diff --git a/headers/posix/sys/select.h b/headers/posix/sys/select.h
index e55afb01c1..c3208e2a35 100644
--- a/headers/posix/sys/select.h
+++ b/headers/posix/sys/select.h
@@ -1,50 +1,59 @@
-/* select.h */
-
 #ifndef _SYS_SELECT_H
 #define _SYS_SELECT_H
+/* 
+** Distributed under the terms of the OpenBeOS License.
+*/
 
-#include <sys/time.h> /* for struct timeval */
-/*
- * You can define your own FDSETSIZE if you want more bits
+#include <sys/time.h>
+
+
+/* If FD_SET is already defined, only the select() prototype is
+ * exported in this header.
  */
+#ifndef FD_SET
 
+/* You can define your own FDSETSIZE if you need more bits - but
+ * it should be enough for most uses.
+ */
 #ifndef FD_SETSIZE
-#define FD_SETSIZE 1024
-#endif /* FD_SETSIZE */
+#	define FD_SETSIZE 1024
+#endif
 
-/* compatability with BSD */
-#define NBBY    8               /* number of bits in a byte */
+/* Compatibily only: use FD_SETSIZE instead */
+#ifndef FDSETSIZE
+#	define FDSETSIZE FD_SETSIZE
+#endif
+
+/* compatibility with BSD */
+#define NBBY	8	/* number of bits in a byte */
 
 typedef unsigned long fd_mask;
 
 #ifndef howmany
-#define howmany(x, y)   (((x) + ((y) - 1)) / (y))
+#	define howmany(x, y) (((x) + ((y) - 1)) / (y))
 #endif
 
-/*
- * Compatibily only: use FD_SETSIZE instead
- */
-#ifndef FDSETSIZE
-#define FDSETSIZE FD_SETSIZE
-#endif /* FDSETSIZE */
-
-#define NFDBITS 32
+#define NFDBITS (sizeof(fd_mask) * NBBY)
 
 typedef struct fd_set {
-	unsigned mask[FDSETSIZE / NFDBITS];
+	fd_mask bits[howmany(FD_SETSIZE, NFDBITS)];
 } fd_set;
 
-#define _FDMSKNO(fd) ((fd) / NFDBITS)
-#define _FDBITNO(fd) ((fd) % NFDBITS)
+#define _FD_BITSINDEX(fd) ((fd) / NFDBITS)
+#define _FD_BIT(fd) (1L << ((fd) % NFDBITS))
 
-#define FD_ZERO(setp) memset((setp)->mask, 0, sizeof((setp)->mask))
-#define FD_SET(fd, setp) ((setp)->mask[_FDMSKNO(fd)] |= (1 << (_FDBITNO(fd))))
-#define FD_CLR(fd, setp) ((setp)->mask[_FDMSKNO(fd)] &= ~(1 << (_FDBITNO(fd))))
-#define FD_ISSET(fd, setp) ((setp)->mask[_FDMSKNO(fd)] & (1 << (_FDBITNO(fd))))
+#define FD_ZERO(set) memset((set), 0, sizeof(fd_set))
+#define FD_SET(fd, set) ((set)->bits[_FD_BITSINDEX(fd)] |= _FD_BIT(fd))
+#define FD_CLR(fd, set) ((set)->bits[_FD_BITSINDEX(fd)] &= ~_FD_BIT(fd))
+#define FD_ISSET(fd, set) ((set)->bits[_FD_BITSINDEX(fd)] & _FD_BIT(fd))
 
-int select(int nbits, struct fd_set *rbits, 
-                      struct fd_set *wbits, 
-                      struct fd_set *ebits, 
-                      struct timeval *timeout);
+#endif	/* FD_SET */
 
-#endif /* _SYS_SELECT_H */
+extern
+#ifdef __cplusplus
+"C"
+#endif
+int select(int nbits, struct fd_set *rbits, struct fd_set *wbits, 
+		struct fd_set *ebits, struct timeval *timeout);
+
+#endif	/* _SYS_SELECT_H */