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/*
* libzvbi - Error correction functions
*
* Copyright (C) 2001, 2002, 2003, 2004 Michael H. Schimek
*
* Based on code from AleVT 1.5.1
* Copyright (C) 1998, 1999 Edgar Toernig <froese@gmx.de>
*
* 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, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/* $Id: hamm.c,v 1.15 2005/06/28 01:00:59 mschimek Exp $ */
#include <limits.h> /* CHAR_BIT */
#include "hamm.h"
const uint8_t
_vbi3_bit_reverse [256] = {
0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,
0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,
0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,
0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,
0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,
0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,
0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,
0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,
0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff
};
/**
* @ingroup Error
*
* @param p Array of unsigned bytes.
* @param n Size of array.
*
* Of each byte of the array, changes the most significant
* bit to make the number of set bits odd.
*/
void
vbi3_par (uint8_t * p,
unsigned long n)
{
while (n-- > 0) {
uint8_t c = *p;
/* if 0 == (inv_par[] & 32) change msb of *p. */
*p++ = c ^ (128 & ~(_vbi3_hamm24_inv_par[0][c] << 2));
}
}
/**
* @ingroup Error
* @param p Array of unsigned bytes.
* @param n Size of array.
*
* Tests the parity and clears the most significant bit of
* each byte of the array.
*
* @return
* A negative value if any byte of the array had even
* parity (sum of bits modulo 2 is 0).
*/
int
vbi3_unpar (uint8_t * p,
unsigned long n)
{
int r = 0;
while (n-- > 0) {
uint8_t c = *p;
/* if 0 == (inv_par[] & 32) set msb of r. */
r |= ~ _vbi3_hamm24_inv_par[0][c]
<< (sizeof (int) * CHAR_BIT - 1 - 5);
*p++ = c & 127;
}
return r;
}
/* ETS 300 706, Section 8.2 Hamming 8/4 */
const uint8_t
_vbi3_hamm8_fwd [16] = {
0x15, 0x02, 0x49, 0x5e, 0x64, 0x73, 0x38, 0x2f,
0xd0, 0xc7, 0x8c, 0x9b, 0xa1, 0xb6, 0xfd, 0xea
};
const int8_t
_vbi3_hamm8_inv [256] = {
0x01, -1, 0x01, 0x01, -1, 0x00, 0x01, -1,
-1, 0x02, 0x01, -1, 0x0a, -1, -1, 0x07,
-1, 0x00, 0x01, -1, 0x00, 0x00, -1, 0x00,
0x06, -1, -1, 0x0b, -1, 0x00, 0x03, -1,
-1, 0x0c, 0x01, -1, 0x04, -1, -1, 0x07,
0x06, -1, -1, 0x07, -1, 0x07, 0x07, 0x07,
0x06, -1, -1, 0x05, -1, 0x00, 0x0d, -1,
0x06, 0x06, 0x06, -1, 0x06, -1, -1, 0x07,
-1, 0x02, 0x01, -1, 0x04, -1, -1, 0x09,
0x02, 0x02, -1, 0x02, -1, 0x02, 0x03, -1,
0x08, -1, -1, 0x05, -1, 0x00, 0x03, -1,
-1, 0x02, 0x03, -1, 0x03, -1, 0x03, 0x03,
0x04, -1, -1, 0x05, 0x04, 0x04, 0x04, -1,
-1, 0x02, 0x0f, -1, 0x04, -1, -1, 0x07,
-1, 0x05, 0x05, 0x05, 0x04, -1, -1, 0x05,
0x06, -1, -1, 0x05, -1, 0x0e, 0x03, -1,
-1, 0x0c, 0x01, -1, 0x0a, -1, -1, 0x09,
0x0a, -1, -1, 0x0b, 0x0a, 0x0a, 0x0a, -1,
0x08, -1, -1, 0x0b, -1, 0x00, 0x0d, -1,
-1, 0x0b, 0x0b, 0x0b, 0x0a, -1, -1, 0x0b,
0x0c, 0x0c, -1, 0x0c, -1, 0x0c, 0x0d, -1,
-1, 0x0c, 0x0f, -1, 0x0a, -1, -1, 0x07,
-1, 0x0c, 0x0d, -1, 0x0d, -1, 0x0d, 0x0d,
0x06, -1, -1, 0x0b, -1, 0x0e, 0x0d, -1,
0x08, -1, -1, 0x09, -1, 0x09, 0x09, 0x09,
-1, 0x02, 0x0f, -1, 0x0a, -1, -1, 0x09,
0x08, 0x08, 0x08, -1, 0x08, -1, -1, 0x09,
0x08, -1, -1, 0x0b, -1, 0x0e, 0x03, -1,
-1, 0x0c, 0x0f, -1, 0x04, -1, -1, 0x09,
0x0f, -1, 0x0f, 0x0f, -1, 0x0e, 0x0f, -1,
0x08, -1, -1, 0x05, -1, 0x0e, 0x0d, -1,
-1, 0x0e, 0x0f, -1, 0x0e, 0x0e, -1, 0x0e
};
/* ETS 300 706, Section 8.3 Hamming 18/24 (code from AleVT) */
/* This table generates the parity checks for hamm24/18 decoding.
Bit 0 is for test A, 1 for B, ...
Thanks to R. Gancarz for this fine table *g* */
const int8_t
_vbi3_hamm24_inv_par [3][256] = {
{
/* Parities of first byte */
0, 33, 34, 3, 35, 2, 1, 32, 36, 5, 6, 39, 7, 38, 37, 4,
37, 4, 7, 38, 6, 39, 36, 5, 1, 32, 35, 2, 34, 3, 0, 33,
38, 7, 4, 37, 5, 36, 39, 6, 2, 35, 32, 1, 33, 0, 3, 34,
3, 34, 33, 0, 32, 1, 2, 35, 39, 6, 5, 36, 4, 37, 38, 7,
39, 6, 5, 36, 4, 37, 38, 7, 3, 34, 33, 0, 32, 1, 2, 35,
2, 35, 32, 1, 33, 0, 3, 34, 38, 7, 4, 37, 5, 36, 39, 6,
1, 32, 35, 2, 34, 3, 0, 33, 37, 4, 7, 38, 6, 39, 36, 5,
36, 5, 6, 39, 7, 38, 37, 4, 0, 33, 34, 3, 35, 2, 1, 32,
40, 9, 10, 43, 11, 42, 41, 8, 12, 45, 46, 15, 47, 14, 13, 44,
13, 44, 47, 14, 46, 15, 12, 45, 41, 8, 11, 42, 10, 43, 40, 9,
14, 47, 44, 13, 45, 12, 15, 46, 42, 11, 8, 41, 9, 40, 43, 10,
43, 10, 9, 40, 8, 41, 42, 11, 15, 46, 45, 12, 44, 13, 14, 47,
15, 46, 45, 12, 44, 13, 14, 47, 43, 10, 9, 40, 8, 41, 42, 11,
42, 11, 8, 41, 9, 40, 43, 10, 14, 47, 44, 13, 45, 12, 15, 46,
41, 8, 11, 42, 10, 43, 40, 9, 13, 44, 47, 14, 46, 15, 12, 45,
12, 45, 46, 15, 47, 14, 13, 44, 40, 9, 10, 43, 11, 42, 41, 8
}, {
/* Parities of second byte */
0, 41, 42, 3, 43, 2, 1, 40, 44, 5, 6, 47, 7, 46, 45, 4,
45, 4, 7, 46, 6, 47, 44, 5, 1, 40, 43, 2, 42, 3, 0, 41,
46, 7, 4, 45, 5, 44, 47, 6, 2, 43, 40, 1, 41, 0, 3, 42,
3, 42, 41, 0, 40, 1, 2, 43, 47, 6, 5, 44, 4, 45, 46, 7,
47, 6, 5, 44, 4, 45, 46, 7, 3, 42, 41, 0, 40, 1, 2, 43,
2, 43, 40, 1, 41, 0, 3, 42, 46, 7, 4, 45, 5, 44, 47, 6,
1, 40, 43, 2, 42, 3, 0, 41, 45, 4, 7, 46, 6, 47, 44, 5,
44, 5, 6, 47, 7, 46, 45, 4, 0, 41, 42, 3, 43, 2, 1, 40,
48, 25, 26, 51, 27, 50, 49, 24, 28, 53, 54, 31, 55, 30, 29, 52,
29, 52, 55, 30, 54, 31, 28, 53, 49, 24, 27, 50, 26, 51, 48, 25,
30, 55, 52, 29, 53, 28, 31, 54, 50, 27, 24, 49, 25, 48, 51, 26,
51, 26, 25, 48, 24, 49, 50, 27, 31, 54, 53, 28, 52, 29, 30, 55,
31, 54, 53, 28, 52, 29, 30, 55, 51, 26, 25, 48, 24, 49, 50, 27,
50, 27, 24, 49, 25, 48, 51, 26, 30, 55, 52, 29, 53, 28, 31, 54,
49, 24, 27, 50, 26, 51, 48, 25, 29, 52, 55, 30, 54, 31, 28, 53,
28, 53, 54, 31, 55, 30, 29, 52, 48, 25, 26, 51, 27, 50, 49, 24
}, {
/* Parities of third byte, xor 0x3F */
63, 14, 13, 60, 12, 61, 62, 15, 11, 58, 57, 8, 56, 9, 10, 59,
10, 59, 56, 9, 57, 8, 11, 58, 62, 15, 12, 61, 13, 60, 63, 14,
9, 56, 59, 10, 58, 11, 8, 57, 61, 12, 15, 62, 14, 63, 60, 13,
60, 13, 14, 63, 15, 62, 61, 12, 8, 57, 58, 11, 59, 10, 9, 56,
8, 57, 58, 11, 59, 10, 9, 56, 60, 13, 14, 63, 15, 62, 61, 12,
61, 12, 15, 62, 14, 63, 60, 13, 9, 56, 59, 10, 58, 11, 8, 57,
62, 15, 12, 61, 13, 60, 63, 14, 10, 59, 56, 9, 57, 8, 11, 58,
11, 58, 57, 8, 56, 9, 10, 59, 63, 14, 13, 60, 12, 61, 62, 15,
31, 46, 45, 28, 44, 29, 30, 47, 43, 26, 25, 40, 24, 41, 42, 27,
42, 27, 24, 41, 25, 40, 43, 26, 30, 47, 44, 29, 45, 28, 31, 46,
41, 24, 27, 42, 26, 43, 40, 25, 29, 44, 47, 30, 46, 31, 28, 45,
28, 45, 46, 31, 47, 30, 29, 44, 40, 25, 26, 43, 27, 42, 41, 24,
40, 25, 26, 43, 27, 42, 41, 24, 28, 45, 46, 31, 47, 30, 29, 44,
29, 44, 47, 30, 46, 31, 28, 45, 41, 24, 27, 42, 26, 43, 40, 25,
30, 47, 44, 29, 45, 28, 31, 46, 42, 27, 24, 41, 25, 40, 43, 26,
43, 26, 25, 40, 24, 41, 42, 27, 31, 46, 45, 28, 44, 29, 30, 47
}
};
/* Table to extract the lower 4 bits from first hamm24/18
encoded byte (P4 D4 D3 D2 P3 D1 P2 P1) */
static const int8_t
_vbi3_hamm24_val [128] = {
0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1,
2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 3, 3, 3, 3,
4, 4, 4, 4, 5, 5, 5, 5, 4, 4, 4, 4, 5, 5, 5, 5,
6, 6, 6, 6, 7, 7, 7, 7, 6, 6, 6, 6, 7, 7, 7, 7,
8, 8, 8, 8, 9, 9, 9, 9, 8, 8, 8, 8, 9, 9, 9, 9,
10, 10, 10, 10, 11, 11, 11, 11, 10, 10, 10, 10, 11, 11, 11, 11,
12, 12, 12, 12, 13, 13, 13, 13, 12, 12, 12, 12, 13, 13, 13, 13,
14, 14, 14, 14, 15, 15, 15, 15, 14, 14, 14, 14, 15, 15, 15, 15
};
/* Correction of single bit error in decoded word,
according to test A ... F in table vbi3_hamm24_inv_tst.
MSB indicates double bit error. */
static const int32_t
_vbi3_hamm24_corr [64] = {
0x00000000, 0x80000000, 0x80000000, 0x80000000,
0x80000000, 0x80000000, 0x80000000, 0x80000000,
0x80000000, 0x80000000, 0x80000000, 0x80000000,
0x80000000, 0x80000000, 0x80000000, 0x80000000,
0x80000000, 0x80000000, 0x80000000, 0x80000000,
0x80000000, 0x80000000, 0x80000000, 0x80000000,
0x80000000, 0x80000000, 0x80000000, 0x80000000,
0x80000000, 0x80000000, 0x80000000, 0x80000000,
0x00000000, 0x00000000, 0x00000000, 0x00000001,
0x00000000, 0x00000002, 0x00000004, 0x00000008,
0x00000000, 0x00000010, 0x00000020, 0x00000040,
0x00000080, 0x00000100, 0x00000200, 0x00000400,
0x00000000, 0x00000800, 0x00001000, 0x00002000,
0x00004000, 0x00008000, 0x00010000, 0x00020000,
0x80000000, 0x80000000, 0x80000000, 0x80000000,
0x80000000, 0x80000000, 0x80000000, 0x80000000,
};
/**
* @ingroup Error
* @param p Pointer to a Hamming 24/18 protected 24 bit word,
* last significant byte first, lsb first transmitted.
*
* Decodes a Hamming 24/18 protected byte triplet
* as specified in ETS 300 706, Section 8.3.
*
* @return
* Triplet data bits D18 [msb] ... D1 [lsb] or a negative value
* if the triplet contained incorrectable errors.
*/
int
vbi3_unham24p (const uint8_t * p)
{
int e = _vbi3_hamm24_inv_par[0][p[0]]
^ _vbi3_hamm24_inv_par[1][p[1]]
^ _vbi3_hamm24_inv_par[2][p[2]];
int x = _vbi3_hamm24_val[p[0] & 127]
+ (p[1] & 127) * 16
+ (p[2] & 127) * 2048;
return x ^ (int) _vbi3_hamm24_corr[e];
}
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