X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=bertos%2Fkern%2Fmsg.h;fp=bertos%2Fkern%2Fmsg.h;h=e4ee21f9b1ab5f2ae7a136aa5f7eaba2953aa257;hb=791e167e053bdd9250d34a9a5ccae6ccde4d6679;hp=0000000000000000000000000000000000000000;hpb=faf2f6bfd5933ff75e6cc01e3d48f9277f731d8f;p=bertos.git diff --git a/bertos/kern/msg.h b/bertos/kern/msg.h new file mode 100644 index 00000000..e4ee21f9 --- /dev/null +++ b/bertos/kern/msg.h @@ -0,0 +1,286 @@ +/** + * \file + * + * + * + * This module implements a common system for executing + * a user defined action calling a hook function. + * + * \version $Id$ + * + * \author Bernardo Innocenti + * + * \brief Simple inter-process messaging system + * + * Handle queues of messages associated an action. + * + * A message port is an abstraction used to exchange information + * asynchronously between processes or other entities such as + * interrupts and call-back functions. + * + * This form of IPC is higher-level than bare signals and + * semaphores, because it sets a policy for exchanging + * structured data with well-defined synchronization and + * ownership semantics. + * + * Before using it, a message port must be initialized by + * calling msg_initPort(), which associates the port with + * an Event object, which can be setup to signal a process + * or invoke a call-back hook. + * + * A process or interrupt routine can deliver messages to any + * message port by calling msg_put(). By sending a message, + * the sender temporarly or permanently transfers ownership + * of its associated data to the receiver. + * + * Queuing a message to a port automatically triggers the + * associated Event to notify the receiver. When the + * receiver wakes up, it usually invokes msg_get() to pick + * the next message from the port. + * + * Message ports can hold any number of pending messages, + * and receivers usually process them in FIFO order. + * Other scheduling policies are possible, but not implemented + * in this API. + * + * After the receiver has done processing a message, it replies + * it back to the sender with msg_reply(), which transfer + * ownership back to the original sender. Replies are delivered + * to a reply port, which is nothing more than another MsgPort + * structure designated by the sender. + * + * Returning messages to senders is not mandatory, but it provides + * a convenient way to provide some kind of result and simplify + * the resource allocation scheme at the same time. + * + * When using signals to receive messages in a process, you + * call sig_wait() in an event-loop to wake up when messages + * are delivered to any of your ports. When your process + * wakes up with the port signal active, multiple messages + * may already have queued up at the message port, and the + * process must process them all before returning to sleep. + * Signals don't keep a nesting count. + * + * A simple message loop works like this: + * + * \code + * // Our message port. + * static MsgPort test_port; + * + * // A test message with two parameters and a result. + * typedef struct + * { + * Msg msg; + * + * int x, y; + * int result; + * } TestMsg; + * + * + * // A process that sends two messages and waits for replies. + * static void sender_proc(void) + * { + * MsgPort test_reply_port; + * TestMsg msg1; + * TestMsg msg2; + * Msg *reply; + * + * msg_initPort(&reply_port, + * event_createSignal(proc_current(), SIGF_SINGLE); + * + * // Fill-in first message and send it out. + * msg1.x = 3; + * msg1.y = 2; + * msg1.msg.replyPort = &test_reply_port; + * msg_put(&test_port, &msg1); + * + * // Fill-in second message and send it out too. + * msg2.x = 5; + * msg2.y = 4; + * msg2.msg.replyPort = &test_reply_port; + * msg_put(&test_port, &msg1); + * + * // Wait for a reply... + * sig_wait(SIG_SINGLE); + * + * reply = (TestMsg *)msg_get(&test_reply_port); + * ASSERT(reply != NULL); + * ASSERT(reply->result == 5); + * + * // Get reply to second message. + * while (!(reply = (TestMsg *)msg_get(&test_reply_port)) + * { + * // Not yet, be patient and wait some more. + * sig_wait(SIG_SINGLE); + * } + * + * ASSERT(reply->result == 9); + * } + * + * + * // Receive messages and do something boring with them. + * static void receiver_proc(void) + * { + * msg_initPort(&test_port, + * event_createSignal(proc_current(), SIGF_EXAMPLE); + * + * proc_new(sender_proc, (iptr_t)&test_port, + * sender_stack, sizeof(sender_stack); + * + * for (;;) + * { + * sigmask_t sigs = sig_wait(SIGF_EXAMPLE | more_signals); + * + * if (sigs & SIGF_EXAMPLE) + * { + * TestMsg *emsg; + * while (emsg = (TestMsg *)msg_get(&test_port) + * { + * // Do something with the message + * emsg->result = emsg->x + emsg->y; + * msg_reply((Msg *)msg); + * } + * } + * } + * } + * \endcode + */ + + */ + +#ifndef KERN_MSG_H +#define KERN_MSG_H + +#include "event.h" +#include + + +typedef struct MsgPort +{ + List queue; /**< Messages queued at this port. */ + Event event; /**< Event to trigger when a message arrives. */ +} MsgPort; + + +typedef struct Msg +{ + Node link; /**< Link into message port queue. */ + MsgPort *replyPort; /**< Port to which the msg is to be replied. */ + /* User data may follow */ +} Msg; + + +/** + * Lock a message port. + * + * This is required before reading or manipulating + * any field of the MsgPort structure. + * + * \note Ports may be locked multiple times and each + * call to msg_lockPort() must be paired with + * a corresponding call to msg_unlockPort(). + * + * \todo Add a configurable policy for locking against + * interrupts and locking with semaphorse. + * + * \see msg_unlockPort() + */ +INLINE void msg_lockPort(MsgPort *port) +{ + proc_forbid(); +} + +/** + * Unlock a message port. + * + * \see msg_lockPort() + */ +INLINE void msg_unlockPort(MsgPort *port) +{ + proc_permit(); +} + + +/** Initialize a message port */ +INLINE void msg_initPort(MsgPort *port, Event event) +{ + LIST_INIT(&port->queue); + port->event = event; +} + +/** Queue \a msg into \a port, triggering the associated event */ +INLINE void msg_put(MsgPort *port, Msg *msg) +{ + msg_portLock(port); + ADDTAIL(&port->queue, &msg->link); + msg_portUnlock(port); + + event_do(&port->event); +} + +/** + * Get the first message from the queue of \a port. + * + * \return Pointer to the message or NULL if the port was empty. + */ +INLINE Msg *msg_get(MsgPort *port) +{ + Msg *msg; + + msg_portLock(port); + msg = (Msg *)REMHEAD(&port->queue); + msg_portUnlock(port); + + return msg; +} + +/** Peek the first message in the queue of \a port, or NULL if the port is empty. */ +INLINE Msg *msg_peek(MsgPort *port) +{ + Msg *msg; + + msg_portLock(port); + msg = (Msg *)port->queue.head; + if (ISLISTEMPTY(&port->queue)) + msg = NULL; + msg_portUnlock(port); + + return msg; +} + +/** Send back (reply) \a msg to its sender. */ +INLINE void msg_reply(Msg *msg) +{ + msg_put(msg->replyPort, msg); +} + +#endif /* KERN_MSG_H */