/*
 * sio.c - Serial I/O emulation
 *
 * Copyright (C) 1995-1998 David Firth
 * Copyright (C) 1998-2010 Atari800 development team (see DOC/CREDITS)
 *
 * This file is part of the Atari800 emulator project which emulates
 * the Atari 400, 800, 800XL, 130XE, and 5200 8-bit computers.
 *
 * Atari800 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.
 *
 * Atari800 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 Atari800; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#define _POSIX_C_SOURCE 200112L /* for snprintf */

#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#include "afile.h"
#include "antic.h"  /* ANTIC_ypos */
#include "atari.h"
#include "binload.h"
#include "cassette.h"
#include "compfile.h"
#include "cpu.h"
#include "esc.h"
#include "log.h"
#include "memory.h"
#include "platform.h"
#include "pokey.h"
#include "pokeysnd.h"
#include "sio.h"
#include "util.h"
#ifndef BASIC
#include "statesav.h"
#endif

#undef DEBUG_PRO
#undef DEBUG_VAPI

/* If ATR image is in double density (256 bytes per sector),
   then the boot sectors (sectors 1-3) can be:
   - logical (as seen by Atari) - 128 bytes in each sector
   - physical (as stored on the disk) - 256 bytes in each sector.
     Only the first half of sector is used for storing data, the rest is zero.
   - SIO2PC (the type used by the SIO2PC program) - 3 * 128 bytes for data
     of boot sectors, then 3 * 128 unused bytes (zero)
   The XFD images in double density have either logical or physical
   boot sectors. */
#define BOOT_SECTORS_LOGICAL	0
#define BOOT_SECTORS_PHYSICAL	1
#define BOOT_SECTORS_SIO2PC		2
static int boot_sectors_type[SIO_MAX_DRIVES];

static int image_type[SIO_MAX_DRIVES];
#define IMAGE_TYPE_XFD  0
#define IMAGE_TYPE_ATR  1
#define IMAGE_TYPE_PRO  2
#define IMAGE_TYPE_VAPI 3
static FILE *disk[SIO_MAX_DRIVES] = { NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL };
static int sectorcount[SIO_MAX_DRIVES];
static int sectorsize[SIO_MAX_DRIVES];
/* these two are used by the 1450XLD parallel disk device */
int SIO_format_sectorcount[SIO_MAX_DRIVES];
int SIO_format_sectorsize[SIO_MAX_DRIVES];
static int io_success[SIO_MAX_DRIVES];
/* stores dup sector counter for PRO images */
typedef struct tagpro_additional_info_t {
	int max_sector;
	unsigned char *count;
} pro_additional_info_t;

#define MAX_VAPI_PHANTOM_SEC  		40
#define VAPI_BYTES_PER_TRACK        26042.0 
#define VAPI_CYCLES_PER_ROT 		372706
#define VAPI_CYCLES_PER_TRACK_STEP 	35780 /*70937*/
#define VAPI_CYCLES_HEAD_SETTLE 	70134
#define VAPI_CYCLES_TRACK_READ_DELTA 1426
#define VAPI_CYCLES_CMD_ACK_TRANS 	3188
#define VAPI_CYCLES_SECTOR_READ 	29014
#define VAPI_CYCLES_MISSING_SECTOR	(2*VAPI_CYCLES_PER_ROT + 14453)
#define VAPI_CYCLES_BAD_SECTOR_NUM	1521

/* stores dup sector information for VAPI images */
typedef struct tagvapi_sec_info_t {
	int sec_count;
	unsigned int sec_offset[MAX_VAPI_PHANTOM_SEC];
	unsigned char sec_status[MAX_VAPI_PHANTOM_SEC];
	unsigned int sec_rot_pos[MAX_VAPI_PHANTOM_SEC];
} vapi_sec_info_t;

typedef struct tagvapi_additional_info_t {
	vapi_sec_info_t *sectors;
	int sec_stat_buff[4];
	int vapi_delay_time;
} vapi_additional_info_t;

/* VAPI Format Header */
typedef struct tagvapi_file_header_t {
	unsigned char signature[4];
	unsigned char majorver;
	unsigned char minorver;
	unsigned char reserved1[22];
	unsigned char startdata[4];
	unsigned char reserved[16];
} vapi_file_header_t;

typedef struct tagvapi_track_header_t {
	unsigned char  next[4];
	unsigned char  type[2];
	unsigned char  reserved1[2];
	unsigned char  tracknum;
	unsigned char  reserved2;
	unsigned char  sectorcnt[2];
	unsigned char  reserved3[8];
	unsigned char  startdata[4];
	unsigned char  reserved4[8];
} vapi_track_header_t;

typedef struct tagvapi_sector_list_header_t {
	unsigned char  sizelist[4];
	unsigned char  type;
	unsigned char  reserved[3];
} vapi_sector_list_header_t;

typedef struct tagvapi_sector_header_t {
	unsigned char  sectornum;
	unsigned char  sectorstatus;
	unsigned char  sectorpos[2];
	unsigned char  startdata[4];
} vapi_sector_header_t;

#define VAPI_32(x) (x[0] + (x[1] << 8) + (x[2] << 16) + (x[3] << 24))
#define VAPI_16(x) (x[0] + (x[1] << 8))

/* Additional Info for all copy protected disk types */
static void *additional_info[SIO_MAX_DRIVES];

SIO_UnitStatus SIO_drive_status[SIO_MAX_DRIVES];
char SIO_filename[SIO_MAX_DRIVES][FILENAME_MAX];

Util_tmpbufdef(static, sio_tmpbuf[SIO_MAX_DRIVES])

int SIO_last_op;
int SIO_last_op_time = 0;
int SIO_last_drive;
int SIO_last_sector;
char SIO_status[256];

/* Serial I/O emulation support */
#define SIO_NoFrame         (0x00)
#define SIO_CommandFrame    (0x01)
#define SIO_StatusRead      (0x02)
#define SIO_ReadFrame       (0x03)
#define SIO_WriteFrame      (0x04)
#define SIO_FinalStatus     (0x05)
#define SIO_FormatFrame     (0x06)
static UBYTE CommandFrame[6];
static int CommandIndex = 0;
static UBYTE DataBuffer[256 + 3];
static int DataIndex = 0;
static int TransferStatus = SIO_NoFrame;
static int ExpectedBytes = 0;

int ignore_header_writeprotect = FALSE;

int SIO_Initialise(int *argc, char *argv[])
{
	int i;
	for (i = 0; i < SIO_MAX_DRIVES; i++) {
		strcpy(SIO_filename[i], "Off");
		SIO_drive_status[i] = SIO_OFF;
		SIO_format_sectorsize[i] = 128;
		SIO_format_sectorcount[i] = 720;
	}
	TransferStatus = SIO_NoFrame;

	return TRUE;
}

/* umount disks so temporary files are deleted */
void SIO_Exit(void)
{
	int i;
	for (i = 1; i <= SIO_MAX_DRIVES; i++)
		SIO_Dismount(i);
}

int SIO_Mount(int diskno, const char *filename, int b_open_readonly)
{
	FILE *f = NULL;
	SIO_UnitStatus status = SIO_READ_WRITE;
	struct AFILE_ATR_Header header;

	/* avoid overruns in SIO_filename[] */
	if (strlen(filename) >= FILENAME_MAX)
		return FALSE;

	/* release previous disk */
	SIO_Dismount(diskno);

	/* open file */
	if (!b_open_readonly)
		f = Util_fopen(filename, "rb+", sio_tmpbuf[diskno - 1]);
	if (f == NULL) {
		f = Util_fopen(filename, "rb", sio_tmpbuf[diskno - 1]);
		if (f == NULL)
			return FALSE;
		status = SIO_READ_ONLY;
	}

	/* read header */
	if (fread(&header, 1, sizeof(struct AFILE_ATR_Header), f) != sizeof(struct AFILE_ATR_Header)) {
		fclose(f);
		return FALSE;
	}

	/* detect compressed image and uncompress */
	switch (header.magic1) {
	case 0xf9:
	case 0xfa:
		/* DCM */
		{
			FILE *f2 = Util_tmpopen(sio_tmpbuf[diskno - 1]);
			if (f2 == NULL)
				return FALSE;
			Util_rewind(f);
			if (!CompFile_DCMtoATR(f, f2)) {
				Util_fclose(f2, sio_tmpbuf[diskno - 1]);
				fclose(f);
				return FALSE;
			}
			fclose(f);
			f = f2;
		}
		Util_rewind(f);
		if (fread(&header, 1, sizeof(struct AFILE_ATR_Header), f) != sizeof(struct AFILE_ATR_Header)) {
			Util_fclose(f, sio_tmpbuf[diskno - 1]);
			return FALSE;
		}
		status = SIO_READ_ONLY;
		/* XXX: status = b_open_readonly ? SIO_READ_ONLY : SIO_READ_WRITE; */
		break;
	case 0x1f:
		if (header.magic2 == 0x8b) {
			/* ATZ/ATR.GZ, XFZ/XFD.GZ */
			fclose(f);
			f = Util_tmpopen(sio_tmpbuf[diskno - 1]);
			if (f == NULL)
				return FALSE;
			if (!CompFile_ExtractGZ(filename, f)) {
				Util_fclose(f, sio_tmpbuf[diskno - 1]);
				return FALSE;
			}
			Util_rewind(f);
			if (fread(&header, 1, sizeof(struct AFILE_ATR_Header), f) != sizeof(struct AFILE_ATR_Header)) {
				Util_fclose(f, sio_tmpbuf[diskno - 1]);
				return FALSE;
			}
			status = SIO_READ_ONLY;
			/* XXX: status = b_open_readonly ? SIO_READ_ONLY : SIO_READ_WRITE; */
		}
		break;
	default:
		break;
	}

	boot_sectors_type[diskno - 1] = BOOT_SECTORS_LOGICAL;

	if (header.magic1 == AFILE_ATR_MAGIC1 && header.magic2 == AFILE_ATR_MAGIC2) {
		/* ATR (may be temporary from DCM or ATR/ATR.GZ) */
		image_type[diskno - 1] = IMAGE_TYPE_ATR;

		sectorsize[diskno - 1] = (header.secsizehi << 8) + header.secsizelo;
		if (sectorsize[diskno - 1] != 128 && sectorsize[diskno - 1] != 256) {
			Util_fclose(f, sio_tmpbuf[diskno - 1]);
			return FALSE;
		}

		if (header.writeprotect != 0 && !ignore_header_writeprotect)
			status = SIO_READ_ONLY;

		/* ATR header contains length in 16-byte chunks. */
		/* First compute number of 128-byte chunks
		   - it's number of sectors on single density disk */
		sectorcount[diskno - 1] = ((header.hiseccounthi << 24)
			+ (header.hiseccountlo << 16)
			+ (header.seccounthi << 8)
			+ header.seccountlo) >> 3;

		/* Fix number of sectors if double density */
		if (sectorsize[diskno - 1] == 256) {
			if ((sectorcount[diskno - 1] & 1) != 0)
				/* logical (128-byte) boot sectors */
				sectorcount[diskno - 1] += 3;
			else {
				/* 256-byte boot sectors */
				/* check if physical or SIO2PC: physical if there's
				   a non-zero byte in bytes 0x190-0x30f of the ATR file */
				UBYTE buffer[0x180];
				int i;
				fseek(f, 0x190, SEEK_SET);
				if (fread(buffer, 1, 0x180, f) != 0x180) {
					Util_fclose(f, sio_tmpbuf[diskno - 1]);
					return FALSE;
				}
				boot_sectors_type[diskno - 1] = BOOT_SECTORS_SIO2PC;
				for (i = 0; i < 0x180; i++)
					if (buffer[i] != 0) {
						boot_sectors_type[diskno - 1] = BOOT_SECTORS_PHYSICAL;
						break;
					}
			}
			sectorcount[diskno - 1] >>= 1;
		}
	}
	else if (header.magic1 == 'A' && header.magic2 == 'T' && header.seccountlo == '8' &&
		 header.seccounthi == 'X') {
		int file_length = Util_flen(f);
		vapi_additional_info_t *info;
		vapi_file_header_t fileheader;
		vapi_track_header_t trackheader;
		int trackoffset, totalsectors;

		/* .atx is read only for now */
#ifndef VAPI_WRITE_ENABLE
		if (!b_open_readonly) {
			fclose(f);
			f = Util_fopen(filename, "rb", sio_tmpbuf[diskno - 1]);
			if (f == NULL)
				return FALSE;
			status = SIO_READ_ONLY;
		}
#endif
		
		image_type[diskno - 1] = IMAGE_TYPE_VAPI;
		sectorsize[diskno - 1] = 128;
		sectorcount[diskno - 1] = 720;
		fseek(f,0,SEEK_SET);
		if (fread(&fileheader,1,sizeof(fileheader),f) != sizeof(fileheader)) {
			Util_fclose(f, sio_tmpbuf[diskno - 1]);
			Log_print("VAPI: Bad File Header");
			return(FALSE);
			}
		trackoffset = VAPI_32(fileheader.startdata);	
		if (trackoffset > file_length) {
			Util_fclose(f, sio_tmpbuf[diskno - 1]);
			Log_print("VAPI: Bad Track Offset");
			return(FALSE);
			}
#ifdef DEBUG_VAPI
		Log_print("VAPI File Version %d.%d",fileheader.majorver,fileheader.minorver);
#endif
		/* Read all of the track headers to get the total sector count */
		totalsectors = 0;
		while (trackoffset > 0 && trackoffset < file_length) {
			ULONG next;
			UWORD tracktype;

			fseek(f,trackoffset,SEEK_SET);
			if (fread(&trackheader,1,sizeof(trackheader),f) != sizeof(trackheader)) {
				Util_fclose(f, sio_tmpbuf[diskno - 1]);
				Log_print("VAPI: Bad Track Header");
				return(FALSE);
				}
			next = VAPI_32(trackheader.next);
			tracktype = VAPI_16(trackheader.type);
			if (tracktype == 0) {
				totalsectors += VAPI_16(trackheader.sectorcnt);
				}
			trackoffset += next;
		}

		info = (vapi_additional_info_t *)Util_malloc(sizeof(vapi_additional_info_t));
		additional_info[diskno-1] = info;
		info->sectors = (vapi_sec_info_t *)Util_malloc(sectorcount[diskno - 1] * 
 					    sizeof(vapi_sec_info_t));
		memset(info->sectors, 0, sectorcount[diskno - 1] * 
 					 sizeof(vapi_sec_info_t));

		/* Now read all the sector data */
		trackoffset = VAPI_32(fileheader.startdata);
		while (trackoffset > 0 && trackoffset < file_length) {
			int sectorcnt, seclistdata,next;
			vapi_sector_list_header_t sectorlist;
			vapi_sector_header_t sectorheader;
			vapi_sec_info_t *sector;
			UWORD tracktype;
			int j;

			fseek(f,trackoffset,SEEK_SET);
			if (fread(&trackheader,1,sizeof(trackheader),f) != sizeof(trackheader)) {
				free(info->sectors);
				free(info);
				Util_fclose(f, sio_tmpbuf[diskno - 1]);
				Log_print("VAPI: Bad Track Header while reading sectors");
				return(FALSE);
				}
			next = VAPI_32(trackheader.next);
			sectorcnt = VAPI_16(trackheader.sectorcnt);
			tracktype = VAPI_16(trackheader.type);
			seclistdata = VAPI_32(trackheader.startdata) + trackoffset;
#ifdef DEBUG_VAPI
			Log_print("Track %d: next %x type %d seccnt %d secdata %x",trackheader.tracknum,
				trackoffset + next,VAPI_16(trackheader.type),sectorcnt,seclistdata);
#endif
			if (tracktype == 0) {
				if (seclistdata > file_length) {
					free(info->sectors);
					free(info);
					Util_fclose(f, sio_tmpbuf[diskno - 1]);
					Log_print("VAPI: Bad Sector List Offset");
					return(FALSE);
					}
				fseek(f,seclistdata,SEEK_SET);
				if (fread(&sectorlist,1,sizeof(sectorlist),f) != sizeof(sectorlist)) {
					free(info->sectors);
					free(info);
					Util_fclose(f, sio_tmpbuf[diskno - 1]);
					Log_print("VAPI: Bad Sector List");
					return(FALSE);
					}
#ifdef DEBUG_VAPI
				Log_print("Size sec list %x type %d",VAPI_32(sectorlist.sizelist),sectorlist.type);
#endif
				for (j=0;j<sectorcnt;j++) {
					double percent_rot;

					if (fread(&sectorheader,1,sizeof(sectorheader),f) != sizeof(sectorheader)) {
						free(info->sectors);
						free(info);
						Util_fclose(f, sio_tmpbuf[diskno - 1]);
						Log_print("VAPI: Bad Sector Header");
						return(FALSE);
						}
					if (sectorheader.sectornum > 18)  {
						Util_fclose(f, sio_tmpbuf[diskno - 1]);
						Log_print("VAPI: Bad Sector Index: Track %d Sec Num %d Index %d",
								trackheader.tracknum,j,sectorheader.sectornum);
						return(FALSE);
						}
					sector = &info->sectors[trackheader.tracknum * 18 + sectorheader.sectornum - 1];

					percent_rot = ((double) VAPI_16(sectorheader.sectorpos))/VAPI_BYTES_PER_TRACK;
					sector->sec_rot_pos[sector->sec_count] = (unsigned int) (percent_rot * VAPI_CYCLES_PER_ROT);
					sector->sec_offset[sector->sec_count] = VAPI_32(sectorheader.startdata) + trackoffset;
					sector->sec_status[sector->sec_count] = ~sectorheader.sectorstatus;
					sector->sec_count++;
					if (sector->sec_count > MAX_VAPI_PHANTOM_SEC) {
						free(info->sectors);
						free(info);
						Util_fclose(f, sio_tmpbuf[diskno - 1]);
						Log_print("VAPI: Too many Phantom Sectors");
						return(FALSE);
						}
#ifdef DEBUG_VAPI
					Log_print("Sector %d status %x position %f %d %d data %x",sectorheader.sectornum,
						sector->sec_status[sector->sec_count-1],percent_rot,
						sector->sec_rot_pos[sector->sec_count-1],
						VAPI_16(sectorheader.sectorpos),
						sector->sec_offset[sector->sec_count-1]);				
#endif				
				}
#ifdef DEBUG_VAPI
				Log_flushlog();
#endif
			} else {
				Log_print("Unknown VAPI track type Track:%d Type:%d",trackheader.tracknum,tracktype);
			}
			trackoffset += next;
		}			
	}
	else {
		int file_length = Util_flen(f);
		/* check for PRO */
		if ((file_length-16)%(128+12) == 0 &&
				(header.magic1*256 + header.magic2 == (file_length-16)/(128+12)) &&
				header.seccountlo == 'P') {
			pro_additional_info_t *info;
			/* .pro is read only for now */
			if (!b_open_readonly) {
				fclose(f);
				f = Util_fopen(filename, "rb", sio_tmpbuf[diskno - 1]);
				if (f == NULL)
					return FALSE;
				status = SIO_READ_ONLY;
			}
			image_type[diskno - 1] = IMAGE_TYPE_PRO;
			sectorsize[diskno - 1] = 128;
			if (file_length >= 1040*(128+12)+16) {
				/* assume enhanced density */
				sectorcount[diskno - 1] = 1040;
			}
			else {
				/* assume single density */
				sectorcount[diskno - 1] = 720;
			}

			info = (pro_additional_info_t *)Util_malloc(sizeof(pro_additional_info_t));
			additional_info[diskno-1] = info;
			info->count = (unsigned char *)Util_malloc(sectorcount[diskno - 1]);
			memset(info->count, 0, sectorcount[diskno -1]);
			info->max_sector = (file_length-16)/(128+12);
		}
		else {
			/* XFD (may be temporary from XFZ/XFD.GZ) */

			image_type[diskno - 1] = IMAGE_TYPE_XFD;

			if (file_length <= (1040 * 128)) {
				/* single density */
				sectorsize[diskno - 1] = 128;
				sectorcount[diskno - 1] = file_length >> 7;
			}
			else {
				/* double density */
				sectorsize[diskno - 1] = 256;
				if ((file_length & 0xff) == 0) {
					boot_sectors_type[diskno - 1] = BOOT_SECTORS_PHYSICAL;
					sectorcount[diskno - 1] = file_length >> 8;
				}
				else
					sectorcount[diskno - 1] = (file_length + 0x180) >> 8;
			}
		}
	}

#ifdef DEBUG
	Log_print("sectorcount = %d, sectorsize = %d",
		   sectorcount[diskno - 1], sectorsize[diskno - 1]);
#endif
	SIO_format_sectorsize[diskno - 1] = sectorsize[diskno - 1];
	SIO_format_sectorcount[diskno - 1] = sectorcount[diskno - 1];
	strcpy(SIO_filename[diskno - 1], filename);
	SIO_drive_status[diskno - 1] = status;
	disk[diskno - 1] = f;
	return TRUE;
}

void SIO_Dismount(int diskno)
{
	if (disk[diskno - 1] != NULL) {
		Util_fclose(disk[diskno - 1], sio_tmpbuf[diskno - 1]);
		disk[diskno - 1] = NULL;
		SIO_drive_status[diskno - 1] = SIO_NO_DISK;
		strcpy(SIO_filename[diskno - 1], "Empty");
		if (image_type[diskno - 1] == IMAGE_TYPE_PRO) {
			free(((pro_additional_info_t *)additional_info[diskno-1])->count);
		}
		else if (image_type[diskno - 1] == IMAGE_TYPE_VAPI) {
			free(((vapi_additional_info_t *)additional_info[diskno-1])->sectors);
		}
		free(additional_info[diskno - 1]);
		additional_info[diskno - 1] = 0;
	}
}

void SIO_DisableDrive(int diskno)
{
	SIO_Dismount(diskno);
	SIO_drive_status[diskno - 1] = SIO_OFF;
	strcpy(SIO_filename[diskno - 1], "Off");
}

void SIO_SizeOfSector(UBYTE unit, int sector, int *sz, ULONG *ofs)
{
	int size;
	ULONG offset;
	int header_size = (image_type[unit] == IMAGE_TYPE_ATR ? 16 : 0);

	if (BINLOAD_start_binloading) {
		if (sz)
			*sz = 128;
		if (ofs)
			*ofs = 0;
		return;
	}

	if (image_type[unit] == IMAGE_TYPE_PRO) {
		size = 128;
		offset = 16 + (128+12)*(sector -1); /* returns offset of header */
	}
	else if (image_type[unit] == IMAGE_TYPE_VAPI) {
		vapi_additional_info_t *info;
		vapi_sec_info_t *secinfo;

		size = 128;
		info = (vapi_additional_info_t *)additional_info[unit];
		if (info == NULL)
			offset = 0;
		else if (sector > sectorcount[unit])
			offset = 0;
		else {
			secinfo = &info->sectors[sector-1];
			if (secinfo->sec_count == 0  )
				offset = 0;
			else
				offset = secinfo->sec_offset[0];
		}
	}
	else if (sector < 4) {
		/* special case for first three sectors in ATR and XFD image */
		size = 128;
		offset = header_size + (sector - 1) * (boot_sectors_type[unit] == BOOT_SECTORS_PHYSICAL ? 256 : 128);
	}
	else {
		size = sectorsize[unit];
		offset = header_size + (boot_sectors_type[unit] == BOOT_SECTORS_LOGICAL ? 0x180 : 0x300) + (sector - 4) * size;
	}

	if (sz)
		*sz = size;

	if (ofs)
		*ofs = offset;
}

static int SeekSector(int unit, int sector)
{
	ULONG offset;
	int size;

	SIO_last_sector = sector;
	snprintf(SIO_status, sizeof(SIO_status), "%d: %d", unit + 1, sector);
	SIO_SizeOfSector((UBYTE) unit, sector, &size, &offset);
	fseek(disk[unit], offset, SEEK_SET);

	return size;
}

/* Unit counts from zero up */
int SIO_ReadSector(int unit, int sector, UBYTE *buffer)
{
	int size;
	if (BINLOAD_start_binloading)
		return BINLOAD_LoaderStart(buffer);

	io_success[unit] = -1;
	if (SIO_drive_status[unit] == SIO_OFF)
		return 0;
	if (disk[unit] == NULL)
		return 'N';
	if (sector <= 0 || sector > sectorcount[unit])
		return 'E';
	SIO_last_op = SIO_LAST_READ;
	SIO_last_op_time = 1;
	SIO_last_drive = unit + 1;
	/* FIXME: what sector size did the user expect? */
	size = SeekSector(unit, sector);
	if (image_type[unit] == IMAGE_TYPE_PRO) {
		pro_additional_info_t *info;
		unsigned char *count;
		info = (pro_additional_info_t *)additional_info[unit];
		count = info->count;
		if (fread(buffer, 1, 12, disk[unit]) < 12) {
			Log_print("Error in header of .pro image: sector:%d", sector);
			return 'E';
		}
		/* handle duplicate sectors */
		if (buffer[5] != 0) {
			int dupnum = count[sector];
#ifdef DEBUG_PRO
			Log_print("duplicate sector:%d dupnum:%d",sector, dupnum);
#endif
			count[sector] = (count[sector]+1) % (buffer[5]+1);
			if (dupnum != 0)  {
				sector = sectorcount[unit] + buffer[6+dupnum];
				/* can dupnum be 5? */
				if (dupnum > 4 || sector <= 0 || sector > info->max_sector) {
					Log_print("Error in .pro image: sector:%d dupnum:%d", sector, dupnum);
					return 'E';
				}
				size = SeekSector(unit, sector);
				/* read sector header */
				if (fread(buffer, 1, 12, disk[unit]) < 12) {
					Log_print("Error in header2 of .pro image: sector:%d dupnum:%d", sector, dupnum);
					return 'E';
				}
			}
		}
		/* bad sector */
		if (buffer[1] != 0xff) {
			if (fread(buffer, 1, size, disk[unit]) < size) {
				Log_print("Error in bad sector of .pro image: sector:%d", sector);
			}
			io_success[unit] = sector;
#ifdef DEBUG_PRO
			Log_print("bad sector:%d", sector);
#endif
			return 'E';
		}
	}
	else if (image_type[unit] == IMAGE_TYPE_VAPI) {
		vapi_additional_info_t *info;
		vapi_sec_info_t *secinfo;
		ULONG secindex = 0;
		static int lasttrack = 0;
		unsigned int currpos, time, delay, rotations, bestdelay;
/*		unsigned char beststatus;*/
		int fromtrack, trackstostep, j;

		info = (vapi_additional_info_t *)additional_info[unit];
		info->vapi_delay_time = 0;

		if (sector > sectorcount[unit]) {
#ifdef DEBUG_VAPI
			Log_print("bad sector num:%d", sector);
#endif
			info->sec_stat_buff[0] = 9;
			info->sec_stat_buff[1] = 0xFF; 
			info->sec_stat_buff[2] = 0xe0;
			info->sec_stat_buff[3] = 0;
			info->vapi_delay_time= VAPI_CYCLES_BAD_SECTOR_NUM;
			return 'E';
		}

		secinfo = &info->sectors[sector-1];
		fromtrack = lasttrack;
		lasttrack = (sector-1)/18;

		if (secinfo->sec_count == 0) {
#ifdef DEBUG_VAPI
			Log_print("missing sector:%d", sector);
#endif
			info->sec_stat_buff[0] = 0xC;
			info->sec_stat_buff[1] = 0xEF; 
			info->sec_stat_buff[2] = 0xe0;
			info->sec_stat_buff[3] = 0;
			info->vapi_delay_time= VAPI_CYCLES_MISSING_SECTOR;
			return 'E';
		}

		trackstostep = abs((sector-1)/18 - fromtrack);
		time = (unsigned int) ANTIC_CPU_CLOCK;
		if (trackstostep)
			time += trackstostep * VAPI_CYCLES_PER_TRACK_STEP + VAPI_CYCLES_HEAD_SETTLE ;
		time += VAPI_CYCLES_CMD_ACK_TRANS;
		rotations = time/VAPI_CYCLES_PER_ROT;
		currpos = time - rotations*VAPI_CYCLES_PER_ROT;

#ifdef DEBUG_VAPI
		Log_print(" sector:%d sector count :%d time %d", sector,secinfo->sec_count,ANTIC_CPU_CLOCK);
#endif

		bestdelay = 10 * VAPI_CYCLES_PER_ROT;
/*		beststatus = 0;*/
		for (j=0;j<secinfo->sec_count;j++) {
			if (secinfo->sec_rot_pos[j]  < currpos)
				delay = (VAPI_CYCLES_PER_ROT - currpos) + secinfo->sec_rot_pos[j];
			else
				delay = secinfo->sec_rot_pos[j] - currpos; 
#ifdef DEBUG_VAPI
			Log_print("%d %d %d %d %d %x",j,secinfo->sec_rot_pos[j],
					  ((unsigned int) ANTIC_CPU_CLOCK) - ((((unsigned int) ANTIC_CPU_CLOCK)/VAPI_CYCLES_PER_ROT)*VAPI_CYCLES_PER_ROT),
					  currpos,delay,secinfo->sec_status[j]);
#endif
			if (delay < bestdelay) {
				bestdelay = delay;
/*				beststatus = secinfo->sec_status[j];*/
				secindex = j;
			}
		}
		if (trackstostep)
			info->vapi_delay_time = bestdelay + trackstostep * VAPI_CYCLES_PER_TRACK_STEP + 
				     VAPI_CYCLES_HEAD_SETTLE   +  VAPI_CYCLES_TRACK_READ_DELTA +
						       VAPI_CYCLES_CMD_ACK_TRANS + VAPI_CYCLES_SECTOR_READ;
		else
			info->vapi_delay_time = bestdelay + 
						       VAPI_CYCLES_CMD_ACK_TRANS + VAPI_CYCLES_SECTOR_READ;
#ifdef DEBUG_VAPI
		Log_print("Bestdelay = %d VapiDelay = %d",bestdelay,info->vapi_delay_time);
		if (secinfo->sec_count > 1)
			Log_print("duplicate sector:%d dupnum:%d delay:%d",sector, secindex,info->vapi_delay_time);
#endif
		fseek(disk[unit],secinfo->sec_offset[secindex],SEEK_SET);
		info->sec_stat_buff[0] = 0x8 | ((secinfo->sec_status[secindex] == 0xFF) ? 0 : 0x04);
		info->sec_stat_buff[1] = secinfo->sec_status[secindex];
		info->sec_stat_buff[2] = 0xe0;
		info->sec_stat_buff[3] = 0;
		if (secinfo->sec_status[secindex] != 0xFF) {
			if (fread(buffer, 1, size, disk[unit]) < size) {
				Log_print("error reading sector:%d", sector);
			}
			io_success[unit] = sector;
			info->vapi_delay_time += VAPI_CYCLES_PER_ROT + 10000;
#ifdef DEBUG_VAPI
			Log_print("bad sector:%d 0x%0X delay:%d", sector, secinfo->sec_status[secindex],info->vapi_delay_time );
#endif
			{
			int i;
				if (secinfo->sec_status[secindex] == 0xB7) {
					for (i=0;i<128;i++) {
						Log_print("0x%02x",buffer[i]);
						if (buffer[i] == 0x33)
							buffer[i] = rand() & 0xFF;
					}
				}
			}
			return 'E';
		}
#ifdef DEBUG_VAPI
		Log_flushlog();
#endif		
	}
	if (fread(buffer, 1, size, disk[unit]) < size) {
		Log_print("incomplete sector num:%d", sector);
	}
	io_success[unit] = 0;
	return 'C';
}

int SIO_WriteSector(int unit, int sector, const UBYTE *buffer)
{
	int size;
	io_success[unit] = -1;
	if (SIO_drive_status[unit] == SIO_OFF)
		return 0;
	if (disk[unit] == NULL)
		return 'N';
	if (SIO_drive_status[unit] != SIO_READ_WRITE || sector <= 0 || sector > sectorcount[unit])
		return 'E';
	SIO_last_op = SIO_LAST_WRITE;
	SIO_last_op_time = 1;
	SIO_last_drive = unit + 1;
#ifdef VAPI_WRITE_ENABLE 	
 	if (image_type[unit] == IMAGE_TYPE_VAPI) {
		vapi_additional_info_t *info;
		vapi_sec_info_t *secinfo;

		info = (vapi_additional_info_t *)additional_info[unit];
		secinfo = &info->sectors[sector-1];
		
		if (secinfo->sec_count != 1) {
			/* No writes to sectors with duplicates or missing sectors */
			return 'E';
		}
		
		if (secinfo->sec_status[0] != 0xFF) {
			/* No writes to bad sectors */
			return 'E';
		}
		
		size = SeekSector(unit, sector);
		fseek(disk[unit],secinfo->sec_offset[0],SEEK_SET);
		fwrite(buffer, 1, size, disk[unit]);
		io_success[unit] = 0;
		return 'C';
#if 0		
	} else if (image_type[unit] == IMAGE_TYPE_PRO) {
		pro_additional_info_t *info;
		pro_phantom_sec_info_t *phantom;
		
		info = (pro_additional_info_t *)additional_info[unit];
		phantom = &info->phantom[sector-1];
		
		if (phantom->phantom_count != 0) {
			/* No writes to sectors with duplicates */
			return 'E';
		}
		
		size = SeekSector(unit, sector);
		if (buffer[1] != 0xff) {
#endif			
	} 
#endif
	size = SeekSector(unit, sector);
	fwrite(buffer, 1, size, disk[unit]);
	io_success[unit] = 0;
	return 'C';
}

int SIO_FormatDisk(int unit, UBYTE *buffer, int sectsize, int sectcount)
{
	char fname[FILENAME_MAX];
	int is_atr;
	int save_boot_sectors_type;
	int bootsectsize;
	int bootsectcount;
	FILE *f;
	int i;
	io_success[unit] = -1;
	if (SIO_drive_status[unit] == SIO_OFF)
		return 0;
	if (disk[unit] == NULL)
		return 'N';
	if (SIO_drive_status[unit] != SIO_READ_WRITE)
		return 'E';
	/* Note formatting the disk can change size of the file.
	   There is no portable way to truncate the file at given position.
	   We have to close the "rb+" open file and open it in "wb" mode.
	   First get the information about the disk image, because we are going
	   to umount it. */
	memcpy(fname, SIO_filename[unit], FILENAME_MAX);
	is_atr = (image_type[unit] == IMAGE_TYPE_ATR);
	save_boot_sectors_type = boot_sectors_type[unit];
	bootsectsize = 128;
	if (sectsize == 256 && save_boot_sectors_type != BOOT_SECTORS_LOGICAL)
		bootsectsize = 256;
	bootsectcount = sectcount < 3 ? sectcount : 3;
	/* Umount the file and open it in "wb" mode (it will truncate the file) */
	SIO_Dismount(unit + 1);
	f = fopen(fname, "wb");
	if (f == NULL) {
		Log_print("SIO_FormatDisk: failed to open %s for writing", fname);
		return 'E';
	}
	/* Write ATR header if necessary */
	if (is_atr) {
		struct AFILE_ATR_Header header;
		ULONG disksize = (bootsectsize * bootsectcount + sectsize * (sectcount - bootsectcount)) >> 4;
		memset(&header, 0, sizeof(header));
		header.magic1 = AFILE_ATR_MAGIC1;
		header.magic2 = AFILE_ATR_MAGIC2;
		header.secsizelo = (UBYTE) sectsize;
		header.secsizehi = (UBYTE) (sectsize >> 8);
		header.seccountlo = (UBYTE) disksize;
		header.seccounthi = (UBYTE) (disksize >> 8);
		header.hiseccountlo = (UBYTE) (disksize >> 16);
		header.hiseccounthi = (UBYTE) (disksize >> 24);
		fwrite(&header, 1, sizeof(header), f);
	}
	/* Write boot sectors */
	memset(buffer, 0, sectsize);
	for (i = 1; i <= bootsectcount; i++)
		fwrite(buffer, 1, bootsectsize, f);
	/* Write regular sectors */
	for ( ; i <= sectcount; i++)
		fwrite(buffer, 1, sectsize, f);
	/* Close file and mount the disk back */
	fclose(f);
	SIO_Mount(unit + 1, fname, FALSE);
	/* We want to keep the current PHYSICAL/SIO2PC boot sectors type
	   (since the image is blank it can't be figured out by SIO_Mount) */
	if (bootsectsize == 256)
		boot_sectors_type[unit] = save_boot_sectors_type;
	/* Return information for Atari (buffer filled with ff's - no bad sectors) */
	memset(buffer, 0xff, sectsize);
	io_success[unit] = 0;
	return 'C';
}

/* Set density and number of sectors
   This function is used before the format (0x21) command
   to set how the disk will be formatted.
   Note this function does *not* affect the currently attached disk
   (previously sectorsize/sectorcount were used which could result in
   a corrupted image).
*/
int SIO_WriteStatusBlock(int unit, const UBYTE *buffer)
{
	int size;
#ifdef DEBUG
	Log_print("Write Status-Block: %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x",
		buffer[0], buffer[1], buffer[2], buffer[3],
		buffer[4], buffer[5], buffer[6], buffer[7],
		buffer[8], buffer[9], buffer[10], buffer[11]);
#endif
	if (SIO_drive_status[unit] == SIO_OFF)
		return 0;
	/* We only care about the density and the sector count here.
	   Setting everything else right here seems to be non-sense.
	   I'm not sure about this density settings, my XF551
	   honors only the sector size and ignores the density */
	size = buffer[6] * 256 + buffer[7];
	if (size == 128 || size == 256)
		SIO_format_sectorsize[unit] = size;
	/* Note that the number of heads are minus 1 */
	SIO_format_sectorcount[unit] = buffer[0] * (buffer[2] * 256 + buffer[3]) * (buffer[4] + 1);
	if (SIO_format_sectorcount[unit] < 1 || SIO_format_sectorcount[unit] > 65535)
		SIO_format_sectorcount[unit] = 720;
	return 'C';
}

int SIO_ReadStatusBlock(int unit, UBYTE *buffer)
{
	UBYTE tracks;
	UBYTE heads;
	int spt;
	if (SIO_drive_status[unit] == SIO_OFF)
		return 0;
	/* default to 1 track, 1 side for non-standard images */
	tracks = 1;
	heads = 1;
	spt = sectorcount[unit];

	if (spt % 40 == 0) {
		/* standard disk */
		tracks = 40;
		spt /= 40;
		if (spt > 26 && spt % 2 == 0) {
			/* double-sided */
			heads = 2;
			spt >>= 1;
			if (spt > 26 && spt % 2 == 0) {
				/* double-sided, 80 tracks */
				tracks = 80;
				spt >>= 1;
			}
		}
	}

	buffer[0] = tracks;              /* # of tracks */
	buffer[1] = 1;                   /* step rate */
	buffer[2] = (UBYTE) (spt >> 8);  /* sectors per track. HI byte */
	buffer[3] = (UBYTE) spt;         /* sectors per track. LO byte */
	buffer[4] = (UBYTE) (heads - 1); /* # of heads minus 1 */
	/* FM for single density, MFM otherwise */
	buffer[5] = (sectorsize[unit] == 128 && sectorcount[unit] <= 720) ? 0 : 4;
	buffer[6] = (UBYTE) (sectorsize[unit] >> 8); /* bytes per sector. HI byte */
	buffer[7] = (UBYTE) sectorsize[unit];        /* bytes per sector. LO byte */
	buffer[8] = 1;                   /* drive is online */
	buffer[9] = 192;                 /* transfer speed, whatever this means */
	buffer[10] = 0;
	buffer[11] = 0;
	return 'C';
}

/*
   Status Request from Atari 400/800 Technical Reference Notes

   DVSTAT + 0   Command Status
   DVSTAT + 1   Hardware Status
   DVSTAT + 2   Timeout
   DVSTAT + 3   Unused

   Command Status Bits

   Bit 0 = 1 indicates an invalid command frame was received
   Bit 1 = 1 indicates an invalid data frame was received
   Bit 2 = 1 indicates that last read/write operation was unsuccessful
   Bit 3 = 1 indicates that the diskette is write protected
   Bit 4 = 1 indicates active/standby

   plus

   Bit 5 = 1 indicates double density
   Bit 7 = 1 indicates dual density disk (1050 format)
 */
int SIO_DriveStatus(int unit, UBYTE *buffer)
{
	if (BINLOAD_start_binloading) {
		buffer[0] = 16 + 8;
		buffer[1] = 255;
		buffer[2] = 1;
		buffer[3] = 0 ;
		return 'C';
	}

	if (SIO_drive_status[unit] == SIO_OFF)
		return 0;

	/* .PRO contains status information in the sector header */
	if (io_success[unit] != 0  && image_type[unit] == IMAGE_TYPE_PRO) {
		int sector = io_success[unit];
		SeekSector(unit, sector);
		if (fread(buffer, 1, 4, disk[unit]) < 4) {
			Log_print("SIO_DriveStatus: failed to read sector header");
		}
		return 'C';
	}
	else if (io_success[unit] != 0  && image_type[unit] == IMAGE_TYPE_VAPI &&
			 SIO_drive_status[unit] != SIO_NO_DISK) {
		vapi_additional_info_t *info;
		info = (vapi_additional_info_t *)additional_info[unit];
		buffer[0] = info->sec_stat_buff[0];
		buffer[1] = info->sec_stat_buff[1];
		buffer[2] = info->sec_stat_buff[2];
		buffer[3] = info->sec_stat_buff[3];
		Log_print("Drive Status unit %d %x %x %x %x",unit,buffer[0], buffer[1], buffer[2], buffer[3]);
		return 'C';
	}	
	buffer[0] = 16;         /* drive active */
	buffer[1] = disk[unit] != NULL ? 255 /* WD 177x OK */ : 127 /* no disk */;
	if (io_success[unit] != 0)
		buffer[0] |= 4;     /* failed RW-operation */
	if (SIO_drive_status[unit] == SIO_READ_ONLY)
		buffer[0] |= 8;     /* write protection */
	if (SIO_format_sectorsize[unit] == 256)
		buffer[0] |= 32;    /* double density */
	if (SIO_format_sectorcount[unit] == 1040)
		buffer[0] |= 128;   /* 1050 enhanced density */
	buffer[2] = 1;
	buffer[3] = 0;
	return 'C';
}

#ifndef NO_SECTOR_DELAY
/* A hack for the "Overmind" demo.  This demo verifies if sectors aren't read
   faster than with a typical disk drive.  We introduce a delay
   of SECTOR_DELAY scanlines between successive reads of sector 1. */
#define SECTOR_DELAY 3200
static int delay_counter = 0;
static int last_ypos = 0;
#endif

/* SIO patch emulation routine */
void SIO_Handler(void)
{
	int sector = MEMORY_dGetWordAligned(0x30a);
	UBYTE unit = MEMORY_dGetByte(0x300) + MEMORY_dGetByte(0x301) + 0xff;
	UBYTE result = 0x00;
	UWORD data = MEMORY_dGetWordAligned(0x304);
	int length = MEMORY_dGetWordAligned(0x308);
	int realsize = 0;
	int cmd = MEMORY_dGetByte(0x302);

	if ((unsigned int)MEMORY_dGetByte(0x300) + (unsigned int)MEMORY_dGetByte(0x301) > 0xff) {
		/* carry */
		unit++;
	}
	/* A real atari just adds the bytes and 0xff. The result could wrap.*/
	/* XL OS: E99D: LDA $0300 ADC $0301 ADC #$FF STA 023A */

	/* The OS SIO routine copies decide ID do CDEVIC, command ID to CCOMND etc.
	   This operation is not needed with the SIO patch enabled, but we perform
	   it anyway, since some programs rely on that. (E.g. the E.T Phone Home!
	   cartridge would crash with SIO patch enabled.)
	   Note: While on a real XL OS the copying is done only for SIO devices
	   (not for PBI ones), here we copy the values for all types of devices -
	   it's probably harmless. */
	MEMORY_dPutByte(0x023a, unit); /* sta CDEVIC */
	MEMORY_dPutByte(0x023b, cmd); /* sta CCOMND */
	MEMORY_dPutWordAligned(0x023c, sector); /* sta CAUX1; sta CAUX2 */

	/* Disk 1 is ASCII '1' = 0x31 etc */
	/* Disk 1 -> unit = 0 */
	unit -= 0x31;

	if (MEMORY_dGetByte(0x300) != 0x60 && unit < SIO_MAX_DRIVES && (SIO_drive_status[unit] != SIO_OFF || BINLOAD_start_binloading)) {	/* UBYTE range ! */
#ifdef DEBUG
		Log_print("SIO disk command is %02x %02x %02x %02x %02x   %02x %02x %02x %02x %02x %02x",
			cmd, MEMORY_dGetByte(0x303), MEMORY_dGetByte(0x304), MEMORY_dGetByte(0x305), MEMORY_dGetByte(0x306),
			MEMORY_dGetByte(0x308), MEMORY_dGetByte(0x309), MEMORY_dGetByte(0x30a), MEMORY_dGetByte(0x30b),
			MEMORY_dGetByte(0x30c), MEMORY_dGetByte(0x30d));
#endif
		switch (cmd) {
		case 0x4e:				/* Read Status Block */
			if (12 == length) {
				result = SIO_ReadStatusBlock(unit, DataBuffer);
				if (result == 'C')
					MEMORY_CopyToMem(DataBuffer, data, 12);
			}
			else
				result = 'E';
			break;
		case 0x4f:				/* Write Status Block */
			if (12 == length) {
				MEMORY_CopyFromMem(data, DataBuffer, 12);
				result = SIO_WriteStatusBlock(unit, DataBuffer);
			}
			else
				result = 'E';
			break;
		case 0x50:				/* Write */
		case 0x57:
		case 0xD0:				/* xf551 hispeed */
		case 0xD7:
			SIO_SizeOfSector(unit, sector, &realsize, NULL);
			if (realsize == length) {
				MEMORY_CopyFromMem(data, DataBuffer, realsize);
				result = SIO_WriteSector(unit, sector, DataBuffer);
			}
			else
				result = 'E';
			break;
		case 0x52:				/* Read */
		case 0xD2:				/* xf551 hispeed */
#ifndef NO_SECTOR_DELAY
			if (sector == 1) {
				if (delay_counter > 0) {
					if (last_ypos != ANTIC_ypos) {
						last_ypos = ANTIC_ypos;
						delay_counter--;
					}
					CPU_regPC = 0xe459;	/* stay at SIO patch */
					return;
				}
				delay_counter = SECTOR_DELAY;
			}
			else {
				delay_counter = 0;
			}
#endif
			SIO_SizeOfSector(unit, sector, &realsize, NULL);
			if (realsize == length) {
				result = SIO_ReadSector(unit, sector, DataBuffer);
				if (result == 'C')
					MEMORY_CopyToMem(DataBuffer, data, realsize);
			}
			else
				result = 'E';
			break;
		case 0x53:				/* Status */
			if (4 == length) {
				result = SIO_DriveStatus(unit, DataBuffer);
				if (result == 'C') {
					MEMORY_CopyToMem(DataBuffer, data, 4);
				}
			}
			else
				result = 'E';
			break;
		/*case 0x66:*/			/* US Doubler Format - I think! */
		case 0x21:				/* Format Disk */
		case 0xA1:				/* xf551 hispeed */
			realsize = SIO_format_sectorsize[unit];
			if (realsize == length) {
				result = SIO_FormatDisk(unit, DataBuffer, realsize, SIO_format_sectorcount[unit]);
				if (result == 'C')
					MEMORY_CopyToMem(DataBuffer, data, realsize);
			}
			else {
				/* there are programs which send the format-command but don't wait for the result (eg xf-tools) */
				SIO_FormatDisk(unit, DataBuffer, realsize, SIO_format_sectorcount[unit]);
				result = 'E';
			}
			break;
		case 0x22:				/* Enhanced Density Format */
		case 0xA2:				/* xf551 hispeed */
			realsize = 128;
			if (realsize == length) {
				result = SIO_FormatDisk(unit, DataBuffer, 128, 1040);
				if (result == 'C')
					MEMORY_CopyToMem(DataBuffer, data, realsize);
			}
			else {
				SIO_FormatDisk(unit, DataBuffer, 128, 1040);
				result = 'E';
			}
			break;
		default:
			result = 'N';
		}
	}
	/* cassette i/o */
	else if (MEMORY_dGetByte(0x300) == 0x60) {
		UBYTE gaps = MEMORY_dGetByte(0x30b);
		switch (cmd){
		case 0x52:	/* read */
			/* set expected Gap */
			CASSETTE_AddGap(gaps == 0 ? 2000 : 160);
			/* get record from storage medium */
			if (CASSETTE_ReadToMemory(data, length))
				result = 'C';
			else
				result = 'E';
			break;
		case 0x57:	/* write */
			/* add pregap length */
			CASSETTE_AddGap(gaps == 0 ? 3000 : 260);
			/* write full record to storage medium */
			if (CASSETTE_WriteFromMemory(data, length))
				result = 'C';
			else
				result = 'E';
			break;
		default:
			result = 'N';
		}
	}

	switch (result) {
	case 0x00:					/* Device disabled, generate timeout */
		CPU_regY = 138; /* TIMOUT: peripheral device timeout error */
		CPU_SetN;
		break;
	case 'A':					/* Device acknowledge */
	case 'C':					/* Operation complete */
		CPU_regY = 1; /* SUCCES: successful operation */
		CPU_ClrN;
		break;
	case 'N':					/* Device NAK */
		CPU_regY = 139; /* DNACK: device does not acknowledge command error */
		CPU_SetN;
		break;
	case 'E':					/* Device error */
		CPU_regY = 144; /* DERROR: device done (operation incomplete) error */
		CPU_SetN;
		break;
	default:
		CPU_regY = 146; /* FNCNOT: function not implemented in handler error */
		CPU_SetN;
		break;
	}
	CPU_regA = 0;	/* MMM */
	MEMORY_dPutByte(0x0303, CPU_regY);
	MEMORY_dPutByte(0x42,0);
	CPU_SetC;

	/* After each SIO operation a routine called SENDDS ($EC5F in OSB) is
	   invoked, which, among other functions, silences the sound
	   generators. With SIO patch we don't call SIOV and in effect SENDDS
	   is not called either, but this causes a problem with tape saving.
	   During tape saving sound generators are enabled before calling
	   SIOV, but are not disabled later (no call to SENDDS). The effect is
	   that after saving to tape the unwanted SIO sounds are left audible.
	   To avoid the problem, we silence the sound registers by hand. */
	POKEY_PutByte(POKEY_OFFSET_AUDC1, 0);
	POKEY_PutByte(POKEY_OFFSET_AUDC2, 0);
	POKEY_PutByte(POKEY_OFFSET_AUDC3, 0);
	POKEY_PutByte(POKEY_OFFSET_AUDC4, 0);
}

UBYTE SIO_ChkSum(const UBYTE *buffer, int length)
{
#if 0
	/* old, less efficient version */
	int i;
	int checksum = 0;
	for (i = 0; i < length; i++, buffer++) {
		checksum += *buffer;
		while (checksum > 255)
			checksum -= 255;
	}
#else
	int checksum = 0;
	while (--length >= 0)
		checksum += *buffer++;
	do
		checksum = (checksum & 0xff) + (checksum >> 8);
	while (checksum > 255);
#endif
	return checksum;
}

static UBYTE Command_Frame(void)
{
	int unit;
	int sector;
	int realsize;

	sector = CommandFrame[2] | (((UWORD) CommandFrame[3]) << 8);
	unit = CommandFrame[0] - '1';

	if (unit < 0 || unit >= SIO_MAX_DRIVES) {
		/* Unknown device */
		Log_print("Unknown command frame: %02x %02x %02x %02x %02x",
			   CommandFrame[0], CommandFrame[1], CommandFrame[2],
			   CommandFrame[3], CommandFrame[4]);
		TransferStatus = SIO_NoFrame;
		return 0;
	}
	switch (CommandFrame[1]) {
	case 0x4e:				/* Read Status */
#ifdef DEBUG
		Log_print("Read-status frame: %02x %02x %02x %02x %02x",
			CommandFrame[0], CommandFrame[1], CommandFrame[2],
			CommandFrame[3], CommandFrame[4]);
#endif
		DataBuffer[0] = SIO_ReadStatusBlock(unit, DataBuffer + 1);
		DataBuffer[13] = SIO_ChkSum(DataBuffer + 1, 12);
		DataIndex = 0;
		ExpectedBytes = 14;
		TransferStatus = SIO_ReadFrame;
		POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL;
		return 'A';
	case 0x4f:				/* Write status */
#ifdef DEBUG
		Log_print("Write-status frame: %02x %02x %02x %02x %02x",
			CommandFrame[0], CommandFrame[1], CommandFrame[2],
			CommandFrame[3], CommandFrame[4]);
#endif
		ExpectedBytes = 13;
		DataIndex = 0;
		TransferStatus = SIO_WriteFrame;
		return 'A';
	case 0x50:				/* Write */
	case 0x57:
	case 0xD0:				/* xf551 hispeed */
	case 0xD7:
#ifdef DEBUG
		Log_print("Write-sector frame: %02x %02x %02x %02x %02x",
			CommandFrame[0], CommandFrame[1], CommandFrame[2],
			CommandFrame[3], CommandFrame[4]);
#endif
		SIO_SizeOfSector((UBYTE) unit, sector, &realsize, NULL);
		ExpectedBytes = realsize + 1;
		DataIndex = 0;
		TransferStatus = SIO_WriteFrame;
		SIO_last_op = SIO_LAST_WRITE;
		SIO_last_op_time = 10;
		SIO_last_drive = unit + 1;
		return 'A';
	case 0x52:				/* Read */
	case 0xD2:				/* xf551 hispeed */
#ifdef DEBUG
		Log_print("Read-sector frame: %02x %02x %02x %02x %02x",
			CommandFrame[0], CommandFrame[1], CommandFrame[2],
			CommandFrame[3], CommandFrame[4]);
#endif
		SIO_SizeOfSector((UBYTE) unit, sector, &realsize, NULL);
		DataBuffer[0] = SIO_ReadSector(unit, sector, DataBuffer + 1);
		DataBuffer[1 + realsize] = SIO_ChkSum(DataBuffer + 1, realsize);
		DataIndex = 0;
		ExpectedBytes = 2 + realsize;
		TransferStatus = SIO_ReadFrame;
		/* wait longer before confirmation because bytes could be lost */
		/* before the buffer was set (see $E9FB & $EA37 in XL-OS) */
		POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL << 2; 
		if (image_type[unit] == IMAGE_TYPE_VAPI) {
			vapi_additional_info_t *info;
			info = (vapi_additional_info_t *)additional_info[unit];
			if (info == NULL)
				POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL << 2; 
			else
				POKEY_DELAYED_SERIN_IRQ = ((info->vapi_delay_time + 114/2) / 114) - 12;
		} 
#ifndef NO_SECTOR_DELAY
		else if (sector == 1) {
			POKEY_DELAYED_SERIN_IRQ += delay_counter;
			delay_counter = SECTOR_DELAY;
		}
		else {
			delay_counter = 0;
		}
#endif
		SIO_last_op = SIO_LAST_READ;
		SIO_last_op_time = 10;
		SIO_last_drive = unit + 1;
		return 'A';
	case 0x53:				/* Status */
#ifdef DEBUG
		Log_print("Status frame: %02x %02x %02x %02x %02x",
			CommandFrame[0], CommandFrame[1], CommandFrame[2],
			CommandFrame[3], CommandFrame[4]);
#endif
		DataBuffer[0] = SIO_DriveStatus(unit, DataBuffer + 1);
		DataBuffer[1 + 4] = SIO_ChkSum(DataBuffer + 1, 4);
		DataIndex = 0;
		ExpectedBytes = 6;
		TransferStatus = SIO_ReadFrame;
		POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL;
		return 'A';
	/*case 0x66:*/			/* US Doubler Format - I think! */
	case 0x21:				/* Format Disk */
	case 0xa1:				/* xf551 hispeed */
#ifdef DEBUG
		Log_print("Format-disk frame: %02x %02x %02x %02x %02x",
			CommandFrame[0], CommandFrame[1], CommandFrame[2],
			CommandFrame[3], CommandFrame[4]);
#endif
		realsize = SIO_format_sectorsize[unit];
		DataBuffer[0] = SIO_FormatDisk(unit, DataBuffer + 1, realsize, SIO_format_sectorcount[unit]);
		DataBuffer[1 + realsize] = SIO_ChkSum(DataBuffer + 1, realsize);
		DataIndex = 0;
		ExpectedBytes = 2 + realsize;
		TransferStatus = SIO_FormatFrame;
		POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL;
		return 'A';
	case 0x22:				/* Dual Density Format */
	case 0xa2:				/* xf551 hispeed */
#ifdef DEBUG
		Log_print("Format-Medium frame: %02x %02x %02x %02x %02x",
			CommandFrame[0], CommandFrame[1], CommandFrame[2],
			CommandFrame[3], CommandFrame[4]);
#endif
		DataBuffer[0] = SIO_FormatDisk(unit, DataBuffer + 1, 128, 1040);
		DataBuffer[1 + 128] = SIO_ChkSum(DataBuffer + 1, 128);
		DataIndex = 0;
		ExpectedBytes = 2 + 128;
		TransferStatus = SIO_FormatFrame;
		POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL;
		return 'A';
	default:
		/* Unknown command for a disk drive */
#ifdef DEBUG
		Log_print("Command frame: %02x %02x %02x %02x %02x",
			CommandFrame[0], CommandFrame[1], CommandFrame[2],
			CommandFrame[3], CommandFrame[4]);
#endif
		TransferStatus = SIO_NoFrame;
		return 'E';
	}
}

/* Enable/disable the command frame */
void SIO_SwitchCommandFrame(int onoff)
{
	if (onoff) {				/* Enabled */
		if (TransferStatus != SIO_NoFrame)
			Log_print("Unexpected command frame at state %x.", TransferStatus);
		CommandIndex = 0;
		DataIndex = 0;
		ExpectedBytes = 5;
		TransferStatus = SIO_CommandFrame;
	}
	else {
		if (TransferStatus != SIO_StatusRead && TransferStatus != SIO_NoFrame &&
			TransferStatus != SIO_ReadFrame) {
			if (!(TransferStatus == SIO_CommandFrame && CommandIndex == 0))
				Log_print("Command frame %02x unfinished.", TransferStatus);
			TransferStatus = SIO_NoFrame;
		}
		CommandIndex = 0;
	}
}

static UBYTE WriteSectorBack(void)
{
	UWORD sector;
	UBYTE unit;

	sector = CommandFrame[2] + (CommandFrame[3] << 8);
	unit = CommandFrame[0] - '1';
	if (unit >= SIO_MAX_DRIVES)		/* UBYTE range ! */
		return 0;
	switch (CommandFrame[1]) {
	case 0x4f:				/* Write Status Block */
		return SIO_WriteStatusBlock(unit, DataBuffer);
	case 0x50:				/* Write */
	case 0x57:
	case 0xD0:				/* xf551 hispeed */
	case 0xD7:
		return SIO_WriteSector(unit, sector, DataBuffer);
	default:
		return 'E';
	}
}

/* Put a byte that comes out of POKEY. So get it here... */
void SIO_PutByte(int byte)
{
	switch (TransferStatus) {
	case SIO_CommandFrame:
		if (CommandIndex < ExpectedBytes) {
			CommandFrame[CommandIndex++] = byte;
			if (CommandIndex >= ExpectedBytes) {
				if (CommandFrame[0] >= 0x31 && CommandFrame[0] <= 0x38 && (SIO_drive_status[CommandFrame[0]-0x31] != SIO_OFF || BINLOAD_start_binloading)) {
					TransferStatus = SIO_StatusRead;
					POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL + SIO_ACK_INTERVAL;
				}
				else
					TransferStatus = SIO_NoFrame;
			}
		}
		else {
			Log_print("Invalid command frame!");
			TransferStatus = SIO_NoFrame;
		}
		break;
	case SIO_WriteFrame:		/* Expect data */
		if (DataIndex < ExpectedBytes) {
			DataBuffer[DataIndex++] = byte;
			if (DataIndex >= ExpectedBytes) {
				UBYTE sum = SIO_ChkSum(DataBuffer, ExpectedBytes - 1);
				if (sum == DataBuffer[ExpectedBytes - 1]) {
					UBYTE result = WriteSectorBack();
					if (result != 0) {
						DataBuffer[0] = 'A';
						DataBuffer[1] = result;
						DataIndex = 0;
						ExpectedBytes = 2;
						POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL + SIO_ACK_INTERVAL;
						TransferStatus = SIO_FinalStatus;
					}
					else
						TransferStatus = SIO_NoFrame;
				}
				else {
					DataBuffer[0] = 'E';
					DataIndex = 0;
					ExpectedBytes = 1;
					POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL + SIO_ACK_INTERVAL;
					TransferStatus = SIO_FinalStatus;
				}
			}
		}
		else {
			Log_print("Invalid data frame!");
		}
		break;
	}
	CASSETTE_PutByte(byte);
	/* POKEY_DELAYED_SEROUT_IRQ = SIO_SEROUT_INTERVAL; */ /* already set in pokey.c */
}

/* Get a byte from the floppy to the pokey. */
int SIO_GetByte(void)
{
	int byte = 0;

	switch (TransferStatus) {
	case SIO_StatusRead:
		byte = Command_Frame();		/* Handle now the command */
		break;
	case SIO_FormatFrame:
		TransferStatus = SIO_ReadFrame;
		POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL << 3;
		/* FALL THROUGH */
	case SIO_ReadFrame:
		if (DataIndex < ExpectedBytes) {
			byte = DataBuffer[DataIndex++];
			if (DataIndex >= ExpectedBytes) {
				TransferStatus = SIO_NoFrame;
			}
			else {
				/* set delay using the expected transfer speed */
				POKEY_DELAYED_SERIN_IRQ = (DataIndex == 1) ? SIO_SERIN_INTERVAL
					: ((SIO_SERIN_INTERVAL * POKEY_AUDF[POKEY_CHAN3] - 1) / 0x28 + 1);
			}
		}
		else {
			Log_print("Invalid read frame!");
			TransferStatus = SIO_NoFrame;
		}
		break;
	case SIO_FinalStatus:
		if (DataIndex < ExpectedBytes) {
			byte = DataBuffer[DataIndex++];
			if (DataIndex >= ExpectedBytes) {
				TransferStatus = SIO_NoFrame;
			}
			else {
				if (DataIndex == 0)
					POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL + SIO_ACK_INTERVAL;
				else
					POKEY_DELAYED_SERIN_IRQ = SIO_SERIN_INTERVAL;
			}
		}
		else {
			Log_print("Invalid read frame!");
			TransferStatus = SIO_NoFrame;
		}
		break;
	default:
		byte = CASSETTE_GetByte();
		break;
	}
	return byte;
}

#if !defined(BASIC) && !defined(__PLUS)
int SIO_RotateDisks(void)
{
	char tmp_filenames[SIO_MAX_DRIVES][FILENAME_MAX];
	int i;
	int bSuccess = TRUE;

	for (i = 0; i < SIO_MAX_DRIVES; i++) {
		strcpy(tmp_filenames[i], SIO_filename[i]);
		SIO_Dismount(i + 1);
	}

	for (i = 1; i < SIO_MAX_DRIVES; i++) {
		if (strcmp(tmp_filenames[i], "None") && strcmp(tmp_filenames[i], "Off") && strcmp(tmp_filenames[i], "Empty") ) {
			if (!SIO_Mount(i, tmp_filenames[i], FALSE)) /* Note that this is NOT i-1 because SIO_Mount is 1 indexed */
				bSuccess = FALSE;
		}
	}

	i = SIO_MAX_DRIVES - 1;
	while (i > -1 && (!strcmp(tmp_filenames[i], "None") || !strcmp(tmp_filenames[i], "Off") || !strcmp(tmp_filenames[i], "Empty")) ) {
		i--;
	}

	if (i > -1)	{
		if (!SIO_Mount(i + 1, tmp_filenames[0], FALSE))
			bSuccess = FALSE;
	}

	return bSuccess;
}
#endif /* !defined(BASIC) && !defined(__PLUS) */

#ifndef BASIC

void SIO_StateSave(void)
{
	int i;

	for (i = 0; i < 8; i++) {
		StateSav_SaveINT((int *) &SIO_drive_status[i], 1);
		StateSav_SaveFNAME(SIO_filename[i]);
	}
}

void SIO_StateRead(void)
{
	int i;

	for (i = 0; i < 8; i++) {
		int saved_drive_status;
		char filename[FILENAME_MAX];

		StateSav_ReadINT(&saved_drive_status, 1);
		SIO_drive_status[i] = (SIO_UnitStatus)saved_drive_status;

		StateSav_ReadFNAME(filename);
		if (filename[0] == 0)
			continue;

		/* If the disk drive wasn't empty or off when saved,
		   mount the disk */
		switch (saved_drive_status) {
		case SIO_READ_ONLY:
			SIO_Mount(i + 1, filename, TRUE);
			break;
		case SIO_READ_WRITE:
			SIO_Mount(i + 1, filename, FALSE);
			break;
		default:
			break;
		}
	}
}

#endif /* BASIC */

/*
vim:ts=4:sw=4:
*/
