path: root/5.18.c

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

#define MAXTOKEN	100
#define OUTLEN		1000
#define MAXBUFF		100

enum { NAME, PARENS, BRACKETS };
enum { NO, YES };

void err(char *s);
void errmsg(char *s);

void dcl(void);
void dirdcl(void);

int gettoken(void);
int tokentype;
int prevtoken;
char token[MAXTOKEN];
char name[MAXTOKEN];
char datatype[MAXTOKEN];
char out[OUTLEN];

char buff[MAXBUFF];
static size_t top;

void errmsg(char *s)
{
	printf("err: %s\n", s);
	prevtoken = YES;
}

void err(char *s)
{
	printf("fatal error: %s\n", s);
	exit(1);
}

void dcl(void)
{
	int ns;

	for (ns = 0; gettoken() == '*';)
		ns++;
	dirdcl();
	while (ns-- > 0)
		strcat(out, " pointer to");
}

void dirdcl(void)
{
	int type;

	if (tokentype == '(') {
		dcl();
		if (tokentype != ')')
			errmsg("missing )");
	} else if (tokentype == NAME) {
		strcpy(name, token);
	} else {
		errmsg("expected name or (dcl)");
	}

	while ((type = gettoken()) == PARENS || type == BRACKETS) {
		if (type == PARENS) {
			strcat(out, " function returning");
		} else {
			strcat(out, " array");
			strcat(out, token);
			strcat(out, " of");
		}
	}
}

int gettoken(void)
{
	char c, *p = token;
	char getch(void);
	void ungetch(char);

	if (prevtoken == YES) {
		prevtoken = NO;
		return tokentype;
	}

	while(isblank(c = getch()))
		;

	if (c == '/') { /* ignore comments */
		if ((c = getch()) == '/') {
			while ((c = getch()) != '\n')
				;
		} else if (c == '*') {
			while (getch() != '*' || (c = getch()) != '/')
				if (c == '*')
					ungetch('*');
			return gettoken();
		} else {
			ungetch(c);
			c = '/';
		}
	}

	if (c == '(') {
		if ((c = getch()) == ')') {
			strcpy(token, "()");
			return tokentype = PARENS;
		} else {
			ungetch(c);
			return tokentype = '(';
		}
	} else if (c == '[') {
		for (*p++ = '['; (*p++ = getch()) != ']';)
			;
		*p = '\0';
		return tokentype = BRACKETS;
	} else if (isalpha(c)) {
		for (*p++ = c; isalnum(c = getch());)
			*p++ = c;
		*p = '\0';
		ungetch(c);
		return tokentype = NAME;
	} else {
		return tokentype = c;
	}
}

void ungetch(char c)
{
	if (top < MAXBUFF)
		buff[top++] = c;
	else
		err("stack overflow");
}

char getch(void)
{
	return (top > 0) ? buff[--top] : getchar();
}

int main(void)
{
	while (gettoken() != EOF) {
		if (tokentype == '\n') /* skip empty lines */
			continue;
		strcpy(datatype, token);
		out[0] = '\0';
		dcl();
		if (tokentype != '\n')
			printf("synatx error\n");
		printf("%s: %s %s\n", name, out, datatype);
	}
	return 0;
}