1 files changed, 145 insertions, 0 deletions
diff --git a/nuttx/libc/misc/lib_filesem.c b/nuttx/libc/misc/lib_filesem.c
new file mode 100644
index 000000000..5cc4624ec
--- /dev/null
+++ b/nuttx/libc/misc/lib_filesem.c
@@ -0,0 +1,145 @@
+/************************************************************************
+ * libc/misc/lib_filesem.c
+ *
+ *   Copyright (C) 2007, 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.
+ *
+ ************************************************************************/
+
+/************************************************************************
+ * Included Files
+ ************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <semaphore.h>
+#include <errno.h>
+#include <assert.h>
+
+#include "lib_internal.h"
+
+#if CONFIG_STDIO_BUFFER_SIZE > 0
+
+/************************************************************************
+ * Pre-processor Definitions
+ ************************************************************************/
+
+/************************************************************************
+ * Private Data
+ ************************************************************************/
+
+/************************************************************************
+ * Global Functions
+ ************************************************************************/
+
+/************************************************************************
+ * lib_sem_initialize
+ ************************************************************************/
+
+void lib_sem_initialize(FAR struct file_struct *stream)
+{
+  /* Initialize the LIB semaphore to one (to support one-at-
+   * a-time access to private data sets.
+   */
+
+  (void)sem_init(&stream->fs_sem, 0, 1);
+
+  stream->fs_holder = -1;
+  stream->fs_counts = 0;
+}
+
+/************************************************************************
+ * lib_take_semaphore
+ ************************************************************************/
+
+void lib_take_semaphore(FAR struct file_struct *stream)
+{
+  pid_t my_pid = getpid();
+
+  /* Do I already have the semaphore? */
+
+  if (stream->fs_holder == my_pid)
+    {
+      /* Yes, just increment the number of references that I have */
+
+      stream->fs_counts++;
+    }
+  else
+    {
+      /* Take the semaphore (perhaps waiting) */
+
+      while (sem_wait(&stream->fs_sem) != 0)
+	{
+	  /* The only case that an error should occr here is if
+	   * the wait was awakened by a signal.
+	   */
+
+	  ASSERT(get_errno() == EINTR);
+	}
+
+      /* We have it.  Claim the stak and return */
+
+      stream->fs_holder = my_pid;
+      stream->fs_counts = 1;
+    }
+}
+
+/************************************************************************
+ * lib_give_semaphore
+ ************************************************************************/
+
+void lib_give_semaphore(FAR struct file_struct *stream)
+{
+  pid_t my_pid = getpid();
+
+  /* I better be holding at least one reference to the semaphore */
+
+  ASSERT(stream->fs_holder == my_pid);
+
+  /* Do I hold multiple references to the semphore */
+
+  if (stream->fs_counts > 1)
+    {
+      /* Yes, just release one count and return */
+
+      stream->fs_counts--;
+    }
+  else
+    {
+      /* Nope, this is the last reference I have */
+
+      stream->fs_holder = -1;
+      stream->fs_counts = 0;
+      ASSERT(sem_post(&stream->fs_sem) == 0);
+    }
+}
+#endif /* CONFIG_STDIO_BUFFER_SIZE */