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sortix--sortix/libc/ungetc.cpp

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/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2011, 2012.
This file is part of the Sortix C Library.
The Sortix C Library is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
The Sortix C Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
ungetc.cpp
Inserts data in front of the current read queue, allowing applications to
peek the incoming data and pretend they didn't.
*******************************************************************************/
#include <stdio.h>
#include <errno.h>
#include <string.h>
extern "C" int ungetc(int c, FILE* fp)
{
if ( !(fp->flags & _FILE_BUFFER_MODE_SET) )
if ( fsetdefaultbuf(fp) != 0 )
return EOF; // TODO: ferror doesn't report error!
if ( !fp->read_func || fp->buffer_mode == _IONBF )
return EOF;
if ( fp->flags & _FILE_LAST_WRITE )
fflush_stop_writing(fp);
fp->flags |= _FILE_LAST_READ;
if ( fp->offset_input_buffer == 0 )
{
size_t amount = fp->amount_input_buffered - fp->offset_input_buffer;
size_t offset = fp->buffersize - amount;
if ( !offset )
return EOF;
memmove(fp->buffer + offset, fp->buffer, sizeof(fp->buffer[0]) * amount);
fp->offset_input_buffer = offset;
fp->amount_input_buffered = offset + amount;
}
fp->buffer[--fp->offset_input_buffer] = c;
return c;
}