library/stdio_dropiobreadbuffer.c
/*
* $Id: stdio_dropiobreadbuffer.c,v 1.9 2006-01-08 12:04:24 obarthel Exp $
*
* :ts=4
*
* Portable ISO 'C' (1994) runtime library for the Amiga computer
* Copyright (c) 2002-2015 by Olaf Barthel <obarthel (at) gmx.net>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Neither the name of Olaf Barthel nor the names of 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.
*/
/* This would otherwise generate far too much (useless) debug output. */
#ifdef DEBUG
#undef DEBUG
#endif /* DEBUG */
#ifndef _STDIO_HEADERS_H
#include "stdio_headers.h"
#endif /* _STDIO_HEADERS_H */
/****************************************************************************/
int
__drop_iob_read_buffer(struct iob * file)
{
int result = OK;
ENTER();
SHOWPOINTER(file);
assert( file != NULL );
if(__check_abort_enabled)
__check_abort();
assert( FLAG_IS_SET(file->iob_Flags,IOBF_IN_USE) );
assert( file->iob_BufferSize > 0 );
if(FLAG_IS_SET(file->iob_Flags,IOBF_IN_USE))
{
CLEAR_FLAG(file->iob_Flags,IOBF_EOF_REACHED);
if(__iob_read_buffer_is_valid(file))
{
LONG num_unread_bytes;
num_unread_bytes = __iob_num_unread_bytes(file);
D(("%ld bytes are to be dropped",num_unread_bytes));
if(num_unread_bytes > 0)
{
struct file_action_message fam;
LONG position;
SHOWMSG("calling the action function");
fam.fam_Action = file_action_seek;
fam.fam_Offset = -num_unread_bytes;
fam.fam_Mode = SEEK_CUR;
assert( file->iob_Action != NULL );
/* Note that a return value of -1 (= SEEK_ERROR) may be a
valid file position in files larger than 2 GBytes. Just
to be sure, we therefore also check the secondary error
to verify that what could be a file position is really
an error indication. */
position = (*file->iob_Action)(file,&fam);
if(position == SEEK_ERROR && fam.fam_Error != OK)
{
SHOWMSG("that didn't work");
result = ERROR;
SET_FLAG(file->iob_Flags,IOBF_ERROR);
__set_errno(fam.fam_Error);
goto out;
}
/* If this is a valid file position, clear 'errno' so that
it cannot be mistaken for an error. */
if(position < 0)
__set_errno(OK);
}
file->iob_BufferReadBytes = 0;
file->iob_BufferPosition = 0;
}
}
out:
RETURN(result);
return(result);
}