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  1. /*
  2.  * Copyright (c) 1990 The Regents of the University of California.
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms are permitted
  6.  * provided that the above copyright notice and this paragraph are
  7.  * duplicated in all such forms and that any documentation,
  8.  * advertising materials, and other materials related to such
  9.  * distribution and use acknowledge that the software was developed
  10.  * by the University of California, Berkeley.  The name of the
  11.  * University may not be used to endorse or promote products derived
  12.  * from this software without specific prior written permission.
  13.  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  14.  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  15.  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  16.  */
  17.  
  18. /*
  19. FUNCTION
  20. <<setvbuf>>---specify file or stream buffering
  21.  
  22. INDEX
  23.         setvbuf
  24.  
  25. ANSI_SYNOPSIS
  26.         #include <stdio.h>
  27.         int setvbuf(FILE *<[fp]>, char *<[buf]>,
  28.                     int <[mode]>, size_t <[size]>);
  29.  
  30. TRAD_SYNOPSIS
  31.         #include <stdio.h>
  32.         int setvbuf(<[fp]>, <[buf]>, <[mode]>, <[size]>)
  33.         FILE *<[fp]>;
  34.         char *<[buf]>;
  35.         int <[mode]>;
  36.         size_t <[size]>;
  37.  
  38. DESCRIPTION
  39. Use <<setvbuf>> to specify what kind of buffering you want for the
  40. file or stream identified by <[fp]>, by using one of the following
  41. values (from <<stdio.h>>) as the <[mode]> argument:
  42.  
  43. o+
  44. o _IONBF
  45. Do not use a buffer: send output directly to the host system for the
  46. file or stream identified by <[fp]>.
  47.  
  48. o _IOFBF
  49. Use full output buffering: output will be passed on to the host system
  50. only when the buffer is full, or when an input operation intervenes.
  51.  
  52. o _IOLBF
  53. Use line buffering: pass on output to the host system at every
  54. newline, as well as when the buffer is full, or when an input
  55. operation intervenes.
  56. o-
  57.  
  58. Use the <[size]> argument to specify how large a buffer you wish.  You
  59. can supply the buffer itself, if you wish, by passing a pointer to a
  60. suitable area of memory as <[buf]>.  Otherwise, you may pass <<NULL>>
  61. as the <[buf]> argument, and <<setvbuf>> will allocate the buffer.
  62.  
  63. WARNINGS
  64. You may only use <<setvbuf>> before performing any file operation other
  65. than opening the file.
  66.  
  67. If you supply a non-null <[buf]>, you must ensure that the associated
  68. storage continues to be available until you close the stream
  69. identified by <[fp]>.
  70.  
  71. RETURNS
  72. A <<0>> result indicates success, <<EOF>> failure (invalid <[mode]> or
  73. <[size]> can cause failure).
  74.  
  75. PORTABILITY
  76. Both ANSI C and the System V Interface Definition (Issue 2) require
  77. <<setvbuf>>. However, they differ on the meaning of a <<NULL>> buffer
  78. pointer: the SVID issue 2 specification says that a <<NULL>> buffer
  79. pointer requests unbuffered output.  For maximum portability, avoid
  80. <<NULL>> buffer pointers.
  81.  
  82. Both specifications describe the result on failure only as a
  83. nonzero value.
  84.  
  85. Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
  86. <<lseek>>, <<read>>, <<sbrk>>, <<write>>.
  87. */
  88.  
  89. #include <_ansi.h>
  90. #include <stdio.h>
  91. #include <stdlib.h>
  92. #include "local.h"
  93.  
  94. /*
  95.  * Set one of the three kinds of buffering, optionally including a buffer.
  96.  */
  97.  
  98. int
  99. _DEFUN(setvbuf, (fp, buf, mode, size),
  100.        register FILE * fp _AND
  101.        char *buf          _AND
  102.        register int mode  _AND
  103.        register size_t size)
  104. {
  105.   int ret = 0;
  106.   struct _reent *reent = _REENT;
  107.  
  108.   CHECK_INIT (reent, fp);
  109.  
  110.   _newlib_flockfile_start (fp);
  111.  
  112.   /*
  113.    * Verify arguments.  The `int' limit on `size' is due to this
  114.    * particular implementation.
  115.    */
  116.  
  117.   if ((mode != _IOFBF && mode != _IOLBF && mode != _IONBF) || (int)(_POINTER_INT) size < 0)
  118.     {
  119.       _newlib_flockfile_exit (fp);
  120.       return (EOF);
  121.     }
  122.  
  123.   /*
  124.    * Write current buffer, if any; drop read count, if any.
  125.    * Make sure putc() will not think fp is line buffered.
  126.    * Free old buffer if it was from malloc().  Clear line and
  127.    * non buffer flags, and clear malloc flag.
  128.    */
  129.  
  130.   _fflush_r (reent, fp);
  131.   fp->_r = 0;
  132.   fp->_lbfsize = 0;
  133.   if (fp->_flags & __SMBF)
  134.     _free_r (reent, (_PTR) fp->_bf._base);
  135.   fp->_flags &= ~(__SLBF | __SNBF | __SMBF);
  136.  
  137.   if (mode == _IONBF)
  138.     goto nbf;
  139.  
  140.   /*
  141.    * Allocate buffer if needed. */
  142.   if (buf == NULL)
  143.     {
  144.       /* we need this here because malloc() may return a pointer
  145.          even if size == 0 */
  146.       if (!size) size = BUFSIZ;
  147.       if ((buf = malloc (size)) == NULL)
  148.         {
  149.           ret = EOF;
  150.           /* Try another size... */
  151.           buf = malloc (BUFSIZ);
  152.           size = BUFSIZ;
  153.         }
  154.       if (buf == NULL)
  155.         {
  156.           /* Can't allocate it, let's try another approach */
  157. nbf:
  158.           fp->_flags |= __SNBF;
  159.           fp->_w = 0;
  160.           fp->_bf._base = fp->_p = fp->_nbuf;
  161.           fp->_bf._size = 1;
  162.           _newlib_flockfile_exit (fp);
  163.           return (ret);
  164.         }
  165.       fp->_flags |= __SMBF;
  166.     }
  167.   /*
  168.    * Now put back whichever flag is needed, and fix _lbfsize
  169.    * if line buffered.  Ensure output flush on exit if the
  170.    * stream will be buffered at all.
  171.    * If buf is NULL then make _lbfsize 0 to force the buffer
  172.    * to be flushed and hence malloced on first use
  173.    */
  174.  
  175.   switch (mode)
  176.     {
  177.     case _IOLBF:
  178.       fp->_flags |= __SLBF;
  179.       fp->_lbfsize = buf ? -size : 0;
  180.       /* FALLTHROUGH */
  181.  
  182.     case _IOFBF:
  183.       /* no flag */
  184.       reent->__cleanup = _cleanup_r;
  185.       fp->_bf._base = fp->_p = (unsigned char *) buf;
  186.       fp->_bf._size = size;
  187.       break;
  188.     }
  189.  
  190.   /*
  191.    * Patch up write count if necessary.
  192.    */
  193.  
  194.   if (fp->_flags & __SWR)
  195.     fp->_w = fp->_flags & (__SLBF | __SNBF) ? 0 : size;
  196.  
  197.   _newlib_flockfile_end (fp);
  198.   return 0;
  199. }
  200.