/*
* readbuffer.c
*
- * Copyright (C) 1997,1998 Ian Jackson <ian@chiark.greenend.org.uk>
+ * 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
#include <errno.h>
#include <unistd.h>
-#define BUFFER 16*1024*1024
-#define WAITEMPTY ((BUFFER*1)/4)
+#include "rwbuffer.h"
-static inline int min(int a, int b) { return a<=b ? a : b; }
+const char *progname= "readbuffer";
-static void nonblock(int fd) {
- int r;
- r= fcntl(fd,F_GETFL,0); if (r == -1) { perror("fcntl getfl"); exit(1); }
- r |= O_NDELAY;
- if (fcntl(fd,F_SETFL,r) == -1) { perror("fcntl setfl"); exit(1); }
-}
+static size_t waitempty;
int main(int argc, const char *const *argv) {
- static unsigned char buf[BUFFER];
-
- unsigned char *wp, *rp;
- int used,r,reading,seeneof;
- fd_set readfds;
- fd_set writefds;
-
- used=0; wp=rp=buf; reading=1; seeneof=0;
- nonblock(0); nonblock(1);
-
- if (argv[1] && !strcmp(argv[1],"--mlock")) {
- if (mlock(buf,sizeof(buf))) { perror("mlock"); exit(1); }
- argv++; argc--;
- }
- if (argv[1]) { fputs("usage: readbuffer [--mlock]\n",stderr); exit(1); }
+ int r,reading;
+ startup(argv);
+ waitempty= (buffersize*1)/4;
+ reading=1;
+
while (!seeneof || used) {
+
FD_ZERO(&readfds);
if (reading) {
- if (used<BUFFER-1) {
+ if (used<buffersize-1) {
FD_SET(0,&readfds);
} else {
-/*fprintf(stderr,"\t buffers full - stopping\n");*/
reading=0;
}
}
FD_ZERO(&writefds); if (used) FD_SET(1,&writefds);
-/*fprintf(stderr,"used %6d reading %d seeneof %d wp %8lx rp %8lx read %d write %d\n",
- used,reading,seeneof,(unsigned long)(wp-buf),(unsigned long)(rp-buf),
- FD_ISSET(0,&readfds),FD_ISSET(1,&writefds));*/
- r= select(2,&readfds,&writefds,0,0);
-/*fprintf(stderr,"\t readable %d writeable %d\n",
- FD_ISSET(0,&readfds),FD_ISSET(1,&writefds));*/
- if (r == -1) {
- if (errno == EINTR) continue;
- perror("select"); exit(1);
- }
+
+ callselect();
+
if (FD_ISSET(0,&readfds)) {
- r= read(0,rp,min(BUFFER-1-used,buf+BUFFER-rp));
+ r= read(0,rp,min(buffersize-1-used,buf+buffersize-rp));
if (!r) {
-/*fprintf(stderr,"\t eof detected\n");*/
seeneof=1; reading=0;
} else if (r<0) {
if (!(errno == EAGAIN || errno == EINTR)) { perror("read"); exit(1); }
-/*fprintf(stderr,"\t read transient error\n");*/
} else {
-/*fprintf(stderr,"\t read %d\n",r);*/
used+= r;
rp+= r;
- if (rp == buf+BUFFER) rp=buf;
+ if (rp == buf+buffersize) rp=buf;
}
}
+
if (FD_ISSET(1,&writefds)) {
assert(used);
- r= write(1,wp,min(used,buf+BUFFER-wp));
+ r= write(1,wp,min(used,buf+buffersize-wp));
if (r<=0) {
if (!(errno == EAGAIN || errno == EINTR)) { perror("write"); exit(1); }
-/*fprintf(stderr,"\t write transient error\n");*/
} else {
-/*fprintf(stderr,"\t wrote %d\n",r);*/
used-= r;
wp+= r;
- if (wp == buf+BUFFER) wp=buf;
+ if (wp == buf+buffersize) wp=buf;
}
- if (used < WAITEMPTY && !seeneof) {
-/*fprintf(stderr,"\t starting writes\n");*/
+ if (used < waitempty && !seeneof) {
reading=1;
}
}