stdio/obstream.c

   1 /* Copyright (C) 1992 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <stdio.h>
  21 #include <obstack.h>
  22 #include <stdarg.h>
  23 #include <string.h>
  24
  25 /* Output-room function for obstack streams.  */
  26
  27 static void
  28 DEFUN(grow, (stream, c), FILE *stream AND int c)
  29 {
  30   struct obstack *const obstack = (struct obstack *) stream->__cookie;
  31
  32   /* Move the end of the object back to include only the portion
  33      of the buffer which the user has already written into.  */
  34   obstack_blank_fast (obstack, - (stream->__put_limit - stream->__bufp));
  35
  36   if (stream->__target > obstack_object_size (obstack))
  37     {
  38       /* Our target (where the buffer maps to) is always zero except when
  39          the user just did a SEEK_END fseek.  If he sought within the
  40          buffer, we need do nothing and will zero the target below.  If he
  41          sought past the end of the object, grow and zero-fill the object
  42          up to the target address.  */
  43
  44       obstack_blank (obstack,
  45                      stream->__target - obstack_object_size (obstack));
  46       /* fseek has just flushed us, so the put limit points
  47          to the end of the written data.  */
  48       bzero (stream->__put_limit,
  49              stream->__target - stream->__bufsize);
  50     }
  51
  52   if (c != EOF)
  53     obstack_1grow (obstack, (unsigned char) c);
  54
  55   /* The stream buffer always maps exactly to the object on the top
  56      of the obstack.  The start of the buffer is the start of the object.
  57      The put limit points just past the end of the object.  On fflush, the
  58      obstack is sync'd so the end of the object points just past the last
  59      character written to the stream.  */
  60
  61   stream->__target = stream->__offset = 0;
  62   stream->__buffer = obstack_base (obstack);
  63   stream->__bufsize = obstack_room (obstack);
  64   stream->__bufp = obstack_next_free (obstack);
  65   stream->__get_limit = stream->__bufp;
  66
  67   if (c == EOF)
  68     /* This is fflush.  Make the stream buffer, the object,
  69        and the characters actually written all match.  */
  70     stream->__put_limit = stream->__get_limit;
  71   else
  72     {
  73       /* Extend the buffer (and the object) to include
  74          the rest of the obstack chunk (which is unitialized).
  75          Data past bufp is undefined.  */
  76       stream->__put_limit = stream->__buffer + stream->__bufsize;
  77       obstack_blank_fast (obstack, stream->__put_limit - stream->__bufp);
  78     }
  79 }
  80
  81 /* Seek function for obstack streams.
  82    There is no external state to munge.  */
  83
  84 static int
  85 DEFUN(seek, (cookie, pos, whence),
  86       PTR cookie AND fpos_t *pos AND int whence)
  87 {
  88   switch (whence)
  89     {
  90     case SEEK_SET:
  91     case SEEK_CUR:
  92       return 0;
  93
  94     case SEEK_END:
  95       /* Return the position relative to the end of the object.
  96          fseek has just flushed us, so the obstack is consistent.  */
  97       *pos += obstack_object_size ((struct obstack *) cookie);
  98       return 0;
  99
 100     default:
 101       __libc_fatal ("obstream::seek called with bogus WHENCE\n");
 102       return -1;
 103     }
 104 }
 105
 106 /* Input room function for obstack streams.
 107    Only what has been written to the stream can be read back.  */
 108
 109 static int
 110 DEFUN(input, (stream), FILE *stream)
 111 {
 112   /* Re-sync with the obstack, growing the object if necessary.  */
 113   grow (stream, EOF);
 114
 115   if (stream->__bufp < stream->__get_limit)
 116     return (unsigned char) *stream->__bufp++;
 117
 118   stream->__eof = 1;
 119   return EOF;
 120 }
 121 \f
 122 /* Initialize STREAM to talk to OBSTACK.  */
 123
 124 static void
 125 DEFUN(init_obstream, (stream, obstack),
 126       FILE *stream AND struct obstack *obstack)
 127 {
 128   stream->__mode.__write = 1;
 129   stream->__mode.__read = 1;
 130
 131   /* Input can read only what has been written.  */
 132   stream->__room_funcs.__input = input;
 133
 134   /* Do nothing for close.  */
 135   stream->__io_funcs.__close = NULL;
 136
 137   /* When the buffer is full, grow the obstack.  */
 138   stream->__room_funcs.__output = grow;
 139
 140   /* Seek within the object, and extend it.  */
 141   stream->__io_funcs.__seek = seek;
 142   stream->__target = stream->__offset = 0;
 143
 144   stream->__seen = 1;
 145
 146   /* Don't deallocate that buffer!  */
 147   stream->__userbuf = 1;
 148
 149   /* We don't have to initialize the buffer.
 150      The first read attempt will call grow, which will do all the work.  */
 151 }
 152
 153 FILE *
 154 open_obstack_stream (obstack)
 155      struct obstack *obstack;
 156 {
 157   register FILE *stream;
 158
 159   stream = __newstream ();
 160   if (stream == NULL)
 161     return NULL;
 162
 163   init_obstream (stream, obstack);
 164   return stream;
 165 }
 166
 167 int
 168 DEFUN(obstack_vprintf, (obstack, format, args),
 169       struct obstack *obstack AND const char *format AND va_list args)
 170 {
 171   FILE f;
 172   bzero (&f, sizeof (f));
 173   init_obstream (&f, obstack);
 174   return vfprintf (&f, format, args);
 175 }
 176
 177 int
 178 DEFUN(obstack_printf, (obstack, format),
 179       struct obstack *obstack AND const char *format DOTS)
 180 {
 181   int result;
 182   va_list ap;
 183   va_start (ap, format);
 184   result = obstack_vprintf (obstack, format, ap);
 185   va_end (ap);
 186   return result;
 187 }