Compiler Using C

/* Palash.cseku@gmail.com */
#include /* load i/o routines */
#include
#include
#include /* load character test routines */
#include Palash.h

FILE *fp,*fout;
char lexemes[STRMAX];
char Terror[20][50];
char line[20],err[50],str[30];
int lastchar = -1; /* last used position in lexemes */

int lastentry = 0; /* last used position in symtable*/
int inc=0,flag=0,gb,gt;
int lookahead,q=2,chkParen=0,chkBegin=0,Int=0;

char lexbuf[BSIZE];
int lineno = 1,check=0;
int tokenval = NONE;

void match(int);
void expr();
void term();
void factor();
void stmt();
void error(char[]);
void emit(int,int);
struct entry /* form of symbol table entry */
{
 char *lexptr;
 int token;

};
struct entry symtable[SYMMAX];
char *allToken[1000];

//struct entry keywords[]={0,0};

struct entry keywords[]={"div",DIV,
  "mod",MOD,
  "if",IF,
  "then",THEN,
  "else",ELSE,
  "do",DO,
  "while",WHILE,
  "repeat",REPEAT,
  "until",UNTIL,
  "begin",BEGIN,
  "end",END,
  "int",INT,
  "char",CHAR,
  0,0
  };

void init()
{
 struct entry *p;
 for(p=keywords; p->token; p++)
  insert(p->lexptr,p->token);
}



void expr()
{
 lookahead = lexan();
 while(lookahead != DONE)
 switch(lookahead)
 {
  case ';' : if(chkParen>0)error(" ) required");
  else if(chkParen<0)error(" chkparen="0;" q="="0)" lookahead="="INT||lookahead="="CHAR||lookahead="="NUM||lookahead="="ID)">'&&lookahead!='='&&lookahead!=NUM&& lookahead!=ID)
  error(" <>' :
  match('>');
  if(lookahead!='='&&lookahead!=NUM&& lookahead!=ID)
  error(" > error");
  break;

  case NUM : match(NUM);
  if(lookahead=='(' )
  error(" NUM error");
  break;
  case ID : match(ID);
  if(lookahead=='('&& lookahead!=INT&& lookahead!=CHAR)
  error("ID error ");
  break;
  case IF : match(IF);match('(');expr();match(')');
  if(lookahead!=THEN)error("Required then");
  break;
  case THEN : match(THEN);
  if(lookahead!=IF&&lookahead!=ID&&lookahead!=ELSE)
  error("if or else or identifier required");
  break;
  case ELSE : match(ELSE);
  if(lookahead!=IF&&lookahead!=ID)
  error("If or id required");
  break;
  case DO : match(DO);
  break;
  case WHILE : match(WHILE);
  break;
  case REPEAT : match(REPEAT);
  break;
  case UNTIL : match(UNTIL);
  break;
  case BEGIN : chkBegin++;
  match(BEGIN);
  break;
  case END : chkBegin--;
  match(END);
  break;
  case INT : Int=1;
  if(q==0)
  {
  insert(str,ID);
  check=0;q=1;
  }
  else error("Duplicate declaration");
  match(INT);
  match(';');
  Int=0;
  break;
  case CHAR : if(q==0)

  {
  insert(str,ID);
  check=0;q=1;
  }
  else error("Duplicate declaration");
  match(CHAR);
  match(';');

  break;
  default :
  error("Unexpected");
  getch();exit(0);
 }

}

int lexan() /* lexixcal analyzer */
{
 int t;
 while(1)
 {
  t = getc(fp);
  if(t == ' '|| t == '\t') ; /* strip out white space */

  else if(t == '\n')
  {
  lineno = lineno + 1;

  }

  else if( isdigit(t))
  {
  ungetc(t,fp);
  scanf("%d",&tokenval);
  return NUM;
  }

  else if( isalpha(t)) /* t is a letter */
  {

  int p,b=0;

  while(isalnum(t)) /* t is a alphanumeric */
  {
  lexbuf[b]=t;
  t=getc(fp);
  b= b + 1;
  if(b >= BSIZE) error("compiler error");
  }

  lexbuf[b] = EOS;

  if(t != EOF)
  ungetc(t,fp);

  p = lookup(lexbuf);

  if(p == 0)
  {
  q=p;
  strcpy(str,lexbuf);
  return ID;
  }
  else check=1;

  tokenval = p;
  return symtable[p].token;
  }

  else if(t ==EOF) return DONE;

  else
  {
  tokenval = NONE;
  return t;
  }

 }
}


void main()
{
 clrscr();
 init();
 fp=fopen("in.cpp","r");
 fout=fopen("out.cpp","w");
 expr();
 if(chkBegin>0){error(" end required");getch();}
 else if(chkBegin<0){error(" int="="1)" lookahead =" lexan();" p =" lastentry;">0 ;p = p-1)
  if(strcmp(symtable[p].lexptr,s) == 0)
  return p;
 return 0;
}


int insert(char s[], int tok)
{
 int len;
 len = strlen(s);
 if(lastentry + 1 >=SYMMAX) error("symbol table full");
 if(lastchar + len +1 >= STRMAX) error("lexemes array full");
 lastentry = lastentry + 1;
 symtable[lastentry].token = tok;
 symtable[lastentry].lexptr = &lexemes[lastchar + 1];
 lastchar = lastchar + len +1;
 strcpy(symtable[lastentry].lexptr,s);
 return lastentry;
}

void error(char *m)
{
 //fprintf(stderr,"line %d: %s\n",lineno,m);
 fprintf(fout,"line %d: %s\n",lineno,m);
}