1 files changed, 85 insertions, 0 deletions
diff --git a/src/include/storage/shm_mq.h b/src/include/storage/shm_mq.h
new file mode 100644
index 0000000..5005f2c
--- /dev/null
+++ b/src/include/storage/shm_mq.h
@@ -0,0 +1,85 @@
+/*-------------------------------------------------------------------------
+ *
+ * shm_mq.h
+ *	  single-reader, single-writer shared memory message queue
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/storage/shm_mq.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SHM_MQ_H
+#define SHM_MQ_H
+
+#include "postmaster/bgworker.h"
+#include "storage/dsm.h"
+#include "storage/proc.h"
+
+/* The queue itself, in shared memory. */
+struct shm_mq;
+typedef struct shm_mq shm_mq;
+
+/* Backend-private state. */
+struct shm_mq_handle;
+typedef struct shm_mq_handle shm_mq_handle;
+
+/* Descriptors for a single write spanning multiple locations. */
+typedef struct
+{
+	const char *data;
+	Size		len;
+} shm_mq_iovec;
+
+/* Possible results of a send or receive operation. */
+typedef enum
+{
+	SHM_MQ_SUCCESS,				/* Sent or received a message. */
+	SHM_MQ_WOULD_BLOCK,			/* Not completed; retry later. */
+	SHM_MQ_DETACHED				/* Other process has detached queue. */
+} shm_mq_result;
+
+/*
+ * Primitives to create a queue and set the sender and receiver.
+ *
+ * Both the sender and the receiver must be set before any messages are read
+ * or written, but they need not be set by the same process.  Each must be
+ * set exactly once.
+ */
+extern shm_mq *shm_mq_create(void *address, Size size);
+extern void shm_mq_set_receiver(shm_mq *mq, PGPROC *);
+extern void shm_mq_set_sender(shm_mq *mq, PGPROC *);
+
+/* Accessor methods for sender and receiver. */
+extern PGPROC *shm_mq_get_receiver(shm_mq *);
+extern PGPROC *shm_mq_get_sender(shm_mq *);
+
+/* Set up backend-local queue state. */
+extern shm_mq_handle *shm_mq_attach(shm_mq *mq, dsm_segment *seg,
+									BackgroundWorkerHandle *handle);
+
+/* Associate worker handle with shm_mq. */
+extern void shm_mq_set_handle(shm_mq_handle *, BackgroundWorkerHandle *);
+
+/* Break connection, release handle resources. */
+extern void shm_mq_detach(shm_mq_handle *mqh);
+
+/* Get the shm_mq from handle. */
+extern shm_mq *shm_mq_get_queue(shm_mq_handle *mqh);
+
+/* Send or receive messages. */
+extern shm_mq_result shm_mq_send(shm_mq_handle *mqh,
+								 Size nbytes, const void *data, bool nowait);
+extern shm_mq_result shm_mq_sendv(shm_mq_handle *mqh,
+								  shm_mq_iovec *iov, int iovcnt, bool nowait);
+extern shm_mq_result shm_mq_receive(shm_mq_handle *mqh,
+									Size *nbytesp, void **datap, bool nowait);
+
+/* Wait for our counterparty to attach to the queue. */
+extern shm_mq_result shm_mq_wait_for_attach(shm_mq_handle *mqh);
+
+/* Smallest possible queue. */
+extern PGDLLIMPORT const Size shm_mq_minimum_size;
+
+#endif							/* SHM_MQ_H */