/****************************************************************************
* drivers/pipe-common.c
*
* Copyright (C) 2008 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.
*
****************************************************************************/
/****************************************************************************
* Compilation Switches
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <string.h>
#include <sched.h>
#include <semaphore.h>
#include <fcntl.h>
#include <errno.h>
#include <assert.h>
#include <nuttx/fs.h>
#include "pipe-common.h"
#if CONFIG_DEV_PIPE_SIZE > 0
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static void pipecommon_semtake(sem_t *sem);
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: pipecommon_semtake
****************************************************************************/
static void pipecommon_semtake(sem_t *sem)
{
while (sem_wait(sem) != 0)
{
/* The only case that an error should occur here is if the wait was
* awakened by a signal.
*/
ASSERT(errno == EINTR);
}
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: pipecommon_allocdev
****************************************************************************/
FAR struct pipe_dev_s *pipecommon_allocdev(void)
{
struct pipe_dev_s *dev;
/* Allocate a private structure to manage the pipe */
dev = (struct pipe_dev_s *)malloc(sizeof(struct pipe_dev_s));
if (dev)
{
/* Initialize the private structure */
memset(&dev->s, 0, sizeof(struct pipe_state_s));
sem_init(&dev->s.d_bfsem, 0, 1);
sem_init(&dev->s.d_rdsem, 0, 0);
sem_init(&dev->s.d_wrsem, 0, 0);
}
return dev;
}
/****************************************************************************
* Name: pipecommon_freedev
****************************************************************************/
void pipecommon_freedev(FAR struct pipe_dev_s *dev)
{
sem_destroy(&dev->s.d_bfsem);
sem_destroy(&dev->s.d_rdsem);
sem_destroy(&dev->s.d_wrsem);
free(dev);
}
/****************************************************************************
* Name: pipecommon_open
****************************************************************************/
int pipecommon_open(FAR struct file *filep)
{
struct inode *inode = filep->f_inode;
struct pipe_dev_s *dev = inode->i_private;
int sval;
/* Some sanity checking */
#if CONFIG_DEBUG
if (!dev)
{
return -EBADF;
}
#endif
/* Make sure that we have exclusive access to the device structure */
if (sem_wait(&dev->s.d_bfsem) == 0)
{
/* Increment the reference count on the pipe instance */
dev->s.d_refs++;
/* If opened for writing, increment the count of writers on on the pipe instance */
if ((filep->f_oflags & O_WROK) != 0)
{
dev->s.d_nwriters++;
/* If this this is the first writer, then the read semaphore indicates the
* number of readers waiting for the first writer. Wake them all up.
*/
if (dev->s.d_nwriters == 1)
{
while (sem_getvalue(&dev->s.d_rdsem, &sval) == 0 && sval < 0)
{
sem_post(&dev->s.d_rdsem);
}
}
}
/* If opened for read-only, then wait for at least one writer on the pipe */
sched_lock();
(void)sem_post(&dev->s.d_bfsem);
if ((filep->f_oflags & O_RDWR) == O_RDONLY && dev->s.d_nwriters < 1)
{
/* NOTE: d_rdsem is normally used when the read logic waits for more
* data to be written. But until the first writer has opened the
* pipe, the meaning is different: it is used prevent O_RDONLY open
* calls from returning until there is at least one writer on the pipe.
* This is required both by spec and also because it prevents
* subsequent read() calls from returning end-of-file because there is
* no writer on the pipe.
*/
pipecommon_semtake(&dev->s.d_rdsem);
}
sched_unlock();
return OK;
}
return ERROR;
}
/****************************************************************************
* Name: pipecommon_close
****************************************************************************/
int pipecommon_close(FAR struct file *filep)
{
struct inode *inode = filep->f_inode;
struct pipe_dev_s *dev = inode->i_private;
int sval;
/* Some sanity checking */
#if CONFIG_DEBUG
if (!dev)
{
return -EBADF;
}
#endif
/* Make sure that we have exclusive access to the device structure.
* NOTE: close() is supposed to return EINTR if interrupted, however
* I've never seen anyone check that.
*/
pipecommon_semtake(&dev->s.d_bfsem);
/* Check if the decremented reference count would be less than zero */
if (dev->s.d_refs > 0)
{
/* No.. then just decrement the reference count */
dev->s.d_refs--;
/* If opened for writing, decrement the count of writers on on the pipe instance */
if ((filep->f_oflags & O_WROK) != 0)
{
/* If there are no longer any writers on the pipe, then notify all of the
* waiting readers that they must return end-of-file.
*/
if (--dev->s.d_nwriters <= 0)
{
while (sem_getvalue(&dev->s.d_rdsem, &sval) == 0 && sval < 0)
{
sem_post(&dev->s.d_rdsem);
}
}
}
}
sem_post(&dev->s.d_bfsem);
return OK;
}
/****************************************************************************
* Name: pipecommon_read
****************************************************************************/
ssize_t pipecommon_read(FAR struct file *filep, FAR char *buffer, size_t len)
{
struct inode *inode = filep->f_inode;
struct pipe_dev_s *dev = inode->i_private;
ssize_t nread = 0;
int sval;
int ret;
/* Some sanity checking */
#if CONFIG_DEBUG
if (!dev)
{
return -ENODEV;
}
#endif
/* Make sure that we have exclusive access to the device structure */
if (sem_wait(&dev->s.d_bfsem) < 0)
{
return ERROR;
}
/* If the pipe is empty, then wait for something to be written to it */
while (dev->s.d_wrndx == dev->s.d_rdndx)
{
/* If O_NONBLOCK was set, then return EGAIN */
if (filep->f_oflags & O_NONBLOCK)
{
sem_post(&dev->s.d_bfsem);
return -EAGAIN;
}
/* If there are no writers on the pipe, then return end of file */
if (dev->s.d_nwriters <= 0)
{
sem_post(&dev->s.d_bfsem);
return 0;
}
/* Otherwise, wait for something to be written to the pipe */
sched_lock();
sem_post(&dev->s.d_bfsem);
ret = sem_wait(&dev->s.d_rdsem);
sched_unlock();
if (ret < 0 || sem_wait(&dev->s.d_bfsem) < 0)
{
return ERROR;
}
}
/* Then return whatever is available in the pipe (which is at least one byte) */
nread = 0;
while (nread < len && dev->s.d_wrndx != dev->s.d_rdndx)
{
*buffer++ = dev->d_buffer[dev->s.d_rdndx];
if (++dev->s.d_rdndx >= CONFIG_DEV_PIPE_SIZE)
{
dev->s.d_rdndx = 0;
}
nread++;
}
/* Notify all waiting writers that bytes have been removed from the buffer */
while (sem_getvalue(&dev->s.d_wrsem, &sval) == 0 && sval < 0)
{
sem_post(&dev->s.d_wrsem);
}
sem_post(&dev->s.d_bfsem);
return nread;
}
/****************************************************************************
* Name: pipecommon_write
****************************************************************************/
ssize_t pipecommon_write(FAR struct file *filep, FAR const char *buffer, size_t len)
{
struct inode *inode = filep->f_inode;
struct pipe_dev_s *dev = inode->i_private;
ssize_t nwritten = 0;
ssize_t last;
int nxtwrndx;
int sval;
/* Some sanity checking */
#if CONFIG_DEBUG
if (!dev)
{
return -ENODEV;
}
#endif
/* Make sure that we have exclusive access to the device structure */
if (sem_wait(&dev->s.d_bfsem) < 0)
{
return ERROR;
}
/* Loop until all of the bytes have been written */
last = 0;
for (;;)
{
/* Calculate the write index AFTER the next byte is written */
nxtwrndx = dev->s.d_wrndx + 1;
if (nxtwrndx >= CONFIG_DEV_PIPE_SIZE)
{
nxtwrndx = 0;
}
/* Would the next write overflow the circular buffer? */
if (nxtwrndx != dev->s.d_rdndx)
{
/* No... copy the byte */
dev->d_buffer[dev->s.d_wrndx] = *buffer++;
dev->s.d_wrndx = nxtwrndx;
/* Is the write complete? */
if (++nwritten >= len)
{
/* Yes.. Notify all of the waiting readers that more data is available */
while (sem_getvalue(&dev->s.d_rdsem, &sval) == 0 && sval < 0)
{
sem_post(&dev->s.d_rdsem);
}
/* Return the number of bytes written */
sem_post(&dev->s.d_bfsem);
return len;
}
}
else
{
/* There is not enough room for the next byte. Was anything written in this pass? */
if (last < nwritten)
{
/* Yes.. Notify all of the waiting readers that more data is available */
while (sem_getvalue(&dev->s.d_rdsem, &sval) == 0 && sval < 0)
{
sem_post(&dev->s.d_rdsem);
}
}
last = nwritten;
/* If O_NONBLOCK was set, then return partial bytes written or EGAIN */
if (filep->f_oflags & O_NONBLOCK)
{
if (nwritten == 0)
{
nwritten = -EAGAIN;
}
sem_post(&dev->s.d_bfsem);
return nwritten;
}
/* There is more to be written.. wait for data to be removed from the pipe */
sched_lock();
sem_post(&dev->s.d_bfsem);
pipecommon_semtake(&dev->s.d_wrsem);
sched_unlock();
pipecommon_semtake(&dev->s.d_bfsem);
}
}
}
#endif /* CONFIG_DEV_PIPE_SIZE > 0 */
