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px4_autopilot/nuttx/libc/misc/lib_sendfile.c

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/************************************************************************
* libc/misc/lib_streamsem.c
*
* Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 <nuttx/config.h>
#include <sys/sendfile.h>
#include <stdbool.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#if CONFIG_NSOCKET_DESCRIPTORS > 0 || CONFIG_NFILE_DESCRIPTORS > 0
/************************************************************************
* Private types
************************************************************************/
/************************************************************************
* Private Variables
************************************************************************/
/************************************************************************
* Public Variables
************************************************************************/
/************************************************************************
* Private Functions
************************************************************************/
/************************************************************************
* Public Functions
************************************************************************/
/************************************************************************
* Name: sendfile
*
* Description:
* sendfile() copies data between one file descriptor and another.
* sendfile() basically just wraps a sequence of reads() and writes()
* to perform a copy. It serves a purpose in systems where there is
* a penalty for copies to between user and kernal space, but really
* nothing in NuttX but provide some Linux compatible (and adding
* another 'almost standard' interface).
*
* NOTE: This interface is *not* specified in POSIX.1-2001, or other
* standards. The implementation here is very similar to the Linux
* sendfile interface. Other UNIX systems implement sendfile() with
* different semantics and prototypes. sendfile() should not be used
* in portable programs.
*
* Input Parmeters:
* infd - A file (or socket) descriptor opened for reading
* outfd - A descriptor opened for writing.
* offset - If 'offset' is not NULL, then it points to a variable
* holding the file offset from which sendfile() will start
* reading data from 'infd'. When sendfile() returns, this
* variable will be set to the offset of the byte following
* the last byte that was read. If 'offset' is not NULL,
* then sendfile() does not modify the current file offset of
* 'infd'; otherwise the current file offset is adjusted to
* reflect the number of bytes read from 'infd.'
*
* If 'offset' is NULL, then data will be read from 'infd'
* starting at the current file offset, and the file offset
* will be updated by the call.
* count - The number of bytes to copy between the file descriptors.
*
* Returned Value:
* If the transfer was successful, the number of bytes written to outfd is
* returned. On error, -1 is returned, and errno is set appropriately.
* There error values are those returned by read() or write() plus:
*
* EINVAL - Bad input parameters.
* ENOMEM - Could not allocated an I/O buffer
*
************************************************************************/
ssize_t sendfile(int outfd, int infd, off_t *offset, size_t count)
{
FAR uint8_t *iobuffer;
FAR uint8_t *wrbuffer;
off_t startpos = 0;
ssize_t nbytesread;
ssize_t nbyteswritten;
size_t ntransferred;
bool endxfr;
/* Get the current file position. */
if (offset)
{
/* Use lseek to get the current file position */
startpos = lseek(infd, 0, SEEK_CUR);
if (startpos == (off_t)-1)
{
return ERROR;
}
/* Use lseek again to set the new file position */
if (lseek(infd, *offset, SEEK_SET) == (off_t)-1)
{
return ERROR;
}
}
/* Allocate an I/O buffer */
iobuffer = (FAR void *)malloc(CONFIG_LIB_SENDFILE_BUFSIZE);
if (!iobuffer)
{
set_errno(ENOMEM);
return ERROR;
}
/* Now transfer 'count' bytes from the infd to the outfd */
for (ntransferred = 0, endxfr = false; ntransferred < count && !endxfr; )
{
/* Loop until the read side of the transfer comes to some conclusion */
do
{
/* Read a buffer of data from the infd */
nbytesread = read(infd, iobuffer, CONFIG_LIB_SENDFILE_BUFSIZE);
/* Check for end of file */
if (nbytesread == 0)
{
/* End of file. Break out and return current number of bytes
* transferred.
*/
endxfr = true;
break;
}
/* Check for a read ERROR. EINTR is a special case. This function
* should break out and return an error if EINTR is returned and
* no data has been transferred. But what should it do if some
* data has been transferred? I suppose just continue?
*/
else if (nbytesread < 0)
{
/* EINTR is not an error (but will still stop the copy) */
#ifndef CONFIG_DISABLE_SIGNALS
if (errno != EINTR || ntransferred == 0)
#endif
{
/* Read error. Break out and return the error condition. */
ntransferred = ERROR;
endxfr = true;
break;
}
}
}
while (nbytesread < 0);
/* Was anything read? */
if (!endxfr)
{
/* Yes.. Loop until the read side of the transfer comes to some
* conclusion.
*/
wrbuffer = iobuffer;
do
{
/* Write the buffer of data to the outfd */
nbyteswritten = write(outfd, wrbuffer, nbytesread);
/* Check for a complete (or parial) write. write() should not
* return zero.
*/
if (nbyteswritten >= 0)
{
/* Advance the buffer pointer and decrement the number of bytes
* remaining in the iobuffer. Typically, nbytesread will now
* be zero.
*/
wrbuffer += nbyteswritten;
nbytesread -= nbyteswritten;
/* Increment the total number of bytes successfully transferred. */
ntransferred += nbyteswritten;
}
/* Otherwise an error occurred */
else
{
/* Check for a read ERROR. EINTR is a special case. This
* function should break out and return an error if EINTR
* is returned and no data has been transferred. But what
* should it do if some data has been transferred? I
* suppose just continue?
*/
#ifndef CONFIG_DISABLE_SIGNALS
if (errno != EINTR || ntransferred == 0)
#endif
{
/* Write error. Break out and return the error condition */
ntransferred = ERROR;
endxfr = true;
break;
}
}
}
while (nbytesread > 0);
}
}
/* Release the I/O buffer */
free(iobuffer);
/* Return the current file position */
if (offset)
{
/* Use lseek to get the current file position */
off_t curpos = lseek(infd, 0, SEEK_CUR);
if (curpos == (off_t)-1)
{
return ERROR;
}
/* Return the current file position */
*offset = curpos;
/* Use lseek again to restore the original file position */
if (lseek(infd, startpos, SEEK_SET) == (off_t)-1)
{
return ERROR;
}
}
/* Finally return the number of bytes actually transferred (or ERROR
* if any failure occurred).
*/
return ntransferred;
}
#endif /* CONFIG_NSOCKET_DESCRIPTORS > 0 || CONFIG_NFILE_DESCRIPTORS > 0 */