1 files changed, 90 insertions, 0 deletions
diff --git a/otherlibs/unix/select.c b/otherlibs/unix/select.c
new file mode 100644
index 000000000..7015cdb75
--- /dev/null
+++ b/otherlibs/unix/select.c
@@ -0,0 +1,90 @@
+#include <mlvalues.h>
+#include <alloc.h>
+#include <memory.h>
+#include "unix.h"
+
+#ifdef HAS_SELECT
+
+#include <sys/types.h>
+#include <sys/time.h>
+
+#ifdef FD_ISSET
+typedef fd_set file_descr_set;
+#else
+typedef int file_descr_set;
+#define FD_SETSIZE (sizeof(int) * 8)
+#define FD_SET(fd,fds) (*(fds) |= 1 << (fd))
+#define FD_CLR(fd,fds) (*(fds) &= ~(1 << (fd)))
+#define FD_ISSET(fd,fds) (*(fds) & (1 << (fd)))
+#define FD_ZERO(fds) (*(fds) = 0)
+#endif
+
+static void fdlist_to_fdset(fdlist, fdset)
+     value fdlist;
+     file_descr_set * fdset;
+{
+  value l;
+  FD_ZERO(fdset);
+  for (l = fdlist; Tag_val(l) == 1; l = Field(l, 1)) {
+    FD_SET(Int_val(Field(l, 0)), fdset);
+  }
+}
+
+static value fdset_to_fdlist(fdset)
+     file_descr_set * fdset;
+{
+  int i;
+  Push_roots(roots, 1)
+#define res roots[0]
+  res = Atom(0);
+  for (i = FD_SETSIZE - 1; i >= 0; i--) {
+    if (FD_ISSET(i, fdset)) {
+      value newres = alloc(2, 1);
+      Field(newres, 0) = Val_int(i);
+      Field(newres, 1) = res;
+      res = newres;
+    }
+  }
+  Pop_roots();
+  return res;
+#undef res
+}
+
+value unix_select(readfds, writefds, exceptfds, timeout) /* ML */
+     value readfds, writefds, exceptfds, timeout;
+{
+  file_descr_set read, write, except;
+  double tm;
+  struct timeval tv;
+  struct timeval * tvp;
+  int retcode;
+  Push_roots(roots, 1)
+#define res roots[0]
+
+  fdlist_to_fdset(readfds, &read);
+  fdlist_to_fdset(writefds, &write);
+  fdlist_to_fdset(exceptfds, &except);
+  tm = Double_val(timeout);
+  if (tm < 0.0)
+    tvp = (struct timeval *) NULL;
+  else {
+    tv.tv_sec = (int) tm;
+    tv.tv_usec = (int) (1e6 * (tm - (int) tm));
+    tvp = &tv;
+  }
+  retcode = select(FD_SETSIZE, &read, &write, &except, tvp);
+  if (retcode == -1) uerror("select", Nothing);
+  res = alloc_tuple(3);
+  Field(res, 0) = fdset_to_fdlist(&read);
+  Field(res, 1) = fdset_to_fdlist(&write);
+  Field(res, 2) = fdset_to_fdlist(&except);
+  Pop_roots();
+  return res;
+#undef res
+}
+
+#else
+
+value unix_select() { invalid_argument("select not implemented"); }
+
+#endif