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/*-------------------------------------------------------------------------
*
* dsm_impl.h
* low-level dynamic shared memory primitives
*
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/storage/dsm_impl.h
*
*-------------------------------------------------------------------------
*/
#ifndef DSM_IMPL_H
#define DSM_IMPL_H
/* Dynamic shared memory implementations. */
#define DSM_IMPL_POSIX 1
#define DSM_IMPL_SYSV 2
#define DSM_IMPL_WINDOWS 3
#define DSM_IMPL_MMAP 4
/*
* Determine which dynamic shared memory implementations will be supported
* on this platform, and which one will be the default.
*/
#ifdef WIN32
#define USE_DSM_WINDOWS
#define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE DSM_IMPL_WINDOWS
#else
#ifdef HAVE_SHM_OPEN
#define USE_DSM_POSIX
#define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE DSM_IMPL_POSIX
#endif
#define USE_DSM_SYSV
#ifndef DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE
#define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE DSM_IMPL_SYSV
#endif
#define USE_DSM_MMAP
#endif
/* GUC. */
extern int dynamic_shared_memory_type;
extern int min_dynamic_shared_memory;
/*
* Directory for on-disk state.
*
* This is used by all implementations for crash recovery and by the mmap
* implementation for storage.
*/
#define PG_DYNSHMEM_DIR "pg_dynshmem"
#define PG_DYNSHMEM_MMAP_FILE_PREFIX "mmap."
/* A "name" for a dynamic shared memory segment. */
typedef uint32 dsm_handle;
/* All the shared-memory operations we know about. */
typedef enum
{
DSM_OP_CREATE,
DSM_OP_ATTACH,
DSM_OP_DETACH,
DSM_OP_DESTROY
} dsm_op;
/* Create, attach to, detach from, resize, or destroy a segment. */
extern bool dsm_impl_op(dsm_op op, dsm_handle handle, Size request_size,
void **impl_private, void **mapped_address, Size *mapped_size,
int elevel);
/* Implementation-dependent actions required to keep segment until shutdown. */
extern void dsm_impl_pin_segment(dsm_handle handle, void *impl_private,
void **impl_private_pm_handle);
extern void dsm_impl_unpin_segment(dsm_handle handle, void **impl_private);
#endif /* DSM_IMPL_H */
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