source: buchla-68k/orig/MT/MBINIT.C@ a838f5b

Last change on this file since a838f5b was 3ae31e9, checked in by Thomas Lopatic <thomas@…>, 8 years ago

Imported original source code.
  • Property mode set to 100755
File size: 5.1 KB
Line 
1/*
2 =============================================================================
3 mbinit.c -- Multi-Tasker -- Mailbox support
4 Version 7 -- 1988-03-29 -- D.N. Lynx Crowe
5 (c) Copyright 1988 -- D.N. LYnx Crowe
6 =============================================================================
7*/
8
9#include "stddefs.h"
10#include "mtdefs.h"
11
12extern short setipl(); /* set processor IPL function */
13extern short SMStat(); /* semaphore check function */
14
15/*
16 =============================================================================
17 MBInit() -- initialize a mailbox
18 =============================================================================
19*/
20
21MBInit(pmbox)
22register MBOX *pmbox;
23{
24 register short oldipl;
25
26 oldipl = setipl(7); /* DISABLE INTERRUPTS */
27
28 pmbox->mail = (SEM)1L; /* reset the mail semaphore */
29 pmbox->mutex = (SEM)3L; /* reset the mutex semaphore */
30 pmbox->head = (MSG *)NIL; /* clear the MSG queue head pointer */
31 pmbox->tail = (MSG *)NIL; /* clear the MSG queue tail pointer */
32
33 setipl(oldipl); /* RESTORE INTERRUPTS */
34}
35
36/*
37
38*/
39
40/*
41 =============================================================================
42 MBSend() -- send a message to a mailbox
43 =============================================================================
44*/
45
46MBSend(pmbox, pmsg)
47register MBOX *pmbox;
48register MSG *pmsg;
49{
50 SMWait(&pmbox->mutex); /* ACQUIRE THE MAILBOX */
51
52 if (pmbox->head) /* is anything in the queue ? */
53 (pmbox->tail)->next = pmsg; /* set next of tail message */
54 else /* ... queue was empty */
55 pmbox->head = pmsg; /* set the head pointer */
56
57 pmbox->tail = pmsg; /* set the tail pointer */
58 pmsg->next = (MSG *)NIL; /* set next of new message */
59
60 SMSig(&pmbox->mail); /* signal that there's mail */
61
62 SMSig(&pmbox->mutex); /* RELEASE THE MAILBOX */
63}
64
65/*
66
67*/
68
69/*
70 =============================================================================
71 MBRecv() -- receive a message from a mailbox
72 =============================================================================
73*/
74
75MSG *
76MBRecv(pmbox)
77register MBOX *pmbox;
78{
79 register MSG *pmsg;
80
81 SMWait(&pmbox->mail); /* WAIT FOR SOME MAIL */
82
83 SMWait(&pmbox->mutex); /* ACQUIRE THE MAILBOX */
84
85 pmsg = pmbox->head; /* get the first message in the queue */
86
87 if (pmbox->head EQ pmbox->tail) { /* only message ? */
88
89 pmbox->head = (MSG *)NIL; /* clear queue head pointer */
90 pmbox->tail = (MSG *)NIL; /* clear queue tail pointer */
91
92 } else {
93
94 pmbox->head = pmsg->next; /* update queue head pointer */
95 }
96
97 pmsg->next = (MSG *)NIL; /* clear next message pointer */
98
99 SMSig(&pmbox->mutex); /* RELEASE THE MAILBOX */
100
101 return(pmsg); /* return the address of the message */
102}
103
104/*
105
106*/
107
108/*
109 =============================================================================
110 MBChek() -- check for and conditionally receive a message from a mailbox
111
112 returns NIL if no messages were in the mailbox, or the
113 address of the first (oldest) message in the mailbox,
114 which will be dequeued from the mailbox as if by MBRecv().
115 =============================================================================
116*/
117
118MSG *
119MBChek(pmbox)
120register MBOX *pmbox;
121{
122 register MSG *pmsg;
123
124 if (SMCWait(&pmbox->mail)) { /* try for some mail */
125
126 SMWait(&pmbox->mutex); /* ACQUIRE THE MAILBOX */
127
128 pmsg = pmbox->head; /* get the first message in the queue */
129
130 if (pmbox->head EQ pmbox->tail) { /* only message ? */
131
132 pmbox->head = (MSG *)NIL; /* clear queue head pointer */
133 pmbox->tail = (MSG *)NIL; /* clear queue tail pointer */
134
135 } else {
136
137 pmbox->head = pmsg->next; /* update queue head pointer */
138 }
139
140 pmsg->next = (MSG *)NIL; /* clear next message pointer */
141
142 SMSig(&pmbox->mutex); /* RELEASE THE MAILBOX */
143
144 return(pmsg); /* return the message pointer */
145
146 } else {
147
148 return((MSG *)NIL); /* return -- no mail */
149 }
150}
151
152/*
153
154*/
155
156/*
157 =============================================================================
158 MBDel() -- delete (cancel) a message from a mailbox
159
160 FAILURE unable to find the message
161 SUCCESS message found and deleted from mailbox
162 =============================================================================
163*/
164
165short
166MBDel(pmbox, pmsg)
167register MBOX *pmbox;
168register MSG *pmsg;
169{
170 register MSG *mprv, *mcur;
171
172 if (SMStat(&pmbox->mail) EQ 1) { /* anything in the mailbox ? */
173
174 SMWait(&pmbox->mutex); /* ACQUIRE THE MAILBOX */
175
176 mcur = pmbox->head; /* point at the first message */
177
178 while (TRUE) {
179
180 mprv = mcur; /* previous MSG = current MSG */
181 mcur = mprv->next; /* current MSG = next MSG */
182
183 if (mcur EQ (MSG *)NIL) { /* end of queue ? */
184
185 SMSig(&pmbox->mutex); /* RELEASE MAILBOX */
186
187 return(FAILURE); /* return -- not found */
188 }
189
190 if (mcur EQ pmsg) { /* message we want ? */
191
192 mprv->next = mcur->next; /* dequeue it */
193 mcur->next = (MSG *)NIL; /* ... */
194
195 SMSig(&pmbox->mutex); /* RELEASE MAILBOX */
196
197 return(SUCCESS); /* return -- deleted */
198 }
199 }
200
201 } else {
202
203 return(FAILURE); /* return -- mailbox emtpy */
204 }
205}
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