/* advexe.c - adventure code executer */

/*

Copyright (c) 1986, by David Michael Betz

All rights reserved

*/

#include "advint.h"

#include "advdbs.h"

/* external variables */

extern char line[];

extern int nouns[],*adjectives[];

/* local variables */

int pc,opcode,p2,p3,sts;

int stack[STKSIZE],*sp,*fp,*top;

long rseed = 1L;

/* external routines */

extern long time();

/* execute - execute adventure code */

int execute(int code)

{

/* setup initial program counter */

if ((pc = code) == NIL)

return (CHAIN);

/* initialize */

sp = fp = top = stack + STKSIZE;

/* execute the code */

for (sts = 0; sts == 0; )

exe_one();

return (sts);

}

/* exe_one - execute one instruction */

void exe_one(void)

{

/* get the opcode */

opcode = getcbyte(pc); pc++;

/* execute the instruction */

switch (opcode) {

case OP_CALL:

*--sp = getboperand();

*--sp = pc;

*--sp = (int)(top - fp);

fp = sp;

pc = getafield(fp[fp[2]+3],A_CODE);

break;

case OP_SEND:

*--sp = getboperand();

*--sp = pc;

*--sp = (int)(top - fp);

fp = sp;

if (p2 = fp[fp[2]+3])

p2 = getofield(p2,O_CLASS);

else

p2 = fp[fp[2]+2];

if (p2 && (p2 = getp(p2,fp[fp[2]+1]))) {

pc = getafield(p2,A_CODE);

break;

}

*sp = NIL;

/* return NIL if there is no method for this message */

case OP_RETURN:

if (fp == top)

sts = CHAIN;

else {

p2 = *sp;

sp = fp;

fp = top - *sp++;

pc = *sp++;

p3 = *sp++;

sp += p3;

*sp = p2;

}

break;

case OP_TSPACE:

sp -= getboperand();

break;

case OP_TMP:

p2 = getboperand();

*sp = fp[-p2-1];

break;

case OP_TSET:

p2 = getboperand();

fp[-p2-1] = *sp;

break;

case OP_ARG:

p2 = getboperand();

if (p2 >= fp[2])

error("too few arguments");

*sp = fp[p2+3];

break;

case OP_ASET:

p2 = getboperand();

if (p2 >= fp[2])

error("too few arguments");

fp[p2+3] = *sp;

break;

case OP_BRT:

pc = (*sp ? getwoperand() : pc+2);

break;

case OP_BRF:

pc = (*sp ? pc+2 : getwoperand());

break;

case OP_BR:

pc = getwoperand();

break;

case OP_T:

*sp = T;

break;

case OP_NIL:

*sp = NIL;

break;

case OP_PUSH:

*--sp = NIL;

break;

case OP_NOT:

*sp = (*sp ? NIL : T);

break;

case OP_ADD:

p2 = *sp++;

*sp += p2;

break;

case OP_SUB:

p2 = *sp++;

*sp -= p2;

break;

case OP_MUL:

p2 = *sp++;

*sp *= p2;

break;

case OP_DIV:

p2 = *sp++;

*sp = (p2 == 0 ? 0 : *sp / p2);

break;

case OP_REM:

p2 = *sp++;

*sp = (p2 == 0 ? 0 : *sp % p2);

break;

case OP_BAND:

p2 = *sp++;

*sp &= p2;

break;

case OP_BOR:

p2 = *sp++;

*sp |= p2;

break;

case OP_BNOT:

*sp = ~*sp;

break;

case OP_LT:

p2 = *sp++;

*sp = (*sp < p2 ? T : NIL);

break;

case OP_EQ:

p2 = *sp++;

*sp = (*sp == p2 ? T : NIL);

break;

case OP_GT:

p2 = *sp++;

*sp = (*sp > p2 ? T : NIL);

break;

case OP_LIT:

*sp = getwoperand();

break;

case OP_SPLIT:

*sp = getboperand();

break;

case OP_SNLIT:

*sp = -getboperand();

break;

case OP_VAR:

*sp = getvalue(getwoperand());

break;

case OP_SVAR:

*sp = getvalue(getboperand());

break;

case OP_SET:

setvalue(getwoperand(),*sp);

break;

case OP_SSET:

setvalue(getboperand(),*sp);

break;

case OP_GETP:

p2 = *sp++;

*sp = getp(*sp,p2);

break;

case OP_SETP:

p3 = *sp++;

p2 = *sp++;

*sp = setp(*sp,p2,p3);

break;

case OP_PRINT:

print(*sp);

break;

case OP_PNUMBER:

pnumber(*sp);

break;

case OP_PNOUN:

show_noun(*sp);

break;

case OP_TERPRI:

trm_chr('\n');

break;

case OP_FINISH:

sts = FINISH;

break;

case OP_CHAIN:

sts = CHAIN;

break;

case OP_ABORT:

sts = ABORT;

break;

case OP_EXIT:

#ifdef MAC

macpause();

#endif

trm_done();

exit();

break;

case OP_YORN:

trm_get(line);

*sp = (line[0] == 'Y' || line[0] == 'y' ? T : NIL);

break;

case OP_CLASS:

*sp = getofield(*sp,O_CLASS);

break;

case OP_MATCH:

p2 = *sp++;

*sp = (match(*sp,nouns[p2-1],adjectives[p2-1]) ? T : NIL);

break;

case OP_SAVE:

*sp = db_save();

break;

case OP_RESTORE:

*sp = db_restore();

break;

case OP_RESTART:

*sp = db_restart();

break;

case OP_RAND:

*sp = getrand(*sp);

break;

case OP_RNDMIZE:

setrand(time(0L));

*sp = NIL;

break;

default:

if (opcode >= OP_XVAR && opcode < OP_XSET)

*sp = getvalue(opcode - OP_XVAR);

else if (opcode >= OP_XSET && opcode < OP_XPLIT)

setvalue(opcode - OP_XSET,*sp);

else if (opcode >= OP_XPLIT && opcode < OP_XNLIT)

*sp = opcode - OP_XPLIT;

else if (opcode >= OP_XNLIT && opcode < 256)

*sp = OP_XNLIT - opcode;

else

trm_str("Bad opcode\n");

break;

}

}

/* getboperand - get data byte */

int getboperand(void)

{

int data;

data = getcbyte(pc); pc += 1;

return (data);

}

/* getwoperand - get data word */

int getwoperand(void)

{

int data;

data = getcword(pc); pc += 2;

return (data);

}

/* print - print a message */

void print(int msg)

{

int ch;

msg_open(msg);

while (ch = msg_byte())

trm_chr(ch);

}

/* pnumber - print a number */

void pnumber(int n)

{

char buf[10];

sprintf(buf,"%d",n);

trm_str(buf);

}

/* getrand - get a random number between 0 and n-1 */

int getrand(int n)

{

long k1;

/* make sure we don't get stuck at zero */

if (rseed == 0L) rseed = 1L;

/* algorithm taken from Dr. Dobbs Journal, November 1985, page 91 */

k1 = rseed / 127773L;

if ((rseed = 16807L * (rseed - k1 * 127773L) - k1 * 2836L) < 0L)

rseed += 2147483647L;

/* return a random number between 0 and n-1 */

return ((int)(rseed % (long)n));

}

/* setrand - set the random number seed */

void setrand(long n)

{

rseed = n;

}