1 files changed, 75 insertions, 0 deletions
diff --git a/src/include/storage/dsm_impl.h b/src/include/storage/dsm_impl.h
new file mode 100644
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--- /dev/null
+++ b/src/include/storage/dsm_impl.h
@@ -0,0 +1,75 @@
+/*-------------------------------------------------------------------------
+ *
+ * dsm_impl.h
+ *	  low-level dynamic shared memory primitives
+ *
+ * Portions Copyright (c) 1996-2020, 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;
+
+/*
+ * 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 */