/***
*fwrite.c - read from a stream
*
*	Copyright (c) 1989-1992, Microsoft Corporation. All rights reserved.
*
*Purpose:
*	Write to the specified stream from the user's buffer.
*
*Revision History:
*	06-23-89  PHG	Module created, based on asm version
*	01-18-90  GJF	Must call _fflush_lk() rather than fflush().
*	02-15-90  GJF	_iob[], _iob2[] merge. Also, fixed copyright and
*			indents.
*	03-19-90  GJF	Made calling type _CALLTYPE1 and added #include
*			<cruntime.h>. Also, fixed compiler warning.
*	05-29-90  SBM   Use _flush, not [_]fflush[_lk]
*	07-26-90  SBM   Added #include <internal.h>
*	08-14-90  SBM	Compiles cleanly with -W3
*	10-02-90  GJF	New-style function declarators.
*	01-22-91  GJF	ANSI naming.
*	03-27-92  DJM	POSIX support.
*	08-26-92  GJF	Include unistd.h for POSIX build.
*
*******************************************************************************/

#include <cruntime.h>
#ifdef	_POSIX_
#include <unistd.h>
#endif
#include <stdio.h>
#include <os2dll.h>
#include <io.h>
#include <string.h>
#include <file2.h>
#include <internal.h>

/***
*size_t fwrite(void *buffer, size_t size, size_t count, FILE *stream) -
*	write to the specified stream from the specified buffer.
*
*Purpose:
*	Write 'count' items of size 'size' to the specified stream from
*	the specified buffer. Return when 'count' items have been written
*	or no more items can be written to the stream.
*
*Entry:
*	buffer	- pointer to user's buffer
*	size	- size of the item to write
*	count	- number of items to write
*	stream	- stream to write to
*
*Exit:
*	Returns the number of (whole) items that were written to the stream.
*	This may be less than 'count' if an error or eof occurred. In this
*	case, ferror() or feof() should be used to distinguish between the
*	two conditions.
*
*Notes:
*	fwrite will attempt to buffer the stream (side effect of the _flsbuf
*	call) if necessary.
*
*	No more than 0xFFFE bytes may be written out at a time by a call to
*	write(). Further, write() does not handle huge buffers. Therefore,
*	in large data models, the write request is broken down into chunks
*	that do not violate these considerations. Each of these chunks is
*	processed much like an fwrite() call in a small data model (by a
*	call to _nfwrite()).
*
*	This code depends on _iob[] being a near array.
*
*	MTHREAD/DLL - Handled in just two layers since it is small data
*	model. The outer layer, fwrite(), handles stream locking/unlocking
*	and calls _fwrite_lk() to do the work. _fwrite_lk() is the same as
*	the single-thread, small data model version of fwrite().
*
*******************************************************************************/


#ifdef MTHREAD
/* define locking/unlocking version */
size_t _CALLTYPE1 fwrite (
	const void *buffer,
	size_t size,
	size_t count,
	FILE *stream
	)
{
	int index;
	size_t retval;

	index = _iob_index(stream);
	_lock_str(index);			/* lock stream */
	retval = _fwrite_lk(buffer, size, count, stream);  /* do the read */
	_unlock_str(index);			/* unlock stream */
	return retval;
}
#endif

/* define the normal version */
#ifdef MTHREAD
size_t _CALLTYPE1 _fwrite_lk (
#else
size_t _CALLTYPE1 fwrite (
#endif
	const void *buffer,
	size_t size,
	size_t num,
	FILE *stream
	)
{
	const char *data;		/* point to where data comes from next */
	unsigned total; 		/* total bytes to write */
	unsigned count; 		/* num bytes left to write */
	unsigned bufsize;		/* size of stream buffer */
	unsigned nbytes;		/* number of bytes to write now */
	unsigned nwritten;		/* number of bytes written */
	int c;				/* a temp char */

	/* initialize local vars */
	data = buffer;
	count = total = size * num;
	if (anybuf(stream))
		/* already has buffer, use its size */
		bufsize = stream->_bufsiz;
	else
		/* assume will get BUFSIZ buffer */
		bufsize = BUFSIZ;

	/* here is the main loop -- we go through here until we're done */
	while (count != 0) {
		/* if the buffer is big and has room, copy data to buffer */
		if (bigbuf(stream) && stream->_cnt != 0) {
			/* how much do we want? */
			nbytes = (count < (unsigned)stream->_cnt) ? count : stream->_cnt;
			memcpy(stream->_ptr, data, nbytes);

			/* update stream and amt of data written */
			count -= nbytes;
			stream->_cnt -= nbytes;
			stream->_ptr += nbytes;
			data += nbytes;
		}
		else if (count >= bufsize) {
			/* If we have more than bufsize chars to write, write
			   data by calling write with an integral number of
			   bufsiz blocks.  If we reach here and we have a big
			   buffer, it must be full so _flush it. */

			if (bigbuf(stream)) {
				if (_flush(stream)) {
					/* error, stream flags set -- we're out
					   of here */
					return (total - count) / size;
				}
			}

			/* calc chars to read -- (count/bufsize) * bufsize */
			nbytes = count - count % bufsize;

#ifdef _POSIX_
			nwritten = write(fileno(stream), data, nbytes);
#else
			nwritten = _write(_fileno(stream), data, nbytes);
#endif
			if (nwritten == (unsigned)EOF) {
				/* error -- out of here */
				stream->_flag |= _IOERR;
				return (total - count) / size;
			}

			/* update count and data to reflect write */

			count -= nwritten;
			data += nwritten;

			if (nwritten < nbytes) {
				/* error -- out of here */
				stream->_flag |= _IOERR;
				return (total - count) / size;
			}
		}
		else {
			/* buffer full and not enough chars to do direct write,
			   so do a _flsbuf. */
			c = *data;  /* _flsbuf write one char, this is it */
			if (_flsbuf(c, stream) == EOF) {
				/* error or eof, stream flags set by _flsbuf */
				return (total - count) / size;
			}

			/* _flsbuf wrote a char -- update count */
			++data;
			--count;

			/* update buffer size */
			bufsize = stream->_bufsiz > 0 ? stream->_bufsiz : 1;
		}
	}

	/* we finished successfully, so just return num */
	return num;
}