diff options
Diffstat (limited to 'nuttx/libc/semaphore/sem_getvalue.c')
-rw-r--r-- | nuttx/libc/semaphore/sem_getvalue.c | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/nuttx/libc/semaphore/sem_getvalue.c b/nuttx/libc/semaphore/sem_getvalue.c new file mode 100644 index 000000000..31c6bb7e0 --- /dev/null +++ b/nuttx/libc/semaphore/sem_getvalue.c @@ -0,0 +1,108 @@ +/**************************************************************************** + * lib/semaphore/sem_getvalue.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 <semaphore.h> +#include <errno.h> + +/**************************************************************************** + * Definitions + ****************************************************************************/ + +/**************************************************************************** + * Private Type Declarations + ****************************************************************************/ + +/**************************************************************************** + * Global Variables + ****************************************************************************/ + +/**************************************************************************** + * Private Variables + ****************************************************************************/ + +/**************************************************************************** + * Private Functions + ****************************************************************************/ + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +/**************************************************************************** + * Function: sem_getvalue + * + * Description: + * This function updates the location referenced by 'sval' argument to + * have the value of the semaphore referenced by 'sem' without effecting + * the state of the semaphore. The updated value represents the actual + * semaphore value that occurred at some unspecified time during the call, + * but may not reflect the actual value of the semaphore when it is + * returned to the calling task. + * + * If 'sem' is locked, the value return by sem_getvalue() will either be + * zero or a negative number whose absolute value represents the number + * of tasks waiting for the semaphore. + * + * Parameters: + * sem - Semaphore descriptor + * sval - Buffer by which the value is returned + * + * Return Value: + * 0 (OK), or -1 (ERROR) if unsuccessful + * + * Assumptions: + * + ****************************************************************************/ + +int sem_getvalue(FAR sem_t *sem, FAR int *sval) +{ + if (sem && sval) + { + *sval = sem->semcount; + return OK; + } + else + { + set_errno(EINVAL); + return ERROR; + } +} |