4 * A program for reading input from devices which don't like constant
5 * stopping and starting, such as tape drives. readbuffer is:
6 * Copyright (C) 1997-1998,2000-2001 Ian Jackson <ian@chiark.greenend.org.uk>
8 * readbuffer is part of chiark backup, a system for backing up GNU/Linux and
9 * other UN*X-compatible machines, as used on chiark.greenend.org.uk.
11 * Copyright (C) 1997-1998,2000-2001 Ian Jackson <ian@chiark.greenend.org.uk>
12 * Copyright (C) 1999 Peter Maydell <pmaydell@chiark.greenend.org.uk>
14 * This is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU General Public License as
16 * published by the Free Software Foundation; either version 2,
17 * or (at your option) any later version.
19 * This is distributed in the hope that it will be useful, but
20 * WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU General Public License for more details.
24 * You should have received a copy of the GNU General Public
25 * License along with this file; if not, write to the Free Software
26 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
31 #include <sys/types.h>
39 #ifndef RWBUFFER_SIZE_MB
40 #define RWBUFFER_SIZE_MB 16
43 #define BUFFER (RWBUFFER_SIZE_MB*1024*1024)
44 #define WAITEMPTY ((BUFFER*1)/4)
46 static inline int min(int a, int b) { return a<=b ? a : b; }
48 static void nonblock(int fd) {
50 r= fcntl(fd,F_GETFL,0); if (r == -1) { perror("fcntl getfl"); exit(1); }
52 if (fcntl(fd,F_SETFL,r) == -1) { perror("fcntl setfl"); exit(1); }
55 int main(int argc, const char *const *argv) {
56 static unsigned char buf[BUFFER];
58 unsigned char *wp, *rp;
59 int used,r,reading,seeneof;
63 used=0; wp=rp=buf; reading=1; seeneof=0;
64 nonblock(0); nonblock(1);
66 if (argv[1] && !strcmp(argv[1],"--mlock")) {
67 if (mlock(buf,sizeof(buf))) { perror("mlock"); exit(1); }
70 if (argv[1]) { fputs("usage: readbuffer [--mlock]\n",stderr); exit(1); }
72 while (!seeneof || used) {
78 /*fprintf(stderr,"\t buffers full - stopping\n");*/
82 FD_ZERO(&writefds); if (used) FD_SET(1,&writefds);
83 /*fprintf(stderr,"used %6d reading %d seeneof %d wp %8lx rp %8lx read %d write %d\n",
84 used,reading,seeneof,(unsigned long)(wp-buf),(unsigned long)(rp-buf),
85 FD_ISSET(0,&readfds),FD_ISSET(1,&writefds));*/
86 r= select(2,&readfds,&writefds,0,0);
87 /*fprintf(stderr,"\t readable %d writeable %d\n",
88 FD_ISSET(0,&readfds),FD_ISSET(1,&writefds));*/
90 if (errno == EINTR) continue;
91 perror("select"); exit(1);
93 if (FD_ISSET(0,&readfds)) {
94 r= read(0,rp,min(BUFFER-1-used,buf+BUFFER-rp));
96 /*fprintf(stderr,"\t eof detected\n");*/
99 if (!(errno == EAGAIN || errno == EINTR)) { perror("read"); exit(1); }
100 /*fprintf(stderr,"\t read transient error\n");*/
102 /*fprintf(stderr,"\t read %d\n",r);*/
105 if (rp == buf+BUFFER) rp=buf;
108 if (FD_ISSET(1,&writefds)) {
110 r= write(1,wp,min(used,buf+BUFFER-wp));
112 if (!(errno == EAGAIN || errno == EINTR)) { perror("write"); exit(1); }
113 /*fprintf(stderr,"\t write transient error\n");*/
115 /*fprintf(stderr,"\t wrote %d\n",r);*/
118 if (wp == buf+BUFFER) wp=buf;
120 if (used < WAITEMPTY && !seeneof) {
121 /*fprintf(stderr,"\t starting writes\n");*/