1 /*-------------------------------------------------------------------------
2  *
3  * proclist_types.h
4  *		doubly-linked lists of pgprocnos
5  *
6  * See proclist.h for functions that operate on these types.
7  *
8  * Portions Copyright (c) 2016-2020, PostgreSQL Global Development Group
9  *
10  * IDENTIFICATION
11  *		src/include/storage/proclist_types.h
12  *-------------------------------------------------------------------------
13  */
14 
15 #ifndef PROCLIST_TYPES_H
16 #define PROCLIST_TYPES_H
17 
18 /*
19  * A node in a doubly-linked list of processes.  The link fields contain
20  * the 0-based PGPROC indexes of the next and previous process, or
21  * INVALID_PGPROCNO in the next-link of the last node and the prev-link
22  * of the first node.  A node that is currently not in any list
23  * should have next == prev == 0; this is not a possible state for a node
24  * that is in a list, because we disallow circularity.
25  */
26 typedef struct proclist_node
27 {
28 	int			next;			/* pgprocno of the next PGPROC */
29 	int			prev;			/* pgprocno of the prev PGPROC */
30 } proclist_node;
31 
32 /*
33  * Header of a doubly-linked list of PGPROCs, identified by pgprocno.
34  * An empty list is represented by head == tail == INVALID_PGPROCNO.
35  */
36 typedef struct proclist_head
37 {
38 	int			head;			/* pgprocno of the head PGPROC */
39 	int			tail;			/* pgprocno of the tail PGPROC */
40 } proclist_head;
41 
42 /*
43  * List iterator allowing some modifications while iterating.
44  */
45 typedef struct proclist_mutable_iter
46 {
47 	int			cur;			/* pgprocno of the current PGPROC */
48 	int			next;			/* pgprocno of the next PGPROC */
49 } proclist_mutable_iter;
50 
51 #endif							/* PROCLIST_TYPES_H */
52