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+/***********************************************************
+Copyright 1991 by Stichting Mathematisch Centrum, Amsterdam, The
+Netherlands.
+
+ All Rights Reserved
+
+Permission to use, copy, modify, and distribute this software and its
+documentation for any purpose and without fee is hereby granted,
+provided that the above copyright notice appear in all copies and that
+both that copyright notice and this permission notice appear in
+supporting documentation, and that the names of Stichting Mathematisch
+Centrum or CWI not be used in advertising or publicity pertaining to
+distribution of the software without specific, written prior permission.
+
+STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
+THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
+FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
+OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+******************************************************************/
+
+/* Asynchronous audio module for Silicon Graphics 4D/20 under IRIX 3.3
+ Copyright 1990 Stichting Mathematisch Centrum, Amsterdam
+ Author: Guido van Rossum, <[email protected]>
+ Last modified: [email protected], Oct 14, 1990
+
+ Callers should #include "asa.h".
+
+ This code is strongly IRIX 3.3 dependent. (Or are sproc() and
+ friends standard SYSV now?)
+
+ Caution: if you put printf's in the slave for debugging, use "-lmpc"
+ to get the semaphore version of stdio!
+
+
+ This file contains two library layers and a test program:
+
+
+ The lower layer implements a simple asynchronous execution facility,
+ built directly on the system calls sproc() and [un]blockproc().
+
+ A slave thread sits in an infinite loop waiting for work assigned to
+ it by the master thread. Work is represented by a function pointer
+ and an argument of type void*. The function returns a void* pointer
+ which is transferred back to the master when it submits the next bit
+ of work. Submitting a NULL function pointer can be used by the
+ master to wait for completion of the previous work. This lower
+ layer could be generally useful, but is currently implemented by
+ static functions, for exclusive by the asynchronous audio layer.
+
+
+ The higher layer implements an asynchronous interface to the
+ /dev/audio device on the Silicon Graphics 4D/20. It defines the
+ following functions:
+
+ int asa_init()
+ Required initialization function. The other functions will call
+ abort() when they are called before asa_init(). It creates the
+ slave process and returns a file descriptor for the audio
+ device which can be used to set the sampling rate and output
+ gain, etc. It prints a message to stderr and returns -1 if the
+ initialization failed. Calling this function more than onece is
+ harmless.
+
+ void asa_start_read(char *buf, int len)
+ Starts an asynchronous read call on the audio device. This
+ waits for completion of the previous request, if any.
+
+ void asa_start_write(char *buf, int len)
+ Starts an asynchronous write call on the audio device. This
+ waits for completion of the previous request, if any.
+
+ int asa_poll()
+ Polls whether the last asynchronous read or write request is
+ finished. Returns -1 if no request was queued, 0 if the request
+ is not yet finished, and 1 if it is finished.
+
+ int asa_wait()
+ Waits for completion if the last asynchronous read or write
+ request. It returns the result of the read or write request,
+ and sets the error code to the error code set by the request if
+ the result is -1. If no request was queued, this also returns
+ -1 but leaves the error code unchanged. Note: to get the error
+ code, don't inspect the global variable errno but call the
+ function oserror().
+
+ int asa_cancel()
+ Cancels the last asynchronous read or write request (by sending
+ the slave thread a signal for which it has a handler) then
+ returns its result and error code as asa_wait().
+
+ void asa_done()
+ Kills the slave process and closes the audio device. After
+ this, if further use of the module is required, asa_init()
+ should be called again. Calling this function when asa_init()
+ has not been called is harmless.
+
+
+ Finally, this file contains a simple test program that is compiled if
+ MAIN is defined (e.g., compile with cc -DMAIN). It makes a recording
+ and plays it back. The user must indicate begin and end of recording
+ and play-back by pressing the Return key.
+*/
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <sys/types.h>
+#include <sys/prctl.h>
+
+#include "asa.h"
+
+
+/* Asynchronous execution facility (lower layer) */
+
+
+/* Signal used to cancel requests in progress */
+#define MYSIG SIGUSR1
+
+/* Respective process IDs */
+static pid_t master_pid = -1;
+static pid_t slave_pid = -1;
+
+/* Work and result "queue" (1 element) */
+static void * (*work_func)();
+static void *work_arg;
+static void *work_result;
+
+/* Signal handler for MYSIG -- interrupts read or write system call */
+
+/*ARGSUSED*/
+static void
+handler(sig)
+ int sig;
+{
+ /* Reinstate the handler (non-BSD signal semantics) */
+ signal(sig, handler);
+}
+
+/* Subroutine to fiddle signals */
+
+static void
+dosig(sig)
+ int sig;
+{
+ if (signal(sig, SIG_IGN) != SIG_IGN)
+ signal(sig, SIG_DFL);
+}
+
+/* Slave control flow */
+
+/*ARGSUSED*/
+static void
+slave(arg)
+ void *arg;
+{
+ void * (*func)();
+ void *arg;
+ void *result;
+
+ /* Reset signal handlers that interactive programs often catch.
+ The assumption is that if the master has a handler for these
+ signals, it will be a cleanup function. The slave must die
+ from these. */
+ dosig(SIGHUP);
+ dosig(SIGQUIT);
+ dosig(SIGTERM);
+ dosig(SIGPIPE);
+
+ /* Ignore SIGINT if caught or ignored */
+ if (signal(SIGINT, SIG_IGN) == SIG_DFL)
+ signal(SIGINT, SIG_DFL);
+
+ /* Let the handler install itself */
+ handler(MYSIG);
+
+ /* Set slave_pid. This is also done in the master thread, but
+ there is a race condition whereby the slave begins execution
+ before the master has assigned the result of sproc() to
+ slave_pid. So we set it here as well -- since this sets the
+ same value it should be OK. */
+ slave_pid = getpid();
+
+ /* Set the dummy result returned by the first rendezvous */
+ result = NULL;
+
+ /* Loop forever, waiting for and executing work */
+ for (;;) {
+ /* First rendezvous: store previous result */
+ if (blockproc(slave_pid) < 0)
+ perror("slave: [result] blockproc(slave_pid)");
+ work_result = result;
+ if (unblockproc(master_pid) < 0)
+ perror("slave: [result] unblockproc(master_pid)");
+
+ /* Second rendezvous: fetch work */
+ if (blockproc(slave_pid) < 0)
+ perror("slave: [func,arg] blockproc(slave_pid)");
+ func = work_func;
+ arg = work_arg;
+ if (unblockproc(master_pid) < 0)
+ perror("slave: [func,arg] unblockproc(master_pid)");
+
+ /* Execute work, computing new result */
+ if (func == NULL) {
+ result = arg;
+ }
+ else {
+ result = (*func)(arg);
+ }
+ }
+}
+
+static int
+slave_init()
+{
+ if (slave_pid > 0)
+ return slave_pid;
+ master_pid = getpid();
+
+ /* Reset the queue, in case this is a re-init after asa_done() */
+ work_result = NULL;
+ work_func = NULL;
+ work_arg = NULL;
+
+ /* Create the slave process, sharing all segments and properties */
+ slave_pid = sproc(slave, PR_SALL, (char *)NULL);
+ if (slave_pid < 0)
+ perror("slave_init: sproc(slave, PR_SALL, NULL)");
+
+ /* Set up initial conditions---tricky!
+ Both the master and the slave start with one credit, since
+ both the result slot and the work/func slots are initially
+ free.
+ Note that we use setblockproccnt() for the master so a
+ possible indeterminate semaphore value caused by a previous
+ asa_done() at an unfortunate moment doesn't harm us.
+ */
+ setblockproccnt(master_pid, 1);
+ unblockproc(slave_pid);
+
+ return slave_pid;
+}
+
+static void
+slave_done()
+{
+ if (slave_pid > 0) {
+ if (kill(slave_pid, SIGKILL) < 0)
+ perror("slave_done: kill(slave_pid, SIGKILL)");
+ }
+ slave_pid = -1;
+}
+
+/* Queue new work and return result of previous work */
+
+static void *
+rendezvous(func, arg)
+ void * (*func)();
+ void *arg;
+{
+ void *result;
+
+ if (slave_pid <= 0)
+ abort(); /* Illegal call: not initialized properly */
+
+ /* First rendezvous: store new work */
+ if (blockproc(master_pid) < 0)
+ perror("rendezvous: [func,arg] blockproc(master_pid)");
+ work_func = func;
+ work_arg = arg;
+ if (unblockproc(slave_pid) < 0)
+ perror("rendezvous: [func,arg] unblockproc(slave_pid)");
+
+ /* Second rendezvous: fetch previous result */
+ if (blockproc(master_pid) < 0)
+ perror("rendezvous: [result] blockproc(master_pid)");
+ result = work_result;
+ if (unblockproc(slave_pid) < 0)
+ perror("rendezvous: [result] unblockproc(slave_pid)");
+
+ return result;
+}
+
+
+/* Asynchronous audio interface (higher layer) */
+
+
+int audio_fd = -1; /* File descriptor -- not initialized yet */
+
+static struct queue {
+ int func; /* 0 = read, 1 = write */
+ char *buf;
+ int len;
+ int result;
+ int error;
+} queue[2];
+
+static int qindex = 0;
+
+int
+asa_init()
+{
+ int fd;
+ char *p;
+
+ if (audio_fd >= 0)
+ return audio_fd;
+ fd = open("/dev/audio", 2);
+ if (fd < 0) {
+ perror("asa_init: Can't open /dev/audio");
+ return -1;
+ }
+ if (slave_init() < 0) {
+ perror("asa_init: Can't create slave process");
+ close(fd);
+ return -1;
+ }
+ audio_fd = fd;
+ return fd;
+}
+
+void
+asa_done()
+{
+ slave_done();
+ if (audio_fd >= 0) {
+ if (close(audio_fd) < 0)
+ perror("asa_done: close(audio_fd)");
+ }
+ audio_fd = -1;
+}
+
+static void *
+runjob(arg)
+ void *arg;
+{
+ extern int errno;
+ struct queue *q = (struct queue *)arg;
+ char *buf = q->buf;
+ int len = q->len;
+ int n = 0;
+
+ if (q->func == 0)
+ n = read(audio_fd, buf, len);
+ else
+ n = write(audio_fd, buf, len);
+ if (q->func == 0 && n >= 0) {
+ while (--len >= n && buf[len] == '\0')
+ ;
+ n = len+1;
+ }
+ q->result = n;
+ q->error = oserror();
+ return arg;
+}
+
+static void
+startjob(func, buf, len)
+ int func;
+ char *buf;
+ int len;
+{
+ struct queue *q;
+
+ q = &queue[qindex];
+ qindex = (qindex+1) & 1;
+ q->func = func;
+ q->buf = buf;
+ q->len = len;
+ (void) rendezvous(runjob, (void *)q);
+}
+
+void
+asa_start_read(buf, len)
+ char *buf;
+ int len;
+{
+ memset(buf, '\0', len);
+ startjob(0, buf, len);
+}
+
+void
+asa_start_write(buf, len)
+ char *buf;
+ int len;
+{
+ startjob(1, buf, len);
+}
+
+int
+asa_wait()
+{
+ struct queue *q;
+
+ q = (struct queue *) rendezvous((void*(*)())NULL, (void *)NULL);
+ if (q == NULL) {
+ setoserror(0);
+ return -1; /* No work was queued */
+ }
+ setoserror(q->error);
+ return q->result;
+}
+
+int
+asa_poll()
+{
+ int err;
+
+ err = prctl(PR_ISBLOCKED, slave_pid);
+ if (err < 0) {
+ perror("prctl(PR_ISBLOCKED, slave_pid)");
+ return -1;
+ }
+ else if (err == 0)
+ return 0;
+ else if (work_result == NULL) {
+ setoserror(0);
+ return -1;
+ }
+ else
+ return 1;
+}
+
+int
+asa_cancel()
+{
+ int result;
+
+ kill(slave_pid, MYSIG);
+ result = asa_wait();
+ return result;
+}
+
+
+#ifdef MAIN
+
+/* Test program */
+
+#include <sys/audio.h>
+
+main()
+{
+ static char buf[10*16*1024]; /* 10 seconds of sound at 16K/sec */
+ int n;
+ int afd;
+
+ if ((afd = asa_init()) < 0)
+ exit(1);
+ ioctl(afd, AUDIOCSETRATE, 3);
+ ioctl(afd, AUDIOCSETOUTGAIN, 0);
+ printf("Poll returns %d\n", asa_poll());
+ go("Hit enter to start recording:\n");
+ asa_start_read(buf, sizeof buf);
+ go("Hit enter to stop recording:\n");
+ /*printf("Poll returns %d\n", asa_poll());*/
+ n = asa_cancel();
+ if (n < 0)
+ perror("Read failed");
+ else {
+ printf("Got %d bytes\n", n);
+ printf("Poll returns %d\n", asa_poll());
+ go("Hit enter to start playing:\n");
+ ioctl(afd, AUDIOCSETOUTGAIN, 50);
+ asa_start_write(buf, n);
+ go("Hit enter to stop playing:\n");
+ printf("Poll returns %d\n", asa_poll());
+ n = asa_cancel();
+ if (n < 0)
+ perror("Write failed");
+ else
+ printf("Stopped at %d bytes\n", n);
+ }
+ ioctl(afd, AUDIOCSETOUTGAIN, 0);
+ asa_done();
+ exit(n < 0 ? 1 : 0);
+}
+
+go(str)
+ char *str;
+{
+ char line[100];
+
+ sleep(1);
+ fputs(str, stdout);
+ fflush(stdout);
+ fgets(line, sizeof line, stdin);
+}
+
+#endif /* MAIN */