stdio/obstream.c

   1 /* Copyright (C) 1992, 1996, 1997 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 not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <stdio.h>
  20 #include <obstack.h>
  21 #include <stdarg.h>
  22 #include <string.h>
  23
  24 /* Output-room function for obstack streams.  */
  25
  26 static void
  27 grow (FILE *stream, int c)
  28 {
  29   struct obstack *const obstack = (struct obstack *) stream->__cookie;
  30
  31   /* Move the end of the object back to include only the portion
  32      of the buffer which the user has already written into.  */
  33   obstack_blank_fast (obstack, - (stream->__put_limit - stream->__bufp));
  34
  35   if ((size_t) stream->__target > obstack_object_size (obstack))
  36     {
  37       /* Our target (where the buffer maps to) is always zero except when
  38          the user just did a SEEK_END fseek.  If he sought within the
  39          buffer, we need do nothing and will zero the target below.  If he
  40          sought past the end of the object, grow and zero-fill the object
  41          up to the target address.  */
  42
  43       obstack_blank (obstack,
  44                      stream->__target - obstack_object_size (obstack));
  45       /* fseek has just flushed us, so the put limit points
  46          to the end of the written data.  */
  47       bzero (stream->__put_limit,
  48              stream->__target - stream->__bufsize);
  49     }
  50
  51   if (c != EOF)
  52     obstack_1grow (obstack, (unsigned char) c);
  53
  54   /* The stream buffer always maps exactly to the object on the top
  55      of the obstack.  The start of the buffer is the start of the object.
  56      The put limit points just past the end of the object.  On fflush, the
  57      obstack is sync'd so the end of the object points just past the last
  58      character written to the stream.  */
  59
  60   stream->__target = stream->__offset = 0;
  61   stream->__buffer = obstack_base (obstack);
  62   stream->__bufsize = obstack_room (obstack);
  63   stream->__bufp = obstack_next_free (obstack);
  64   stream->__get_limit = stream->__bufp;
  65
  66   if (c == EOF)
  67     /* This is fflush.  Make the stream buffer, the object,
  68        and the characters actually written all match.  */
  69     stream->__put_limit = stream->__get_limit;
  70   else
  71     {
  72       /* Extend the buffer (and the object) to include
  73          the rest of the obstack chunk (which is uninitialized).
  74          Data past bufp is undefined.  */
  75       stream->__put_limit = stream->__buffer + stream->__bufsize;
  76       obstack_blank_fast (obstack, stream->__put_limit - stream->__bufp);
  77     }
  78 }
  79
  80 /* Seek function for obstack streams.
  81    There is no external state to munge.  */
  82
  83 static int
  84 seek (void *cookie, fpos_t *pos, int whence)
  85 {
  86   switch (whence)
  87     {
  88     case SEEK_SET:
  89     case SEEK_CUR:
  90       return 0;
  91
  92     case SEEK_END:
  93       /* Return the position relative to the end of the object.
  94          fseek has just flushed us, so the obstack is consistent.  */
  95       *pos += obstack_object_size ((struct obstack *) cookie);
  96       return 0;
  97
  98     default:
  99       __libc_fatal ("obstream::seek called with bogus WHENCE\n");
 100       return -1;
 101     }
 102 }
 103
 104 /* Input room function for obstack streams.
 105    Only what has been written to the stream can be read back.  */
 106
 107 static int
 108 input (FILE *stream)
 109 {
 110   /* Re-sync with the obstack, growing the object if necessary.  */
 111   grow (stream, EOF);
 112
 113   if (stream->__bufp < stream->__get_limit)
 114     return (unsigned char) *stream->__bufp++;
 115
 116   stream->__eof = 1;
 117   return EOF;
 118 }
 119 \f
 120 /* Initialize STREAM to talk to OBSTACK.  */
 121
 122 static void
 123 init_obstream (FILE *stream, struct obstack *obstack)
 124 {
 125   stream->__mode.__write = 1;
 126   stream->__mode.__read = 1;
 127
 128   /* Input can read only what has been written.  */
 129   stream->__room_funcs.__input = input;
 130
 131   /* Do nothing for close.  */
 132   stream->__io_funcs.__close = NULL;
 133
 134   /* When the buffer is full, grow the obstack.  */
 135   stream->__room_funcs.__output = grow;
 136
 137   /* Seek within the object, and extend it.  */
 138   stream->__io_funcs.__seek = seek;
 139   stream->__target = stream->__offset = 0;
 140
 141   stream->__seen = 1;
 142
 143   /* Don't deallocate that buffer!  */
 144   stream->__userbuf = 1;
 145
 146   /* We don't have to initialize the buffer.
 147      The first read attempt will call grow, which will do all the work.  */
 148 }
 149
 150 FILE *
 151 open_obstack_stream (obstack)
 152      struct obstack *obstack;
 153 {
 154   register FILE *stream;
 155
 156   stream = __newstream ();
 157   if (stream == NULL)
 158     return NULL;
 159
 160   init_obstream (stream, obstack);
 161   return stream;
 162 }
 163
 164 int
 165 obstack_vprintf (obstack, format, args)
 166       struct obstack *obstack;
 167       const char *format;
 168       va_list args;
 169 {
 170   FILE f;
 171   bzero (&f, sizeof (f));
 172   init_obstream (&f, obstack);
 173   return vfprintf (&f, format, args);
 174 }
 175
 176 int
 177 obstack_printf (struct obstack *obstack, const char *format, ...)
 178 {
 179   int result;
 180   va_list ap;
 181   va_start (ap, format);
 182   result = obstack_vprintf (obstack, format, ap);
 183   va_end (ap);
 184   return result;
 185 }