139 lines
4.9 KiB
C
139 lines
4.9 KiB
C
/****************************************************************************
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* libs/libc/stdio/lib_readv.c
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*
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* Copyright (C) 2017=-2018 Gregory Nutt. All rights 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 <sys/types.h>
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#include <sys/uio.h>
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#include <unistd.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: readv()
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*
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* Description:
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* The readv() function is equivalent to read(), except as described below.
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* The readv() function places the input data into the 'iovcnt' buffers
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* specified by the members of the 'iov' array: iov[0], iov[1], ...,
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* iov['iovcnt'-1]. The 'iovcnt' argument is valid if greater than 0 and
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* less than or equal to IOV_MAX as defined in limits.h.
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*
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* Each iovec entry specifies the base address and length of an area in
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* memory where data should be placed. The readv() function will always
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* fill an area completely before proceeding to the next.
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*
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* TODO: pon successful completion, readv() will mark for update the
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* st_atime field of the file.
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*
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* Input Parameters:
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* filedes - The open file descriptor for the file to be read
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* iov - Array of read buffer descriptors
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* iovcnt - Number of elements in iov[]
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*
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* Returned Value:
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* Upon successful completion, readv() will return a non-negative integer
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* indicating the number of bytes actually read. Otherwise, the functions
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* will return -1 and set errno to indicate the error. See read() for the
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* list of returned errno values. In addition, the readv() function will
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* fail if:
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*
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* EINVAL.
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* The sum of the iov_len values in the iov array overflowed an ssize_t
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* or The 'iovcnt' argument was less than or equal to 0, or greater than
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* IOV_MAX (Not implemented).
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*
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****************************************************************************/
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ssize_t readv(int fildes, FAR const struct iovec *iov, int iovcnt)
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{
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ssize_t ntotal;
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ssize_t nread;
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size_t remaining;
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FAR uint8_t *buffer;
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int i;
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/* Process each entry in the struct iovec array */
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for (i = 0, ntotal = 0; i < iovcnt; i++)
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{
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/* Ignore zero-length reads */
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if (iov[i].iov_len > 0)
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{
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buffer = iov[i].iov_base;
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remaining = iov[i].iov_len;
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/* Read repeatedly as necessary to fill buffer */
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do
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{
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/* NOTE: read() is a cancellation point */
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nread = read(fildes, buffer, remaining);
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/* Check for a read error */
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if (nread < 0)
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{
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return nread;
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}
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/* Check for an end-of-file condition */
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else if (nread == 0)
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{
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return ntotal;
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}
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/* Update pointers and counts in order to handle partial
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* buffer reads.
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*/
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buffer += nread;
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remaining -= nread;
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ntotal += nread;
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}
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while (remaining > 0);
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}
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}
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return ntotal;
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}
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