307 lines
8.0 KiB
C
307 lines
8.0 KiB
C
/*
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* baudot.c
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*
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* Copyright (C) 2011 Kamal Mostafa <kamal@whence.com>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <assert.h>
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#include <ctype.h>
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#include <stdio.h>
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//#define BAUDOT_DEBUG
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#ifdef BAUDOT_DEBUG
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# define debug_log(format, args...) fprintf(stderr, format, ## args)
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#else
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# define debug_log(format, args...)
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#endif
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static char
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baudot_decode_table[32][3] = {
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// letter, U.S. figs, CCITT No.2 figs (Europe)
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{ '_', '^', '^' }, // NUL (underscore and caret marks for debugging)
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{ 'E', '3', '3' },
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{ 0xA, 0xA, 0xA }, // LF
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{ 'A', '-', '-' },
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{ ' ', ' ', ' ' }, // SPACE
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{ 'S', 0x7, '\'' }, // BELL or apostrophe
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{ 'I', '8', '8' },
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{ 'U', '7', '7' },
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{ 0xD, 0xD, 0xD }, // CR
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{ 'D', '$', '^' }, // '$' or ENQ
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{ 'R', '4', '4' },
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{ 'J', '\'', 0x7 }, // apostrophe or BELL
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{ 'N', ',', ',' },
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{ 'F', '!', '!' },
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{ 'C', ':', ':' },
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{ 'K', '(', '(' },
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{ 'T', '5', '5' },
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{ 'Z', '"', '+' },
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{ 'L', ')', ')' },
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{ 'W', '2', '2' },
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{ 'H', '#', '%' }, // '#' or British pounds symbol // FIXME
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{ 'Y', '6', '6' },
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{ 'P', '0', '0' },
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{ 'Q', '1', '1' },
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{ 'O', '9', '9' },
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{ 'B', '?', '?' },
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{ 'G', '&', '&' },
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{ '%', '%', '%' }, // FIGS (symbol % for debug; won't be printed)
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{ 'M', '.', '.' },
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{ 'X', '/', '/' },
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{ 'V', ';', '=' },
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{ '%', '%', '%' }, // LTRS (symbol % for debug; won't be printed)
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};
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static char
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baudot_encode_table[0x60][2] = {
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// index: ascii char; values: bits, ltrs_or_figs_or_neither_or_both
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/* 0x00 */
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/* NUL */ { 0x00, 3 }, // NUL
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* BEL */ { 0x05, 2 }, // BELL (or CCITT2 apostrophe)
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/* BS */ { 0, 0 }, // non-encodable (FIXME???)
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/* xxx */ { 0, 0 }, // non-encodable
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/* LF */ { 0x02, 3 }, // LF
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* 0xD */ { 0x08, 3 }, // CR
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* 0x10 */
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* xxx */ { 0, 0 }, // non-encodable
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/* 0x20 */
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/* */ { 0x04, 3 }, // SPACE
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/* ! */ { 0x0d, 2 }, //
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/* " */ { 0x11, 2 }, //
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/* # */ { 0x14, 2 }, // '#' (or CCITT2 British pounds symbol)
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/* $ */ { 0x09, 2 }, // '$' (or CCITT2 ENQ)
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/* % */ { 0, 0 }, // non-encodable
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/* & */ { 0x1a, 2 }, //
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/* ' */ { 0x0b, 2 }, // apostrophe (or CCITT2 BELL)
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/* ( */ { 0x0f, 2 }, //
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/* ) */ { 0x12, 2 }, //
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/* * */ { 0, 0 }, // non-encodable
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/* + */ { 0x12, 2 }, //
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/* , */ { 0x0c, 2 }, //
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/* - */ { 0x03, 2 }, //
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/* . */ { 0x1c, 2 }, //
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/* / */ { 0x1d, 2 }, //
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/* 0x30 */
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/* 0 */ { 0x16, 2 }, //
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/* 1 */ { 0x17, 2 }, //
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/* 2 */ { 0x13, 2 }, //
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/* 3 */ { 0x01, 2 }, //
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/* 4 */ { 0x0a, 2 }, //
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/* 5 */ { 0x10, 2 }, //
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/* 6 */ { 0x15, 2 }, //
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/* 7 */ { 0x07, 2 }, //
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/* 8 */ { 0x06, 2 }, //
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/* 9 */ { 0x18, 2 }, //
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/* : */ { 0x0e, 2 }, //
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/* ; */ { 0x1e, 2 }, //
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/* < */ { 0, 0 }, // non-encodable
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/* = */ { 0, 0 }, // non-encodable
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/* > */ { 0, 0 }, // non-encodable
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/* ? */ { 0x19, 2 }, //
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/* 0x40 */
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/* @ */ { 0, 0 }, // non-encodable
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/* A */ { 0x03, 1 }, //
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/* B */ { 0x19, 1 }, //
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/* C */ { 0x0e, 1 }, //
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/* D */ { 0x09, 1 }, //
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/* E */ { 0x01, 1 }, //
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/* F */ { 0x0d, 1 }, //
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/* G */ { 0x1a, 1 }, //
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/* H */ { 0x14, 1 }, //
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/* I */ { 0x06, 1 }, //
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/* J */ { 0x0b, 1 }, //
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/* K */ { 0x0f, 1 }, //
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/* L */ { 0x12, 1 }, //
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/* M */ { 0x1c, 1 }, //
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/* N */ { 0x0c, 1 }, //
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/* O */ { 0x18, 1 }, //
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/* 0x50 */
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/* P */ { 0x16, 1 }, //
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/* Q */ { 0x17, 1 }, //
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/* R */ { 0x0a, 1 }, //
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/* S */ { 0x05, 1 }, //
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/* T */ { 0x10, 1 }, //
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/* U */ { 0x07, 1 }, //
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/* V */ { 0x1e, 1 }, //
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/* W */ { 0x13, 1 }, //
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/* X */ { 0x1d, 1 }, //
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/* Y */ { 0x15, 1 }, //
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/* Z */ { 0x11, 1 }, //
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/* [ */ { 0, 0 }, // non-encodable
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/* \\ */ { 0, 0 }, // non-encodable
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/* ] */ { 0, 0 }, // non-encodable
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/* ^ */ { 0, 0 }, // non-encodable
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/* _ */ { 0, 0 }, // non-encodable
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};
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#define BAUDOT_LTRS 0x1F
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#define BAUDOT_FIGS 0x1B
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#define BAUDOT_SPACE 0x04
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/*
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* 0 unknown state
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* 1 LTRS state
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* 2 FIGS state
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*/
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static unsigned int baudot_charset = 0; // FIXME
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void
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baudot_reset()
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{
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baudot_charset = 1;
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}
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/*
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* Returns 1 if *char_outp was stuffed with an output character
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* or 0 if no output character was stuffed (in other words, returns
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* the count of characters decoded and stuffed).
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*/
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int
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baudot_decode( char *char_outp, unsigned char databits )
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{
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/* Baudot (RTTY) */
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assert( (databits & ~0x1F) == 0 );
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int stuff_char = 1;
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if ( databits == BAUDOT_FIGS ) {
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baudot_charset = 2;
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stuff_char = 0;
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} else if ( databits == BAUDOT_LTRS ) {
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baudot_charset = 1;
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stuff_char = 0;
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} else if ( databits == BAUDOT_SPACE ) { /* RX un-shift on space */
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baudot_charset = 1;
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}
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if ( stuff_char ) {
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int t;
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if ( baudot_charset == 1 )
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t = 0;
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else
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t = 1; // U.S. figs
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// t = 2; // CCITT figs
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*char_outp = baudot_decode_table[databits][t];
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}
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return stuff_char;
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}
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static void
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baudot_skip_warning( char char_out )
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{
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unsigned char byte = char_out;
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fprintf(stderr, "W: baudot skipping non-encodable character '%c' 0x%02x\n",
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char_out, byte);
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}
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/*
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* Returns the number of 5-bit data words stuffed into *databits_outp (1 or 2)
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*/
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int
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baudot_encode( unsigned int *databits_outp, char char_out )
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{
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char_out = toupper(char_out);
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if( char_out >= 0x60 || char_out < 0 ) {
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baudot_skip_warning(char_out);
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return 0;
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}
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unsigned char ind = char_out;
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int n = 0;
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unsigned char charset_mask = baudot_encode_table[ind][1];
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debug_log("I: (baudot_charset==%u) input character '%c' 0x%02x charset_mask=%u\n", baudot_charset, char_out, char_out, charset_mask);
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if ( (baudot_charset & charset_mask ) == 0 ) {
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if ( charset_mask == 0 ) {
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baudot_skip_warning(char_out);
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return 0;
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}
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if ( baudot_charset == 0 )
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baudot_charset = 1;
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if ( charset_mask != 3 )
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baudot_charset = charset_mask;
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if ( baudot_charset == 1 )
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databits_outp[n++] = BAUDOT_LTRS;
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else if ( baudot_charset == 2 )
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databits_outp[n++] = BAUDOT_FIGS;
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else
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assert(0);
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debug_log("I: emit charset select 0x%02X\n", databits_outp[n-1]);
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}
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if ( !( baudot_charset == 1 || baudot_charset == 2 ) ) {
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fprintf(stderr, "E: baudot input character failed '%c' 0x%02x\n",
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char_out, char_out);
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fprintf(stderr, "E: baudot_charset==%u\n", baudot_charset);
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assert(0);
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}
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databits_outp[n++] = baudot_encode_table[ind][0];
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/* TX un-shift on space */
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if ( char_out == ' ' )
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baudot_charset = 1;
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return n;
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}
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