feat(select): poll/select and fd_set

src/select/select.c

@@ -0,0 +1,38 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <sys/select.h>
+
+#include <errno.h>
+
+#include "../internal/syscall.h"
+
+/*
+ * select: plain POSIX select over SYS_pselect6. The kernel wants a struct
+ * timespec, so the struct timeval timeout is converted here (NULL passes
+ * through as "block indefinitely") and the sigset pair stays NULL: select
+ * never changes the signal mask. select() and pselect() share this syscall
+ * on Linux; the 6th argument of pselect6 is a { sigset_t *, size_t } pair
+ * pointer that is NULL when the mask is left alone.
+ */
+int
+select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout)
+{
+    struct timespec ts;
+    struct timespec *tsp = NULL;
+
+    if (timeout != NULL)
+    {
+        if (timeout->tv_sec < 0 || timeout->tv_usec < 0 || timeout->tv_usec >= 1000000L)
+        {
+            errno = EINVAL;
+            return -1;
+        }
+        ts.tv_sec = timeout->tv_sec;
+        ts.tv_nsec = (long)timeout->tv_usec * 1000;
+        tsp = &ts;
+    }
+    return syscall_ret(__syscall6(SYS_pselect6, (long)nfds, (long)readfds, (long)writefds,
+                                  (long)exceptfds, (long)tsp, 0L));
+}