/* sbbsexec.c */

/* Synchronet Windows NT/2000 VDD for FOSSIL and DOS I/O Interrupts */

/* $Id: sbbsexec.c,v 1.38 2006/10/28 03:56:36 rswindell Exp $ */

/****************************************************************************
 * @format.tab-size 4		(Plain Text/Source Code File Header)			*
 * @format.use-tabs true	(see http://www.synchro.net/ptsc_hdr.html)		*
 *																			*
 * Copyright 2006 Rob Swindell - http://www.synchro.net/copyright.html		*
 *																			*
 * 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.					*
 * See the GNU General Public License for more details: gpl.txt or			*
 * http://www.fsf.org/copyleft/gpl.html										*
 *																			*
 * Anonymous FTP access to the most recent released source is available at	*
 * ftp://vert.synchro.net, ftp://cvs.synchro.net and ftp://ftp.synchro.net	*
 *																			*
 * Anonymous CVS access to the development source and modification history	*
 * is available at cvs.synchro.net:/cvsroot/sbbs, example:					*
 * cvs -d :pserver:anonymous@cvs.synchro.net:/cvsroot/sbbs login			*
 *     (just hit return, no password is necessary)							*
 * cvs -d :pserver:anonymous@cvs.synchro.net:/cvsroot/sbbs checkout src		*
 *																			*
 * For Synchronet coding style and modification guidelines, see				*
 * http://www.synchro.net/source.html										*
 *																			*
 * You are encouraged to submit any modifications (preferably in Unix diff	*
 * format) via e-mail to mods@synchro.net									*
 *																			*
 * Note: If this box doesn't appear square, then you need to fix your tabs.	*
 ****************************************************************************/

#include <windows.h> 
#include <stdio.h>
#include <vddsvc.h>
#include "uartdefs.h"
#include "vdd_func.h"
#include "ringbuf.h"
#include "genwrap.h"
#include "dirwrap.h"
#include "threadwrap.h"
#include "ini_file.h"

#define INI_FILENAME			"sbbsexec.ini"
#define RINGBUF_SIZE_IN			10000
#define DEFAULT_MAX_MSG_SIZE	4000
#define LINEAR_RX_BUFLEN		5000

/* UART Parameters and virtual registers */
WORD uart_io_base				= UART_COM1_IO_BASE;	/* COM1 */
BYTE uart_irq					= UART_COM1_IRQ;
BYTE uart_ier_reg				= 0;
BYTE uart_lcr_reg				= UART_LCR_8_DATA_BITS;
BYTE uart_mcr_reg				= UART_MCR_RTS | UART_MCR_DTR;
BYTE uart_lsr_reg				= UART_LSR_EMPTY_DATA | UART_LSR_EMPTY_XMIT;
BYTE uart_msr_reg				= UART_MSR_CTS | UART_MSR_DSR;
BYTE uart_scratch_reg			= 0;
BYTE uart_divisor_latch_lsb		= 0x03;	/* 38400 */
BYTE uart_divisor_latch_msb		= 0x00;

#if defined (_DEBUG)
	int log_level = LOG_DEBUG;
#else
	int log_level = LOG_WARNING;
#endif

BOOL		virtualize_uart=TRUE;
double		yield_interval=1.0;
BOOL		hangup_supported=TRUE;
HANDLE		hangup_event=NULL;
HANDLE		hungup_event=NULL;
HANDLE		interrupt_event=NULL;
HANDLE		rdslot=INVALID_HANDLE_VALUE;
HANDLE		wrslot=INVALID_HANDLE_VALUE;
RingBuf		rdbuf;
str_list_t	ini;
char		ini_fname[MAX_PATH+1];
char		revision[16];

void lputs(int level, char* msg)
{	
	char buf[1024];
	if(level > log_level)
		return;

	SAFEPRINTF(buf,"SBBS: %s\r\n", msg);
	OutputDebugString(buf);
}

static void lprintf(int level, const char *fmt, ...)
{
	char sbuf[1024];
	va_list argptr;

	if(level > log_level)
		return;

    va_start(argptr,fmt);
    _vsnprintf(sbuf,sizeof(sbuf),fmt,argptr);
	sbuf[sizeof(sbuf)-1]=0;
    va_end(argptr);
    lputs(level,sbuf);
}

void hangup()
{
	if(hangup_supported && hangup_event!=NULL) {
		lprintf(LOG_DEBUG,"Hanging-up at application request");
		SetEvent(hangup_event);
	}
}

void parse_ini(char* program)
{
	char section[MAX_PATH+1];

	if(ini==NULL)	/* no initialization file */
		return;

	/* Read the root section of the sbbsexec.ini file */
	log_level=iniGetLogLevel(ini,program,"LogLevel",log_level);
	if(iniGetBool(ini,program,"Debug",FALSE))
		log_level=LOG_DEBUG;
	yield_interval=iniGetFloat(ini,program,"YieldInterval",yield_interval);
	hangup_supported=iniGetBool(ini,program,"CanDisconnect",hangup_supported);

	lprintf(LOG_INFO,"Parsed %s section of %s"
		,program==ROOT_SECTION ? "root" : program
		,ini_fname);

	/* [UART] section */
	if(program==ROOT_SECTION)
		SAFECOPY(section,"UART");
	else
		SAFEPRINTF(section,"%s.UART",program);

	virtualize_uart=iniGetBool(ini,section,"Virtualize",virtualize_uart);
	switch(iniGetInteger(ini,section,"ComPort",0)) {
		case 1:	/* COM1 */
			uart_irq		=UART_COM1_IRQ;
			uart_io_base	=UART_COM1_IO_BASE;
			break;
		case 2:	/* COM2 */
			uart_irq		=UART_COM2_IRQ;
			uart_io_base	=UART_COM2_IO_BASE;
			break;
		case 3:	/* COM3 */
			uart_irq		=UART_COM3_IRQ;
			uart_io_base	=UART_COM3_IO_BASE;
			break;
		case 4:	/* COM4 */
			uart_irq		=UART_COM4_IRQ;
			uart_io_base	=UART_COM4_IO_BASE;
			break;
	}
	uart_irq=(BYTE)iniGetShortInt(ini,section,"IRQ",uart_irq);
	uart_io_base=iniGetShortInt(ini,section,"Address",uart_io_base);

	lprintf(LOG_INFO,"Parsed %s section of %s"
		,section
		,ini_fname);
}


/* Mutex-protected pending interrupt "queue" */
int pending_interrupts = 0;
CRITICAL_SECTION interrupt_mutex;

void set_interrupt_pending(BYTE intr, BOOL assert)
{
	EnterCriticalSection(&interrupt_mutex);
	lprintf(LOG_DEBUG,"%sasserting interrupt %02X (pending: %02X, IER: %02X)"
		,assert ? "" : "de-", intr
		,pending_interrupts
		,uart_ier_reg);
	if(assert) {
		if(uart_ier_reg&intr) {					/* is interrupt enabled? */
			pending_interrupts |= intr;			/* flag as pending */
			SetEvent(interrupt_event);
		}
	} else /* de-assert */
		pending_interrupts &= ~intr;		/* remove as pending */

	LeaveCriticalSection(&interrupt_mutex);
}

#define assert_interrupt(i)		set_interrupt_pending(i, TRUE)
#define deassert_interrupt(i)	set_interrupt_pending(i, FALSE)

void _cdecl interrupt_thread(void *arg)
{
	while(1) {
		if(WaitForSingleObject(interrupt_event,INFINITE)!=WAIT_OBJECT_0)
			break;
		if((uart_ier_reg&pending_interrupts) != 0) {
			lprintf(LOG_DEBUG,"VDDSimulateInterrupt (pending: %02X) - IER: %02X"
				,pending_interrupts, uart_ier_reg);
			VDDSimulateInterrupt(ICA_MASTER, uart_irq, /* count: */1);
		}
#if 0
		/* "Real 16550s should always reassert
		 *  this interrupt whenever the transmitter is idle and
		 *  the interrupt is enabled."
		 */
		if(pending_interrupts==0 && uart_ier_reg&UART_IER_TX_EMPTY)
			pending_interrupts|=UART_IER_TX_EMPTY;
#endif
	}
}

void _cdecl input_thread(void* arg)
{
	char	buf[LINEAR_RX_BUFLEN];
	int		count;

	while(1) {
		count=0;
		if(!ReadFile(rdslot,buf,sizeof(buf),&count,NULL)) {
			if(GetLastError()==ERROR_HANDLE_EOF)	/* closed by VDD_CLOSE */
				break;
			lprintf(LOG_ERR,"!input_thread: ReadFile Error %d (size=%d)"
				,GetLastError(),count);
			continue;
		}
		if(count==0) {
			lprintf(LOG_ERR,"!input_thread: ReadFile read 0");
			continue;
		}
		RingBufWrite(&rdbuf,buf,count);
		/* Set the "Data ready" bit in the LSR */
		uart_lsr_reg |= UART_LSR_DATA_READY;

		assert_interrupt(UART_IER_RX_DATA); /* assert rx data interrupt */
	}
}

unsigned vdd_read(BYTE* p, unsigned count)
{
	sem_wait(rdbuf.sem);
	count=RingBufRead(&rdbuf,p,count);
	if(count==0)
		lprintf(LOG_ERR,"!VDD_READ: RingBufRead read 0");

	return(count);
}

unsigned yields=0;

void yield()
{
	yields++;
	lprintf(LOG_DEBUG,"Yielding (yields=%u)", yields);
	Sleep(1);
}

long double last_yield=0;

void maybe_yield()
{
	long double t;

	t=xp_timer();

	if(yield_interval && (t-last_yield)*1000.0 >= yield_interval) {
		yield();
		last_yield=t;
	}
}

void reset_yield()
{
	last_yield=xp_timer();
}

/***********************/
/* UART Virtualization */
/***********************/

static char *chr(uchar ch)
{
	static char str[25];

	if(ch>=' ' && ch<='~')
		sprintf(str,"'%c' (%02Xh)",ch,ch);
	else if(ch<' ')
		sprintf(str,"^%c  (%02Xh)",'@'+ch,ch);
	else
		sprintf(str,"%u (%02Xh)",ch,ch);
	return(str); 
}

VOID uart_wrport(WORD port, BYTE data)
{
	int reg = port - uart_io_base;
	int retval;

	lprintf(LOG_DEBUG,"write of port: %x (%s) <- %02X", port, uart_reg_desc[reg], data);

	switch(reg) {
		case UART_BASE:
			if(uart_lcr_reg&UART_LCR_DLAB) {
				uart_divisor_latch_lsb = data;
				lprintf(LOG_DEBUG,"set divisor latch low byte: %02X", data);
			} else {
				lprintf(LOG_DEBUG,"WRITE DATA: %s", chr(data));
				if(!WriteFile(wrslot,&data,sizeof(BYTE),&retval,NULL)) {
					lprintf(LOG_ERR,"!VDD_WRITE: WriteFile Error %d (size=%d)"
						,GetLastError(),retval);
				} else {
					assert_interrupt(UART_IER_TX_EMPTY);
					reset_yield();
				}
			}
			break;
		case UART_IER:
			if(uart_lcr_reg&UART_LCR_DLAB) {
				uart_divisor_latch_msb = data;
				lprintf(LOG_DEBUG,"set divisor latch high byte: %02X", data);
			} else
				uart_ier_reg = data;
			assert_interrupt(UART_IER_TX_EMPTY);	/* should this be re-asserted for all writes? */
			break;
		case UART_IIR: /* FCR not supported */
			break;
		case UART_LCR:
			uart_lcr_reg = data;
			break;
		case UART_MCR:
			uart_mcr_reg = data;
			if((uart_mcr_reg&UART_MCR_DTR) == 0)	/* Dropping DTR (i.e. "hangup") */
				hangup();
			break;
		case UART_SCRATCH:
			uart_scratch_reg = data;
			break;
		default:
			lprintf(LOG_ERR,"UNSUPPORTED register: %u", reg);
			break;
			
	}
}

VOID uart_rdport(WORD port, PBYTE data)
{
	int reg = port - uart_io_base;
	DWORD avail;

	lprintf(LOG_DEBUG,"read of port: %x (%s)", port, uart_reg_desc[reg]);

	switch(reg) {
		case UART_BASE:
			if(uart_lcr_reg&UART_LCR_DLAB) {
				lprintf(LOG_DEBUG,"reading divisor latch LSB");
				*data = uart_divisor_latch_lsb;
				break;
			}
			if((avail=RingBufFull(&rdbuf))!=0) {
				vdd_read(data,sizeof(BYTE));
				lprintf(LOG_DEBUG,"READ DATA: %s", chr(*data));
				avail--;
				reset_yield();
			} else
				*data=0;
			if(avail==0) {
				lprintf(LOG_DEBUG,"No more data");
				/* Clear the data ready bit in the LSR */
				uart_lsr_reg &= ~UART_LSR_DATA_READY;

				/* Clear data ready interrupt identification in IIR */
				deassert_interrupt(UART_IER_RX_DATA);
			} else	/* re-assert RX data (increment the semaphore) */
				assert_interrupt(UART_IER_RX_DATA);
			break;
		case UART_IER:
			if(uart_lcr_reg&UART_LCR_DLAB) {
				lprintf(LOG_DEBUG,"reading divisor latch MSB");
				*data = uart_divisor_latch_msb;
			} else
				*data = uart_ier_reg;
			break;
		case UART_IIR:
			/* Report IIR based on *priority* of pending interrupts */
			if(pending_interrupts & UART_IER_LINE_STATUS)
				*data = UART_IIR_LINE_STATUS;
			else if(pending_interrupts & UART_IER_RX_DATA)
				*data = UART_IIR_RX_DATA;
			else if(pending_interrupts & UART_IER_TX_EMPTY) {
				*data = UART_IIR_TX_EMPTY;
				/* "Transmit Holding Register Empty" interrupt */
				/*  is reset on read of IIR */
				deassert_interrupt(UART_IER_TX_EMPTY);
			}
			else if(pending_interrupts & UART_IER_MODEM_STATUS)
				*data = UART_IIR_MODEM_STATUS;
			else
				*data = UART_IIR_NONE;
			break;
		case UART_LCR:
			*data = uart_lcr_reg;
			break;
		case UART_MCR:
			*data = uart_mcr_reg;
			break;
		case UART_LSR:
			*data = uart_lsr_reg;
			maybe_yield();
			/* Clear line status interrupt pending */
			deassert_interrupt(UART_IER_LINE_STATUS);
			break;
		case UART_MSR:
			if(WaitForSingleObject(hungup_event,0)==WAIT_OBJECT_0)
				uart_msr_reg &=~ UART_MSR_DCD;
			else
				uart_msr_reg |= UART_MSR_DCD;
			*data = uart_msr_reg;
			maybe_yield();
			/* Clear modem status interrupt pending */
			deassert_interrupt(UART_IER_MODEM_STATUS);
			break;
		case UART_SCRATCH:
			*data = uart_scratch_reg;
			break;
		default:
			lprintf(LOG_ERR,"UNSUPPORTED register: %u", reg);
			break;
	}

	if(reg!=UART_BASE)
		lprintf(LOG_DEBUG, "returning 0x%02X", *data);
}

/* VDD DOS Interface (mainly for FOSSIL driver in dosxtrn.exe) */

__declspec(dllexport) void __cdecl VDDDispatch(void) 
{
	char			str[512];
	DWORD			count;
	DWORD			msgs;
	int				retval;
	int				node_num;
	BYTE*			p;
	vdd_status_t*	status;
	static  DWORD	writes;
	static  DWORD	bytes_written;
	static	DWORD	reads;
	static  DWORD	bytes_read;
	static  DWORD	inbuf_poll;
	static	DWORD	online_poll;
	static	DWORD	status_poll;
	static	DWORD	vdd_yields;
	static	DWORD	vdd_calls;
	VDD_IO_HANDLERS  IOHandlers = { NULL };
	static VDD_IO_PORTRANGE PortRange;

	retval=0;
	node_num=getBH();

	lprintf(LOG_DEBUG,"VDD_OP: (handle=%d) %d (arg=%X)", getAX(),getBL(),getCX());
	vdd_calls++;

	switch(getBL()) {

		case VDD_OPEN:

			sscanf("$Revision: 1.38 $", "%*s %s", revision);

			lprintf(LOG_INFO,"Synchronet Virtual Device Driver, rev %s %s %s"
				,revision, __DATE__, __TIME__);
#if 0
			sprintf(str,"sbbsexec%d.log",node_num);
			fp=fopen(str,"wb");
#endif

			sprintf(str,"\\\\.\\mailslot\\sbbsexec\\wr%d",node_num);
			rdslot=CreateMailslot(str
				,LINEAR_RX_BUFLEN		/* Max message size (0=any) */
				,MAILSLOT_WAIT_FOREVER 	/* Read timeout */
				,NULL);
			if(rdslot==INVALID_HANDLE_VALUE) {
				lprintf(LOG_ERR,"!VDD_OPEN: Error %d opening %s"
					,GetLastError(),str);
				retval=1;
				break;
			}

			sprintf(str,"\\\\.\\mailslot\\sbbsexec\\rd%d",node_num);
			wrslot=CreateFile(str
				,GENERIC_WRITE
				,FILE_SHARE_READ
				,NULL
				,OPEN_EXISTING
				,FILE_ATTRIBUTE_NORMAL
				,(HANDLE) NULL);
			if(wrslot==INVALID_HANDLE_VALUE) {
				lprintf(LOG_ERR,"!VDD_OPEN: Error %d opening %s"
					,GetLastError(),str);
				retval=2;
				break;
			}

			if(RingBufInit(&rdbuf, RINGBUF_SIZE_IN)!=0) {
				retval=3;
				break;
			}

			sprintf(str,"sbbsexec_hungup%d",node_num);
			hungup_event=OpenEvent(
				EVENT_ALL_ACCESS,	/* access flag  */
				FALSE,				/* inherit flag  */
				str);				/* pointer to event-object name  */
			if(hungup_event==NULL) {
				lprintf(LOG_ERR,"!VDD_OPEN: Error %d opening %s"
					,GetLastError(),str);
				retval=4;
				break;
			}

			sprintf(str,"sbbsexec_hangup%d",node_num);
			hangup_event=OpenEvent(
				EVENT_ALL_ACCESS,	/* access flag  */
				FALSE,				/* inherit flag  */
				str);				/* pointer to event-object name  */
			if(hangup_event==NULL) {
				lprintf(LOG_WARNING,"!VDD_OPEN: Error %d opening %s"
					,GetLastError(),str);
			}

			status_poll=0;
			inbuf_poll=0;
			online_poll=0;
			yields=0;

			lprintf(LOG_INFO,"Yield interval: %f milliseconds", yield_interval);

			if(virtualize_uart) {
				lprintf(LOG_INFO,"Virtualizing UART (0x%x, IRQ %u)"
					,uart_io_base, uart_irq);

				IOHandlers.inb_handler = uart_rdport;
				IOHandlers.outb_handler = uart_wrport;
				PortRange.First=uart_io_base;
				PortRange.Last=uart_io_base + UART_IO_RANGE;

				VDDInstallIOHook((HANDLE)getAX(), 1, &PortRange, &IOHandlers);

				interrupt_event=CreateEvent(NULL,FALSE,FALSE,NULL);
				InitializeCriticalSection(&interrupt_mutex);

				_beginthread(interrupt_thread, 0, NULL);
			}

			lprintf(LOG_DEBUG,"VDD_OPEN: Opened successfully");

			_beginthread(input_thread, 0, NULL);

			retval=0;
			break;

		case VDD_CLOSE:
			lprintf(LOG_INFO,"VDD_CLOSE: rdbuf=%u "
				"status_poll=%u inbuf_poll=%u online_poll=%u yields=%u vdd_yields=%u vdd_calls=%u"
				,RingBufFull(&rdbuf),status_poll,inbuf_poll,online_poll
				,yields,vdd_yields,vdd_calls);
			lprintf(LOG_INFO,"           read=%u bytes (in %u calls)",bytes_read,reads);
			lprintf(LOG_INFO,"           wrote=%u bytes (in %u calls)",bytes_written,writes);

			if(virtualize_uart) {
				lprintf(LOG_INFO,"Uninstalling Virtualizaed UART IO Hook");
				VDDDeInstallIOHook((HANDLE)getAX(), 1, &PortRange);
			}

			CloseHandle(rdslot);
			CloseHandle(wrslot);
			if(hungup_event!=NULL)
				CloseHandle(hungup_event);
			if(hangup_event!=NULL)
				CloseHandle(hangup_event);

#if 0	/* This isn't strictly necessary... 
		   and possibly the cause of a NULL dereference in the input_thread */
			RingBufDispose(&rdbuf);
#endif
			status_poll=0;
			retval=0;

			break;

		case VDD_READ:
			count = getCX();
			if(count != 1)
				lprintf(LOG_DEBUG,"VDD_READ of %d",count);
			p = (BYTE*) GetVDMPointer((ULONG)((getES() << 16)|getDI())
				,count,FALSE); 
			retval=vdd_read(p, count);
			reads++;
			bytes_read+=retval;
			reset_yield();
			break;

		case VDD_PEEK:
			count = getCX();
			if(count != 1)
				lprintf(LOG_DEBUG,"VDD_PEEK of %d",count);

			p = (BYTE*) GetVDMPointer((ULONG)((getES() << 16)|getDI())
				,count,FALSE); 
			retval=RingBufPeek(&rdbuf,p,count);
			reset_yield();
			break;

		case VDD_WRITE:
			count = getCX();
			if(count != 1)
				lprintf(LOG_DEBUG,"VDD_WRITE of %d",count);
			p = (BYTE*) GetVDMPointer((ULONG)((getES() << 16)|getDI())
				,count,FALSE); 
			if(!WriteFile(wrslot,p,count,&retval,NULL)) {
				lprintf(LOG_ERR,"!VDD_WRITE: WriteFile Error %d (size=%d)"
					,GetLastError(),retval);
				retval=0;
			} else {
				writes++;
				bytes_written+=retval;
				reset_yield();
			}
			break;

		case VDD_STATUS:

			status_poll++;
			count = getCX();
			if(count != sizeof(vdd_status_t)) {
				lprintf(LOG_DEBUG,"!VDD_STATUS: wrong size (%d!=%d)",count,sizeof(vdd_status_t));
				retval=sizeof(vdd_status_t);
				break;
			}
			status = (vdd_status_t*) GetVDMPointer((ULONG)((getES() << 16)|getDI())
				,count,FALSE); 

			status->inbuf_full=RingBufFull(&rdbuf);

			/* OUTBUF FULL/SIZE */
			if(!GetMailslotInfo(
				wrslot,					/* mailslot handle  */
 				&status->outbuf_size,	/* address of maximum message size  */
				&status->outbuf_full,	/* address of size of next message  */
				&msgs,					/* address of number of messages  */
 				NULL					/* address of read time-out  */
				)) {
				status->outbuf_full=0;
				status->outbuf_size=DEFAULT_MAX_MSG_SIZE;
			}
			if(status->outbuf_full==MAILSLOT_NO_MESSAGE)
				status->outbuf_full=0;
			status->outbuf_full*=msgs;
			
			/* ONLINE */
			if(WaitForSingleObject(hungup_event,0)==WAIT_OBJECT_0)
				status->online=0;
			else
				status->online=1;

			retval=0;	/* success */
			break;

		case VDD_INBUF_PURGE:
			RingBufReInit(&rdbuf);
			retval=0;
			break;

		case VDD_OUTBUF_PURGE:
			lprintf(LOG_WARNING,"!VDD_OUTBUF_PURGE: NOT IMPLEMENTED");
			retval=0;
			break;

		case VDD_INBUF_FULL:
			retval=RingBufFull(&rdbuf);
			inbuf_poll++;
			break;

		case VDD_INBUF_SIZE:
			retval=RINGBUF_SIZE_IN;
			break;

		case VDD_OUTBUF_FULL:
			if(!GetMailslotInfo(
				wrslot,		/* mailslot handle  */
 				NULL,		/* address of maximum message size  */
				&retval,	/* address of size of next message  */
				&msgs,		/* address of number of messages  */
 				NULL		/* address of read time-out  */
				))
				retval=0;
			if(retval==MAILSLOT_NO_MESSAGE)
				retval=0;
			retval*=msgs;
			break;

		case VDD_OUTBUF_SIZE:
			if(!GetMailslotInfo(
				wrslot,		/* mailslot handle  */
 				&retval,	/* address of maximum message size  */
				NULL,		/* address of size of next message  */
				NULL,		/* address of number of messages  */
 				NULL		/* address of read time-out  */
				)) 
				retval=DEFAULT_MAX_MSG_SIZE;
			break;

		case VDD_ONLINE:
			if(WaitForSingleObject(hungup_event,0)==WAIT_OBJECT_0)
				retval=0;
			else
				retval=1;
			online_poll++;
			break;

		case VDD_YIELD:			/* forced yield */
			vdd_yields++;
			yield();
			break;

		case VDD_MAYBE_YIELD:	/* yield if YieldInterval is enabled and expired */
			maybe_yield();
			break;

		case VDD_LOAD_INI_FILE:	/* Load and parse settings file */
			{
				FILE*	fp;
				char	cwd[MAX_PATH+1];

				/* Load exec/sbbsexec.ini first (setting default values) */
				count = getCX();
				p = (BYTE*)GetVDMPointer((ULONG)((getES() << 16)|getDI())
					,count,FALSE); 
				iniFileName(ini_fname, sizeof(ini_fname), p, INI_FILENAME);
				if((fp=fopen(ini_fname,"r"))!=NULL) {
					ini=iniReadFile(fp);
					fclose(fp);
					parse_ini(ROOT_SECTION);
				}

				/* Load cwd/sbbsexec.ini second (over-riding default values) */
				GetCurrentDirectory(sizeof(cwd),cwd);
				iniFileName(ini_fname, sizeof(ini_fname), cwd, INI_FILENAME);
				if((fp=fopen(ini_fname,"r"))!=NULL) {
					ini=iniReadFile(fp);
					fclose(fp);
					parse_ini(ROOT_SECTION);
				}
			}
			break;

		case VDD_LOAD_INI_SECTION:	/* Parse (program-specific) sub-section of settings file */
			count = getCX();
			p = (BYTE*)GetVDMPointer((ULONG)((getES() << 16)|getDI())
				,count,FALSE); 
			parse_ini(p);
			break;

		case VDD_DEBUG_OUTPUT:	/* Send string to debug output */
			count = getCX();
			p = (BYTE*)GetVDMPointer((ULONG)((getES() << 16)|getDI())
				,count,FALSE); 
			lputs(LOG_INFO, p);
			break;

		case VDD_HANGUP:
			hangup();
			break;

		default:
			lprintf(LOG_ERR,"!UNKNOWN VDD_OP: %d",getBL());
			break;
	}
	setAX((WORD)retval);
}
