aft.c: Move definition of "buf" down a bit.
[paraslash.git] / sched.h
1 /*
2 * Copyright (C) 2006 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file sched.h sched and task structures and exported symbols from sched.c */
8
9
10 /**
11 * paraslash's scheduler
12 *
13 * Designed with KISS in mind. It manages two lists of tasks. The pre_select
14 * list contains pointers to functions that are called before calling select()
15 * from the main loop. Similarly, \a post_select_list is a list of function
16 * pointers each of which is called after the select call. Tasks add hooks to
17 * these lists by registering themselves to the scheduler.
18 */
19 struct sched {
20 /** initial value before any pre_select call */
21 struct timeval default_timeout;
22 /** the current timeout for the upcoming select call */
23 struct timeval timeout;
24 /** fds that should be watched for readability */
25 fd_set rfds;
26 /** fds that should be watched for writability */
27 fd_set wfds;
28 /** highest numbered file descriptor in any of the above fd sets */
29 int max_fileno;
30 /** the return value of the previous select call */
31 int select_ret;
32 };
33
34 /**
35 * paraslash's task structure
36 *
37 * before registering a task to the scheduler, the task structure must be
38 * filled in properly by the caller.
39 *
40 * If one of these functions return a negative value via \a t->ret the
41 * (optional) event_handler gets called (it may also be called in case another
42 * event happened). In many cases the only possible event is an error or an eof
43 * condition and the event handler simply unregisters the task from the
44 * scheduler.
45 *
46 * \sa struct sched
47 */
48 struct task {
49 /** pointer to the struct this task is embedded in */
50 void *private_data;
51 /**
52 * the pre select hook of \a t
53 *
54 * Its purpose is to add file descriptors to the fd sets of the
55 * scheduler and to decrease the select timeout if necessary.
56 */
57 void (*pre_select)(struct sched *s, struct task *t);
58 /**
59 * the postselect hook of \a t
60 *
61 * evaluate and act upon the results of the previous select call.
62 */
63 void (*post_select)(struct sched *s, struct task *t);
64 /** gets called if pre_select or post_select returned an error */
65 void (*event_handler)(struct task *t);
66 /** pre_select() and post_select store their return value here */
67 int ret;
68 /** position of the task in the pre_select list of the scheduler */
69 struct list_head pre_select_node;
70 /** position of the task in the post_select list of the scheduler */
71 struct list_head post_select_node;
72 /** descriptive text and current status of the task */
73 char status[MAXLINE];
74 };
75
76 /**
77 * This is set by the scheduler at the beginning of its main loop. It may be
78 * used (read-only) from everywhere. As none of the functions called by the
79 * scheduler are allowed to block, this value should be accurate enough so that
80 * there is no need to call gettimeofday() directly.
81 */
82 extern struct timeval *now;
83
84 void register_task(struct task *t);
85 void unregister_task(struct task *t);
86 int schedule(struct sched *s);
87 char *get_task_list(void);
88 int kill_task(char *id);