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);