cached_gpio.h

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#pragma once
 
#include <array>
#include <cstdint>
#include <cstring>
#include <limits>
#include "esphome/core/hal.h"
 
namespace esphome::gpio_expander {
 
template<typename T, T N> class CachedGpioExpander {
 public:
  bool digital_read(T pin) {
    const uint8_t bank = pin / BANK_SIZE;
    const T pin_mask = (1 << (pin % BANK_SIZE));
    // Check if specific pin cache is valid
    if (this->read_cache_valid_[bank] & pin_mask) {
      // Invalidate pin
      this->read_cache_valid_[bank] &= ~pin_mask;
    } else {
      // Read whole bank from hardware
      if (!this->digital_read_hw(pin))
        return false;
      // Mark bank cache as valid except the pin that is being returned now
      this->read_cache_valid_[bank] = std::numeric_limits<T>::max() & ~pin_mask;
    }
    return this->digital_read_cache(pin);
  }
 
  void digital_write(T pin, bool value) { this->digital_write_hw(pin, value); }
 
 protected:
  virtual bool digital_read_hw(T pin) = 0;
  virtual bool digital_read_cache(T pin) = 0;
  virtual void digital_write_hw(T pin, bool value) = 0;
 
  void reset_pin_cache_() { memset(this->read_cache_valid_, 0x00, CACHE_SIZE_BYTES); }
 
  static constexpr uint8_t BITS_PER_BYTE = 8;
  static constexpr uint8_t BANK_SIZE = sizeof(T) * BITS_PER_BYTE;
  static constexpr size_t BANKS = N / BANK_SIZE;
  static constexpr size_t CACHE_SIZE_BYTES = BANKS * sizeof(T);
 
  T read_cache_valid_[BANKS]{0};
};
 
}  // namespace esphome::gpio_expander