prepare transition to poll()

usage of select() is inefficient (because a huge fd_set array has to
be initialized on each call) and insecure (because an fd >= FD_SETSIZE
will cause out-of-bounds accesses using the FD_*SET macros, and a system
can be set up to allow more than that number of fds using ulimit).
for the moment we prepared a poll-like wrapper that still runs select()
to test for regressions, and so we have fallback code for systems without
poll().

1 files changed, 42 insertions, 0 deletions

diff --git a/src/mypoll.c b/src/mypoll.c
new file mode 100644
index 0000000..0e06805
--- /dev/null
+++ b/src/mypoll.c
@@ -0,0 +1,42 @@
+#include "mypoll.h"
+
+#define MYPOLL_READ (1<<1)
+#define MYPOLL_WRITE (1<<2)
+
+int mypoll(pollfd_struct* fds, int nfds, int timeout) {
+	fd_set rset, wset, *r=0, *w=0;
+	int i, ret, maxfd=-1;
+	struct timeval tv = {0}, *t = 0;
+
+	for(i=0; i<nfds; ++i) {
+		if(fds[i].events & MYPOLL_READ) r = &rset;
+		if(fds[i].events & MYPOLL_WRITE) w = &wset;
+		if(r && w) break;
+	}
+	if(r) FD_ZERO(r);
+	if(w) FD_ZERO(w);
+	for(i=0; i<nfds; ++i) {
+		if(fds[i].fd > maxfd) maxfd = fds[i].fd;
+		if(fds[i].events & MYPOLL_READ) FD_SET(fds[i].fd, r);
+		if(fds[i].events & MYPOLL_WRITE) FD_SET(fds[i].fd, w);
+	}
+
+	if(timeout >= 0) t = &tv;
+	if(timeout > 0) tv.tv_sec = timeout;
+
+	ret = select(maxfd+1, r, w, 0, t);
+
+	switch(ret) {
+		case -1:
+		case 0:
+			return ret;
+	}
+
+	for(i=0; i<nfds; ++i) {
+		fds[i].revents = 0;
+		if(r && FD_ISSET(fds[i].fd, r)) fds[i].revents |= MYPOLL_READ;
+		if(w && FD_ISSET(fds[i].fd, w)) fds[i].revents |= MYPOLL_WRITE;
+	}
+	return ret;
+}
+