1 files changed, 206 insertions, 0 deletions
diff --git a/nuttx/sched/sem_open.c b/nuttx/sched/sem_open.c
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+/************************************************************
+ * sem_open.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * 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 Gregory Nutt 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.
+ *
+ ************************************************************/
+
+/************************************************************
+ * Included Files
+ ************************************************************/
+
+#include <sys/types.h>
+#include <stdarg.h>
+#include <string.h>
+#include <semaphore.h>
+#include <nuttx/kmalloc.h>
+#include "sem_internal.h"
+
+/************************************************************
+ * Compilation Switches
+ ************************************************************/
+
+/************************************************************
+ * Definitions
+ ************************************************************/
+
+/************************************************************
+ * Private Type Declarations
+ ************************************************************/
+
+/************************************************************
+ * Global Variables
+ ************************************************************/
+
+/************************************************************
+ * Private Variables
+ ************************************************************/
+
+/************************************************************
+ * Private Functions
+ ************************************************************/
+
+/************************************************************
+ * Public Functions
+ ************************************************************/
+
+/************************************************************
+ * Function: sem_open
+ *
+ * Description:
+ *   This function establishes a connection between named
+ *   semaphores and a task.  Following a call to sem_open()
+ *   with the semaphore name, the task may reference the
+ *   semaphore associated with name using the address
+ *   returned by this call.  The semaphore may be used in
+ *   subsequent calls to sem_wait(), sem_trywait(), and
+ *   sem_post().  The semaphore remains usable until the
+ *   semaphore is closed by a successful call to sem_close().
+ *
+ *   If a task makes multiple calls to sem_open() with the
+ *   same name, then the same semaphore address is returned
+ *   (provided there have been no calls to sem_unlink()).
+ *
+ * Parameters:
+ *   name  - Semaphore name
+ *   oflag - Semaphore creation options.  This may either
+ *     or both of the following bit settings.
+ *     oflag = 0:  Connect to the semaphore only if it
+ *        already exists.
+ *     oflag = O_CREAT:  Connect to the semaphore if it
+ *        exists, otherwise create the semaphore.
+ *     oflag = O_CREAT|O_EXCL:  Create a new semaphore
+ *        unless one of this name already exists.
+ *   Optional parameters.  When the O_CREAT flag is specified,
+ *     two optional parameters are expected:
+ *     1. mode_t mode (ignored), and
+ *     2. unsigned int value.  This initial value of the semaphore.
+ *        valid initial values of the semaphore must be less than
+ *         or equal to SEM_MAX_VALUE.
+ *
+ * Return Value:
+ *   A pointer to sem_t or -1 (ERROR) if unsuccessful.
+ *
+ * Assumptions:
+ *
+ ************************************************************/
+
+sem_t *sem_open (const char *name, int oflag, ...)
+{
+  int          namelen;
+  nsem_t      *psem;
+  sem_t       *sem = (sem_t*)ERROR;
+  va_list      arg;          /* Points to each un-named argument */
+  mode_t       mode;         /* Creation mode parameter (ignored) */
+  unsigned int value;        /* Semaphore value parameter */
+
+  /* Make sure that a non-NULL name is supplied */
+
+  if (name)
+    {
+      /* The POSIX specification requires that the "check for the
+       * existence of a semaphore and the creation of the semaphore
+       * if it does not exist shall be atomic with respect to other
+       * processes executing sem_open()..."  A simple sched_lock()
+       * should be sufficient to meet this requirement.
+       */
+
+      sched_lock();
+      namelen = strlen(name);
+      if (namelen > 0)
+        {
+          /* See if the semaphore already exists */
+
+          psem = sem_findnamed(name);
+          if (psem)
+            {
+              /* It does.  Check if the caller wanted to created 
+               * a new semahore with this name.
+               */
+
+              if (!(oflag & O_CREAT) || !(oflag & O_EXCL))
+                {
+                  /* Allow a new connection to the semaphore */
+
+                  psem->nconnect++;
+                  sem = &psem->sem;
+                }
+            }
+
+          /* It doesn't exist.  Should we create one? */
+
+          else if ((oflag & O_CREAT) != 0)
+            {
+              /* Set up to get the optional arguments needed to create
+               * a message queue.
+               */
+
+              va_start(arg, oflag);
+              mode = va_arg(arg, mode_t);
+              value = va_arg(arg, unsigned int);
+
+              /* Verify that a legal initial value was selected. */
+
+              if (value <= SEM_MAX_VALUE)
+                {
+                  /* Allocate memory for the new semaphore */
+
+                  psem = (nsem_t*)kmalloc((sizeof(nsem_t) + namelen + 1));
+                  if (psem)
+                    {
+                      /* Initialize the named semaphore */
+
+                      sem = &psem->sem;
+                      sem_init(sem, 0, value);
+
+                      psem->nconnect = 1;
+                      psem->unlinked = FALSE;
+                      psem->name = (char*)psem + sizeof(nsem_t);
+                      strcpy(psem->name, name);
+
+                      /* Add the new semaphore to the list of named
+                       * semaphores
+                       */
+
+                      dq_addfirst((dq_entry_t*)psem, &g_nsems);
+                    }
+
+                  /* Clean-up variable argument stuff */
+
+                  va_end(arg);
+                }
+            }
+        }
+      sched_unlock();
+    }
+
+  return sem;
+}