+/*
+ * Copyright (C) 2006 Andre Noll <maan@systemlinux.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
+ */
+
+/** \file sched.c Paraslash's task and scheduling functions */
+
+
+/**
+ * paraslash's scheduler
+ *
+ * desinged with KISS in mind. It maintains two lists: The pre_select list
+ * and the post_select list. Tasks add hokks to these lists by registering
+ * themselves to the scheduler.
+ */
struct sched {
- struct timeval now, timeout;
+ /** initial value before any pre_select call */
+ struct timeval default_timeout;
+ /** the current timeout for the upcoming select call */
+ struct timeval timeout;
+ /** fds that should be watched for readability */
+ fd_set rfds;
+ /** fds that should be watched for writability */
+ fd_set wfds;
+ /** highest numbered file descriptor in any of the above fd sets */
int max_fileno;
- fd_set rfds, wfds;
+ /** the return value of the previous select call */
int select_ret;
- struct timeval default_timeout;
};
+/**
+ * paraslash's task structure
+ *
+ * before registering a task to the scheduler, the task structure must be
+ * filled in properly by the caller.
+ *
+ * The pre_select or the post_select pointer, but not both may be NULL. Once
+ * a task is registered, its pre_select and post_select function gets called
+ * from the scheduler's mainloop. The purpose of the pre_select loop is to add
+ * file descriptors to the fd sets of the scheduler and to decrease the select
+ * timeout if neccessary. The post_select function may then evaluate these fd
+ * sets and act upon the results.
+
+ * If one of these functions return a negative value via \a t->ret the
+ * (optional) event_handler gets called (it may also be called in case another
+ * event happend). In many cases the only possible event is an error or an eof
+ * condition and the event handler simply unregisters the task from the
+ * scheduler.
+ *
+ * \sa struct sched
+ */
struct task {
+ /** pointer to the struct this task is embedded in */
void *private_data;
- int ret;
+ /** pre_select hook */
void (*pre_select)(struct sched *s, struct task *t);
+ /** post_select hook */
void (*post_select)(struct sched *s, struct task *t);
+ /** gets called */
void (*event_handler)(struct task *t);
+ /** pre_select() and post_select store their return value here */
+ int ret;
+ /** position of the task in the pre_select list of the scheduler */
struct list_head pre_select_node;
+ /** position of the task in the post_select list of the scheduler */
struct list_head post_select_node;
+ /** descriptive text and current status of the task */
char status[MAXLINE];
};
+/**
+ * This is set by the scheduler at the beginning of its main loop. It may be
+ * used (read-only) from everywhere. As none of the functions called by the
+ * scheduler are allowed to block, this value should be accurate enough so that
+ * there is no need to call gettimeofday() directly.
+ */
extern struct timeval *now;
void *register_task(struct task *t);
projects / paraslash.git / blobdiff