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shm_mq.h
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1 /*-------------------------------------------------------------------------
2  *
3  * shm_mq.h
4  * single-reader, single-writer shared memory message queue
5  *
6  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
7  * Portions Copyright (c) 1994, Regents of the University of California
8  *
9  * src/include/storage/shm_mq.h
10  *
11  *-------------------------------------------------------------------------
12  */
13 #ifndef SHM_MQ_H
14 #define SHM_MQ_H
15 
16 #include "postmaster/bgworker.h"
17 #include "storage/dsm.h"
18 #include "storage/proc.h"
19 
20 /* The queue itself, in shared memory. */
21 struct shm_mq;
22 typedef struct shm_mq shm_mq;
23 
24 /* Backend-private state. */
25 struct shm_mq_handle;
27 
28 /* Descriptors for a single write spanning multiple locations. */
29 typedef struct
30 {
31  const char *data;
33 } shm_mq_iovec;
34 
35 /* Possible results of a send or receive operation. */
36 typedef enum
37 {
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. */
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 read
47  * or written, but they need not be set by the same process. Each must be
48  * set exactly once.
49  */
50 extern shm_mq *shm_mq_create(void *address, Size size);
51 extern void shm_mq_set_receiver(shm_mq *mq, PGPROC *);
52 extern void shm_mq_set_sender(shm_mq *mq, PGPROC *);
53 
54 /* Accessor methods for sender and receiver. */
57 
58 /* Set up backend-local queue state. */
60  BackgroundWorkerHandle *handle);
61 
62 /* Associate worker handle with shm_mq. */
64 
65 /* Break connection, release handle resources. */
66 extern void shm_mq_detach(shm_mq_handle *mqh);
67 
68 /* Get the shm_mq from handle. */
70 
71 /* Send or receive messages. */
73  Size nbytes, const void *data, bool nowait);
75  shm_mq_iovec *iov, int iovcnt, bool nowait);
77  Size *nbytesp, void **datap, bool nowait);
78 
79 /* Wait for our counterparty to attach to the queue. */
81 
82 /* Smallest possible queue. */
84 
85 #endif /* SHM_MQ_H */
void shm_mq_set_handle(shm_mq_handle *, BackgroundWorkerHandle *)
Definition: shm_mq.c:315
shm_mq * shm_mq_get_queue(shm_mq_handle *mqh)
Definition: shm_mq.c:831
PGDLLIMPORT const Size shm_mq_minimum_size
Definition: shm_mq.c:161
shm_mq * shm_mq_create(void *address, Size size)
Definition: shm_mq.c:170
#define PGDLLIMPORT
Definition: c.h:1052
Size len
Definition: shm_mq.h:32
const char * data
Definition: shm_mq.h:31
shm_mq_result shm_mq_send(shm_mq_handle *mqh, Size nbytes, const void *data, bool nowait)
Definition: shm_mq.c:325
shm_mq_result shm_mq_wait_for_attach(shm_mq_handle *mqh)
Definition: shm_mq.c:752
void shm_mq_set_sender(shm_mq *mq, PGPROC *)
Definition: shm_mq.c:218
void shm_mq_set_receiver(shm_mq *mq, PGPROC *)
Definition: shm_mq.c:199
shm_mq_result shm_mq_sendv(shm_mq_handle *mqh, shm_mq_iovec *iov, int iovcnt, bool nowait)
Definition: shm_mq.c:351
shm_mq_result
Definition: shm_mq.h:36
size_t Size
Definition: c.h:350
PGPROC * shm_mq_get_receiver(shm_mq *)
Definition: shm_mq.c:237
PGPROC * shm_mq_get_sender(shm_mq *)
Definition: shm_mq.c:253
shm_mq_handle * shm_mq_attach(shm_mq *mq, dsm_segment *seg, BackgroundWorkerHandle *handle)
Definition: shm_mq.c:287
Definition: shm_mq.c:69
void shm_mq_detach(shm_mq_handle *mqh)
Definition: shm_mq.c:775
Definition: proc.h:95
shm_mq_result shm_mq_receive(shm_mq_handle *mqh, Size *nbytesp, void **datap, bool nowait)
Definition: shm_mq.c:522