aboutsummaryrefslogtreecommitdiff
path: root/gdb/guile/scm-ports.c
blob: a7c0bd410c5cf20374a34bf229a4be3e3908a990 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
/* Support for connecting Guile's stdio to GDB's.
   as well as r/w memory via ports.

   Copyright (C) 2014-2017 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* See README file in this directory for implementation notes, coding
   conventions, et.al.  */

#include "defs.h"
#include "gdb_select.h"
#include "top.h"
#include "target.h"
#include "guile-internal.h"
#include "common/gdb_optional.h"

#ifdef HAVE_POLL
#if defined (HAVE_POLL_H)
#include <poll.h>
#elif defined (HAVE_SYS_POLL_H)
#include <sys/poll.h>
#endif
#endif

/* A ui-file for sending output to Guile.  */

class ioscm_file_port : public ui_file
{
public:
  /* Return a ui_file that writes to PORT.  */
  explicit ioscm_file_port (SCM port);

  void flush () override;
  void write (const char *buf, long length_buf) override;

private:
  SCM m_port;
};

/* Data for a memory port.  */

typedef struct
{
  /* Bounds of memory range this port is allowed to access: [start, end).
     This means that 0xff..ff is not accessible.  I can live with that.  */
  CORE_ADDR start, end;

  /* (end - start), recorded for convenience.  */
  ULONGEST size;

  /* Think of this as the lseek value maintained by the kernel.
     This value is always in the range [0, size].  */
  ULONGEST current;

  /* The size of the internal r/w buffers.
     Scheme ports aren't a straightforward mapping to memory r/w.
     Generally the user specifies how much to r/w and all access is
     unbuffered.  We don't try to provide equivalent access, but we allow
     the user to specify these values to help get something similar.  */
  unsigned read_buf_size, write_buf_size;
} ioscm_memory_port;

/* Copies of the original system input/output/error ports.
   These are recorded for debugging purposes.  */
static SCM orig_input_port_scm;
static SCM orig_output_port_scm;
static SCM orig_error_port_scm;

/* This is the stdio port descriptor, scm_ptob_descriptor.  */
static scm_t_bits stdio_port_desc;

/* Note: scm_make_port_type takes a char * instead of a const char *.  */
static /*const*/ char stdio_port_desc_name[] = "gdb:stdio-port";

/* Names of each gdb port.  */
static const char input_port_name[] = "gdb:stdin";
static const char output_port_name[] = "gdb:stdout";
static const char error_port_name[] = "gdb:stderr";

/* This is the actual port used from Guile.
   We don't expose these to the user though, to ensure they're not
   overwritten.  */
static SCM input_port_scm;
static SCM output_port_scm;
static SCM error_port_scm;

/* Magic number to identify port ui-files.
   Actually, the address of this variable is the magic number.  */
static int file_port_magic;

/* Internal enum for specifying output port.  */
enum oport { GDB_STDOUT, GDB_STDERR };

/* This is the memory port descriptor, scm_ptob_descriptor.  */
static scm_t_bits memory_port_desc;

/* Note: scm_make_port_type takes a char * instead of a const char *.  */
static /*const*/ char memory_port_desc_name[] = "gdb:memory-port";

/* The default amount of memory to fetch for each read/write request.
   Scheme ports don't provide a way to specify the size of a read,
   which is important to us to minimize the number of inferior interactions,
   which over a remote link can be important.  To compensate we augment the
   port API with a new function that let's the user specify how much the next
   read request should fetch.  This is the initial value for each new port.  */
static const unsigned default_read_buf_size = 16;
static const unsigned default_write_buf_size = 16;

/* Arbitrarily limit memory port buffers to 1 byte to 4K.  */
static const unsigned min_memory_port_buf_size = 1;
static const unsigned max_memory_port_buf_size = 4096;

/* "out of range" error message for buf sizes.  */
static char *out_of_range_buf_size;

/* Keywords used by open-memory.  */
static SCM mode_keyword;
static SCM start_keyword;
static SCM size_keyword;

/* Helper to do the low level work of opening a port.
   Newer versions of Guile (2.1.x) have scm_c_make_port.  */

static SCM
ioscm_open_port (scm_t_bits port_type, long mode_bits)
{
  SCM port;

#if 0 /* TODO: Guile doesn't export this.  What to do?  */
  scm_i_scm_pthread_mutex_lock (&scm_i_port_table_mutex);
#endif

  port = scm_new_port_table_entry (port_type);

  SCM_SET_CELL_TYPE (port, port_type | mode_bits);

#if 0 /* TODO: Guile doesn't export this.  What to do?  */
  scm_i_pthread_mutex_unlock (&scm_i_port_table_mutex);
#endif

  return port;
}

/* Support for connecting Guile's stdio ports to GDB's stdio ports.  */

/* The scm_t_ptob_descriptor.input_waiting "method".
   Return a lower bound on the number of bytes available for input.  */

static int
ioscm_input_waiting (SCM port)
{
  int fdes = 0;

  if (! scm_is_eq (port, input_port_scm))
    return 0;

#ifdef HAVE_POLL
  {
    /* This is copied from libguile/fports.c.  */
    struct pollfd pollfd = { fdes, POLLIN, 0 };
    static int use_poll = -1;

    if (use_poll < 0)
      {
	/* This is copied from event-loop.c: poll cannot be used for stdin on
	   m68k-motorola-sysv.  */
	struct pollfd test_pollfd = { fdes, POLLIN, 0 };

	if (poll (&test_pollfd, 1, 0) == 1 && (test_pollfd.revents & POLLNVAL))
	  use_poll = 0;
	else
	  use_poll = 1;
      }

    if (use_poll)
      {
	/* Guile doesn't export SIGINT hooks like Python does.
	   For now pass EINTR to scm_syserror, that's what fports.c does.  */
	if (poll (&pollfd, 1, 0) < 0)
	  scm_syserror (FUNC_NAME);

	return pollfd.revents & POLLIN ? 1 : 0;
      }
  }
  /* Fall through.  */
#endif

  {
    struct timeval timeout;
    fd_set input_fds;
    int num_fds = fdes + 1;
    int num_found;

    memset (&timeout, 0, sizeof (timeout));
    FD_ZERO (&input_fds);
    FD_SET (fdes, &input_fds);

    num_found = interruptible_select (num_fds,
				      &input_fds, NULL, NULL,
				      &timeout);
    if (num_found < 0)
      {
	/* Guile doesn't export SIGINT hooks like Python does.
	   For now pass EINTR to scm_syserror, that's what fports.c does.  */
        scm_syserror (FUNC_NAME);
      }
    return num_found > 0 && FD_ISSET (fdes, &input_fds);
  }
}

/* The scm_t_ptob_descriptor.fill_input "method".  */

static int
ioscm_fill_input (SCM port)
{
  /* Borrowed from libguile/fports.c.  */
  long count;
  scm_t_port *pt = SCM_PTAB_ENTRY (port);

  /* If we're called on stdout,stderr, punt.  */
  if (! scm_is_eq (port, input_port_scm))
    return (scm_t_wchar) EOF; /* Set errno and return -1?  */

  gdb_flush (gdb_stdout);
  gdb_flush (gdb_stderr);

  count = ui_file_read (gdb_stdin, (char *) pt->read_buf, pt->read_buf_size);
  if (count == -1)
    scm_syserror (FUNC_NAME);
  if (count == 0)
    return (scm_t_wchar) EOF;

  pt->read_pos = pt->read_buf;
  pt->read_end = pt->read_buf + count;
  return *pt->read_buf;
}

/* Like fputstrn_filtered, but don't escape characters, except nul.
   Also like fputs_filtered, but a length is specified.  */

static void
fputsn_filtered (const char *s, size_t size, struct ui_file *stream)
{
  size_t i;

  for (i = 0; i < size; ++i)
    {
      if (s[i] == '\0')
	fputs_filtered ("\\000", stream);
      else
	fputc_filtered (s[i], stream);
    }
}

/* Write to gdb's stdout or stderr.  */

static void
ioscm_write (SCM port, const void *data, size_t size)
{

  /* If we're called on stdin, punt.  */
  if (scm_is_eq (port, input_port_scm))
    return;

  TRY
    {
      if (scm_is_eq (port, error_port_scm))
	fputsn_filtered ((const char *) data, size, gdb_stderr);
      else
	fputsn_filtered ((const char *) data, size, gdb_stdout);
    }
  CATCH (except, RETURN_MASK_ALL)
    {
      GDBSCM_HANDLE_GDB_EXCEPTION (except);
    }
  END_CATCH
}

/* Flush gdb's stdout or stderr.  */

static void
ioscm_flush (SCM port)
{
  /* If we're called on stdin, punt.  */
  if (scm_is_eq (port, input_port_scm))
    return;

  if (scm_is_eq (port, error_port_scm))
    gdb_flush (gdb_stderr);
  else
    gdb_flush (gdb_stdout);
}

/* Initialize the gdb stdio port type.

   N.B. isatty? will fail on these ports, it is only supported for file
   ports.  IWBN if we could "subclass" file ports.  */

static void
ioscm_init_gdb_stdio_port (void)
{
  stdio_port_desc = scm_make_port_type (stdio_port_desc_name,
					ioscm_fill_input, ioscm_write);

  scm_set_port_input_waiting (stdio_port_desc, ioscm_input_waiting);
  scm_set_port_flush (stdio_port_desc, ioscm_flush);
}

/* Subroutine of ioscm_make_gdb_stdio_port to simplify it.
   Set up the buffers of port PORT.
   MODE_BITS are the mode bits of PORT.  */

static void
ioscm_init_stdio_buffers (SCM port, long mode_bits)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
#define GDB_STDIO_BUFFER_DEFAULT_SIZE 1024
  int size = mode_bits & SCM_BUF0 ? 0 : GDB_STDIO_BUFFER_DEFAULT_SIZE;
  int writing = (mode_bits & SCM_WRTNG) != 0;

  /* This is heavily copied from scm_fport_buffer_add.  */

  if (!writing && size > 0)
    {
      pt->read_buf
	= (unsigned char *) scm_gc_malloc_pointerless (size, "port buffer");
      pt->read_pos = pt->read_end = pt->read_buf;
      pt->read_buf_size = size;
    }
  else
    {
      pt->read_pos = pt->read_buf = pt->read_end = &pt->shortbuf;
      pt->read_buf_size = 1;
    }

  if (writing && size > 0)
    {
      pt->write_buf
	= (unsigned char *) scm_gc_malloc_pointerless (size, "port buffer");
      pt->write_pos = pt->write_buf;
      pt->write_buf_size = size;
    }
  else
    {
      pt->write_buf = pt->write_pos = &pt->shortbuf;
      pt->write_buf_size = 1;
    }
  pt->write_end = pt->write_buf + pt->write_buf_size;
}

/* Create a gdb stdio port.  */

static SCM
ioscm_make_gdb_stdio_port (int fd)
{
  int is_a_tty = isatty (fd);
  const char *name;
  const char *mode_str;
  long mode_bits;
  SCM port;

  switch (fd)
    {
    case 0:
      name = input_port_name;
      mode_str = is_a_tty ? "r0" : "r";
      break;
    case 1:
      name = output_port_name;
      mode_str = is_a_tty ? "w0" : "w";
      break;
    case 2:
      name = error_port_name;
      mode_str = is_a_tty ? "w0" : "w";
      break;
    default:
      gdb_assert_not_reached ("bad stdio file descriptor");
    }

  mode_bits = scm_mode_bits ((char *) mode_str);
  port = ioscm_open_port (stdio_port_desc, mode_bits);

  scm_set_port_filename_x (port, gdbscm_scm_from_c_string (name));

  ioscm_init_stdio_buffers (port, mode_bits);

  return port;
}

/* (stdio-port? object) -> boolean */

static SCM
gdbscm_stdio_port_p (SCM scm)
{
  /* This is copied from SCM_FPORTP.  */
  return scm_from_bool (!SCM_IMP (scm)
			&& (SCM_TYP16 (scm) == stdio_port_desc));
}

/* GDB's ports are accessed via functions to keep them read-only.  */

/* (input-port) -> port */

static SCM
gdbscm_input_port (void)
{
  return input_port_scm;
}

/* (output-port) -> port */

static SCM
gdbscm_output_port (void)
{
  return output_port_scm;
}

/* (error-port) -> port */

static SCM
gdbscm_error_port (void)
{
  return error_port_scm;
}

/* Support for sending GDB I/O to Guile ports.  */

ioscm_file_port::ioscm_file_port (SCM port)
  : m_port (port)
{}

void
ioscm_file_port::flush ()
{
}

void
ioscm_file_port::write (const char *buffer, long length_buffer)
{
  scm_c_write (m_port, buffer, length_buffer);
}


/* Helper routine for with-{output,error}-to-port.  */

static SCM
ioscm_with_output_to_port_worker (SCM port, SCM thunk, enum oport oport,
				  const char *func_name)
{
  SCM result;

  SCM_ASSERT_TYPE (gdbscm_is_true (scm_output_port_p (port)), port,
		   SCM_ARG1, func_name, _("output port"));
  SCM_ASSERT_TYPE (gdbscm_is_true (scm_thunk_p (thunk)), thunk,
		   SCM_ARG2, func_name, _("thunk"));

  set_batch_flag_and_restore_page_info save_page_info;

  scoped_restore restore_async = make_scoped_restore (&current_ui->async, 0);

  ui_file_up port_file (new ioscm_file_port (port));

  scoped_restore save_file = make_scoped_restore (oport == GDB_STDERR
						  ? &gdb_stderr : &gdb_stdout);

  {
    gdb::optional<ui_out_redirect_pop> redirect_popper;
    if (oport == GDB_STDERR)
      gdb_stderr = port_file.get ();
    else
      {
	current_uiout->redirect (port_file.get ());
	redirect_popper.emplace (current_uiout);

	gdb_stdout = port_file.get ();
      }

    result = gdbscm_safe_call_0 (thunk, NULL);
  }

  if (gdbscm_is_exception (result))
    gdbscm_throw (result);

  return result;
}

/* (%with-gdb-output-to-port port thunk) -> object
   This function is experimental.
   IWBN to not include "gdb" in the name, but it would collide with a standard
   procedure, and it's common to import the gdb module without a prefix.
   There are ways around this, but they're more cumbersome.

   This has % in the name because it's experimental, and we want the
   user-visible version to come from module (gdb experimental).  */

static SCM
gdbscm_percent_with_gdb_output_to_port (SCM port, SCM thunk)
{
  return ioscm_with_output_to_port_worker (port, thunk, GDB_STDOUT, FUNC_NAME);
}

/* (%with-gdb-error-to-port port thunk) -> object
   This function is experimental.
   IWBN to not include "gdb" in the name, but it would collide with a standard
   procedure, and it's common to import the gdb module without a prefix.
   There are ways around this, but they're more cumbersome.

   This has % in the name because it's experimental, and we want the
   user-visible version to come from module (gdb experimental).  */

static SCM
gdbscm_percent_with_gdb_error_to_port (SCM port, SCM thunk)
{
  return ioscm_with_output_to_port_worker (port, thunk, GDB_STDERR, FUNC_NAME);
}

/* Support for r/w memory via ports.  */

/* Perform an "lseek" to OFFSET,WHENCE on memory port IOMEM.
   OFFSET must be in the range [0,size].
   The result is non-zero for success, zero for failure.  */

static int
ioscm_lseek_address (ioscm_memory_port *iomem, LONGEST offset, int whence)
{
  CORE_ADDR new_current;

  gdb_assert (iomem->current <= iomem->size);

  switch (whence)
    {
    case SEEK_CUR:
      /* Catch over/underflow.  */
      if ((offset < 0 && iomem->current + offset > iomem->current)
	  || (offset > 0 && iomem->current + offset < iomem->current))
	return 0;
      new_current = iomem->current + offset;
      break;
    case SEEK_SET:
      new_current = offset;
      break;
    case SEEK_END:
      if (offset == 0)
	{
	  new_current = iomem->size;
	  break;
	}
      /* TODO: Not supported yet.  */
      return 0;
    default:
      return 0;
    }

  if (new_current > iomem->size)
    return 0;
  iomem->current = new_current;
  return 1;
}

/* "fill_input" method for memory ports.  */

static int
gdbscm_memory_port_fill_input (SCM port)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  ioscm_memory_port *iomem = (ioscm_memory_port *) SCM_STREAM (port);
  size_t to_read;

  /* "current" is the offset of the first byte we want to read.  */
  gdb_assert (iomem->current <= iomem->size);
  if (iomem->current == iomem->size)
    return EOF;

  /* Don't read outside the allowed memory range.  */
  to_read = pt->read_buf_size;
  if (to_read > iomem->size - iomem->current)
    to_read = iomem->size - iomem->current;

  if (target_read_memory (iomem->start + iomem->current, pt->read_buf,
			  to_read) != 0)
    gdbscm_memory_error (FUNC_NAME, _("error reading memory"), SCM_EOL);

  iomem->current += to_read;
  pt->read_pos = pt->read_buf;
  pt->read_end = pt->read_buf + to_read;
  return *pt->read_buf;
}

/* "end_input" method for memory ports.
   Clear the read buffer and adjust the file position for unread bytes.  */

static void
gdbscm_memory_port_end_input (SCM port, int offset)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  ioscm_memory_port *iomem = (ioscm_memory_port *) SCM_STREAM (port);
  size_t remaining = pt->read_end - pt->read_pos;

  /* Note: Use of "int offset" is specified by Guile ports API.  */
  if ((offset < 0 && remaining + offset > remaining)
      || (offset > 0 && remaining + offset < remaining))
    {
      gdbscm_out_of_range_error (FUNC_NAME, 0, scm_from_int (offset),
				 _("overflow in offset calculation"));
    }
  offset += remaining;

  if (offset > 0)
    {
      pt->read_pos = pt->read_end;
      /* Throw error if unread-char used at beginning of file
	 then attempting to write.  Seems correct.  */
      if (!ioscm_lseek_address (iomem, -offset, SEEK_CUR))
	{
	  gdbscm_out_of_range_error (FUNC_NAME, 0, scm_from_int (offset),
				     _("bad offset"));
	}
    }

  pt->rw_active = SCM_PORT_NEITHER;
}

/* "flush" method for memory ports.  */

static void
gdbscm_memory_port_flush (SCM port)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  ioscm_memory_port *iomem = (ioscm_memory_port *) SCM_STREAM (port);
  size_t to_write = pt->write_pos - pt->write_buf;

  if (to_write == 0)
    return;

  /* There's no way to indicate a short write, so if the request goes past
     the end of the port's memory range, flag an error.  */
  if (to_write > iomem->size - iomem->current)
    {
      gdbscm_out_of_range_error (FUNC_NAME, 0,
				 gdbscm_scm_from_ulongest (to_write),
				 _("writing beyond end of memory range"));
    }

  if (target_write_memory (iomem->start + iomem->current, pt->write_buf,
			   to_write) != 0)
    gdbscm_memory_error (FUNC_NAME, _("error writing memory"), SCM_EOL);

  iomem->current += to_write;
  pt->write_pos = pt->write_buf;
  pt->rw_active = SCM_PORT_NEITHER;
}

/* "write" method for memory ports.  */

static void
gdbscm_memory_port_write (SCM port, const void *void_data, size_t size)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  ioscm_memory_port *iomem = (ioscm_memory_port *) SCM_STREAM (port);
  const gdb_byte *data = (const gdb_byte *) void_data;

  /* There's no way to indicate a short write, so if the request goes past
     the end of the port's memory range, flag an error.  */
  if (size > iomem->size - iomem->current)
    {
      gdbscm_out_of_range_error (FUNC_NAME, 0, gdbscm_scm_from_ulongest (size),
				 _("writing beyond end of memory range"));
    }

  if (pt->write_buf == &pt->shortbuf)
    {
      /* Unbuffered port.  */
      if (target_write_memory (iomem->start + iomem->current, data, size) != 0)
	gdbscm_memory_error (FUNC_NAME, _("error writing memory"), SCM_EOL);
      iomem->current += size;
      return;
    }

  /* Note: The edge case of what to do when the buffer exactly fills is
     debatable.  Guile flushes when the buffer exactly fills up, so we
     do too.  It's counter-intuitive to my mind, but in case there's a
     subtlety somewhere that depends on this, we do the same.  */

  {
    size_t space = pt->write_end - pt->write_pos;

    if (size < space)
      {
	/* Data fits in buffer, and does not fill it.  */
	memcpy (pt->write_pos, data, size);
	pt->write_pos += size;
      }
    else
      {
	memcpy (pt->write_pos, data, space);
	pt->write_pos = pt->write_end;
	gdbscm_memory_port_flush (port);
	{
	  const gdb_byte *ptr = data + space;
	  size_t remaining = size - space;

	  if (remaining >= pt->write_buf_size)
	    {
	      if (target_write_memory (iomem->start + iomem->current, ptr,
				       remaining) != 0)
		gdbscm_memory_error (FUNC_NAME, _("error writing memory"),
				     SCM_EOL);
	      iomem->current += remaining;
	    }
	  else
	    {
	      memcpy (pt->write_pos, ptr, remaining);
	      pt->write_pos += remaining;
	    }
	}
      }
  }
}

/* "seek" method for memory ports.  */

static scm_t_off
gdbscm_memory_port_seek (SCM port, scm_t_off offset, int whence)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  ioscm_memory_port *iomem = (ioscm_memory_port *) SCM_STREAM (port);
  CORE_ADDR result;
  int rc;

  if (pt->rw_active == SCM_PORT_WRITE)
    {
      if (offset != 0 || whence != SEEK_CUR)
	{
	  gdbscm_memory_port_flush (port);
	  rc = ioscm_lseek_address (iomem, offset, whence);
	  result = iomem->current;
	}
      else
	{
	  /* Read current position without disturbing the buffer,
	     but flag an error if what's in the buffer goes outside the
	     allowed range.  */
	  CORE_ADDR current = iomem->current;
	  size_t delta = pt->write_pos - pt->write_buf;

	  if (current + delta < current
	      || current + delta > iomem->size)
	    rc = 0;
	  else
	    {
	      result = current + delta;
	      rc = 1;
	    }
	}
    }
  else if (pt->rw_active == SCM_PORT_READ)
    {
      if (offset != 0 || whence != SEEK_CUR)
	{
	  scm_end_input (port);
	  rc = ioscm_lseek_address (iomem, offset, whence);
	  result = iomem->current;
	}
      else
	{
	  /* Read current position without disturbing the buffer
	     (particularly the unread-char buffer).  */
	  CORE_ADDR current = iomem->current;
	  size_t remaining = pt->read_end - pt->read_pos;

	  if (current - remaining > current
	      || current - remaining < iomem->start)
	    rc = 0;
	  else
	    {
	      result = current - remaining;
	      rc = 1;
	    }

	  if (rc != 0 && pt->read_buf == pt->putback_buf)
	    {
	      size_t saved_remaining = pt->saved_read_end - pt->saved_read_pos;

	      if (result - saved_remaining > result
		  || result - saved_remaining < iomem->start)
		rc = 0;
	      else
		result -= saved_remaining;
	    }
	}
    }
  else /* SCM_PORT_NEITHER */
    {
      rc = ioscm_lseek_address (iomem, offset, whence);
      result = iomem->current;
    }

  if (rc == 0)
    {
      gdbscm_out_of_range_error (FUNC_NAME, 0,
				 gdbscm_scm_from_longest (offset),
				 _("bad seek"));
    }

  /* TODO: The Guile API doesn't support 32x64.  We can't fix that here,
     and there's no need to throw an error if the new address can't be
     represented in a scm_t_off.  But we could return something less
     clumsy.  */
  return result;
}

/* "close" method for memory ports.  */

static int
gdbscm_memory_port_close (SCM port)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  ioscm_memory_port *iomem = (ioscm_memory_port *) SCM_STREAM (port);

  gdbscm_memory_port_flush (port);

  if (pt->read_buf == pt->putback_buf)
    pt->read_buf = pt->saved_read_buf;
  if (pt->read_buf != &pt->shortbuf)
    xfree (pt->read_buf);
  if (pt->write_buf != &pt->shortbuf)
    xfree (pt->write_buf);
  scm_gc_free (iomem, sizeof (*iomem), "memory port");

  return 0;
}

/* "free" method for memory ports.  */

static size_t
gdbscm_memory_port_free (SCM port)
{
  gdbscm_memory_port_close (port);

  return 0;
}

/* "print" method for memory ports.  */

static int
gdbscm_memory_port_print (SCM exp, SCM port, scm_print_state *pstate)
{
  ioscm_memory_port *iomem = (ioscm_memory_port *) SCM_STREAM (exp);
  char *type = SCM_PTOBNAME (SCM_PTOBNUM (exp));

  scm_puts ("#<", port);
  scm_print_port_mode (exp, port);
  /* scm_print_port_mode includes a trailing space.  */
  gdbscm_printf (port, "%s %s-%s", type,
		 hex_string (iomem->start), hex_string (iomem->end));
  scm_putc ('>', port);
  return 1;
}

/* Create the port type used for memory.  */

static void
ioscm_init_memory_port_type (void)
{
  memory_port_desc = scm_make_port_type (memory_port_desc_name,
					 gdbscm_memory_port_fill_input,
					 gdbscm_memory_port_write);

  scm_set_port_end_input (memory_port_desc, gdbscm_memory_port_end_input);
  scm_set_port_flush (memory_port_desc, gdbscm_memory_port_flush);
  scm_set_port_seek (memory_port_desc, gdbscm_memory_port_seek);
  scm_set_port_close (memory_port_desc, gdbscm_memory_port_close);
  scm_set_port_free (memory_port_desc, gdbscm_memory_port_free);
  scm_set_port_print (memory_port_desc, gdbscm_memory_port_print);
}

/* Helper for gdbscm_open_memory to parse the mode bits.
   An exception is thrown if MODE is invalid.  */

static long
ioscm_parse_mode_bits (const char *func_name, const char *mode)
{
  const char *p;
  long mode_bits;

  if (*mode != 'r' && *mode != 'w')
    {
      gdbscm_out_of_range_error (func_name, 0,
				 gdbscm_scm_from_c_string (mode),
				 _("bad mode string"));
    }
  for (p = mode + 1; *p != '\0'; ++p)
    {
      switch (*p)
	{
	case '0':
	case 'b':
	case '+':
	  break;
	default:
	  gdbscm_out_of_range_error (func_name, 0,
				     gdbscm_scm_from_c_string (mode),
				     _("bad mode string"));
	}
    }

  /* Kinda awkward to convert the mode from SCM -> string only to have Guile
     convert it back to SCM, but that's the API we have to work with.  */
  mode_bits = scm_mode_bits ((char *) mode);

  return mode_bits;
}

/* Helper for gdbscm_open_memory to finish initializing the port.
   The port has address range [start,end).
   This means that address of 0xff..ff is not accessible.
   I can live with that.  */

static void
ioscm_init_memory_port (SCM port, CORE_ADDR start, CORE_ADDR end)
{
  scm_t_port *pt;
  ioscm_memory_port *iomem;
  int buffered = (SCM_CELL_WORD_0 (port) & SCM_BUF0) == 0;

  gdb_assert (start <= end);

  iomem = (ioscm_memory_port *) scm_gc_malloc_pointerless (sizeof (*iomem),
							   "memory port");

  iomem->start = start;
  iomem->end = end;
  iomem->size = end - start;
  iomem->current = 0;
  if (buffered)
    {
      iomem->read_buf_size = default_read_buf_size;
      iomem->write_buf_size = default_write_buf_size;
    }
  else
    {
      iomem->read_buf_size = 1;
      iomem->write_buf_size = 1;
    }

  pt = SCM_PTAB_ENTRY (port);
  /* Match the expectation of `binary-port?'.  */
  pt->encoding = NULL;
  pt->rw_random = 1;
  pt->read_buf_size = iomem->read_buf_size;
  pt->write_buf_size = iomem->write_buf_size;
  if (buffered)
    {
      pt->read_buf = (unsigned char *) xmalloc (pt->read_buf_size);
      pt->write_buf = (unsigned char *) xmalloc (pt->write_buf_size);
    }
  else
    {
      pt->read_buf = &pt->shortbuf;
      pt->write_buf = &pt->shortbuf;
    }
  pt->read_pos = pt->read_end = pt->read_buf;
  pt->write_pos = pt->write_buf;
  pt->write_end = pt->write_buf + pt->write_buf_size;

  SCM_SETSTREAM (port, iomem);
}

/* Re-initialize a memory port, updating its read/write buffer sizes.
   An exception is thrown if the port is unbuffered.
   TODO: Allow switching buffered/unbuffered.
   An exception is also thrown if data is still buffered, except in the case
   where the buffer size isn't changing (since that's just a nop).  */

static void
ioscm_reinit_memory_port (SCM port, size_t read_buf_size,
			  size_t write_buf_size, const char *func_name)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  ioscm_memory_port *iomem = (ioscm_memory_port *) SCM_STREAM (port);

  gdb_assert (read_buf_size >= min_memory_port_buf_size
	      && read_buf_size <= max_memory_port_buf_size);
  gdb_assert (write_buf_size >= min_memory_port_buf_size
	      && write_buf_size <= max_memory_port_buf_size);

  /* First check if the port is unbuffered.  */

  if (pt->read_buf == &pt->shortbuf)
    {
      gdb_assert (pt->write_buf == &pt->shortbuf);
      scm_misc_error (func_name, _("port is unbuffered: ~a"),
		      scm_list_1 (port));
    }

  /* Next check if anything is buffered.  */

  if (read_buf_size != pt->read_buf_size
      && pt->read_end != pt->read_buf)
    {
      scm_misc_error (func_name, _("read buffer not empty: ~a"),
		      scm_list_1 (port));
    }

  if (write_buf_size != pt->write_buf_size
      && pt->write_pos != pt->write_buf)
    {
      scm_misc_error (func_name, _("write buffer not empty: ~a"),
		      scm_list_1 (port));
    }

  /* Now we can update the buffer sizes, but only if the size has changed.  */

  if (read_buf_size != pt->read_buf_size)
    {
      iomem->read_buf_size = read_buf_size;
      pt->read_buf_size = read_buf_size;
      xfree (pt->read_buf);
      pt->read_buf = (unsigned char *) xmalloc (pt->read_buf_size);
      pt->read_pos = pt->read_end = pt->read_buf;
    }

  if (write_buf_size != pt->write_buf_size)
    {
      iomem->write_buf_size = write_buf_size;
      pt->write_buf_size = write_buf_size;
      xfree (pt->write_buf);
      pt->write_buf = (unsigned char *) xmalloc (pt->write_buf_size);
      pt->write_pos = pt->write_buf;
      pt->write_end = pt->write_buf + pt->write_buf_size;
    }
}

/* (open-memory [#:mode string] [#:start address] [#:size integer]) -> port
   Return a port that can be used for reading and writing memory.
   MODE is a string, and must be one of "r", "w", or "r+".
   "0" may be appended to MODE to mark the port as unbuffered.
   For compatibility "b" (binary) may also be appended, but we ignore it:
   memory ports are binary only.

   The chunk of memory that can be accessed can be bounded.
   If both START,SIZE are unspecified, all of memory can be accessed
   (except 0xff..ff).  If only START is specified, all of memory from that
   point on can be accessed (except 0xff..ff).  If only SIZE if specified,
   all memory in [0,SIZE) can be accessed.  If both are specified, all memory
   in [START,START+SIZE) can be accessed.

   Note: If it becomes useful enough we can later add #:end as an alternative
   to #:size.  For now it is left out.

   The result is a Scheme port, and its semantics are a bit odd for accessing
   memory (e.g., unget), but we don't try to hide this.  It's a port.

   N.B. Seeks on the port must be in the range [0,size].
   This is for similarity with bytevector ports, and so that one can seek
   to the first byte.  */

static SCM
gdbscm_open_memory (SCM rest)
{
  const SCM keywords[] = {
    mode_keyword, start_keyword, size_keyword, SCM_BOOL_F
  };
  char *mode = NULL;
  CORE_ADDR start = 0;
  CORE_ADDR end;
  int mode_arg_pos = -1, start_arg_pos = -1, size_arg_pos = -1;
  ULONGEST size;
  SCM port;
  long mode_bits;

  gdbscm_parse_function_args (FUNC_NAME, SCM_ARG1, keywords, "#sUU", rest,
			      &mode_arg_pos, &mode,
			      &start_arg_pos, &start,
			      &size_arg_pos, &size);

  scm_dynwind_begin ((scm_t_dynwind_flags) 0);

  if (mode == NULL)
    mode = xstrdup ("r");
  scm_dynwind_free (mode);

  if (size_arg_pos > 0)
    {
      /* For now be strict about start+size overflowing.  If it becomes
	 a nuisance we can relax things later.  */
      if (start + size < start)
	{
	  gdbscm_out_of_range_error (FUNC_NAME, 0,
				scm_list_2 (gdbscm_scm_from_ulongest (start),
					    gdbscm_scm_from_ulongest (size)),
				     _("start+size overflows"));
	}
      end = start + size;
    }
  else
    end = ~(CORE_ADDR) 0;

  mode_bits = ioscm_parse_mode_bits (FUNC_NAME, mode);

  port = ioscm_open_port (memory_port_desc, mode_bits);

  ioscm_init_memory_port (port, start, end);

  scm_dynwind_end ();

  /* TODO: Set the file name as "memory-start-end"?  */
  return port;
}

/* Return non-zero if OBJ is a memory port.  */

static int
gdbscm_is_memory_port (SCM obj)
{
  return !SCM_IMP (obj) && (SCM_TYP16 (obj) == memory_port_desc);
}

/* (memory-port? obj) -> boolean */

static SCM
gdbscm_memory_port_p (SCM obj)
{
  return scm_from_bool (gdbscm_is_memory_port (obj));
}

/* (memory-port-range port) -> (start end) */

static SCM
gdbscm_memory_port_range (SCM port)
{
  ioscm_memory_port *iomem;

  SCM_ASSERT_TYPE (gdbscm_is_memory_port (port), port, SCM_ARG1, FUNC_NAME,
		   memory_port_desc_name);

  iomem = (ioscm_memory_port *) SCM_STREAM (port);
  return scm_list_2 (gdbscm_scm_from_ulongest (iomem->start),
		     gdbscm_scm_from_ulongest (iomem->end));
}

/* (memory-port-read-buffer-size port) -> integer */

static SCM
gdbscm_memory_port_read_buffer_size (SCM port)
{
  ioscm_memory_port *iomem;

  SCM_ASSERT_TYPE (gdbscm_is_memory_port (port), port, SCM_ARG1, FUNC_NAME,
		   memory_port_desc_name);

  iomem = (ioscm_memory_port *) SCM_STREAM (port);
  return scm_from_uint (iomem->read_buf_size);
}

/* (set-memory-port-read-buffer-size! port size) -> unspecified
   An exception is thrown if read data is still buffered or if the port
   is unbuffered.  */

static SCM
gdbscm_set_memory_port_read_buffer_size_x (SCM port, SCM size)
{
  ioscm_memory_port *iomem;

  SCM_ASSERT_TYPE (gdbscm_is_memory_port (port), port, SCM_ARG1, FUNC_NAME,
		   memory_port_desc_name);
  SCM_ASSERT_TYPE (scm_is_integer (size), size, SCM_ARG2, FUNC_NAME,
		   _("integer"));

  if (!scm_is_unsigned_integer (size, min_memory_port_buf_size,
				max_memory_port_buf_size))
    {
      gdbscm_out_of_range_error (FUNC_NAME, SCM_ARG2, size,
				 out_of_range_buf_size);
    }

  iomem = (ioscm_memory_port *) SCM_STREAM (port);
  ioscm_reinit_memory_port (port, scm_to_uint (size), iomem->write_buf_size,
			    FUNC_NAME);

  return SCM_UNSPECIFIED;
}

/* (memory-port-write-buffer-size port) -> integer */

static SCM
gdbscm_memory_port_write_buffer_size (SCM port)
{
  ioscm_memory_port *iomem;

  SCM_ASSERT_TYPE (gdbscm_is_memory_port (port), port, SCM_ARG1, FUNC_NAME,
		   memory_port_desc_name);

  iomem = (ioscm_memory_port *) SCM_STREAM (port);
  return scm_from_uint (iomem->write_buf_size);
}

/* (set-memory-port-write-buffer-size! port size) -> unspecified
   An exception is thrown if write data is still buffered or if the port
   is unbuffered.  */

static SCM
gdbscm_set_memory_port_write_buffer_size_x (SCM port, SCM size)
{
  ioscm_memory_port *iomem;

  SCM_ASSERT_TYPE (gdbscm_is_memory_port (port), port, SCM_ARG1, FUNC_NAME,
		   memory_port_desc_name);
  SCM_ASSERT_TYPE (scm_is_integer (size), size, SCM_ARG2, FUNC_NAME,
		   _("integer"));

  if (!scm_is_unsigned_integer (size, min_memory_port_buf_size,
				max_memory_port_buf_size))
    {
      gdbscm_out_of_range_error (FUNC_NAME, SCM_ARG2, size,
				 out_of_range_buf_size);
    }

  iomem = (ioscm_memory_port *) SCM_STREAM (port);
  ioscm_reinit_memory_port (port, iomem->read_buf_size, scm_to_uint (size),
			    FUNC_NAME);

  return SCM_UNSPECIFIED;
}

/* Initialize gdb ports.  */

static const scheme_function port_functions[] =
{
  { "input-port", 0, 0, 0, as_a_scm_t_subr (gdbscm_input_port),
    "\
Return gdb's input port." },

  { "output-port", 0, 0, 0, as_a_scm_t_subr (gdbscm_output_port),
    "\
Return gdb's output port." },

  { "error-port", 0, 0, 0, as_a_scm_t_subr (gdbscm_error_port),
    "\
Return gdb's error port." },

  { "stdio-port?", 1, 0, 0, as_a_scm_t_subr (gdbscm_stdio_port_p),
    "\
Return #t if the object is a gdb:stdio-port." },

  { "open-memory", 0, 0, 1, as_a_scm_t_subr (gdbscm_open_memory),
    "\
Return a port that can be used for reading/writing inferior memory.\n\
\n\
  Arguments: [#:mode string] [#:start address] [#:size integer]\n\
  Returns: A port object." },

  { "memory-port?", 1, 0, 0, as_a_scm_t_subr (gdbscm_memory_port_p),
    "\
Return #t if the object is a memory port." },

  { "memory-port-range", 1, 0, 0, as_a_scm_t_subr (gdbscm_memory_port_range),
    "\
Return the memory range of the port as (start end)." },

  { "memory-port-read-buffer-size", 1, 0, 0,
    as_a_scm_t_subr (gdbscm_memory_port_read_buffer_size),
    "\
Return the size of the read buffer for the memory port." },

  { "set-memory-port-read-buffer-size!", 2, 0, 0,
    as_a_scm_t_subr (gdbscm_set_memory_port_read_buffer_size_x),
    "\
Set the size of the read buffer for the memory port.\n\
\n\
  Arguments: port integer\n\
  Returns: unspecified." },

  { "memory-port-write-buffer-size", 1, 0, 0,
    as_a_scm_t_subr (gdbscm_memory_port_write_buffer_size),
    "\
Return the size of the write buffer for the memory port." },

  { "set-memory-port-write-buffer-size!", 2, 0, 0,
    as_a_scm_t_subr (gdbscm_set_memory_port_write_buffer_size_x),
    "\
Set the size of the write buffer for the memory port.\n\
\n\
  Arguments: port integer\n\
  Returns: unspecified." },

  END_FUNCTIONS
};

static const scheme_function private_port_functions[] =
{
#if 0 /* TODO */
  { "%with-gdb-input-from-port", 2, 0, 0,
    as_a_scm_t_subr (gdbscm_percent_with_gdb_input_from_port),
    "\
Temporarily set GDB's input port to PORT and then invoke THUNK.\n\
\n\
  Arguments: port thunk\n\
  Returns: The result of calling THUNK.\n\
\n\
This procedure is experimental." },
#endif

  { "%with-gdb-output-to-port", 2, 0, 0,
    as_a_scm_t_subr (gdbscm_percent_with_gdb_output_to_port),
    "\
Temporarily set GDB's output port to PORT and then invoke THUNK.\n\
\n\
  Arguments: port thunk\n\
  Returns: The result of calling THUNK.\n\
\n\
This procedure is experimental." },

  { "%with-gdb-error-to-port", 2, 0, 0,
    as_a_scm_t_subr (gdbscm_percent_with_gdb_error_to_port),
    "\
Temporarily set GDB's error port to PORT and then invoke THUNK.\n\
\n\
  Arguments: port thunk\n\
  Returns: The result of calling THUNK.\n\
\n\
This procedure is experimental." },

  END_FUNCTIONS
};

void
gdbscm_initialize_ports (void)
{
  /* Save the original stdio ports for debugging purposes.  */

  orig_input_port_scm = scm_current_input_port ();
  orig_output_port_scm = scm_current_output_port ();
  orig_error_port_scm = scm_current_error_port ();

  /* Set up the stdio ports.  */

  ioscm_init_gdb_stdio_port ();
  input_port_scm = ioscm_make_gdb_stdio_port (0);
  output_port_scm = ioscm_make_gdb_stdio_port (1);
  error_port_scm = ioscm_make_gdb_stdio_port (2);

  /* Set up memory ports.  */

  ioscm_init_memory_port_type ();

  /* Install the accessor functions.  */

  gdbscm_define_functions (port_functions, 1);
  gdbscm_define_functions (private_port_functions, 0);

  /* Keyword args for open-memory.  */

  mode_keyword = scm_from_latin1_keyword ("mode");
  start_keyword = scm_from_latin1_keyword ("start");
  size_keyword = scm_from_latin1_keyword ("size");

  /* Error message text for "out of range" memory port buffer sizes.  */

  out_of_range_buf_size = xstrprintf ("size not between %u - %u",
				      min_memory_port_buf_size,
				      max_memory_port_buf_size);
}