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/*-------------------------------------------------------------------------
*
* dsa.h
* Dynamic shared memory areas.
*
* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/include/utils/dsa.h
*
*-------------------------------------------------------------------------
*/
#ifndef DSA_H
#define DSA_H
#include "postgres.h"
#include "port/atomics.h"
#include "storage/dsm.h"
/* The opaque type used for an area. */
struct dsa_area;
typedef struct dsa_area dsa_area;
/*
* If this system doesn't support atomic operations on 64 bit values then
* we fall back to 32 bit dsa_pointer. For testing purposes,
* USE_SMALL_DSA_POINTER can be defined to force the use of 32 bit
* dsa_pointer even on systems that support 64 bit atomics.
*/
#ifndef PG_HAVE_ATOMIC_U64_SUPPORT
#define SIZEOF_DSA_POINTER 4
#else
#ifdef USE_SMALL_DSA_POINTER
#define SIZEOF_DSA_POINTER 4
#else
#define SIZEOF_DSA_POINTER 8
#endif
#endif
/*
* The type of 'relative pointers' to memory allocated by a dynamic shared
* area. dsa_pointer values can be shared with other processes, but must be
* converted to backend-local pointers before they can be dereferenced. See
* dsa_get_address. Also, an atomic version and appropriately sized atomic
* operations.
*/
#if SIZEOF_DSA_POINTER == 4
typedef uint32 dsa_pointer;
typedef pg_atomic_uint32 dsa_pointer_atomic;
#define dsa_pointer_atomic_init pg_atomic_init_u32
#define dsa_pointer_atomic_read pg_atomic_read_u32
#define dsa_pointer_atomic_write pg_atomic_write_u32
#define dsa_pointer_atomic_fetch_add pg_atomic_fetch_add_u32
#define dsa_pointer_atomic_compare_exchange pg_atomic_compare_exchange_u32
#else
typedef uint64 dsa_pointer;
typedef pg_atomic_uint64 dsa_pointer_atomic;
#define dsa_pointer_atomic_init pg_atomic_init_u64
#define dsa_pointer_atomic_read pg_atomic_read_u64
#define dsa_pointer_atomic_write pg_atomic_write_u64
#define dsa_pointer_atomic_fetch_add pg_atomic_fetch_add_u64
#define dsa_pointer_atomic_compare_exchange pg_atomic_compare_exchange_u64
#endif
/* A sentinel value for dsa_pointer used to indicate failure to allocate. */
#define InvalidDsaPointer ((dsa_pointer) 0)
/* Check if a dsa_pointer value is valid. */
#define DsaPointerIsValid(x) ((x) != InvalidDsaPointer)
/*
* The type used for dsa_area handles. dsa_handle values can be shared with
* other processes, so that they can attach to them. This provides a way to
* share allocated storage with other processes.
*
* The handle for a dsa_area is currently implemented as the dsm_handle
* for the first DSM segment backing this dynamic storage area, but client
* code shouldn't assume that is true.
*/
typedef dsm_handle dsa_handle;
extern void dsa_startup(void);
extern dsa_area *dsa_create(int tranche_id, const char *tranche_name);
extern dsa_area *dsa_create_in_place(void *place, Size size,
int tranche_id, const char *tranche_name,
dsm_segment *segment);
extern dsa_area *dsa_attach(dsa_handle handle);
extern dsa_area *dsa_attach_in_place(void *place, dsm_segment *segment);
extern void dsa_release_in_place(void *place);
extern void dsa_on_dsm_detach_release_in_place(dsm_segment *, Datum);
extern void dsa_on_shmem_exit_release_in_place(int, Datum);
extern void dsa_pin_mapping(dsa_area *area);
extern void dsa_detach(dsa_area *area);
extern void dsa_pin(dsa_area *area);
extern void dsa_unpin(dsa_area *area);
extern void dsa_set_size_limit(dsa_area *area, Size limit);
extern Size dsa_minimum_size(void);
extern dsa_handle dsa_get_handle(dsa_area *area);
extern dsa_pointer dsa_allocate(dsa_area *area, Size size);
extern void dsa_free(dsa_area *area, dsa_pointer dp);
extern void *dsa_get_address(dsa_area *area, dsa_pointer dp);
extern void dsa_trim(dsa_area *area);
extern void dsa_dump(dsa_area *area);
#endif /* DSA_H */
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