legs16.c_old

#include <stdio.h>
#include <stdlib.h>


#define CELL 2           // width of cell in bytes
#define MEMZ 16384       // Memory Store size
#define RVECT   0*CELL  
#define EVECT   1*CELL
#define IVECT   2*CELL
#define MMAX    3*CELL
#define C0      4*CELL
#define DH      5*CELL

typedef unsigned short int cell ;
typedef void prim() ;

unsigned char m[MEMZ];   // The Memory Store

cell ip=0;          // The Instruction Pointer
cell rp=MEMZ ;      // The Return Stack Pointer
cell sp=MEMZ-0x80 ; // The Data Stack Pointer
cell t=0 ;          // top popped working reg
cell n=0 ;          // next on stack working reg

prim *p[256];       // primitive function pointer table

int debugf=0;       // debug flag
int dlevel=0;       // debug level

// Fetches a Cell from Memory Store
cell mfetch( cell addr ){
  // fprintf(stderr,"fetch addr: %x = %x\n", addr, (cell)m[addr]<<8+m[addr+1] );
  return m[addr]*256 + m[addr+1] ;
}

// Stores a Cell to Memory Store
void mstore( cell data, cell addr ){
  m[addr]=data >> 8;
  m[addr+1]=data & 0xff ;
}

// Drop cell off stack
void drop(){
  sp=sp+CELL;
}

// Pops data off the data stack
cell mpop(){
  cell t=mfetch( sp );
  drop();
  return t;
}

// Pops 2 cells off data stack
void m2pop(){
  t=mpop();
  n=mpop();
}

// Pushes data onto the data stack
void mpush( cell data ){
  sp=sp-CELL;
  mstore( data, sp );
}

//
//  VM Primitives
//

void push(){
  r[--rp]=mpop();
}

void pull(){
  mpush(r[rp++]);
}


void dup(){
  cell t=mpop();
  mpush(t);
  mpush(t);
}

void swap(){
  m2pop();
  mpush( t );
  mpush( n );
}

void over(){
  push();
  dup();
  pull();
  swap();
}

void bra(){
  ip=mfetch( ip );
}

void zbra(){
  if( mpop() ) ip=ip+CELL;
  else bra();
}

void dofor(){
  if( r[rp] ){
    r[rp]=r[rp]-1;
    ip=ip+CELL;
    return;
  }
  rp++;
  bra();
}

void fexit(){
  ip=r[rp++];
}

void mint(){
  mpush( 0x8000 );
}

void and(){
  m2pop();
  mpush( t & n );
}

void or(){
  m2pop();
  mpush( t | n );
}

void xor(){
  m2pop();
  mpush( t ^ n );
}

void com(){
  mpush( ~mpop() );
}

void plus(){
  m2pop();
  mpush( t + n );
}

void shl(){
  mpush( mpop()<<1 );
}

void shr(){
  mpush( mpop()>>1 );
}

void oneplus(){
  mpush( mpop()+1 );
}

void oneminus(){
  mpush( mpop()-1 );
}

void spat(){
  mpush(sp);
}

void spbang(){
  sp=mpop();
}

void rzero(){
  rp=RSTACKZ;
}

// this doesn't belong here 
void pexec( cell xt ){
  if( xt<256 ) p[xt]();
  else{
    r[--rp]=ip;
    ip=xt;
  }
}

void exec(){
  pexec( mpop() );
}

void at(){
  mpush( mfetch( mpop() ) );
}

void bang(){
  m2pop();
  mstore( n, t );
}

void cat(){
  mpush( m[mpop()] );
}

void cbang(){
  m2pop();
  m[t]=n&255;
}

void fcell(){
  mpush( CELL );
}

void fchar(){
  mpush( 1 );
}

void lit(){
  mpush( mfetch( ip ) );
  ip+=CELL;
}

void key(){
  mpush( getchar() );
}

void emit(){
  putchar( mpop() );
}

void bye(){
  exit(0);
}

void noop(){
  printf("noop!\n" );
  printf("@ip: 0x%x\n", ip-CELL );
  exit(-1);
}

void debugon(){
  debugf=~debugf;
  dlevel=rp;
}

void init(){
  int x;
  FILE *f;
  for( x=0; x<MEMZ; x++){
    m[x]=0;
  }
  // load the memory store
  f=fopen("forth.img","r");
  if( !f ){
    fprintf(stderr,"Fatal error loading memory image.\n" );
    exit(-1);
  }
  fread( m, 1, MEMZ, f );
  fclose( f );
  // setup the primitive function table 
  for( x=0; x<256; x++) p[x]=noop;
  p[1]=push;
  p[2]=pull;
  p[3]=drop;
  p[4]=dup;
  p[5]=swap;
  p[6]=over;
  p[7]=bra;
  p[8]=zbra;
  p[9]=dofor;
  p[10]=fexit;
  p[11]=mint;
  p[12]=and;
  p[13]=or;
  p[14]=xor;
  p[15]=com;
  p[16]=plus;
  p[17]=shl;
  p[18]=shr;
  p[19]=oneplus;
  p[20]=oneminus;
  p[21]=spat;
  p[22]=spbang;
  p[23]=rzero;
  p[24]=exec;
  p[25]=at;
  p[26]=bang;
  p[27]=cat;
  p[28]=cbang;
  p[29]=fcell;
  p[30]=fchar;
  p[31]=lit;
  p[32]=key;
  p[33]=emit;
  p[34]=bye;
  p[255]=debugon;
  ip=mfetch( RVECT );
  fprintf(stderr,"init ip: 0x%x\n", ip );
  mstore( MEMZ, MMAX );
}

void rfind(cell xt){
  cell x=mfetch( DH );
  while(1){
    if (!x){ 
      fprintf(stderr,"???\n" );
      return;
    }
    if (mfetch(x+2)==xt){
      cell i;
      for( i=x+8; i<x+8+mfetch(x+6); i++ ){
	fprintf(stderr, "%c", m[i] );
      }
      fprintf(stderr, "\n" );
      return;
    }
    x=mfetch(x);
  }
}

void debug(){
  int x;
  fprintf(stderr,"ip: %x next: %x  ", ip, mfetch(ip) );
  rfind( mfetch(ip) );
  fprintf(stderr,"data: " );
  for( x=MEMZ-CELL; x>=sp; x=x-CELL ){
    fprintf( stderr,"%x ", mfetch(x) );
  }
  fprintf( stderr, "\n" );
  fprintf(stderr,"ret: " );
  for( x=RSTACKZ-1; x>=rp; x-- ){
    fprintf( stderr,"%x ", r[x] );
  }
  fprintf( stderr, "\n>" );
  x=getchar();
  if( x=='i' ) dlevel--;
  if( x=='o' ) dlevel++;
  if( x=='s' ) debugf=~debugf;
  if( x=='q' ) exit(0);
  if( x=='m' ){
    int i;
    int x;
    fscanf( stdin, "%x", &x );
    for( i=0; i<8; i++ ){
      fprintf(stderr,"%2x ", m[ x+i ] );
    }
    fprintf(stderr,"\n");
  }
}


void loop(){
  cell t;
  while(1){
    if (debugf && rp==dlevel) debug();
    t=mfetch(ip);
    ip+=CELL;
    pexec(t);
  }
}



void main(){
  init();
  loop();
}