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baudot.h
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baudot.h
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#include <limits.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <sys/types.h>
#define BAUDOT_START_BITS ((uint8_t) 0x00)
#define BAUDOT_STOP_BITS ((uint8_t) 0xC0)
#define BAUDOT_FIGURES_SHIFT ((uint8_t) 0x1B)
#define BAUDOT_LETTERS_SHIFT ((uint8_t) 0x1F)
#ifndef BAUDOT_PREAMBLE_LENGTH
#define BAUDOT_PREAMBLE_LENGTH 2
#endif
#ifndef BAUDOT_PREAMBLE_SYMBOL
#define BAUDOT_PREAMBLE_SYMBOL BAUDOT_LETTERS_SHIFT // LTRS
#endif
#define BAUDOT_NONE 0
#define BAUDOT_LTRS 1
#define BAUDOT_FIGS 2
// BAUDOT_BOTH must be BAUDOT_LTRS | BAUDOT_FIGS
#define BAUDOT_BOTH (BAUDOT_LTRS | BAUDOT_FIGS)
#define BAUDOT_LTRS_AFTER 4
#define BAUDOT_FIGS_AFTER 8
typedef struct {
uint8_t bits;
uint8_t shift;
} baudot_symbol_t_;
static const
baudot_symbol_t_ baudot_ccitt_from_ascii[UINT8_MAX] = {
['\0'] = {0x00, BAUDOT_BOTH},
['e'] = {0x01, BAUDOT_LTRS},
['E'] = {0x01, BAUDOT_LTRS},
['3'] = {0x01, BAUDOT_FIGS},
['\n'] = {0x02, BAUDOT_BOTH},
['a'] = {0x03, BAUDOT_LTRS},
['A'] = {0x03, BAUDOT_LTRS},
['-'] = {0x03, BAUDOT_FIGS},
[' '] = {0x04, BAUDOT_BOTH | BAUDOT_LTRS_AFTER},
['s'] = {0x05, BAUDOT_LTRS},
['S'] = {0x05, BAUDOT_LTRS},
['\''] = {0x05, BAUDOT_FIGS},
['i'] = {0x06, BAUDOT_LTRS},
['I'] = {0x06, BAUDOT_LTRS},
['8'] = {0x06, BAUDOT_FIGS},
['u'] = {0x07, BAUDOT_LTRS},
['U'] = {0x07, BAUDOT_LTRS},
['7'] = {0x07, BAUDOT_FIGS},
['\r'] = {0x08, BAUDOT_BOTH},
['d'] = {0x09, BAUDOT_LTRS},
['D'] = {0x09, BAUDOT_LTRS},
// WRU / ENQ / "WHO ARE YOU"
[5] = {0x09, BAUDOT_FIGS},
['r'] = {0x0A, BAUDOT_LTRS},
['R'] = {0x0A, BAUDOT_LTRS},
['4'] = {0x0A, BAUDOT_FIGS},
['j'] = {0x0B, BAUDOT_LTRS},
['J'] = {0x0B, BAUDOT_LTRS},
['\a'] = {0x0B, BAUDOT_FIGS},
['n'] = {0x0C, BAUDOT_LTRS},
['N'] = {0x0C, BAUDOT_LTRS},
[','] = {0x0C, BAUDOT_FIGS},
['f'] = {0x0D, BAUDOT_LTRS},
['F'] = {0x0D, BAUDOT_LTRS},
['!'] = {0x0D, BAUDOT_FIGS},
['c'] = {0x0E, BAUDOT_LTRS},
['C'] = {0x0E, BAUDOT_LTRS},
[':'] = {0x0E, BAUDOT_FIGS},
['k'] = {0x0F, BAUDOT_LTRS},
['K'] = {0x0F, BAUDOT_LTRS},
['('] = {0x0F, BAUDOT_FIGS},
['t'] = {0x10, BAUDOT_LTRS},
['T'] = {0x10, BAUDOT_LTRS},
['5'] = {0x10, BAUDOT_FIGS},
['z'] = {0x11, BAUDOT_LTRS},
['Z'] = {0x11, BAUDOT_LTRS},
['+'] = {0x11, BAUDOT_FIGS},
['l'] = {0x12, BAUDOT_LTRS},
['L'] = {0x12, BAUDOT_LTRS},
[')'] = {0x12, BAUDOT_FIGS},
['w'] = {0x13, BAUDOT_LTRS},
['W'] = {0x13, BAUDOT_LTRS},
['2'] = {0x13, BAUDOT_FIGS},
['h'] = {0x14, BAUDOT_LTRS},
['H'] = {0x14, BAUDOT_LTRS},
['#'] = {0x14, BAUDOT_FIGS},
['y'] = {0x15, BAUDOT_LTRS},
['Y'] = {0x15, BAUDOT_LTRS},
['6'] = {0x15, BAUDOT_FIGS},
['p'] = {0x16, BAUDOT_LTRS},
['P'] = {0x16, BAUDOT_LTRS},
['0'] = {0x16, BAUDOT_FIGS},
['q'] = {0x17, BAUDOT_LTRS},
['Q'] = {0x17, BAUDOT_LTRS},
['1'] = {0x17, BAUDOT_FIGS},
['o'] = {0x18, BAUDOT_LTRS},
['O'] = {0x18, BAUDOT_LTRS},
['9'] = {0x18, BAUDOT_FIGS},
['b'] = {0x19, BAUDOT_LTRS},
['B'] = {0x19, BAUDOT_LTRS},
['?'] = {0x19, BAUDOT_FIGS},
['g'] = {0x1A, BAUDOT_LTRS},
['G'] = {0x1A, BAUDOT_LTRS},
['&'] = {0x1A, BAUDOT_FIGS},
// 0x1B is FIGURES SHIFT
['m'] = {0x1C, BAUDOT_LTRS},
['M'] = {0x1C, BAUDOT_LTRS},
['.'] = {0x1C, BAUDOT_FIGS},
['x'] = {0x1D, BAUDOT_LTRS},
['X'] = {0x1D, BAUDOT_LTRS},
['/'] = {0x1D, BAUDOT_FIGS},
['v'] = {0x1E, BAUDOT_LTRS},
['V'] = {0x1E, BAUDOT_LTRS},
['='] = {0x1E, BAUDOT_FIGS},
// 0x1F is LETTERS SHIFT
};
static inline
size_t bytes_required_for_word(uintmax_t word) {
if (word < 0x100ULL) return 1;
if (word < 0x10000ULL) return 2;
if (word < 0x1000000ULL) return 3;
if (word < 0x100000000ULL) return 4;
if (word < 0x10000000000ULL) return 5;
if (word < 0x1000000000000ULL) return 6;
if (word < 0x100000000000000ULL) return 7;
return 8;
}
static inline
uint16_t baudot_get_next(uint8_t ascii_letter, uint8_t *current_shift) {
baudot_symbol_t_ symbol = baudot_ccitt_from_ascii[ascii_letter];
uint16_t finished_symbol = 0;
// Not found
if (symbol.shift == BAUDOT_NONE) {
return 0;
}
// Case/shift mismatch? Change case and insert shift symbol
if ((symbol.shift & *current_shift) == 0) {
if (symbol.shift == BAUDOT_LTRS) {
finished_symbol |= BAUDOT_STOP_BITS | (BAUDOT_LETTERS_SHIFT << 1) | BAUDOT_START_BITS;
} else {
finished_symbol |= BAUDOT_STOP_BITS | (BAUDOT_FIGURES_SHIFT << 1) | BAUDOT_START_BITS;
}
*current_shift = symbol.shift;
finished_symbol <<= 8;
}
// Actual symbol
finished_symbol |= BAUDOT_STOP_BITS | (symbol.bits << 1) | BAUDOT_START_BITS;
// Special case -- mostly used to handle space returning to letters
if (symbol.shift & BAUDOT_LTRS_AFTER) {
*current_shift = BAUDOT_LTRS;
} else if (symbol.shift & BAUDOT_FIGS_AFTER) {
*current_shift = BAUDOT_FIGS;
}
return finished_symbol;
}
ssize_t baudot_from_ascii(uint8_t *buffer, size_t buffer_size, char const *string) {
if (!buffer)
return -1;
if (!string)
return -1;
size_t bytes_read = 0;
size_t bytes_written = 0;
uint8_t current_shift = BAUDOT_LTRS;
if (BAUDOT_PREAMBLE_LENGTH > buffer_size) {
return bytes_written;
}
memset(buffer,
BAUDOT_STOP_BITS | (BAUDOT_PREAMBLE_SYMBOL << 1) | BAUDOT_STOP_BITS,
BAUDOT_PREAMBLE_LENGTH);
bytes_written += BAUDOT_PREAMBLE_LENGTH;
while (string[bytes_read] != '\0') {
uint16_t next_bits = baudot_get_next(string[bytes_read], ¤t_shift);
ssize_t bytes_required = bytes_required_for_word(next_bits);
if (bytes_written + bytes_required > buffer_size) {
// Buffer full, writing ends here
break;
}
// Possible shift character
if (bytes_required > 1) {
buffer[bytes_written] = (next_bits & 0xFF00) >> 8;
bytes_written++;
}
// Actual character
buffer[bytes_written] = next_bits & 0xFF;
bytes_written++;
bytes_read++;
}
return bytes_written;
}