225 lines
6.8 KiB
C
225 lines
6.8 KiB
C
/****************************************************************************
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* fs/vfs/fs_read.c
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*
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* Copyright (C) 2007-2009, 2012-2014, 2016-2017 Gregory Nutt. All rights
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* reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <sched.h>
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#include <errno.h>
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#include <nuttx/cancelpt.h>
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#include <nuttx/net/net.h>
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#include "inode/inode.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: file_read
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*
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* Description:
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* file_read() is an interanl OS interface. It is functionally similar to
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* the standard read() interface except:
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*
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* - It does not modify the errno variable,
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* - It is not a cancellation point,
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* - It does not handle socket descriptors, and
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* - It accepts a file structure instance instead of file descriptor.
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*
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* Input Parameters:
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* filep - File structure instance
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* buf - User-provided to save the data
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* nbytes - The maximum size of the user-provided buffer
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*
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* Returned Value:
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* The positive non-zero number of bytes read on success, 0 on if an
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* end-of-file condition, or a negated errno value on any failure.
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*
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****************************************************************************/
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ssize_t file_read(FAR struct file *filep, FAR void *buf, size_t nbytes)
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{
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FAR struct inode *inode;
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int ret = -EBADF;
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DEBUGASSERT(filep);
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inode = filep->f_inode;
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/* Was this file opened for read access? */
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if ((filep->f_oflags & O_RDOK) == 0)
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{
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/* No.. File is not read-able */
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ret = -EACCES;
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}
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/* Is a driver or mountpoint registered? If so, does it support the read
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* method?
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*/
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else if (inode != NULL && inode->u.i_ops && inode->u.i_ops->read)
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{
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/* Yes.. then let it perform the read. NOTE that for the case of the
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* mountpoint, we depend on the read methods being identical in
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* signature and position in the operations vtable.
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*/
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ret = (int)inode->u.i_ops->read(filep, (FAR char *)buf, (size_t)nbytes);
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}
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/* Return the number of bytes read (or possibly an error code) */
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return ret;
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}
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/****************************************************************************
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* Name: nx_read
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*
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* Description:
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* nx_read() is an internal OS interface. It is functionally similar to
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* the standard read() interface except:
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*
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* - It does not modify the errno variable, and
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* - It is not a cancellation point.
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*
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* Input Parameters:
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* fd - File descriptor to read from
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* buf - User-provided to save the data
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* nbytes - The maximum size of the user-provided buffer
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*
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* Returned Value:
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* The positive non-zero number of bytes read on success, 0 on if an
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* end-of-file condition, or a negated errno value on any failure.
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*
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****************************************************************************/
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ssize_t nx_read(int fd, FAR void *buf, size_t nbytes)
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{
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/* Did we get a valid file descriptor? */
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#if CONFIG_NFILE_DESCRIPTORS > 0
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if ((unsigned int)fd >= CONFIG_NFILE_DESCRIPTORS)
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#endif
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{
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#if defined(CONFIG_NET) && CONFIG_NSOCKET_DESCRIPTORS > 0
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/* No.. If networking is enabled, read() is the same as recv() with
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* the flags parameter set to zero.
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*/
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return nx_recv(fd, buf, nbytes, 0);
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#else
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/* No networking... it is a bad descriptor in any event */
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return -EBADF;
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#endif
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}
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#if CONFIG_NFILE_DESCRIPTORS > 0
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else
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{
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FAR struct file *filep;
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ssize_t ret;
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/* The descriptor is in a valid range to file descriptor... do the
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* read. First, get the file structure. Note that on failure,
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* fs_getfilep() will set the errno variable.
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*/
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ret = (ssize_t)fs_getfilep(fd, &filep);
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if (ret < 0)
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{
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return ret;
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}
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/* Then let file_read do all of the work. */
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return file_read(filep, buf, nbytes);
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}
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#else
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/* I don't think we can get here */
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return -ENOSYS;
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#endif
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}
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/****************************************************************************
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* Name: read
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*
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* Description:
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* The standard, POSIX read interface.
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*
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* Input Parameters:
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* fd - File descriptor to read from
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* buf - User-provided to save the data
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* nbytes - The maximum size of the user-provided buffer
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*
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* Returned Value:
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* The positive non-zero number of bytes read on success, 0 on if an
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* end-of-file condition, or -1 on failure with errno set appropriately.
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*
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****************************************************************************/
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ssize_t read(int fd, FAR void *buf, size_t nbytes)
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{
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ssize_t ret;
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/* read() is a cancellation point */
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(void)enter_cancellation_point();
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/* Let nx_read() do the real work */
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ret = nx_read(fd, buf, nbytes);
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if (ret < 0)
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{
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set_errno(-ret);
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ret = ERROR;
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}
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leave_cancellation_point();
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return ret;
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}
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