libguile/strports.c

   1 /*      Copyright (C) 1995,1996,1998,1999 Free Software Foundation, Inc.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2, or (at your option)
   6  * any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this software; see the file COPYING.  If not, write to
  15  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  16  * Boston, MA 02111-1307 USA
  17  *
  18  * As a special exception, the Free Software Foundation gives permission
  19  * for additional uses of the text contained in its release of GUILE.
  20  *
  21  * The exception is that, if you link the GUILE library with other files
  22  * to produce an executable, this does not by itself cause the
  23  * resulting executable to be covered by the GNU General Public License.
  24  * Your use of that executable is in no way restricted on account of
  25  * linking the GUILE library code into it.
  26  *
  27  * This exception does not however invalidate any other reasons why
  28  * the executable file might be covered by the GNU General Public License.
  29  *
  30  * This exception applies only to the code released by the
  31  * Free Software Foundation under the name GUILE.  If you copy
  32  * code from other Free Software Foundation releases into a copy of
  33  * GUILE, as the General Public License permits, the exception does
  34  * not apply to the code that you add in this way.  To avoid misleading
  35  * anyone as to the status of such modified files, you must delete
  36  * this exception notice from them.
  37  *
  38  * If you write modifications of your own for GUILE, it is your choice
  39  * whether to permit this exception to apply to your modifications.
  40  * If you do not wish that, delete this exception notice.  */
  41
  42 /* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
  43    gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
  44
  45 \f
  46
  47 #include "_scm.h"
  48
  49 #include <stdio.h>
  50 #ifdef HAVE_UNISTD_H
  51 #include <unistd.h>
  52 #endif
  53
  54 #include "unif.h"
  55 #include "eval.h"
  56 #include "read.h"
  57
  58 #include "strports.h"
  59
  60 #ifdef HAVE_STRING_H
  61 #include <string.h>
  62 #endif
  63
  64 \f
  65
  66 /* {Ports - string ports}
  67  *
  68  */
  69
  70 /* NOTES:
  71    write_buf/write_end point to the ends of the allocated string.
  72    read_buf/read_end in principle point to the part of the string which
  73    has been written to, but this is only updated after a flush.
  74    read_pos and write_pos in principle should be equal, but this is only true
  75    when rw_active is SCM_PORT_NEITHER.
  76 */
  77
  78 static int
  79 stfill_buffer (SCM port)
  80 {
  81   scm_port *pt = SCM_PTAB_ENTRY (port);
  82
  83   if (pt->read_pos >= pt->read_end)
  84     return EOF;
  85   else
  86     return scm_return_first (*pt->read_pos, port);
  87 }
  88
  89 /* change the size of a port's string to new_size.  this doesn't
  90    change read_buf_size.  */
  91 static void
  92 st_resize_port (scm_port *pt, off_t new_size)
  93 {
  94   off_t index = pt->write_pos - pt->write_buf;
  95
  96   pt->write_buf_size = new_size;
  97
  98   scm_vector_set_length_x (pt->stream, SCM_MAKINUM (new_size));
  99
 100   /* reset buffer in case reallocation moved the string. */
 101   {
 102     pt->read_buf = pt->write_buf = SCM_CHARS (pt->stream);
 103     pt->read_pos = pt->write_pos = pt->write_buf + index;
 104     pt->write_end = pt->write_buf + pt->write_buf_size;
 105     pt->read_end = pt->read_buf + pt->read_buf_size;
 106   }
 107 }
 108
 109 /* amount by which write_buf is expanded.  */
 110 #define SCM_WRITE_BLOCK 80
 111
 112 /* ensure that write_pos < write_end by enlarging the buffer when
 113    necessary.  update read_buf to account for written chars.  */
 114 static void
 115 st_flush (SCM port)
 116 {
 117   scm_port *pt = SCM_PTAB_ENTRY (port);
 118
 119   if (pt->write_pos == pt->write_end)
 120     {
 121       st_resize_port (pt, pt->write_buf_size + SCM_WRITE_BLOCK);
 122     }
 123   pt->read_pos = pt->write_pos;
 124   if (pt->read_pos > pt->read_end)
 125     {
 126       pt->read_end = (unsigned char *) pt->read_pos;
 127       pt->read_buf_size = pt->read_end - pt->read_buf;
 128     }
 129   pt->rw_active = SCM_PORT_NEITHER;
 130 }
 131
 132 static void
 133 st_write (SCM port, void *data, size_t size)
 134 {
 135   scm_port *pt = SCM_PTAB_ENTRY (port);
 136   const char *input = (char *) data;
 137
 138   while (size > 0)
 139     {
 140       int space = pt->write_end - pt->write_pos;
 141       int write_len = (size > space) ? space : size;
 142
 143       strncpy (pt->write_pos, input, write_len);
 144       pt->write_pos += write_len;
 145       size -= write_len;
 146       input += write_len;
 147       if (write_len == space)
 148         st_flush (port);
 149     }
 150 }
 151
 152 static void
 153 st_end_input (SCM port, int offset)
 154 {
 155   scm_port *pt = SCM_PTAB_ENTRY (port);
 156
 157   if (pt->read_pos - pt->read_buf < offset)
 158     scm_misc_error ("st_end_input", "negative position", SCM_EOL);
 159
 160   pt->write_pos = (unsigned char *) pt->read_pos = pt->read_pos - offset;
 161   pt->rw_active = SCM_PORT_NEITHER;
 162 }
 163
 164 static off_t
 165 st_seek (SCM port, off_t offset, int whence)
 166 {
 167   scm_port *pt = SCM_PTAB_ENTRY (port);
 168   off_t target;
 169
 170   if (pt->rw_active == SCM_PORT_READ && offset == 0 && whence == SEEK_CUR)
 171     /* special case to avoid disturbing the unread-char buffer.  */
 172     {
 173       if (pt->read_buf == pt->putback_buf)
 174         {
 175           target = pt->saved_read_pos - pt->saved_read_buf
 176             - (pt->read_end - pt->read_pos);
 177         }
 178       else
 179         {
 180           target = pt->read_pos - pt->read_buf;
 181         }
 182     }
 183   else
 184     /* all other cases.  */
 185     {
 186       if (pt->rw_active == SCM_PORT_WRITE)
 187         st_flush (port);
 188
 189       if (pt->rw_active == SCM_PORT_READ)
 190         scm_end_input (port);
 191
 192       switch (whence)
 193         {
 194         case SEEK_CUR:
 195           target = pt->read_pos - pt->read_buf + offset;
 196           break;
 197         case SEEK_END:
 198           target = pt->read_end - pt->read_buf + offset;
 199           break;
 200         default: /* SEEK_SET */
 201           target = offset;
 202           break;
 203         }
 204
 205       if (target < 0)
 206         scm_misc_error ("st_seek", "negative offset", SCM_EOL);
 207
 208       if (target >= pt->write_buf_size)
 209         {
 210           if (!(SCM_CAR (port) & SCM_WRTNG))
 211             {
 212               if (target > pt->write_buf_size)
 213                 {
 214                   scm_misc_error ("st_seek",
 215                                   "seek past end of read-only strport",
 216                                   SCM_EOL);
 217                 }
 218             }
 219           else
 220             {
 221               st_resize_port (pt, target + (target == pt->write_buf_size
 222                                             ? SCM_WRITE_BLOCK
 223                                             : 0));
 224             }
 225         }
 226       pt->read_pos = pt->write_pos = pt->read_buf + target;
 227       if (pt->read_pos > pt->read_end)
 228         {
 229           pt->read_end = (unsigned char *) pt->read_pos;
 230           pt->read_buf_size = pt->read_end - pt->read_buf;
 231         }
 232     }
 233   return target;
 234 }
 235
 236 static void
 237 st_truncate (SCM port, off_t length)
 238 {
 239   scm_port *pt = SCM_PTAB_ENTRY (port);
 240
 241   if (length > pt->write_buf_size)
 242     st_resize_port (pt, length);
 243
 244   pt->read_buf_size = length;
 245   pt->read_end = pt->read_buf + length;
 246   if (pt->read_pos > pt->read_end)
 247     pt->read_pos = pt->read_end;
 248
 249   if (pt->write_pos > pt->read_end)
 250     pt->write_pos = pt->read_end;
 251 }
 252
 253 SCM
 254 scm_mkstrport (SCM pos, SCM str, long modes, const char *caller)
 255 {
 256   SCM z;
 257   scm_port *pt;
 258   int str_len;
 259
 260   SCM_ASSERT (SCM_INUMP(pos) && SCM_INUM(pos) >= 0, pos, SCM_ARG1, caller);
 261   SCM_ASSERT (SCM_ROSTRINGP(str), str, SCM_ARG1, caller);
 262   str_len = SCM_ROLENGTH (str);
 263   if (SCM_INUM (pos) > str_len)
 264     scm_out_of_range (caller, pos);
 265   if (!((modes & SCM_WRTNG) || (modes & SCM_RDNG)))
 266     scm_misc_error ("scm_mkstrport", "port must read or write", SCM_EOL);
 267   SCM_NEWCELL (z);
 268   SCM_DEFER_INTS;
 269   pt = scm_add_to_port_table (z);
 270   SCM_SETCAR (z, scm_tc16_strport | modes);
 271   SCM_SETPTAB_ENTRY (z, pt);
 272   SCM_SETSTREAM (z, str);
 273   pt->write_buf = pt->read_buf = SCM_ROCHARS (str);
 274   pt->read_pos = pt->write_pos = pt->read_buf + SCM_INUM (pos);
 275   pt->write_buf_size = pt->read_buf_size = str_len;
 276   pt->write_end = pt->read_end = pt->read_buf + pt->read_buf_size;
 277
 278   pt->rw_random = 1;
 279
 280   SCM_ALLOW_INTS;
 281
 282   /* ensure write_pos is writable. */
 283   if ((modes & SCM_WRTNG) && pt->write_pos == pt->write_end)
 284     st_flush (z);
 285   return z;
 286 }
 287
 288 /* create a new string from a string port's buffer.  */
 289 SCM scm_strport_to_string (SCM port)
 290 {
 291   scm_port *pt = SCM_PTAB_ENTRY (port);
 292
 293   if (pt->rw_active == SCM_PORT_WRITE)
 294     st_flush (port);
 295   return scm_makfromstr (pt->read_buf, pt->read_buf_size, 0);
 296 }
 297
 298 SCM_DEFINE(scm_call_with_output_string, "call-with-output-string", 1, 0, 0,
 299            (SCM proc),
 300 "Calls the one-argument procedure @var{proc} with a newly created output
 301 port.  When the function returns, the string composed of the characters
 302 written into the port is returned.")
 303 #define FUNC_NAME s_scm_call_with_output_string
 304 {
 305   SCM p;
 306
 307   p = scm_mkstrport (SCM_INUM0,
 308                      scm_make_string (SCM_INUM0, SCM_UNDEFINED),
 309                      SCM_OPN | SCM_WRTNG,
 310                      FUNC_NAME);
 311   scm_apply (proc, p, scm_listofnull);
 312
 313   return scm_strport_to_string (p);
 314 }
 315 #undef FUNC_NAME
 316
 317
 318
 319 /* Return a Scheme string obtained by printing a given object.
 320  */
 321
 322
 323 SCM
 324 scm_strprint_obj (SCM obj)
 325 {
 326   SCM str;
 327   SCM port;
 328
 329   str = scm_makstr (0, 0);
 330   port = scm_mkstrport (SCM_INUM0, str, SCM_OPN | SCM_WRTNG, "scm_strprint_obj");
 331   scm_prin1 (obj, port, 1);
 332   {
 333     return scm_strport_to_string (port);
 334   }
 335 }
 336
 337
 338
 339
 340 SCM_DEFINE(scm_call_with_input_string, "call-with-input-string", 2, 0, 0,
 341            (SCM str, SCM proc),
 342 "Calls the one-argument procedure @var{proc} with a newly created input
 343 port from which @var{string}'s contents may be read.  The value yielded
 344 by the @var{proc} is returned.")
 345 #define FUNC_NAME s_scm_call_with_input_string
 346 {
 347   SCM p = scm_mkstrport(SCM_INUM0, str, SCM_OPN | SCM_RDNG, FUNC_NAME);
 348   return scm_apply (proc, p, scm_listofnull);
 349 }
 350 #undef FUNC_NAME
 351
 352
 353
 354 /* Given a null-terminated string EXPR containing a Scheme expression
 355    read it, and return it as an SCM value. */
 356 SCM
 357 scm_read_0str (char *expr)
 358 {
 359   SCM port = scm_mkstrport (SCM_INUM0,
 360                             scm_makfrom0str (expr),
 361                             SCM_OPN | SCM_RDNG,
 362                             "scm_eval_0str");
 363   SCM form;
 364
 365   /* Read expressions from that port; ignore the values.  */
 366   form = scm_read (port);
 367
 368   scm_close_port (port);
 369   return form;
 370 }
 371
 372 /* Given a null-terminated string EXPR containing Scheme program text,
 373    evaluate it, and return the result of the last expression evaluated.  */
 374 SCM
 375 scm_eval_0str (const char *expr)
 376 {
 377   return scm_eval_string (scm_makfrom0str (expr));
 378 }
 379
 380
 381 SCM_DEFINE (scm_eval_string, "eval-string", 1, 0, 0,
 382             (SCM string),
 383 "Evaluate @var{string} as the text representation of a Scheme form
 384 or forms, and return whatever value they produce.")
 385 #define FUNC_NAME s_scm_eval_string
 386 {
 387   SCM port = scm_mkstrport (SCM_INUM0, string, SCM_OPN | SCM_RDNG,
 388                             "scm_eval_0str");
 389   SCM form;
 390   SCM ans = SCM_UNSPECIFIED;
 391
 392   /* Read expressions from that port; ignore the values.  */
 393   while (!SCM_EOF_OBJECT_P (form = scm_read (port)))
 394     ans = scm_eval_x (form);
 395
 396   /* Don't close the port here; if we re-enter this function via a
 397      continuation, then the next time we enter it, we'll get an error.
 398      It's a string port anyway, so there's no advantage to closing it
 399      early.  */
 400
 401   return ans;
 402 }
 403 #undef FUNC_NAME
 404
 405 void scm_make_stptob (void); /* Called from ports.c */
 406
 407 void
 408 scm_make_stptob ()
 409 {
 410   long tc = scm_make_port_type ("string", stfill_buffer, st_write);
 411   scm_set_port_mark        (tc, scm_markstream);
 412   scm_set_port_end_input   (tc, st_end_input);
 413   scm_set_port_flush       (tc, st_flush);
 414   scm_set_port_seek        (tc, st_seek);
 415   scm_set_port_truncate    (tc, st_truncate);
 416 }
 417
 418 void
 419 scm_init_strports ()
 420 {
 421 #include "strports.x"
 422 }
 423