/*
 * Copyright (c) 2000-2001 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/gen.h>
SM_RCSID("@(#)$Id: fread.c,v 1.26 2001/02/28 20:54:03 ca Exp $")
#include <string.h>
#include <errno.h>
#include <sm/io.h>
#include <sm/assert.h>
#include "local.h"

/*
**  SM_IO_READ -- read data from the file pointer
**
**      Parameters:
**              fp -- file pointer to read from
**              timeout -- time to complete the read
**              buf -- location to place read data
**              size -- size of each chunk of data
**
**      Returns:
**              Failure: returns 0 (zero) _and_ sets errno
**              Success: returns the number of whole chunks read.
**
**      A read returning 0 (zero) is only an indication of error when errno
**      has been set.
*/

size_t
sm_io_read(fp, timeout, buf, size)
        SM_FILE_T *fp;
        int timeout;
        void *buf;
        size_t size;
{
        register size_t resid = size;
        register char *p;
        register int r;

        SM_REQUIRE_ISA(fp, SmFileMagic);

        if (fp->f_read == NULL)
        {
                errno = ENODEV;
                return 0;
        }

        /*
        **  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.
        */

        if (resid == 0)
                return 0;
        if (fp->f_r < 0)
                fp->f_r = 0;
        p = buf;
        while ((int) resid > (r = fp->f_r))
        {
                (void) memcpy((void *) p, (void *) fp->f_p, (size_t) r);
                fp->f_p += r;
                /* fp->f_r = 0 ... done in sm_refill */
                p += r;
                resid -= r;
                if ((fp->f_flags & SMNOW) != 0 && r > 0)
                {
                        /*
                        **  Take whatever we have available. Spend no more time
                        **  trying to get all that has been requested.
                        **  This is needed on some file types (such as
                        **  SASL) that would jam when given extra, untimely
                        **  reads.
                        */

                        fp->f_r -= r;
                        return size - resid;
                }
                if (sm_refill(fp, timeout) != 0)
                {
                        /* no more input: return partial result */
                        return size - resid;
                }
        }
        (void) memcpy((void *) p, (void *) fp->f_p, resid);
        fp->f_r -= resid;
        fp->f_p += resid;
        return size;
}