Mailboxes

Xinu's mailbox subsystem allows threads to send and receive messages to each other. More...

Functions
syscall	mailboxAlloc (uint count)
syscall	mailboxCount (mailbox box)
syscall	mailboxFree (mailbox box)
syscall	mailboxInit (void)
syscall	mailboxReceive (mailbox box)
syscall	mailboxSend (mailbox box, int mailmsg)

Detailed Description

Xinu's mailbox subsystem allows threads to send and receive messages to each other.

Function Documentation

syscall mailboxAlloc

(

uint

count

)

Allocate a mailbox that allows up to the specified number of outstanding messages.

Parameters

count

Maximum number of messages allowed for the mailbox.

Returns

The index of the newly allocated mailbox, or ::SYSERR if all mailboxes are already in use or other resources could not be allocated.

syscall mailboxCount

(

mailbox

box

)

Retrieve the number of outstanding messages in the specified mailbox.

Parameters

box	The index of the mailbox for which to retrieve the number of outstanding messages.

Returns

The number of messages in the mailbox, or ::SYSERR if box did not specify a valid allocated mailbox.

syscall mailboxFree

(

mailbox

box

)

Free the specified mailbox.

Parameters

box	The index of the mailbox to free.

Returns

::OK if the mailbox was successfully freed, or ::SYSERR if box did not specify a valid allocated mailbox.

syscall mailboxInit

(

void

)

Initialize mailbox structures.

Returns

::OK if all mailboxes were initialized successfully, otherwise ::SYSERR.

syscall mailboxReceive

(

mailbox

box

)

Receive a message from the specified mailbox.

Parameters

box	The index of the mailbox to receive the message from.

Returns

On success, returns the message that was dequeued; on failure (box did not specify an allocated mailbox, or the mailbox was freed while waiting for a message) returns ::SYSERR. Note that it may be impossible to disambiguate ::SYSERR from a successful return value.

syscall mailboxSend	(	mailbox	box,
		int	mailmsg
	)

Send a message to the specified mailbox.

Parameters

box	The index of the mailbox to send the message to.
mailmsg	The message to send.

Returns

::OK if the message was successfully enqueued, otherwise ::SYSERR. ::SYSERR is returned only if box did not specify a valid allocated mailbox or if the mailbox was freed while waiting for room in the queue.