87 lines
2.7 KiB
C
87 lines
2.7 KiB
C
/*-------------------------------------------------------------------------
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*
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* shm_mq.h
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* single-reader, single-writer shared memory message queue
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*
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* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/storage/shm_mq.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef SHM_MQ_H
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#define SHM_MQ_H
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#include "postmaster/bgworker.h"
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#include "storage/dsm.h"
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#include "storage/proc.h"
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/* The queue itself, in shared memory. */
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struct shm_mq;
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typedef struct shm_mq shm_mq;
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/* Backend-private state. */
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struct shm_mq_handle;
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typedef struct shm_mq_handle shm_mq_handle;
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/* Descriptors for a single write spanning multiple locations. */
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typedef struct
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{
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const char *data;
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Size len;
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} shm_mq_iovec;
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/* Possible results of a send or receive operation. */
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typedef enum
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{
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SHM_MQ_SUCCESS, /* Sent or received a message. */
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SHM_MQ_WOULD_BLOCK, /* Not completed; retry later. */
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SHM_MQ_DETACHED, /* Other process has detached queue. */
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} shm_mq_result;
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/*
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* Primitives to create a queue and set the sender and receiver.
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*
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* Both the sender and the receiver must be set before any messages are read
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* or written, but they need not be set by the same process. Each must be
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* set exactly once.
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*/
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extern shm_mq *shm_mq_create(void *address, Size size);
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extern void shm_mq_set_receiver(shm_mq *mq, PGPROC *);
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extern void shm_mq_set_sender(shm_mq *mq, PGPROC *);
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/* Accessor methods for sender and receiver. */
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extern PGPROC *shm_mq_get_receiver(shm_mq *);
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extern PGPROC *shm_mq_get_sender(shm_mq *);
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/* Set up backend-local queue state. */
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extern shm_mq_handle *shm_mq_attach(shm_mq *mq, dsm_segment *seg,
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BackgroundWorkerHandle *handle);
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/* Associate worker handle with shm_mq. */
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extern void shm_mq_set_handle(shm_mq_handle *, BackgroundWorkerHandle *);
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/* Break connection, release handle resources. */
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extern void shm_mq_detach(shm_mq_handle *mqh);
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/* Get the shm_mq from handle. */
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extern shm_mq *shm_mq_get_queue(shm_mq_handle *mqh);
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/* Send or receive messages. */
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extern shm_mq_result shm_mq_send(shm_mq_handle *mqh,
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Size nbytes, const void *data, bool nowait,
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bool force_flush);
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extern shm_mq_result shm_mq_sendv(shm_mq_handle *mqh, shm_mq_iovec *iov,
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int iovcnt, bool nowait, bool force_flush);
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extern shm_mq_result shm_mq_receive(shm_mq_handle *mqh,
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Size *nbytesp, void **datap, bool nowait);
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/* Wait for our counterparty to attach to the queue. */
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extern shm_mq_result shm_mq_wait_for_attach(shm_mq_handle *mqh);
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/* Smallest possible queue. */
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extern PGDLLIMPORT const Size shm_mq_minimum_size;
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#endif /* SHM_MQ_H */
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