Implementation

These keep and drop calls for simple objects are generally implemented by using one of a set of standard functions. There are a range of these, depending on the expected size of the reference counts, and all handle the locking required to ensure thread safety:

$\begin{lstlisting} void *fz_keep_imp(fz_context *ctx, void *p, int *refs); void ... ...s); int fz_drop_imp16(fz_context *ctx, void *p, int16_t *refs); \end{lstlisting}$

As an example, a fz_path structure is defined as:

$\begin{lstlisting} typedef struct { int8_t refs; } fz_path; \end{lstlisting}$

and thus appropriate keep and drop functions can be defined simply:

$\begin{lstlisting} fz_path *fz_keep_path(fz_context *ctx, fz_path *path) { retu... ...; /* code to free the contents of the path structure */ ... } \end{lstlisting}$

More complex variations of these functions are available to cope with `storable' objects, and still more complex versions to cope with `key storable' objects - these are explained in the following sections.

However they are implemented, these objects all look basically the same to most users - they can simply be `kept' and `dropped' as required.