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Diffstat (limited to 'nuttx/lib/misc/lib_filesem.c')
-rw-r--r-- | nuttx/lib/misc/lib_filesem.c | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/nuttx/lib/misc/lib_filesem.c b/nuttx/lib/misc/lib_filesem.c new file mode 100644 index 000000000..e6a3fdb67 --- /dev/null +++ b/nuttx/lib/misc/lib_filesem.c @@ -0,0 +1,145 @@ +/************************************************************************ + * lib/misc/lib_filesem.c + * + * Copyright (C) 2007, 2009, 2011 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 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 */ |