net: socket: Split select-related declaration to separate header

select() is a rather peculiar construct, defining/depending on many
types and symbols. Making that to coexist with POSIX subsystem is
an ongoing challange. To facilitate that, let's split those
definitions to a separate header (which e.g. can be included without
including all the rest of socket defines).

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>

include/net/socket_select.h

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2019 Linaro Limited
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_INCLUDE_NET_SOCKET_SELECT_H_
+#define ZEPHYR_INCLUDE_NET_SOCKET_SELECT_H_
+
+#include <zephyr/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct zsock_timeval {
+	/* Using longs, as many (?) implementations seem to use it. */
+	long tv_sec;
+	long tv_usec;
+};
+
+typedef struct zsock_fd_set {
+	u32_t bitset[(CONFIG_POSIX_MAX_FDS + 31) / 32];
+} zsock_fd_set;
+
+/* select() API is inefficient, and implemented as inefficient wrapper on
+ * top of poll(). Avoid select(), use poll directly().
+ */
+int zsock_select(int nfds, zsock_fd_set *readfds, zsock_fd_set *writefds,
+		 zsock_fd_set *exceptfds, struct zsock_timeval *timeout);
+
+#define ZSOCK_FD_SETSIZE (sizeof(((zsock_fd_set *)0)->bitset) * 8)
+
+void ZSOCK_FD_ZERO(zsock_fd_set *set);
+int ZSOCK_FD_ISSET(int fd, zsock_fd_set *set);
+void ZSOCK_FD_CLR(int fd, zsock_fd_set *set);
+void ZSOCK_FD_SET(int fd, zsock_fd_set *set);
+
+#ifdef CONFIG_NET_SOCKETS_POSIX_NAMES
+
+#define fd_set zsock_fd_set
+#define timeval zsock_timeval
+#define FD_SETSIZE ZSOCK_FD_SETSIZE
+
+static inline int select(int nfds, zsock_fd_set *readfds,
+			 zsock_fd_set *writefds, zsock_fd_set *exceptfds,
+			 struct timeval *timeout)
+{
+	return zsock_select(nfds, readfds, writefds, exceptfds, timeout);
+}
+
+static inline void FD_ZERO(zsock_fd_set *set)
+{
+	ZSOCK_FD_ZERO(set);
+}
+
+static inline int FD_ISSET(int fd, zsock_fd_set *set)
+{
+	return ZSOCK_FD_ISSET(fd, set);
+}
+
+static inline void FD_CLR(int fd, zsock_fd_set *set)
+{
+	ZSOCK_FD_CLR(fd, set);
+}
+
+static inline void FD_SET(int fd, zsock_fd_set *set)
+{
+	ZSOCK_FD_SET(fd, set);
+}
+
+#endif /* CONFIG_NET_SOCKETS_POSIX_NAMES */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_INCLUDE_NET_SOCKET_SELECT_H_ */