text: // license:BSD-3-Clause
  // copyright-holders:S. Smith,David Haywood,Fabio Priuli
  
  
  #include "emu.h"
  #include "prot_pcm2.h"
  
  
  DEFINE_DEVICE_TYPE(NG_PCM2_PROT, pcm2_prot_device, "ng_pcm2_prot", "Neo Geo NEOPCM2 Protection")
  
  
  pcm2_prot_device::pcm2_prot_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
  	: device_t(mconfig, NG_PCM2_PROT, tag, owner, clock)
  {
  }
  
  
  void pcm2_prot_device::device_start()
  {
  }
  
  void pcm2_prot_device::device_reset()
  {
  }
  
  
  /***************************************************************************
  
  NeoGeo 'V' (PCM) ROM encryption
    NEOPCM2 chip
  
  ***************************************************************************/
  
  // Neo-Pcm2 Drivers for Encrypted V Roms
  void pcm2_prot_device::decrypt(uint8_t* ymrom, uint32_t ymsize, int value)
  {
  	// thanks to Elsemi for the NEO-PCM2 info
  	uint16_t *rom = (uint16_t *)ymrom;
  	int size = ymsize;
  
  	if (rom != nullptr)
  	{
  		// swap address lines on the whole ROMs
  		std::vector<uint16_t> buffer(value / 2);
  
  		for (int i = 0; i < size / 2; i += (value / 2))
  		{
  			memcpy(&buffer[0], &rom[i], value);
  			for (int j = 0; j < (value / 2); j++)
  			{
  				rom[i + j] = buffer[j ^ (value/4)];
  			}
  		}
  	}
  }
  
  
  // the later PCM2 games have additional scrambling
  void pcm2_prot_device::swap(uint8_t* ymrom, uint32_t ymsize, int value)
  {
  	static const uint32_t addrs[7][2]={
  		{0x000000,0xa5000},
  		{0xffce20,0x01000},
  		{0xfe2cf6,0x4e001},
  		{0xffac28,0xc2000},
  		{0xfeb2c0,0x0a000},
  		{0xff14ea,0xa7001},
  		{0xffb440,0x02000}};
  	static const uint8_t xordata[7][8]={
  		{0xf9,0xe0,0x5d,0xf3,0xea,0x92,0xbe,0xef},
  		{0xc4,0x83,0xa8,0x5f,0x21,0x27,0x64,0xaf},
  		{0xc3,0xfd,0x81,0xac,0x6d,0xe7,0xbf,0x9e},
  		{0xc3,0xfd,0x81,0xac,0x6d,0xe7,0xbf,0x9e},
  		{0xcb,0x29,0x7d,0x43,0xd2,0x3a,0xc2,0xb4},
  		{0x4b,0xa4,0x63,0x46,0xf0,0x91,0xea,0x62},
  		{0x4b,0xa4,0x63,0x46,0xf0,0x91,0xea,0x62}};
  
  	std::vector<uint8_t> buf(0x1000000);
  	int j, d;
  	uint8_t* src = ymrom;
  	memcpy(&buf[0], src, 0x1000000);
  
  	for (int i = 0; i < 0x1000000; i++)
  	{
  		j = bitswap<24>(i,23,22,21,20,19,18,17,0,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,16);
  		j ^= addrs[value][1];
  		d = ((i + addrs[value][0]) & 0xffffff);
  		src[j] = buf[d] ^ xordata[value][j & 0x7];
  	}
  }
  