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nuttx-bb/nuttx/drivers/pipe_common.c

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/****************************************************************************
* 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 <debug.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);
}
}
/****************************************************************************
* Name: pipecommon_pollnotify
****************************************************************************/
#ifndef CONFIG_DISABLE_POLL
static void pipecommon_pollnotify(FAR struct pipe_dev_s *dev, pollevent_t eventset)
{
int i;
for (i = 0; i < CONFIG_DEV_PIPE_NPOLLWAITERS; i++)
{
struct pollfd *fds = dev->d_fds[i];
if (fds)
{
fds->revents |= (fds->events & eventset);
if (fds->revents != 0)
{
fvdbg("Report events: %02x\n", fds->revents);
sem_post(fds->sem);
}
}
}
}
#else
# define pipecommon_pollnotify(dev,event)
#endif
/****************************************************************************
* 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, 0, sizeof(struct pipe_dev_s));
sem_init(&dev->d_bfsem, 0, 1);
sem_init(&dev->d_rdsem, 0, 0);
sem_init(&dev->d_wrsem, 0, 0);
}
return dev;
}
/****************************************************************************
* Name: pipecommon_freedev
****************************************************************************/
void pipecommon_freedev(FAR struct pipe_dev_s *dev)
{
sem_destroy(&dev->d_bfsem);
sem_destroy(&dev->d_rdsem);
sem_destroy(&dev->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->d_bfsem) == 0)
{
/* If this the first reference on the device, then allocate the buffer */
if (dev->d_refs == 0)
{
dev->d_buffer = (ubyte*)malloc(CONFIG_DEV_PIPE_SIZE);
if (!dev->d_buffer)
{
(void)sem_post(&dev->d_bfsem);
return -ENOMEM;
}
}
/* Increment the reference count on the pipe instance */
dev->d_refs++;
/* If opened for writing, increment the count of writers on on the pipe instance */
if ((filep->f_oflags & O_WROK) != 0)
{
dev->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->d_nwriters == 1)
{
while (sem_getvalue(&dev->d_rdsem, &sval) == 0 && sval < 0)
{
sem_post(&dev->d_rdsem);
}
}
}
/* If opened for read-only, then wait for at least one writer on the pipe */
sched_lock();
(void)sem_post(&dev->d_bfsem);
if ((filep->f_oflags & O_RDWR) == O_RDONLY && dev->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->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->d_bfsem);
/* Check if the decremented reference count would go to zero */
if (dev->d_refs > 1)
{
/* No.. then just decrement the reference count */
dev->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->d_nwriters <= 0)
{
while (sem_getvalue(&dev->d_rdsem, &sval) == 0 && sval < 0)
{
sem_post(&dev->d_rdsem);
}
}
}
}
else
{
/* Yes... deallocate the buffer */
free(dev->d_buffer);
dev->d_buffer = NULL;
/* And reset all counts and indices */
dev->d_wrndx = 0;
dev->d_rdndx = 0;
dev->d_refs = 0;
dev->d_nwriters = 0;
}
sem_post(&dev->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->d_bfsem) < 0)
{
return ERROR;
}
/* If the pipe is empty, then wait for something to be written to it */
while (dev->d_wrndx == dev->d_rdndx)
{
/* If O_NONBLOCK was set, then return EGAIN */
if (filep->f_oflags & O_NONBLOCK)
{
sem_post(&dev->d_bfsem);
return -EAGAIN;
}
/* If there are no writers on the pipe, then return end of file */
if (dev->d_nwriters <= 0)
{
sem_post(&dev->d_bfsem);
return 0;
}
/* Otherwise, wait for something to be written to the pipe */
sched_lock();
sem_post(&dev->d_bfsem);
ret = sem_wait(&dev->d_rdsem);
sched_unlock();
if (ret < 0 || sem_wait(&dev->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->d_wrndx != dev->d_rdndx)
{
*buffer++ = dev->d_buffer[dev->d_rdndx];
if (++dev->d_rdndx >= CONFIG_DEV_PIPE_SIZE)
{
dev->d_rdndx = 0;
}
nread++;
}
/* Notify all waiting writers that bytes have been removed from the buffer */
while (sem_getvalue(&dev->d_wrsem, &sval) == 0 && sval < 0)
{
sem_post(&dev->d_wrsem);
}
/* Notify all poll/select waiters that they can write to the FIFO */
pipecommon_pollnotify(dev, POLLOUT);
sem_post(&dev->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->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->d_wrndx + 1;
if (nxtwrndx >= CONFIG_DEV_PIPE_SIZE)
{
nxtwrndx = 0;
}
/* Would the next write overflow the circular buffer? */
if (nxtwrndx != dev->d_rdndx)
{
/* No... copy the byte */
dev->d_buffer[dev->d_wrndx] = *buffer++;
dev->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->d_rdsem, &sval) == 0 && sval < 0)
{
sem_post(&dev->d_rdsem);
}
/* Notify all poll/select waiters that they can write to the FIFO */
pipecommon_pollnotify(dev, POLLIN);
/* Return the number of bytes written */
sem_post(&dev->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->d_rdsem, &sval) == 0 && sval < 0)
{
sem_post(&dev->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->d_bfsem);
return nwritten;
}
/* There is more to be written.. wait for data to be removed from the pipe */
sched_lock();
sem_post(&dev->d_bfsem);
pipecommon_semtake(&dev->d_wrsem);
sched_unlock();
pipecommon_semtake(&dev->d_bfsem);
}
}
}
/****************************************************************************
* Name: pipecommon_poll
****************************************************************************/
#ifndef CONFIG_DISABLE_POLL
int pipecommon_poll(FAR struct file *filep, FAR struct pollfd *fds,
boolean setup)
{
FAR struct inode *inode = filep->f_inode;
FAR struct pipe_dev_s *dev = inode->i_private;
pollevent_t eventset;
pipe_ndx_t nbytes;
int ret = OK;
int i;
/* Some sanity checking */
#if CONFIG_DEBUG
if (!dev || !fds)
{
return -ENODEV;
}
#endif
/* Are we setting up the poll? Or tearing it down? */
pipecommon_semtake(&dev->d_bfsem);
if (setup)
{
/* This is a request to set up the poll. Find an available
* slot for the poll structure reference
*/
for (i = 0; i < CONFIG_DEV_PIPE_NPOLLWAITERS; i++)
{
/* Find an available slot */
if (!dev->d_fds[i])
{
/* Bind the poll structure and this slot */
dev->d_fds[i] = fds;
fds->private = &dev->d_fds[i];
break;
}
}
if (i >= CONFIG_DEV_PIPE_NPOLLWAITERS)
{
fds->private = NULL;
ret = -EBUSY;
goto errout;
}
/* Should immediately notify on any of the requested events?
* First, determine how many bytes are in the buffer
*/
if (dev->d_wrndx >= dev->d_rdndx)
{
nbytes = dev->d_wrndx - dev->d_rdndx;
}
else
{
nbytes = (CONFIG_DEV_PIPE_SIZE-1) + dev->d_wrndx - dev->d_rdndx;
}
/* Notify the POLLOUT event if the pipe is not full */
eventset = 0;
if (nbytes < (CONFIG_DEV_PIPE_SIZE-1))
{
eventset |= POLLOUT;
}
/* Notify the POLLIN event if the pipe is not empty */
if (nbytes > 0)
{
eventset |= POLLIN;
}
if (eventset)
{
pipecommon_pollnotify(dev, eventset);
}
}
else
{
/* This is a request to tear down the poll. */
struct pollfd **slot = (struct pollfd **)fds->private;
#ifdef CONFIG_DEBUG
if (!slot)
{
ret = -EIO;
goto errout;
}
#endif
/* Remove all memory of the poll setup */
*slot = NULL;
fds->private = NULL;
}
errout:
sem_post(&dev->d_bfsem);
return ret;
}
#endif
#endif /* CONFIG_DEV_PIPE_SIZE > 0 */
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