsil %0, 1" : "=a"(flags)::"memory");
  return flags;
}

static inline void arch_local_irq_restore(unsigned long flags) {
  asm volatile("wsr %0, ps; rsync" ::"a"(flags) : "memory");
}

bool cas(volatile uint8_t *mem, uint8_t expected, uint8_t desired) {
  bool status = true;
  // noInterrupts();
  if (*mem == expected)
    *mem = desired;
  else
    status = false;
  // interrupts();

  return status;
}