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setvbuf.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.
 */

#include <sm/gen.h>
SM_RCSID("@(#)$Id: setvbuf.c,v 1.32 2001/09/11 04:04:49 gshapiro Exp $")
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <sm/io.h>
#include <sm/heap.h>
#include <sm/assert.h>
#include <sm/conf.h>
#include "local.h"

/*
**  SM_IO_SETVBUF -- set the buffering type for a file
**
**  Set one of the different kinds of buffering, optionally including
**  a buffer.
**  If 'size' is == 0 then an "optimal" size will be selected.
**  If 'buf' is == NULL then space will be allocated at 'size'.
**
**    Parameters:
**          fp -- the file that buffering is to be changed for
**          timeout -- time allowed for completing the function
**          buf -- buffer to use
**          mode -- buffering method to use
**          size -- size of 'buf'
**
**    Returns:
**          Failure: SM_IO_EOF
**          Success: 0 (zero)
*/

int
sm_io_setvbuf(fp, timeout, buf, mode, size)
      SM_FILE_T *fp;
      int timeout;
      char *buf;
      int mode;
      size_t size;
{
      int ret, flags;
      size_t iosize;
      int ttyflag;
#ifndef WIN32
      int fd;
      struct timeval to;
#endif /* WIN32 */

      SM_REQUIRE_ISA(fp, SmFileMagic);

      /*
      **  Verify arguments.  The `int' limit on `size' is due to this
      **  particular implementation.  Note, buf and size are ignored
      **  when setting SM_IO_NBF.
      */

      if (mode != SM_IO_NBF)
            if ((mode != SM_IO_FBF && mode != SM_IO_LBF &&
                mode != SM_IO_NOW) || (int) size < 0)
                  return SM_IO_EOF;

      /*
      **  Write current buffer, if any.  Discard unread input (including
      **  ungetc data), cancel line buffering, and free old buffer if
      **  malloc()ed.  We also clear any eof condition, as if this were
      **  a seek.
      */

      ret = 0;
      SM_CONVERT_TIME(fp, fd, timeout, &to);
      (void) sm_flush(fp, &timeout);
      if (HASUB(fp))
            FREEUB(fp);
      fp->f_r = fp->f_lbfsize = 0;
      flags = fp->f_flags;
      if (flags & SMMBF)
      {
            sm_free((void *) fp->f_bf.smb_base);
            fp->f_bf.smb_base = NULL;
      }
      flags &= ~(SMLBF | SMNBF | SMMBF | SMOPT | SMNPT | SMFEOF | SMNOW |
               SMFBF);

      /* If setting unbuffered mode, skip all the hard work. */
      if (mode == SM_IO_NBF)
            goto nbf;

      /*
      **  Find optimal I/O size for seek optimization.  This also returns
      **  a `tty flag' to suggest that we check isatty(fd), but we do not
      **  care since our caller told us how to buffer.
      */

      flags |= sm_whatbuf(fp, &iosize, &ttyflag);
      if (size == 0)
      {
            buf = NULL; /* force local allocation */
            size = iosize;
      }

      /* Allocate buffer if needed. */
      if (buf == NULL)
      {
            if ((buf = sm_malloc(size)) == NULL)
            {
                  /*
                  **  Unable to honor user's request.  We will return
                  **  failure, but try again with file system size.
                  */

                  ret = SM_IO_EOF;
                  if (size != iosize)
                  {
                        size = iosize;
                        buf = sm_malloc(size);
                  }
            }
            if (buf == NULL)
            {
                  /* No luck; switch to unbuffered I/O. */
nbf:
                  fp->f_flags = flags | SMNBF;
                  fp->f_w = 0;
                  fp->f_bf.smb_base = fp->f_p = fp->f_nbuf;
                  fp->f_bf.smb_size = 1;
                  return ret;
            }
            flags |= SMMBF;
      }

      /*
      **  Kill any seek optimization if the buffer is not the
      **  right size.
      **
      **  SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
      */

      if (size != iosize)
            flags |= SMNPT;

      /*
      **  Fix up the SM_FILE_T fields, and set sm_cleanup for output flush on
      **  exit (since we are buffered in some way).
      */

      if (mode == SM_IO_LBF)
            flags |= SMLBF;
      else if (mode == SM_IO_NOW)
            flags |= SMNOW;
      else if (mode == SM_IO_FBF)
            flags |= SMFBF;
      fp->f_flags = flags;
      fp->f_bf.smb_base = fp->f_p = (unsigned char *)buf;
      fp->f_bf.smb_size = size;
      /* fp->f_lbfsize is still 0 */
      if (flags & SMWR)
      {
            /*
            **  Begin or continue writing: see sm_wsetup().  Note
            **  that SMNBF is impossible (it was handled earlier).
            */

            if (flags & SMLBF)
            {
                  fp->f_w = 0;
                  fp->f_lbfsize = -fp->f_bf.smb_size;
            }
            else
                  fp->f_w = size;
      }
      else
      {
            /* begin/continue reading, or stay in intermediate state */
            fp->f_w = 0;
      }

      atexit(sm_cleanup);
      return ret;
}

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