/**************************************************************************** * fs/vfs/fs_read.c * * Copyright (C) 2007-2009, 2012-2014, 2016-2017 Gregory Nutt. All rights * reserved. * Author: Gregory Nutt * * 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 #include #include #include #include #include #include #include #include #include "inode/inode.h" /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: file_read * * Description: * file_read() is an interanl OS interface. It is functionally similar to * the standard read() interface except: * * - It does not modify the errno variable, * - It is not a cancellation point, * - It does not handle socket descriptors, and * - It accepts a file structure instance instead of file descriptor. * * Input Parameters: * filep - File structure instance * buf - User-provided to save the data * nbytes - The maximum size of the user-provided buffer * * Returned Value: * The positive non-zero number of bytes read on success, 0 on if an * end-of-file condition, or a negated errno value on any failure. * ****************************************************************************/ ssize_t file_read(FAR struct file *filep, FAR void *buf, size_t nbytes) { FAR struct inode *inode; int ret = -EBADF; DEBUGASSERT(filep); inode = filep->f_inode; /* Was this file opened for read access? */ if ((filep->f_oflags & O_RDOK) == 0) { /* No.. File is not read-able */ ret = -EACCES; } /* Is a driver or mountpoint registered? If so, does it support the read * method? */ else if (inode != NULL && inode->u.i_ops && inode->u.i_ops->read) { /* Yes.. then let it perform the read. NOTE that for the case of the * mountpoint, we depend on the read methods being identical in * signature and position in the operations vtable. */ ret = (int)inode->u.i_ops->read(filep, (FAR char *)buf, (size_t)nbytes); } /* Return the number of bytes read (or possibly an error code) */ return ret; } /**************************************************************************** * Name: nx_read * * Description: * nx_read() is an internal OS interface. It is functionally similar to * the standard read() interface except: * * - It does not modify the errno variable, and * - It is not a cancellation point. * * Input Parameters: * fd - File descriptor to read from * buf - User-provided to save the data * nbytes - The maximum size of the user-provided buffer * * Returned Value: * The positive non-zero number of bytes read on success, 0 on if an * end-of-file condition, or a negated errno value on any failure. * ****************************************************************************/ ssize_t nx_read(int fd, FAR void *buf, size_t nbytes) { /* Did we get a valid file descriptor? */ if ((unsigned int)fd >= CONFIG_NFILE_DESCRIPTORS) { #ifdef CONFIG_NET /* No.. If networking is enabled, read() is the same as recv() with * the flags parameter set to zero. */ return nx_recv(fd, buf, nbytes, 0); #else /* No networking... it is a bad descriptor in any event */ return -EBADF; #endif } else { FAR struct file *filep; ssize_t ret; /* The descriptor is in a valid range to file descriptor... do the * read. First, get the file structure. Note that on failure, * fs_getfilep() will set the errno variable. */ ret = (ssize_t)fs_getfilep(fd, &filep); if (ret < 0) { return ret; } /* Then let file_read do all of the work. */ return file_read(filep, buf, nbytes); } } /**************************************************************************** * Name: read * * Description: * The standard, POSIX read interface. * * Input Parameters: * fd - File descriptor to read from * buf - User-provided to save the data * nbytes - The maximum size of the user-provided buffer * * Returned Value: * The positive non-zero number of bytes read on success, 0 on if an * end-of-file condition, or -1 on failure with errno set appropriately. * ****************************************************************************/ ssize_t read(int fd, FAR void *buf, size_t nbytes) { ssize_t ret; /* read() is a cancellation point */ enter_cancellation_point(); /* Let nx_read() do the real work */ ret = nx_read(fd, buf, nbytes); if (ret < 0) { set_errno(-ret); ret = ERROR; } leave_cancellation_point(); return ret; }