microbit-dal/inc/RefCounted.h

#ifndef REF_COUNTED_H
#define REF_COUNTED_H

#include "mbed.h"

/**
  * Base class for payload for ref-counted objects. Used by ManagedString and MicroBitImage.
  * There is no constructor, as this struct is typically malloc()ed.
  */
struct RefCounted
{
public:
    /**
      * The high 15 bits hold the number of outstanding references. The lowest bit is always 1
      * to make sure it doesn't look like vtable.
      * Should never be even or one (object should be deleted then).
      * When it's set to 0xffff, it means the object sits in flash and should not be counted.
      */
    uint16_t refCount;

    /** Increment reference count. */
    void incr();

    /** Decrement reference count. */
    void decr();

    /** Initializes for one outstanding reference. */
    void init();

    /** Checks if the object sits in flash memory. */
    bool isReadOnly();
};

#endif