harvey/sys/src/cmd/gs/src/isave.h

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/*$Id: isave.h,v 1.2 2000/09/19 19:00:46 lpd Exp $ */
/* Procedures for save/restore */
/* Requires imemory.h */

#ifndef isave_INCLUDED
#  define isave_INCLUDED

#include "idosave.h"

/*
 * According to the PostScript language definition, save objects are simple,
 * not composite.  Consequently, we cannot use their natural representation,
 * namely a t_struct pointing to an alloc_save_t, since we aren't willing to
 * allocate them all in global VM and rely on garbage collection to clean
 * them up.  Instead, we assign each one a unique "save ID", and store this
 * in the alloc_save_t object.  Mapping the number to the object requires
 * at most searching the local save chain for the current gs_dual_memory_t,
 * and this approach means we don't have to do anything to invalidate
 * save objects when we do a restore.
 */
#ifndef alloc_save_t_DEFINED	/* also in inamedef.h */
typedef struct alloc_save_s alloc_save_t;
#  define alloc_save_t_DEFINED
#endif

/* Initialize the save machinery. */
extern void alloc_save_init(P1(gs_dual_memory_t *));

/* Map a save ID to its save object.  Return 0 if the ID is invalid. */
alloc_save_t *alloc_find_save(P2(const gs_dual_memory_t *, ulong));

/*
 * Save the state.  Return 0 if we can't allocate the save object,
 * otherwise return the save ID.  The second argument is a client data
 * pointer, assumed to point to an object.
 */
ulong alloc_save_state(P2(gs_dual_memory_t *, void *));

/* Get the client pointer passed to alloc_saved_state. */
void *alloc_save_client_data(P1(const alloc_save_t *));

/* Return (the id of) the innermost externally visible save object. */
ulong alloc_save_current_id(P1(const gs_dual_memory_t *));
alloc_save_t *alloc_save_current(P1(const gs_dual_memory_t *));

/* Check whether a pointer refers to an object allocated since a given save. */
bool alloc_is_since_save(P2(const void *, const alloc_save_t *));

/* Check whether a name was created since a given save. */
bool alloc_name_is_since_save(P2(const ref *, const alloc_save_t *));
bool alloc_name_index_is_since_save(P2(uint, const alloc_save_t *));

/*
 * Check whether any names have been created since a given save
 * that might be released by the restore.
 */
bool alloc_any_names_since_save(P1(const alloc_save_t *));

/*
 * Do one step of restoring the state.  Return true if the argument
 * was the innermost save, in which case this is the last (or only) step.
 * Assume the caller obtained the argument by calling alloc_find_save;
 * if this is the case, the operation cannot fail.
 */
bool alloc_restore_step_in(P2(gs_dual_memory_t *, alloc_save_t *));
/* Backward compatibility */
#define alloc_restore_state_step(save) alloc_restore_step_in(idmemory, save)

/*
 * Forget a save -- like committing a transaction (restore is like
 * aborting a transaction).  Assume the caller obtained the argument
 * by calling alloc_find_save.  Note that forgetting a save does not
 * require checking pointers for recency.
 */
void alloc_forget_save_in(P2(gs_dual_memory_t *, alloc_save_t *));
/* Backward compatibility */
#define alloc_forget_save(save) alloc_forget_save_in(idmemory, save)

/* Release all memory -- like doing a restore "past the bottom". */
void alloc_restore_all(P1(gs_dual_memory_t *));

/* ------ Internals ------ */

/*
 * If we are in a save, we want to save the old contents if l_new is
 * not set; if we are not in a save, we never want to save old contents.
 * We can test this quickly with a single mask that is l_new if we are
 * in a save, and -1 if we are not, since type_attrs of a valid ref
 * cannot be 0; this is the test_mask in a gs_dual_memory_t.  Similarly,
 * we want to set the l_new bit in newly allocated objects iff we are in
 * a save; this is the new_mask in a gs_dual_memory_t.
 */

/* Record that we are in a save. */
void alloc_set_in_save(P1(gs_dual_memory_t *));

/* Record that we are not in a save. */
void alloc_set_not_in_save(P1(gs_dual_memory_t *));

#endif /* isave_INCLUDED */