98 lines
2.9 KiB
C
98 lines
2.9 KiB
C
/****************************************************************************
|
|
* libs/libc/uio/lib_preadv.c
|
|
*
|
|
* Licensed to the Apache Software Foundation (ASF) under one or more
|
|
* contributor license agreements. See the NOTICE file distributed with
|
|
* this work for additional information regarding copyright ownership. The
|
|
* ASF licenses this file to you under the Apache License, Version 2.0 (the
|
|
* "License"); you may not use this file except in compliance with the
|
|
* License. You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
|
|
* License for the specific language governing permissions and limitations
|
|
* under the License.
|
|
*
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#include <sys/types.h>
|
|
#include <sys/uio.h>
|
|
#include <unistd.h>
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: preadv()
|
|
*
|
|
* Description:
|
|
* The preadv() function is equivalent to pread(), except it takes
|
|
* an iov array.
|
|
*
|
|
****************************************************************************/
|
|
|
|
ssize_t preadv(int fildes, FAR const struct iovec *iov, int iovcnt,
|
|
off_t offset)
|
|
{
|
|
ssize_t ntotal;
|
|
ssize_t nread;
|
|
size_t remaining;
|
|
FAR uint8_t *buffer;
|
|
int i;
|
|
|
|
/* Process each entry in the struct iovec array */
|
|
|
|
for (i = 0, ntotal = 0; i < iovcnt; i++)
|
|
{
|
|
/* Ignore zero-length reads */
|
|
|
|
if (iov[i].iov_len > 0)
|
|
{
|
|
buffer = iov[i].iov_base;
|
|
remaining = iov[i].iov_len;
|
|
|
|
/* Read repeatedly as necessary to fill buffer */
|
|
|
|
do
|
|
{
|
|
/* NOTE: pread() is a cancellation point */
|
|
|
|
nread = pread(fildes, buffer, remaining, offset + ntotal);
|
|
|
|
/* Check for a read error */
|
|
|
|
if (nread < 0)
|
|
{
|
|
return nread;
|
|
}
|
|
|
|
/* Check for an end-of-file condition */
|
|
|
|
else if (nread == 0)
|
|
{
|
|
return ntotal;
|
|
}
|
|
|
|
/* Update pointers and counts in order to handle partial
|
|
* buffer reads.
|
|
*/
|
|
|
|
buffer += nread;
|
|
remaining -= nread;
|
|
ntotal += nread;
|
|
}
|
|
while (remaining > 0);
|
|
}
|
|
}
|
|
|
|
return ntotal;
|
|
}
|