/*
 * Copyright (c) 2000-2002, 2005 Sendmail, Inc. and its suppliers.
 *      All rights reserved.
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * By using this file, you agree to the terms and conditions set
 * forth in the LICENSE file which can be found at the top level of
 * the sendmail distribution.
 */

#include "sm/generic.h"
SM_RCSID("@(#)$Id: fread.c,v 1.18 2006/07/14 14:42:25 ca Exp $")
#include "sm/error.h"
#include "sm/io.h"
#include "sm/assert.h"
#include "sm/memops.h"
#include "io-int.h"

/*
**  SM_IO_READ -- read data from the file pointer
**
**	Parameters:
**		fp -- file pointer to read from
**		buf -- location to place read data
**		size -- size of each chunk of data
**		bytesread -- number of bytes read (output)
**
**	Returns:
**		usual sm_error code
*/

sm_ret_T
sm_io_read(sm_file_T *fp, uchar *buf, size_t size, ssize_t *bytesread)
{
	size_t ltr;
	uchar *p;
	int r;
	sm_ret_T res;

	SM_IS_FP(fp);

	if (f_read(*fp) == NULL)
		return sm_error_perm(SM_EM_IO, ENODEV);

	/*
	**  The ANSI standard requires a return value of 0 for a count
	**  or a size of 0.  Peculiarily, it imposes no such requirements
	**  on fwrite; it only requires read to be broken.
	*/

	ltr = size;
	if (ltr == 0)
	{
		*bytesread = 0;
		return SM_SUCCESS;
	}
	if (f_r(*fp) < 0)
		f_r(*fp) = 0;
	p = buf;
	while ((int) ltr > (r = f_r(*fp)))
	{
		if (r > 0)
		{
			(void) sm_memcpy((void *) p, (void *) f_p(*fp),
					(size_t) r);
			f_p(*fp) += r;
			f_r(*fp) = 0;	/* same as f_r(*fp) -= r */
			p += r;
			ltr -= r;
		}

		/* non blocking and have data? return with that */
		/* XXX is this correct? */
		if (!sm_io_blocking(fp) && r > 0)
		{
			*bytesread = size - ltr;
			if (*bytesread > 0)
				return SM_SUCCESS;
			return sm_error_temp(SM_EM_IO, EAGAIN);
		}

		res = sm_refill(fp);
		if (sm_is_err(res))
		{
			/* no more input: return partial result */
			*bytesread = size - ltr;
			if (*bytesread > 0 &&
			    (sm_is_temp_err(res) || res == SM_IO_EOF))
				return SM_SUCCESS;
			return res;
		}
	}
	(void) sm_memcpy((void *) p, (void *) f_p(*fp), ltr);
	f_r(*fp) -= ltr;
	f_p(*fp) += ltr;
	*bytesread = size;
	return SM_SUCCESS;
}