Date: Fri, 26 Dec 1997 11:57:19 -0800 From: Amancio Hasty <hasty@rah.star-gate.com> To: multimedia@freebsd.org Cc: Randall Hopper <rhh@ct.picker.com> Subject: async i/o code example for -current Message-ID: <199712261957.LAA01833@rah.star-gate.com>
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I asked Dyson to repost his aio example and he didn't so I dig up his
old posting.
This is useful for applications such as fxtv when is recording to disk.
Cheers,
Amancio
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From: "John S. Dyson" <toor@dyson.iquest.net>
Message-Id: <199712011926.OAA00376@dyson.iquest.net>
Subject: FYI: usage of new AIO calls
To: current@FreeBSD.ORG
Date: Mon, 1 Dec 1997 14:26:34 -0500 (EST)
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For fun (and actually as a result of a comment by Justin Gibbs), I have put
together a small program that could maybe be used for streaming tape drives
using the new AIO code. Note that if you try this, it must be used only
on current kernels on/after 19:00 GMT, Dec 1.
This code is NOT pretty, but does show example usage. The code will
likely have problems on SMP kernels (unless you are writing to a VCHR
device.)
- --
John
dyson@freebsd.org
jdyson@nc.com
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/fcntl.h>
#include <sys/time.h>
#include <sys/errno.h>
#include <sys/aio.h>
#include <sys/syscall.h>
#define NBUFS 16
#define BUFSZ (1024*64)
struct aiocb *olist[NBUFS];
void *bufaddrs[NBUFS];
int activeflags[NBUFS];
int nactive;
int eof;
int
main( int argc, char *argv[]) {
int i;
int fd1, fd2;
off_t curptr;
int nread;
int rtval;
int errval;
if (argc != 2) {
fprintf(stderr, "usage: fcp destfile");
exit(0);
}
fd1 = 0;
fd2 = open(argv[1], O_RDWR|O_CREAT|O_TRUNC, 0666);
if (fd2 == -1) {
perror(argv[1]);
exit(1);
}
for(i=0;i<NBUFS;i++) {
olist[i] = malloc(sizeof (struct aiocb));
bzero(olist[i], sizeof (struct aiocb));
bufaddrs[i] = malloc(BUFSZ);
activeflags[i] = 0;
}
nactive = 0;
curptr = 0;
eof = 0;
while ((eof == 0) || (nactive > 0)) {
if ((eof && (nactive > 0)) || (nactive == NBUFS)) {
for (i = 0; i < NBUFS; i++ ) {
if (activeflags[i]) {
errval = aio_suspend(&olist[i], 1, NULL);
if (errval) {
perror("aio_suspend");
exit(1);
}
break;
}
}
}
if (nactive > 0) {
for (i = 0; i < NBUFS; i++) {
if (activeflags[i] == 0)
continue;
errval = aio_error(olist[i]);
if (errval) {
if (errval == EINPROGRESS)
continue;
perror("aio_error1");
exit(1);
}
activeflags[i] = 0;
--nactive;
rtval = aio_return(olist[i]);
if (rtval != olist[i]->aio_nbytes) {
perror("buffer not fully written");
exit(1);
}
}
}
for (i = 0;
((eof == 0) && (nactive < NBUFS) && (i < NBUFS));
i++) {
if (activeflags[i] == 0) {
nread = read( fd1, bufaddrs[i], BUFSZ);
if (nread == 0) {
eof = 1;
break;
}
if (nread == -1) {
perror("read");
exit(1);
}
olist[i]->aio_offset = curptr;
curptr += nread;
olist[i]->aio_nbytes = nread;
olist[i]->aio_fildes = fd2;
olist[i]->aio_buf = bufaddrs[i];
errval = aio_write(olist[i]);
activeflags[i] = 1;
nactive++;
if (errval) {
perror("aio_write");
exit(1);
}
}
}
}
}
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