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+/****************************************************************************
+ * include/sys/select.h
+ *
+ * Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
+ * Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ * used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_SYS_SELECT_H
+#define __INCLUDE_SYS_SELECT_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdint.h>
+#include <time.h>
+
+#if CONFIG_NFILE_DESCRIPTORS > 0 || CONFIG_NSOCKET_DESCRIPTORS > 0
+
+/****************************************************************************
+ * Pre-Processor Definitions
+ ****************************************************************************/
+
+/* Get the total number of descriptors that we will have to support */
+
+#define __SELECT_NDESCRIPTORS (CONFIG_NFILE_DESCRIPTORS + CONFIG_NSOCKET_DESCRIPTORS)
+
+/* We will use a 32-bit bitsets to represent the set of descriptors. How
+ * many uint32_t's do we need to span all descriptors?
+ */
+
+#if __SELECT_NDESCRIPTORS <= 32
+# define __SELECT_NUINT32 1
+#elif __SELECT_NDESCRIPTORS <= 64
+# define __SELECT_NUINT32 2
+#elif __SELECT_NDESCRIPTORS <= 96
+# define __SELECT_NUINT32 3
+#elif __SELECT_NDESCRIPTORS <= 128
+# define __SELECT_NUINT32 4
+#elif __SELECT_NDESCRIPTORS <= 160
+# define __SELECT_NUINT32 5
+#elif __SELECT_NDESCRIPTORS <= 192
+# define __SELECT_NUINT32 6
+#elif __SELECT_NDESCRIPTORS <= 224
+# define __SELECT_NUINT32 7
+#elif __SELECT_NDESCRIPTORS <= 256
+# define __SELECT_NUINT32 8
+#else
+# warning "Large fd_set needed"
+#endif
+
+/* These macros map a file descripto to an index and bit number */
+
+#define _FD_NDX(fd) ((fd) >> 5)
+#define _FD_BIT(fd) ((fd) & 0x1f)
+
+/* Standard helper macros */
+
+#define FD_CLR(fd,set) (((uint32_t*)(set))[_FD_NDX(fd)] &= ~(1 << _FD_BIT(fd)))
+#define FD_SET(fd,set) (((uint32_t*)(set))[_FD_NDX(fd)] |= (1 << _FD_BIT(fd)))
+#define FD_ISSET(fd,set) ((((uint32_t*)(set))[_FD_NDX(fd)] & (1 << _FD_BIT(fd))) != 0)
+#define FD_ZERO(set) memset(set, 0, sizeof(fd_set))
+
+/****************************************************************************
+ * Type Definitions
+ ****************************************************************************/
+
+typedef uint32_t fd_set[__SELECT_NUINT32];
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+#undef EXTERN
+#if defined(__cplusplus)
+#define EXTERN extern "C"
+extern "C" {
+#else
+#define EXTERN extern
+#endif
+
+EXTERN int select(int nfds, FAR fd_set *readfds, FAR fd_set *writefds,
+ FAR fd_set *exceptfds, FAR struct timeval *timeout);
+
+#undef EXTERN
+#if defined(__cplusplus)
+}
+#endif
+
+#endif /* CONFIG_NFILE_DESCRIPTORS || CONFIG_NSOCKET_DESCRIPTORS */
+#endif /* __INCLUDE_SYS_SELECT_H */