codekingpro/portable-devtools

1/*-------------------------------------------------------------------------2 *3 * shm_mq.h4 *	  single-reader, single-writer shared memory message queue5 *6 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group7 * Portions Copyright (c) 1994, Regents of the University of California8 *9 * src/include/storage/shm_mq.h10 *11 *-------------------------------------------------------------------------12 */13#ifndef SHM_MQ_H14#define SHM_MQ_H15 16#include "postmaster/bgworker.h"17#include "storage/dsm.h"18#include "storage/proc.h"19 20/* The queue itself, in shared memory. */21struct shm_mq;22typedef struct shm_mq shm_mq;23 24/* Backend-private state. */25struct shm_mq_handle;26typedef struct shm_mq_handle shm_mq_handle;27 28/* Descriptors for a single write spanning multiple locations. */29typedef struct30{31	const char *data;32	Size		len;33} shm_mq_iovec;34 35/* Possible results of a send or receive operation. */36typedef enum37{38	SHM_MQ_SUCCESS,				/* Sent or received a message. */39	SHM_MQ_WOULD_BLOCK,			/* Not completed; retry later. */40	SHM_MQ_DETACHED				/* Other process has detached queue. */41} shm_mq_result;42 43/*44 * Primitives to create a queue and set the sender and receiver.45 *46 * Both the sender and the receiver must be set before any messages are read47 * or written, but they need not be set by the same process.  Each must be48 * set exactly once.49 */50extern shm_mq *shm_mq_create(void *address, Size size);51extern void shm_mq_set_receiver(shm_mq *mq, PGPROC *);52extern void shm_mq_set_sender(shm_mq *mq, PGPROC *);53 54/* Accessor methods for sender and receiver. */55extern PGPROC *shm_mq_get_receiver(shm_mq *);56extern PGPROC *shm_mq_get_sender(shm_mq *);57 58/* Set up backend-local queue state. */59extern shm_mq_handle *shm_mq_attach(shm_mq *mq, dsm_segment *seg,60									BackgroundWorkerHandle *handle);61 62/* Associate worker handle with shm_mq. */63extern void shm_mq_set_handle(shm_mq_handle *, BackgroundWorkerHandle *);64 65/* Break connection, release handle resources. */66extern void shm_mq_detach(shm_mq_handle *mqh);67 68/* Get the shm_mq from handle. */69extern shm_mq *shm_mq_get_queue(shm_mq_handle *mqh);70 71/* Send or receive messages. */72extern shm_mq_result shm_mq_send(shm_mq_handle *mqh,73								 Size nbytes, const void *data, bool nowait,74								 bool force_flush);75extern shm_mq_result shm_mq_sendv(shm_mq_handle *mqh, shm_mq_iovec *iov,76								  int iovcnt, bool nowait, bool force_flush);77extern shm_mq_result shm_mq_receive(shm_mq_handle *mqh,78									Size *nbytesp, void **datap, bool nowait);79 80/* Wait for our counterparty to attach to the queue. */81extern shm_mq_result shm_mq_wait_for_attach(shm_mq_handle *mqh);82 83/* Smallest possible queue. */84extern PGDLLIMPORT const Size shm_mq_minimum_size;85 86#endif							/* SHM_MQ_H */87