/* * 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 * * 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 1.7 2006/10/08 06:19:48 mschimek Exp $ */ #ifdef HAVE_CONFIG_H # include "config.h" #endif #include /* CHAR_BIT */ #include "hamm.h" const uint8_t _vbi_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. * * @since 0.2.12 */ void vbi_par (uint8_t * p, unsigned int n) { while (n-- > 0) { uint8_t c = *p; /* if 0 == (inv_par[] & 32) change msb of *p. */ *p++ = c ^ (128 & ~(_vbi_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). * * @since 0.2.12 */ int vbi_unpar (uint8_t * p, unsigned int n) { int r = 0; while (n-- > 0) { uint8_t c = *p; /* if 0 == (inv_par[] & 32) set msb of r. */ r |= ~ _vbi_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 _vbi_hamm8_fwd [16] = { 0x15, 0x02, 0x49, 0x5e, 0x64, 0x73, 0x38, 0x2f, 0xd0, 0xc7, 0x8c, 0x9b, 0xa1, 0xb6, 0xfd, 0xea }; const int8_t _vbi_hamm8_inv [256] = { 0x01, 0xff, 0x01, 0x01, 0xff, 0x00, 0x01, 0xff, 0xff, 0x02, 0x01, 0xff, 0x0a, 0xff, 0xff, 0x07, 0xff, 0x00, 0x01, 0xff, 0x00, 0x00, 0xff, 0x00, 0x06, 0xff, 0xff, 0x0b, 0xff, 0x00, 0x03, 0xff, 0xff, 0x0c, 0x01, 0xff, 0x04, 0xff, 0xff, 0x07, 0x06, 0xff, 0xff, 0x07, 0xff, 0x07, 0x07, 0x07, 0x06, 0xff, 0xff, 0x05, 0xff, 0x00, 0x0d, 0xff, 0x06, 0x06, 0x06, 0xff, 0x06, 0xff, 0xff, 0x07, 0xff, 0x02, 0x01, 0xff, 0x04, 0xff, 0xff, 0x09, 0x02, 0x02, 0xff, 0x02, 0xff, 0x02, 0x03, 0xff, 0x08, 0xff, 0xff, 0x05, 0xff, 0x00, 0x03, 0xff, 0xff, 0x02, 0x03, 0xff, 0x03, 0xff, 0x03, 0x03, 0x04, 0xff, 0xff, 0x05, 0x04, 0x04, 0x04, 0xff, 0xff, 0x02, 0x0f, 0xff, 0x04, 0xff, 0xff, 0x07, 0xff, 0x05, 0x05, 0x05, 0x04, 0xff, 0xff, 0x05, 0x06, 0xff, 0xff, 0x05, 0xff, 0x0e, 0x03, 0xff, 0xff, 0x0c, 0x01, 0xff, 0x0a, 0xff, 0xff, 0x09, 0x0a, 0xff, 0xff, 0x0b, 0x0a, 0x0a, 0x0a, 0xff, 0x08, 0xff, 0xff, 0x0b, 0xff, 0x00, 0x0d, 0xff, 0xff, 0x0b, 0x0b, 0x0b, 0x0a, 0xff, 0xff, 0x0b, 0x0c, 0x0c, 0xff, 0x0c, 0xff, 0x0c, 0x0d, 0xff, 0xff, 0x0c, 0x0f, 0xff, 0x0a, 0xff, 0xff, 0x07, 0xff, 0x0c, 0x0d, 0xff, 0x0d, 0xff, 0x0d, 0x0d, 0x06, 0xff, 0xff, 0x0b, 0xff, 0x0e, 0x0d, 0xff, 0x08, 0xff, 0xff, 0x09, 0xff, 0x09, 0x09, 0x09, 0xff, 0x02, 0x0f, 0xff, 0x0a, 0xff, 0xff, 0x09, 0x08, 0x08, 0x08, 0xff, 0x08, 0xff, 0xff, 0x09, 0x08, 0xff, 0xff, 0x0b, 0xff, 0x0e, 0x03, 0xff, 0xff, 0x0c, 0x0f, 0xff, 0x04, 0xff, 0xff, 0x09, 0x0f, 0xff, 0x0f, 0x0f, 0xff, 0x0e, 0x0f, 0xff, 0x08, 0xff, 0xff, 0x05, 0xff, 0x0e, 0x0d, 0xff, 0xff, 0x0e, 0x0f, 0xff, 0x0e, 0x0e, 0xff, 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 _vbi_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 _vbi_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 vbi_hamm24_inv_tst. MSB indicates double bit error. */ static const int32_t _vbi_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. * * @since 0.2.12 */ int vbi_unham24p (const uint8_t * p) { int e = _vbi_hamm24_inv_par[0][p[0]] ^ _vbi_hamm24_inv_par[1][p[1]] ^ _vbi_hamm24_inv_par[2][p[2]]; int x = _vbi_hamm24_val[p[0] & 127] + (p[1] & 127) * 16 + (p[2] & 127) * 2048; return x ^ (int) _vbi_hamm24_corr[e]; }