Subversion Repositories open8_urisc

#include <ctype.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include "defines.h"

#include "memory.h"

#include "compute.h"

extern unsigned char *rom;

extern int romsize, sms_checksum, gb_checksum, gb_complement_check, snes_checksum;

extern int snes_rom_mode;

int compute_checksums(void) {

  if (sms_checksum != 0)

    compute_sms_checksum();

  if (gb_complement_check != 0)

    compute_gb_complement_check();

  if (gb_checksum != 0)

    compute_gb_checksum();

  if (snes_checksum != 0)

    compute_snes_checksum();

  return SUCCEEDED;

}

int compute_gb_complement_check(void) {

  unsigned int i, x;

  if (romsize < 0x8000) {

    fprintf(stderr, "COMPUTE_GB_COMPLEMENT_CHECK: GB complement check computing requires a ROM of at least 32KB.\n");

    return FAILED;

  }

  i = 0;

  for (x = 0x134; x <= 0x14C; x++)

    i += rom[x];

  i += 25;

  mem_insert(0x14D, 0 - (i & 0xFF));

  return SUCCEEDED;

}

int compute_gb_checksum(void) {

  unsigned int i, x;

  if (romsize < 0x8000) {

    fprintf(stderr, "COMPUTE_GB_CHECKSUM: GB checksum computing requires a ROM of at least 32KB.\n");

    return FAILED;

  }

  i = 0;

  for (x = 0; x < 0x14E; x++)

    i += rom[x];

  for (x = 0x150; x < romsize; x++)

    i += rom[x];

  mem_insert(0x14E, (i >> 8) & 0xFF);

  mem_insert(0x14F, i & 0xFF);

  return SUCCEEDED;

}

int compute_snes_checksum(void) {

  unsigned int i, x, n, m, l, o;

  if (snes_rom_mode == SNES_ROM_MODE_LOROM) {

    if (romsize < 0x8000) {

      fprintf(stderr, "COMPUTE_SNES_CHECKSUM: SNES checksum computing for a LoROM image requires a ROM of at least 32KB.\n");

      return FAILED;

    }

  }

  else {

    if (romsize < 0x10000) {

      fprintf(stderr, "COMPUTE_SNES_CHECKSUM: SNES checksum computing for a HiROM image requires a ROM of at least 64KB.\n");

      return FAILED;

    }

  }

  /* n = data inside 4mbit blocks, m = data outside that */

  if (romsize < 512*1024) {

    n = romsize;

    m = 0;

  }

  else {

    n = (romsize/(512*1024))*512*1024;

    m = romsize - n;

  }

  /* sum all the bytes inside the 4mbit blocks */

  x = 0;

  for (i = 0; i < n; i++) {

    if (snes_rom_mode == SNES_ROM_MODE_LOROM) {

      /* skip the checksum bytes */

      if (!(i == 0x7FDC || i == 0x7FDD || i == 0x7FDE || i == 0x7FDF))

        x += rom[i];

    }

    else {

      /* skip the checksum bytes */

      if (!(i == 0xFFDC || i == 0xFFDD || i == 0xFFDE || i == 0xFFDF))

        x += rom[i];

    }

  }

  /* add to that the data outside the 4mbit blocks, ringbuffer style repeating

     the remaining block until the the final part reaches 4mbits */

  for (o = 0, l = i; i < romsize; i++, o++)

    x += rom[(o % m) + l];

  /* 2*255 is for the checksum and its complement bytes, which we skipped earlier */

  x += 2*255;

  /* compute the inverse checksum */

  l = (x & 0xFFFF) ^ 0xFFFF;

  /* insert the checksum bytes */

  if (snes_rom_mode == SNES_ROM_MODE_LOROM) {

    mem_insert(0x7FDC, l & 0xFF);

    mem_insert(0x7FDD, (l >> 8) & 0xFF);

    mem_insert(0x7FDE, x & 0xFF);

    mem_insert(0x7FDF, (x >> 8) & 0xFF);

  }

  else {

    mem_insert(0xFFDC, l & 0xFF);

    mem_insert(0xFFDD, (l >> 8) & 0xFF);

    mem_insert(0xFFDE, x & 0xFF);

    mem_insert(0xFFDF, (x >> 8) & 0xFF);

  }

  return SUCCEEDED;

}

int compute_sms_checksum(void) {

  unsigned int i, x;

  if (romsize < 0x8000) {

    fprintf(stderr, "COMPUTE_SMS_CHECKSUM: SMS/GG checksum computing requires a ROM of at least 32KBs.\n");

    return SUCCEEDED;

  }

  /* add together 32KB minus SMS/GG header */

  i = 0;

  for (x = 0; x < 0x7FF0; x++)

    i += rom[x];

  mem_insert(0x7FFA, i & 0xFF);

  mem_insert(0x7FFB, (i >> 8) & 0xFF);

  /* 32KB checksum and SMS export */

  mem_insert(0x7FFF, 0x4C);

  return SUCCEEDED;

}