beetle-psx-libretro/mednafen/cdrom/lec.c

/*  cdrdao - write audio CD-Rs in disc-at-once mode
 *
 *  Copyright (C) 1998-2002 Andreas Mueller <andreas@daneb.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.
 */

#include <assert.h>
#include <sys/types.h>
#include <stdint.h>

#include "lec.h"

#define GF8_PRIM_POLY 0x11d /* x^8 + x^4 + x^3 + x^2 + 1 */

#define EDC_POLY 0x8001801b /* (x^16 + x^15 + x^2 + 1) (x^16 + x^2 + x + 1) */

#define LEC_HEADER_OFFSET 12
#define LEC_DATA_OFFSET 16
#define LEC_MODE1_DATA_LEN 2048
#define LEC_MODE1_EDC_OFFSET 2064
#define LEC_MODE1_INTERMEDIATE_OFFSET 2068
#define LEC_MODE1_P_PARITY_OFFSET 2076
#define LEC_MODE1_Q_PARITY_OFFSET 2248
#define LEC_MODE2_FORM1_DATA_LEN (2048+8)
#define LEC_MODE2_FORM1_EDC_OFFSET 2072
#define LEC_MODE2_FORM2_DATA_LEN (2324+8)
#define LEC_MODE2_FORM2_EDC_OFFSET 2348

static uint8_t GF8_LOG[256];
static uint8_t GF8_ILOG[256];

uint16_t cf8_table[43][256];
uint32_t crc_table[256];
uint8_t scramble_table[2340];

/* Addition in the GF(8) domain: just the XOR of the values.
 */
#define gf8_add(a,  b) (a) ^ (b)

/* Division in the GF(8) domain: Like multiplication but logarithms a
 * subtracted.
 */
static uint8_t gf8_div(uint8_t a, uint8_t b)
{
  int16_t sum;

  assert(b != 0);

  if (a == 0)
    return 0;

  sum = GF8_LOG[a] - GF8_LOG[b];

  if (sum < 0)
    sum += 255;

  return GF8_ILOG[sum];
}


/* Reverses the bits in 'd'. 'bits' defines the bit width of 'd'.
 */
static uint32_t mirror_bits(uint32_t d, int bits)
{
  int i;
  uint32_t r = 0;

  for (i = 0; i < bits; i++)
  {
    r <<= 1;

    if ((d & 0x1) != 0)
      r |= 0x1;

    d >>= 1;
  }

  return r;
}


/* Calculates the CRC of given data with given lengths based on the
 * table lookup algorithm.
 */
static uint32_t calc_edc(uint8_t *data, int len)
{
  uint32_t crc = 0;

  while (len--)
    crc = crc_table[(int)(crc ^ *data++) & 0xff] ^ (crc >> 8);

  return crc;
}

/* Build the scramble table as defined in the yellow book. The bytes
   12 to 2351 of a sector will be XORed with the data of this table.
 */
static void scramble_table_init(void)
{
   uint8_t d;
   uint16_t i, j;
   uint16_t reg = 1;

   for (i = 0; i < 2340; i++)
   {
      d = 0;

      for (j = 0; j < 8; j++)
      {
         d >>= 1;

         if ((reg & 0x1) != 0)
            d |= 0x80;

         reg >>= 1;
         if ((reg & 0x1) != ((reg >> 1) & 0x1))
            reg |= 0x4000; /* 15-bit register */
      }

      scramble_table[i] = d;
   }
}

/* Build the CRC lookup table for EDC_POLY poly. The CRC is 32 bit wide
 * and reversed (i.e. the bit stream is divided by the EDC_POLY with the
 * LSB first order).
 */
static void crc_table_init(void)
{
   uint32_t i, j;
   uint32_t r;

   for (i = 0; i < 256; i++)
   {
      r = mirror_bits(i, 8);

      r <<= 24;

      for (j = 0; j < 8; j++)
      {
         r <<= 1;
         if ((r & 0x80000000) != 0)
            r ^= EDC_POLY;
      }

      r = mirror_bits(r, 32);

      crc_table[i] = r;
   }
}

/* Creates the logarithm and inverse logarithm table that is required
 * for performing multiplication in the GF(8) domain.
 */
static void gf8_create_log_tables(void)
{
   uint8_t log;
   uint16_t b;

   for (b = 0; b <= 255; b++)
   {
      GF8_LOG[b] = 0;
      GF8_ILOG[b] = 0;
   }

   b = 1;

   for (log = 0; log < 255; log++)
   {
      GF8_LOG[(uint8_t)b] = log;
      GF8_ILOG[log] = (uint8_t)b;

      b <<= 1;

      if ((b & 0x100) != 0) 
         b ^= GF8_PRIM_POLY;
   }
}

static void cf8_table_init(void)
{
   int i, j;
   uint16_t c;
   uint8_t GF8_COEFFS_HELP[2][45]; 
   uint8_t GF8_Q_COEFFS[2][45];

   gf8_create_log_tables();

   /* build matrix H:
    *  1    1   ...  1   1
    * a^44 a^43 ... a^1 a^0
    *
    * 
    */

   for (j = 0; j < 45; j++)
   {
      GF8_COEFFS_HELP[0][j] = 1;               /* e0 */
      GF8_COEFFS_HELP[1][j] = GF8_ILOG[44-j];  /* e1 */
   }


   /* resolve equation system for parity byte 0 and 1 */

   /* e1' = e1 + e0 */
   for (j = 0; j < 45; j++)
      GF8_Q_COEFFS[1][j] = gf8_add(GF8_COEFFS_HELP[1][j],
            GF8_COEFFS_HELP[0][j]);

   /* e1'' = e1' / (a^1 + 1) */
   for (j = 0; j < 45; j++)
      GF8_Q_COEFFS[1][j] = gf8_div(GF8_Q_COEFFS[1][j], GF8_Q_COEFFS[1][43]);

   /* e0' = e0 + e1 / a^1 */
   for (j = 0; j < 45; j++)
      GF8_Q_COEFFS[0][j] = gf8_add(GF8_COEFFS_HELP[0][j],
            gf8_div(GF8_COEFFS_HELP[1][j],
               GF8_ILOG[1]));

   /* e0'' = e0' / (1 + 1 / a^1) */
   for (j = 0; j < 45; j++)
      GF8_Q_COEFFS[0][j] = gf8_div(GF8_Q_COEFFS[0][j], GF8_Q_COEFFS[0][44]);

   /* 
    * Compute the products of 0..255 with all of the Q coefficients in
    * advance. When building the scalar product between the data vectors
    * and the P/Q vectors the individual products can be looked up in
    * this table
    *
    * The P parity coefficients are just a subset of the Q coefficients so
    * that we do not need to create a separate table for them. 
    */

   for (j = 0; j < 43; j++)
   {

      cf8_table[j][0] = 0;

      for (i = 1; i < 256; i++)
      {
         c = GF8_LOG[i] + GF8_LOG[GF8_Q_COEFFS[0][j]];
         if (c >= 255) c -= 255;
         cf8_table[j][i] = GF8_ILOG[c];

         c = GF8_LOG[i] + GF8_LOG[GF8_Q_COEFFS[1][j]];
         if (c >= 255) c -= 255;
         cf8_table[j][i] |= GF8_ILOG[c]<<8;
      }
   }
}

void lec_tables_init(void)
{
   scramble_table_init();
   crc_table_init();
   cf8_table_init();
}

/* Calc EDC for a MODE 1 sector
 */
static void calc_mode1_edc(uint8_t *sector)
{
   uint32_t crc = calc_edc(sector, LEC_MODE1_DATA_LEN + 16);

   sector[LEC_MODE1_EDC_OFFSET] = crc & 0xffL;
   sector[LEC_MODE1_EDC_OFFSET + 1] = (crc >> 8) & 0xffL;
   sector[LEC_MODE1_EDC_OFFSET + 2] = (crc >> 16) & 0xffL;
   sector[LEC_MODE1_EDC_OFFSET + 3] = (crc >> 24) & 0xffL;
}

/* Calc EDC for a XA form 1 sector
 */
static void calc_mode2_form1_edc(uint8_t *sector)
{
  uint32_t crc = calc_edc(sector + LEC_DATA_OFFSET,
			   LEC_MODE2_FORM1_DATA_LEN);

  sector[LEC_MODE2_FORM1_EDC_OFFSET] = crc & 0xffL;
  sector[LEC_MODE2_FORM1_EDC_OFFSET + 1] = (crc >> 8) & 0xffL;
  sector[LEC_MODE2_FORM1_EDC_OFFSET + 2] = (crc >> 16) & 0xffL;
  sector[LEC_MODE2_FORM1_EDC_OFFSET + 3] = (crc >> 24) & 0xffL;
}

/* Calc EDC for a XA form 2 sector
 */
static void calc_mode2_form2_edc(uint8_t *sector)
{
   uint32_t crc = calc_edc(sector + LEC_DATA_OFFSET,
         LEC_MODE2_FORM2_DATA_LEN);

   sector[LEC_MODE2_FORM2_EDC_OFFSET] = crc & 0xffL;
   sector[LEC_MODE2_FORM2_EDC_OFFSET + 1] = (crc >> 8) & 0xffL;
   sector[LEC_MODE2_FORM2_EDC_OFFSET + 2] = (crc >> 16) & 0xffL;
   sector[LEC_MODE2_FORM2_EDC_OFFSET + 3] = (crc >> 24) & 0xffL;
}

/* Writes the sync pattern to the given sector.
 */
static void set_sync_pattern(uint8_t *sector)
{
   sector[0] = 0;

   sector[1] = sector[2] = sector[3] = sector[4] = sector[5] = 
      sector[6] = sector[7] = sector[8] = sector[9] = sector[10] = 0xff;

   sector[11] = 0;
}


static uint8_t bin2bcd(uint8_t b)
{
   return (((b/10) << 4) & 0xf0) | ((b%10) & 0x0f);
}

/* Builds the sector header.
 */
static void set_sector_header(uint8_t mode, uint32_t adr, uint8_t *sector)
{
  sector[LEC_HEADER_OFFSET] = bin2bcd(adr / (60*75));
  sector[LEC_HEADER_OFFSET + 1] = bin2bcd((adr / 75) % 60);
  sector[LEC_HEADER_OFFSET + 2] = bin2bcd(adr % 75);
  sector[LEC_HEADER_OFFSET + 3] = mode;
}

/* Calculate the P parities for the sector.
 * The 43 P vectors of length 24 are combined with the GF8_P_COEFFS.
 */
static void calc_P_parity(uint8_t *sector)
{
   int i, j;
   uint16_t p01_msb, p01_lsb;
   uint8_t *p_lsb_start;
   uint8_t *p_lsb;
   uint8_t *p0, *p1;
   uint8_t d0,d1;

   p_lsb_start = sector + LEC_HEADER_OFFSET;

   p1 = sector + LEC_MODE1_P_PARITY_OFFSET;
   p0 = sector + LEC_MODE1_P_PARITY_OFFSET + 2 * 43;

   for (i = 0; i <= 42; i++)
   {
      p_lsb = p_lsb_start;

      p01_lsb = p01_msb = 0;

      for (j = 19; j <= 42; j++)
      {
         d0 = *p_lsb;
         d1 = *(p_lsb+1);

         p01_lsb ^= cf8_table[j][d0];
         p01_msb ^= cf8_table[j][d1];

         p_lsb += 2 * 43;
      }

      *p0 = p01_lsb;
      *(p0 + 1) = p01_msb;

      *p1 = p01_lsb>>8;
      *(p1 + 1) = p01_msb>>8;

      p0 += 2;
      p1 += 2;

      p_lsb_start += 2;
   }
}

/* Calculate the Q parities for the sector.
 * The 26 Q vectors of length 43 are combined with the GF8_Q_COEFFS.
 */
static void calc_Q_parity(uint8_t *sector)
{
   int i, j;
   uint16_t q01_lsb, q01_msb;
   uint8_t *q_lsb_start;
   uint8_t *q_lsb;
   uint8_t *q0, *q1, *q_start;
   uint8_t d0,d1;

   q_lsb_start = sector + LEC_HEADER_OFFSET;

   q_start = sector + LEC_MODE1_Q_PARITY_OFFSET;
   q1 = sector + LEC_MODE1_Q_PARITY_OFFSET;
   q0 = sector + LEC_MODE1_Q_PARITY_OFFSET + 2 * 26;

   for (i = 0; i <= 25; i++)
   {
      q_lsb = q_lsb_start;

      q01_lsb = q01_msb = 0;

      for (j = 0; j <= 42; j++)
      {
         d0 = *q_lsb;
         d1 = *(q_lsb+1);

         q01_lsb ^= cf8_table[j][d0];
         q01_msb ^= cf8_table[j][d1];

         q_lsb += 2 * 44;

         if (q_lsb >= q_start)
            q_lsb -= 2 * 1118;
      }

      *q0 = q01_lsb;
      *(q0 + 1) = q01_msb;

      *q1 = q01_lsb>>8;
      *(q1 + 1) = q01_msb>>8;

      q0 += 2;
      q1 += 2;

      q_lsb_start += 2 * 43;
   }
}

/* Encodes a MODE 0 sector.
 * 'adr' is the current physical sector address
 * 'sector' must be 2352 byte wide
 */
void lec_encode_mode0_sector(uint32_t adr, uint8_t *sector)
{
   uint16_t i;

   set_sync_pattern(sector);
   set_sector_header(0, adr, sector);

   sector += 16;

   for (i = 0; i < 2336; i++)
      *sector++ = 0;
}

/* Encodes a MODE 1 sector.
 * 'adr' is the current physical sector address
 * 'sector' must be 2352 byte wide containing 2048 bytes user data at
 * offset 16
 */
void lec_encode_mode1_sector(uint32_t adr, uint8_t *sector)
{
   set_sync_pattern(sector);
   set_sector_header(1, adr, sector);

   calc_mode1_edc(sector);

   /* clear the intermediate field */
   sector[LEC_MODE1_INTERMEDIATE_OFFSET] =
      sector[LEC_MODE1_INTERMEDIATE_OFFSET + 1] =
      sector[LEC_MODE1_INTERMEDIATE_OFFSET + 2] =
      sector[LEC_MODE1_INTERMEDIATE_OFFSET + 3] =
      sector[LEC_MODE1_INTERMEDIATE_OFFSET + 4] =
      sector[LEC_MODE1_INTERMEDIATE_OFFSET + 5] =
      sector[LEC_MODE1_INTERMEDIATE_OFFSET + 6] =
      sector[LEC_MODE1_INTERMEDIATE_OFFSET + 7] = 0;

   calc_P_parity(sector);
   calc_Q_parity(sector);
}

/* Encodes a MODE 2 sector.
 * 'adr' is the current physical sector address
 * 'sector' must be 2352 byte wide containing 2336 bytes user data at
 * offset 16
 */
void lec_encode_mode2_sector(uint32_t adr, uint8_t *sector)
{
   set_sync_pattern(sector);
   set_sector_header(2, adr, sector);
}

/* Encodes a XA form 1 sector.
 * 'adr' is the current physical sector address
 * 'sector' must be 2352 byte wide containing 2048+8 bytes user data at
 * offset 16
 */
void lec_encode_mode2_form1_sector(uint32_t adr, uint8_t *sector)
{
   set_sync_pattern(sector);

   calc_mode2_form1_edc(sector);

   /* P/Q partiy must not contain the sector header so clear it */
   sector[LEC_HEADER_OFFSET] =
      sector[LEC_HEADER_OFFSET + 1] =
      sector[LEC_HEADER_OFFSET + 2] =
      sector[LEC_HEADER_OFFSET + 3] = 0;

   calc_P_parity(sector);
   calc_Q_parity(sector);

   /* finally add the sector header */
   set_sector_header(2, adr, sector);
}

/* Encodes a XA form 2 sector.
 * 'adr' is the current physical sector address
 * 'sector' must be 2352 byte wide containing 2324+8 bytes user data at
 * offset 16
 */
void lec_encode_mode2_form2_sector(uint32_t adr, uint8_t *sector)
{
   set_sync_pattern(sector);

   calc_mode2_form2_edc(sector);

   set_sector_header(2, adr, sector);
}

/* Scrambles and byte swaps an encoded sector.
 * 'sector' must be 2352 byte wide.
 */
void lec_scramble(uint8_t *sector)
{
   uint16_t i;
   uint8_t *p = sector;
   uint8_t tmp;
   const uint8_t *stable = scramble_table;

   for (i = 0; i < 6; i++)
   {
      /* just swap bytes of sector sync */
      tmp = *p;
      *p = *(p + 1);
      p++;
      *p++ = tmp;
   }

   for (;i < (2352 / 2); i++)
   {
      /* scramble and swap bytes */
      tmp = *p ^ *stable++;
      *p = *(p + 1) ^ *stable++;
      p++;
      *p++ = tmp;
   }
}