sendmail/libsm/makebuf.c

/*
 * 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: makebuf.c,v 1.26 2001/10/31 16:04:08 ca Exp $")
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sm/io.h>
#include <sm/heap.h>
#include <sm/conf.h>
#include "local.h"

/*
**  SM_MAKEBUF -- make a buffer for the file
**
**  Parameters:
**      fp -- the file to be buffered
**
**  Returns:
**      nothing
**
**  Allocate a file buffer, or switch to unbuffered I/O.
**  By default tty devices default to line buffered.
*/

void
sm_makebuf(fp)
    register SM_FILE_T *fp;
{
    register void *p;
    register int flags;
    size_t size;
    int couldbetty;

    if (fp->f_flags & SMNBF)
    {
        fp->f_bf.smb_base = fp->f_p = fp->f_nbuf;
        fp->f_bf.smb_size = 1;
        return;
    }
    flags = sm_whatbuf(fp, &size, &couldbetty);
    if ((p = sm_malloc(size)) == NULL)
    {
        fp->f_flags |= SMNBF;
        fp->f_bf.smb_base = fp->f_p = fp->f_nbuf;
        fp->f_bf.smb_size = 1;
        return;
    }
    if (!Sm_IO_DidInit)
        sm_init();
    flags |= SMMBF;
    fp->f_bf.smb_base = fp->f_p = p;
    fp->f_bf.smb_size = size;
    if (couldbetty && isatty(fp->f_file))
        flags |= SMLBF;
    fp->f_flags |= flags;
}

/*
**  SM_WHATBUF -- determine proper buffer for a file (internal)
**
**  Plus it fills in 'bufsize' for recommended buffer size and
**  fills in flag to indicate if 'fp' could be a tty (nothing
**  to do with "betty" :-) ).
**
**  Parameters:
**      fp -- file pointer to be buffered
**      bufsize -- new buffer size (a return)
**      couldbetty -- could be a tty (returns)
**
**  Returns:
**      Success:
**      on error:
**          SMNPT -- not seek opimized
**          SMOPT -- seek opimized
*/

int
sm_whatbuf(fp, bufsize, couldbetty)
    register SM_FILE_T *fp;
    size_t *bufsize;
    int *couldbetty;
{
    struct stat st;

    if (fp->f_file < 0 || fstat(fp->f_file, &st) < 0)
    {
        *couldbetty = 0;
        *bufsize = SM_IO_BUFSIZ;
        return SMNPT;
    }

    /* could be a tty iff it is a character device */
    *couldbetty = S_ISCHR(st.st_mode);
    if (st.st_blksize == 0)
    {
        *bufsize = SM_IO_BUFSIZ;
        return SMNPT;
    }

#if SM_IO_MAX_BUF_FILE > 0
    if (S_ISREG(st.st_mode) && st.st_blksize > SM_IO_MAX_BUF_FILE)
        st.st_blksize = SM_IO_MAX_BUF_FILE;
#endif /* SM_IO_MAX_BUF_FILE > 0 */

#if SM_IO_MAX_BUF > 0 || SM_IO_MIN_BUF > 0
    if (!S_ISREG(st.st_mode))
    {
# if SM_IO_MAX_BUF > 0
        if (st.st_blksize > SM_IO_MAX_BUF)
            st.st_blksize = SM_IO_MAX_BUF;
#  if SM_IO_MIN_BUF > 0
        else
#  endif /* SM_IO_MIN_BUF > 0 */
# endif /* SM_IO_MAX_BUF > 0 */
# if SM_IO_MIN_BUF > 0
        if (st.st_blksize < SM_IO_MIN_BUF)
            st.st_blksize = SM_IO_MIN_BUF;
# endif /* SM_IO_MIN_BUF > 0 */
    }
#endif /* SM_IO_MAX_BUF > 0 || SM_IO_MIN_BUF > 0 */

    /*
    **  Optimise fseek() only if it is a regular file.  (The test for
    **  sm_std_seek is mainly paranoia.)  It is safe to set _blksize
    **  unconditionally; it will only be used if SMOPT is also set.
    */

    if ((fp->f_flags & SMSTR) == 0)
    {
        *bufsize = st.st_blksize;
        fp->f_blksize = st.st_blksize;
    }
    else
        *bufsize = SM_IO_BUFSIZ;
    if ((st.st_mode & S_IFMT) == S_IFREG &&
        fp->f_seek == sm_stdseek)
        return SMOPT;
    else
        return SMNPT;
}