pass1.c

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

#define TAB_SIZE 100
#define SYMBOL_SIZE 30

#define OPCODE_SIZE 10

typedef unsigned int uint;

typedef struct{
	char sym[SYMBOL_SIZE];
	int loc;
}Symbol;

typedef struct{
	char opcode[OPCODE_SIZE];
	int val;
}Opcode;


Symbol symtab[TAB_SIZE];
Opcode optab[TAB_SIZE];


uint hash_str(char* str){
	uint hash = 0;
	uint n,i;


	for(i=0;*(str+i) != '\0';++i){
		if(isalpha(*(str+i)))
			n = tolower(*(str+i)) - 'a' + 1;
		else
			n = 27;
		hash = ((hash << 3) + n) % TAB_SIZE;
	}

	return hash;
}


void initialize_optab(char* filename){
	FILE *fp = fopen(filename,"r");
	char buf[OPCODE_SIZE];
	int val,hash;
	
	for(val=0;val<TAB_SIZE;++val){
		optab[val].val = -1;
		optab[val].opcode[0] = '\0';
	}

	if(fp !=NULL){
		while(!feof(fp)){
			fscanf(fp,"%s %d\n",buf,&val);
			hash = hash_str(buf);
			optab[hash].val = val;
			strcpy(optab[hash].opcode,buf);
		}
		fclose(fp);
	}
	else
		exit(1);

}

int in_optab(char* opcode){
	return optab[hash_str(opcode)].val != -1;
}

void initialize_symtab(){
	int i;
	for(i=0;i<TAB_SIZE;++i){
		symtab[i].sym[0] = '\0';
		symtab[i].loc = -1;
	}
}

void insert_to_symtab(char* sym,int loc){
	int hash = hash_str(sym);
	strcpy(symtab[hash].sym,sym);
	symtab[hash].loc=loc;
}


int in_symtab(char* sym){
	return symtab[hash_str(sym)].loc != -1;
}


void parse_line(char* line,char* label,char* opcode,char* operands){
	char* p=line,buf[3][50];
	int flag=0,i=0;
	for(;*p;p++)
		if(*p == ':'){
			flag=1;
			break;
		}


	p = strtok(line,": \n");

	while(p != NULL){
		sprintf(buf[i],"%s",p);
		++i;
		p = strtok(NULL,": \n");
	}

	label[0] = '\0';
	opcode[0] = '\0';
	operands[0] = '\0';

	switch(i){
		case 1:{
			strcpy(opcode,buf[0]);
			break;
		}

		case 2:{
			if(flag){
				strcpy(label,buf[0]);
				strcpy(opcode,buf[1]);
			}else{
				strcpy(opcode,buf[0]);
				strcpy(operands,buf[1]);
			}
			break;	
		}

		case 3:{
			strcpy(label,buf[0]);
			strcpy(opcode,buf[1]);
			strcpy(operands,buf[2]);
			break;	
		}
	}
}


int str_to_i(char* str){
	int dec = 0;
	for(;*str;++str)
		dec = dec*10 + (*str - '0');

	return dec;
}


void print_symtab(){
	int i=0;
	printf("\nSYMTAB\n");
	for(;i<TAB_SIZE;++i)
		if(symtab[i].loc != -1)
			printf("%s %d\n",symtab[i].sym,symtab[i].loc);
	printf("\n");
}

void print_optab(){
	int i=0;
	printf("\nOPTAB\n");
	for(;i<TAB_SIZE;++i)
		if(optab[i].val != -1)
			printf("%s %d\n",optab[i].opcode,optab[i].val);
	printf("\n");
}

int main(int argc,char* argv[]){
	char label[30],opcode[30],operands[30],str[100];
	FILE *fp = fopen(argv[1],"r");
	int locctr = 0,starting_addr=0;

	initialize_symtab();
	initialize_optab("optab.txt");

	if(fp == NULL)
		exit(1);

	fgets(str,100,fp);
	parse_line(str,label,opcode,operands);
	if(strcmp(opcode,"START") == 0){
		starting_addr = str_to_i(operands);
		locctr = starting_addr;
		fgets(str,100,fp);
		parse_line(str,label,opcode,operands);
	}

	while(!feof(fp) && strcmp(opcode,"END") != 0){
		printf("%d %s %s %s\n",locctr,label[0]?label:"  -  ",opcode,operands );
		if(label[0]){
			if(in_symtab(label)){
				printf("Duplicate Symbol!\n%s\n",label);
				exit(1);
			}else
				insert_to_symtab(label,locctr);
		}

		if(in_optab(opcode) || strcmp(opcode,"WORD") == 0)
			locctr+=3;
		else if(strcmp(opcode,"RESW") == 0)
			locctr+= 3*str_to_i(operands);
		else if(strcmp(opcode,"RESB") == 0)
			locctr+= str_to_i(operands);
		else if(strcmp(opcode,"BYTE") == 0)
			locctr += strlen(operands);
		else{
			printf("Invalid opcode!\n%s\n",opcode);
			exit(1);
		}
		fgets(str,100,fp);
		parse_line(str,label,opcode,operands);
		
	}
	print_optab();
	print_symtab();
	printf("Length: %d\n",locctr - starting_addr);
	fclose(fp);
	return 0;
}