Add support for 36-bit words at stored on a Xerox Alto.

Binary .SAV, .REL, and .UNV files stored here are encoded with five
octets per word: 0000AAAA BBBBBBBB CCCCCCCC DDDDDDDD EEEEEEEE.
https://xeroxalto.computerhistory.org/_cd8_/pup/

Author: larsbrinkhoff

Makefile

@@ -6,9 +6,9 @@ FILES =  sblk-file.o pdump-file.o dmp-file.o raw-file.o exe-file.o \
 	 cross-file.o hex-file.o atari-file.o iml-file.o exb-file.o \
 	 tenex-file.o csave-file.o hiseg-file.o
 
-WORDS =  aa-word.o bin-word.o cadr-word.o core-word.o data8-word.o \
-	 dta-word.o its-word.o oct-word.o pt-word.o sail-word.o tape-word.o \
-	 x-word.o
+WORDS =  aa-word.o alto-word.o bin-word.o cadr-word.o core-word.o \
+	 data8-word.o dta-word.o its-word.o oct-word.o pt-word.o \
+	 sail-word.o tape-word.o x-word.o
 
 OBJS =	pdp10-opc.o info.o dis.o symbols.o \
 	timing.o timing_ka10.o timing_ki10.o memory.o weenix.o

README.md

@@ -40,6 +40,7 @@ Most tools support these PDP-10 36-bit word encodings:
 - Paper tape image.
 - Saildart.org UTF-8.
 - Tape images, 7 or 9 track.
+- Files stored in an Alto file system.
 
 Most tools that work with executable programs support these formats:
 

alto-word.c

@@ -0,0 +1,65 @@
+/* Copyright (C) 2022 Lars Brinkhoff <lars@nocrew.org>
+
+    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 2 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/>.  */
+
+#include <stdio.h>
+
+#include "dis.h"
+
+static int
+get_byte (FILE *f)
+{
+  int c = fgetc (f);
+  return c == EOF ? 0 : c;
+}
+
+word_t
+get_alto_word (FILE *f)
+{
+  word_t x1, x2, x3, x4, x5;
+  word_t word;
+
+  if (feof (f))
+    return -1;
+
+  x1 = get_byte (f);
+  if (feof (f))
+    return -1;
+  x2 = get_byte (f);
+  x3 = get_byte (f);
+  x4 = get_byte (f);
+  x5 = get_byte (f);
+  word = (x1 << 32) | (x2 << 24) | (x3 << 16) | (x4 << 8) | x5;
+  word &= 0777777777777LL;
+
+  return word;
+}
+
+void
+write_alto_word (FILE *f, word_t word)
+{
+  fputc ((word >> 32) & 0x0F, f);
+  fputc ((word >> 24) & 0xFF, f);
+  fputc ((word >> 16) & 0xFF, f);
+  fputc ((word >>  8) & 0xFF, f);
+  fputc ( word        & 0xFF, f);
+}
+
+struct word_format alto_word_format = {
+  "alto",
+  get_alto_word,
+  NULL,
+  write_alto_word,
+  NULL
+};

check.sh

@@ -74,6 +74,7 @@ test_dis10 dired.dmp      "-6 -mka10sail -Wascii -Sddt"
 test_dis10 two.tapes      "-r -Wtape"
 test_dis10 boot.exb       "-Fexb -Wascii"
 test_dis10 cerber.sav     "-Sall -Fcsave -Wascii"
+test_dis10 eftp.sav       "-Ftenex -Walto"
 
 test_itsarc arc.code
 test_ipak stink.-ipak-

dis.h

@@ -88,6 +88,7 @@ extern struct file_format tenex_file_format;
 extern struct word_format *input_word_format;
 extern struct word_format *output_word_format;
 extern struct word_format aa_word_format;
+extern struct word_format alto_word_format;
 extern struct word_format bin_word_format;
 extern struct word_format cadr_word_format;
 extern struct word_format core_word_format;

samples/eftp.sav

@@ -23,6 +23,7 @@ struct word_format *output_word_format = &its_word_format;
 
 static struct word_format *word_formats[] = {
   &aa_word_format,
+  &alto_word_format,
   &bin_word_format,
   &cadr_word_format,
   &core_word_format,