#include <errno.h>
#include "stdio.h"

extern int __fflush(FILE *);

int __swbuf(int c, FILE *stream) /* Get next output block */
{
	int out, lbs;
	short flags = stream->_flags;

	__STDIO_LOCK(stream);

	if (flags & (__SSTR | __SERR | __SRD)) {
		if (flags & (__SSTR | __SERR)) /* sprintf buffer | error on stream */
		{
			stream->_w = 0;
			errno = EPERM;
			__STDIO_UNLOCK(stream);
			return EOF;
		}

		if (flags & __SRD) { /* was in read mode */
			stream->_r = 0; /* throw away input buffer */
			stream->tmpp = NULL;
			stream->_flags = flags &= ~__SRD;
		}
	}

	lbs = flags & __SLBF ? -stream->_bf._size : 0;
	out = (flags & __SNBF ? 0 : stream->_bf._size - 1) + lbs;

	if (!(flags & __SWR)) /* File wasn't in write mode */
	{
		stream->_p = stream->_bf._base; /* set buffer */
		stream->_w = --out; /* and buffercount */
		stream->_flags = flags |= __SWR;
	} /* and write mode */

	*stream->_p++ = c; /* put this character */
	if (stream->_w < 0 && (stream->_w < lbs || (char) c == '\n')) {
		if (__fflush(stream)) /* Buffer full */
		{
			__STDIO_UNLOCK(stream);
			return EOF;
		}
		stream->_p = stream->_bf._base; /* reset buffer */
		stream->_flags = flags; /* set again - __fflush cleared it. */
	}
	stream->linebufsize = lbs;
	stream->_w = out;
	__STDIO_UNLOCK(stream);

	return c;
}