/* as.c */

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

typedef unsigned char byte;

union { int i;
        float f;
        struct { byte a,b,c,d; } b; } converter;

typedef struct S { char *name; int value, defnd; struct S *next; } symbolentry;
symbolentry *hashtable[1000];

FILE *source, *fout;
char *filename;
int errors;
int line_number;
char line[100];
int location_counter;
int total_size;

symbolentry *lookup(char *name)
{ int i,h;
  symbolentry *s;
  h=4521;
  for (i=0; name[i]!=0; i+=1)
    h=h*21+name[i];
  if (h<0) h=-h;
  h=h%1000;
  s=hashtable[h];
  while (s!=NULL && strcmp(s->name,name)!=0)
    s=s->next;
  if (s==NULL)
  { s=malloc(sizeof(symbolentry));
    s->name=malloc(strlen(name)+1);
    strcpy(s->name,name);
    s->value=0;
    s->defnd=0;
    s->next=hashtable[h];
    hashtable[h]=s; }
  return (s); }

void define(char *n, int v)
{ symbolentry *s;
  s=lookup(n);
  s->value=v;
  s->defnd=1; }

void init_all(void)
{ int i;
  for (i=0; i<1000; i+=1) hashtable[i]=NULL; 
  define("BADP",(OPCODE  0));
  define("LOAD",(OPCODE  1 +OPERAND));
  define("STOR",(OPCODE  2 +OPERAND));
  define("LOADN",(OPCODE  3 +OPERAND));
  define("LOADF",(OPCODE  4 +OPERAND));
  define("POP",(OPCODE  5));
  define("STI",(OPCODE  6));
  define("LDI",(OPCODE  7));
  define("DUP",(OPCODE  8));
  define("ADD",(OPCODE  9));
  define("ADDF",(OPCODE 10));
  define("SUB",(OPCODE 11));
  define("SUBF",(OPCODE 12));
  define("MUL",(OPCODE 13));
  define("MULF",(OPCODE 14));
  define("DIV",(OPCODE 15));
  define("DIVF",(OPCODE 16));
  define("MOD",(OPCODE 17));
  define("FLOAT",(OPCODE 18));
  define("FIX",(OPCODE 19));
  define("NOT",(OPCODE 20));
  define("AND",(OPCODE 21));
  define("OR",(OPCODE 22));
  define("EQL",(OPCODE 23));
  define("EQLF",(OPCODE 24));
  define("NEQ",(OPCODE 25));
  define("NEQF",(OPCODE 26));
  define("LSS",(OPCODE 27));
  define("LSSF",(OPCODE 28));
  define("GTR",(OPCODE 29));
  define("GTRF",(OPCODE 30));
  define("LEQ",(OPCODE 31));
  define("LEQF",(OPCODE 32));
  define("GEQ",(OPCODE 33));
  define("GEQF",(OPCODE 34));
  define("INCSP",(OPCODE 35 +OPERAND));
  define("DECSP",(OPCODE 36 +OPERAND));
  define("INCFP",(OPCODE 37 +OPERAND));
  define("DECFP",(OPCODE 38 +OPERAND));
  define("JUMP",(OPCODE 39 +OPERAND));
  define("PJZ",(OPCODE 40 +OPERAND));
  define("POPJMP",(OPCODE 41));
  define("POPFP",(OPCODE 42));
  define("LDFP",(OPCODE 43));
  define("INIT",(OPCODE 44));
  define("STOP",(OPCODE 45));
  define("BADN",(OPCODE 127));
  define("PRINTINT",1);
  define("PRINTFLOAT",2);
  define("PRINTSTRING",3);
  define("READINT",4);
  define("READFLOAT",5);
  errors=0;
  total_size=0;
  source=fopen(filename,"r");
  if (source==NULL)
  { fprintf(stderr,"can't open \"%s\"\n",filename);
    exit(1); } }

void init_pass(void)
{ line_number=0;
  if (errors!=0)
    exit(1);
  fseek(source,0,SEEK_SET);
  location_counter=FIRST_ADDRESS; }

void split(char *in, char **label, char **opcode, char **operand)
{ int next;
  char *out;
  char *start[4];
  next=0;
  *label=NULL;
  start[0]=NULL;
  start[1]=NULL;
  while (next<3)
  { while (*in==' ' || *in=='\t')
      in+=1;
    if (*in=='\n' || *in=='\r' || *in=='/' || *in==0)
      break;
    start[next]=in;
    next+=1;
    out=in;
    while (*in>' ' && *in!='/' && *in!=':')
    { if (*in>='a' && *in<='z')
        *out=*in-'a'+'A';
      else
        *out=*in;
      out+=1;
      in+=1;
      if (next==2)
        while (*in==' ' || *in=='\t')
          in+=1; }
    if (*in==':')
    { next=0;
      if (*start[0]!=':')
        *label=start[0];
      start[0]=NULL; }
    if (*in=='/')
    { *out=0;
      break; }
    if (*in!=0)
      in+=1;
    *out=0; }
  *opcode=start[0];
  *operand=start[1]; }

void error(char *msg, char *detail)
{ fprintf(stderr,"Line %d of %s: ", line_number, filename);
  fprintf(stderr, msg, detail);
  fprintf(stderr,"\n");
  errors+=1; }

void first_pass(void)
{ char *label, *opcode, *operand, *in;
  symbolentry *s;
  init_pass();
  while (1)
  { if (errors>5)
    { fprintf(stderr,"Too many errors, I give up\n");
      return; }
    in=fgets(line,99,source);
    if (in==NULL) break;
    line_number+=1;
    split(line,&label,&opcode,&operand);
    if (label!=NULL)
    { s=lookup(label);
      if (s->defnd)
        error("label %s is already defined", label);
      else
      { s->defnd=1;
        s->value=location_counter; } }
    if (opcode==NULL)
      continue;
    if (strcmp(opcode,"BYTES")==0)
    { int i=0;
      if (operand==NULL)
      { error("BYTES requires a number", NULL);
        continue; }
      if (sscanf(operand,"%d",&i)!=1)
        error("bad number %s after BYTES", operand);
      location_counter+=i;
      continue; }
    if (strcmp(opcode,"BYTE")==0)
    { location_counter+=1;
      continue; }
    s=lookup(opcode);
    if (!s->defnd)
      error("unknown name %s as opcode", opcode);
    else
      location_counter+=1;
    if (operand==NULL)
    { if (s->defnd && s->value&OPERAND!=0)
        error("%s instruction requires an operand", opcode); }
    else
    { if (s->defnd && s->value&OPERAND==0)
        error("instruction %s does not take an operand", opcode);
      location_counter+=4; } } }

void second_pass(void)
{ char *label, *opcode, *operand, *in;
  int opcode_value;
  symbolentry *s;
  init_pass();
  s=lookup("MAIN");
  if (!s->defnd)
    error("MAIN has not been defined", NULL);
  converter.i=s->value;
  fputc(converter.b.a, fout);
  fputc(converter.b.b, fout);
  fputc(converter.b.c, fout);
  fputc(converter.b.d, fout);
  converter.i=location_counter;
  fputc(converter.b.a, fout);
  fputc(converter.b.b, fout);
  fputc(converter.b.c, fout);
  fputc(converter.b.d, fout);
  while (1)
  { if (errors>5)
    { fprintf(stderr,"Too many errors, I give up\n");
      return; }
    in=fgets(line,99,source);
    if (in==NULL) break;
    line_number+=1;
    split(line,&label,&opcode,&operand);
    if (label!=NULL)
    { s=lookup(label);
      if (!s->defnd)
        error("use of undefined label %s", label);
      else if (s->value!=location_counter)
        error("problem with assembly: label %s has moved", label); }
    if (opcode==NULL)
      continue;
    if (strcmp(opcode,"BYTES")==0)
    { int i;
      if (operand==NULL)
      { error("BYTES requires a number", NULL);
        continue; }
      sscanf(operand,"%d",&i);
      while (i>0)
      { fputc(0, fout);
        i-=1;
        location_counter+=1; }
      continue; }
    if (strcmp(opcode,"BYTE")==0)
    { int i,k;
      if (operand==NULL)
      { error("BYTE requires a number", NULL);
        continue; }
       i=0;
      k=sscanf(operand,"%d",&i);
      location_counter+=1;
      fputc(i, fout);
      if (k!=1)
        error("improper BYTE operand %s",operand);
      continue; }
    s=lookup(opcode);
    opcode_value=s->value&~OPERAND;
    if (operand==NULL)
    { fputc(opcode_value, fout);
      location_counter+=1; }
    else
    { if (operand[0]=='+' || operand[0]=='-' || operand[0]=='.' ||
          operand[0]>='0' && operand[0]<='9')
      { int i, flt=0;
        opcode_value|=CONSTANT_OPERAND;
        for (i=0; operand[i]!=0; i+=1)
          if (operand[i]=='.' || operand[i]=='E' || operand[i]=='e')
          { flt=1;
            break; }
        if (flt)
        { i=sscanf(operand,"%f",&converter.f);
          if (i!=1)
            error("incorrect floating point operand %s", operand); }
        else
        { i=sscanf(operand,"%d",&converter.i);
          if (i!=1)
            error("incorrect integer operand %s", operand); } }
      else if (operand[0]=='F' && operand[1]=='P' &&
               (operand[2]=='+' || operand[2]=='-'))
      { int i=sscanf(operand+2,"%d",&converter.i);
        if (i!=1)
          error("improper offset %s after FP in operand", operand+2);
        opcode_value|=FP_RELATIVE_OPERAND; }
      else if (operand[0]=='@' && operand[1]=='F' && operand[2]=='P' &&
               (operand[3]=='+' || operand[3]=='-'))
      { int i;
        if (opcode_value!=LOAD&~OPERAND)
          error("@FP+offset operand only valid with LOAD instruction", NULL);
        i=sscanf(operand+3,"%d",&converter.i);
        if (i!=1)
          error("improper offset %s after @FP in operand", operand+3);
        opcode_value=(LOADN&~OPERAND)|FP_RELATIVE_OPERAND; }
      else if (operand[0]=='@')
      { if (opcode_value!=LOAD&~OPERAND)
          error("@label operand only valid with LOAD instruction", NULL);
        s=lookup(operand+1);
        if (!s->defnd)
          error("operand %s has not been defined", operand);
        opcode_value=LOADN|CONSTANT_OPERAND;
        converter.i=s->value; }
      else
      { opcode_value|=CONSTANT_OPERAND;
        s=lookup(operand);
        if (!s->defnd)
          error("operand %s has not been defined", operand);
        converter.i=s->value; }
      fputc(opcode_value, fout);
      fputc(converter.b.a, fout);
      fputc(converter.b.b, fout);
      fputc(converter.b.c, fout);
      fputc(converter.b.d, fout);
      location_counter+=5; } } }

void main(int argc, char *argv[])
{ if (argc<2)
    filename="a.asm";
  else
    filename=argv[1];
  init_all();
  first_pass();
  total_size=location_counter;
  fout=fopen("a.exe", "w");
  if (fout==NULL)
  { fprintf(stderr,"Can't create a.exe\n");
    exit(1); }
  second_pass();
  if (total_size!=location_counter)
    error("Assembly problem - size has changed", NULL);
  fclose(fout);
  fclose(source); }