12 #define BUFFER 16*1024*1024
13 #define WAITEMPTY ((BUFFER*1)/4)
15 static inline int min(int a, int b) { return a<=b ? a : b; }
17 static void nonblock(int fd) {
19 r= fcntl(fd,F_GETFL,0); if (r == -1) { perror("fcntl getfl"); exit(1); }
21 if (fcntl(fd,F_SETFL,r) == -1) { perror("fcntl setfl"); exit(1); }
24 int main(int argc, const char *const *argv) {
25 static unsigned char buf[BUFFER];
27 unsigned char *wp, *rp;
28 int used,r,reading,seeneof;
32 used=0; wp=rp=buf; reading=1; seeneof=0;
33 nonblock(0); nonblock(1);
34 if (argv[1] && !strcmp(argv[1],"--mlock")) {
35 if (mlock(buf,sizeof(buf))) { perror("mlock"); exit(1); }
38 if (argv[1]) { fputs("usage: readbuffer [--mlock]\n",stderr); exit(1); }
39 while (!seeneof || used) {
45 /*fprintf(stderr,"\t buffers full - stopping\n");*/
49 FD_ZERO(&writefds); if (used) FD_SET(1,&writefds);
50 /*fprintf(stderr,"used %6d reading %d seeneof %d wp %8lx rp %8lx read %d write %d\n",
51 used,reading,seeneof,(unsigned long)(wp-buf),(unsigned long)(rp-buf),
52 FD_ISSET(0,&readfds),FD_ISSET(1,&writefds));*/
53 r= select(2,&readfds,&writefds,0,0);
54 /*fprintf(stderr,"\t readable %d writeable %d\n",
55 FD_ISSET(0,&readfds),FD_ISSET(1,&writefds));*/
57 if (errno == EINTR) continue;
58 perror("select"); exit(1);
60 if (FD_ISSET(0,&readfds)) {
61 r= read(0,rp,min(BUFFER-1-used,buf+BUFFER-rp));
63 /*fprintf(stderr,"\t eof detected\n");*/
66 if (!(errno == EAGAIN || errno == EINTR)) { perror("read"); exit(1); }
67 /*fprintf(stderr,"\t read transient error\n");*/
69 /*fprintf(stderr,"\t read %d\n",r);*/
72 if (rp == buf+BUFFER) rp=buf;
75 if (FD_ISSET(1,&writefds)) {
77 r= write(1,wp,min(used,buf+BUFFER-wp));
79 if (!(errno == EAGAIN || errno == EINTR)) { perror("write"); exit(1); }
80 /*fprintf(stderr,"\t write transient error\n");*/
82 /*fprintf(stderr,"\t wrote %d\n",r);*/
85 if (wp == buf+BUFFER) wp=buf;
87 if (used < WAITEMPTY && !seeneof) {
88 /*fprintf(stderr,"\t starting writes\n");*/