sendmail/libsm/fread.c

	fread.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * 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.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#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;
}