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/*
* readbuffer.c
*
* A program for reading input from devices which don't like constant
* stopping and starting, such as tape drives. readbuffer is:
* Copyright (C) 1997-1998,2000-2001 Ian Jackson <ian@chiark.greenend.org.uk>
*
* readbuffer is part of chiark backup, a system for backing up GNU/Linux and
* other UN*X-compatible machines, as used on chiark.greenend.org.uk.
* chiark backup is:
* Copyright (C) 1997-1998,2000-2001 Ian Jackson <ian@chiark.greenend.org.uk>
* Copyright (C) 1999 Peter Maydell <pmaydell@chiark.greenend.org.uk>
*
* This is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2,
* or (at your option) any later version.
*
* This is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this file; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/
#include "rwbuffer.h"
const char *progname= "readbuffer";
static size_t waitempty;
int main(int argc, const char *const *argv) {
int r,reading;
startup(argv);
waitempty= (buffersize*1)/4;
reading=1;
maxselfd=2;
while (!seeneof || used) {
FD_ZERO(&readfds);
if (reading) {
if (used<buffersize-1) {
FD_SET(0,&readfds);
} else {
reading=0;
}
}
FD_ZERO(&writefds); if (used) FD_SET(1,&writefds);
callselect();
if (FD_ISSET(0,&readfds)) {
r= read(0,rp,min(buffersize-1-used,buf+buffersize-rp));
if (!r) {
seeneof=1; reading=0;
} else if (r<0) {
if (!(errno == EAGAIN || errno == EINTR)) { perror("read"); exit(1); }
} else {
used+= r;
rp+= r;
if (rp == buf+buffersize) rp=buf;
}
}
if (FD_ISSET(1,&writefds)) {
assert(used);
r= write(1,wp,min(used,buf+buffersize-wp));
if (r<=0) {
if (!(errno == EAGAIN || errno == EINTR)) { perror("write"); exit(1); }
} else {
used-= r;
wp+= r;
if (wp == buf+buffersize) wp=buf;
}
if (used < waitempty && !seeneof) {
reading=1;
}
}
}
exit(0);
}
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