code: plan9front

ref: 5622b0bbd878dbc34045cc6fd37cffa64461eabe
dir: /sys/src/cmd/spin/tl_lex.c/

/***** tl_spin: tl_lex.c *****/

/*
 * This file is part of the public release of Spin. It is subject to the
 * terms in the LICENSE file that is included in this source directory.
 * Tool documentation is available at http://spinroot.com
 *
 * Based on the translation algorithm by Gerth, Peled, Vardi, and Wolper,
 * presented at the PSTV Conference, held in 1995, Warsaw, Poland 1995.
 */

#include <stdlib.h>
#include <ctype.h>
#include "tl.h"

static Symbol	*symtab[Nhash+1];
static int	tl_lex(void);
extern int tl_peek(int);

extern YYSTYPE	tl_yylval;
extern char	yytext[];

#define Token(y)        tl_yylval = tl_nn(y,ZN,ZN); return y

static void
tl_getword(int first, int (*tst)(int))
{	int i=0; int c;

	yytext[i++] = (char ) first;

	c = tl_Getchar();
	while (c != -1 && tst(c))
	{	yytext[i++] = (char) c;
		c = tl_Getchar();
	}

/*	while (tst(c = tl_Getchar()))
 *		yytext[i++] = c;
 */
	yytext[i] = '\0';
	tl_UnGetchar();
}

static int
tl_follow(int tok, int ifyes, int ifno)
{	int c;
	char buf[32];
	extern int tl_yychar;

	if ((c = tl_Getchar()) == tok)
		return ifyes;
	tl_UnGetchar();
	tl_yychar = c;
	sprintf(buf, "expected '%c'", tok);
	tl_yyerror(buf);	/* no return from here */
	return ifno;
}

int
tl_yylex(void)
{	int c = tl_lex();
#if 0
	printf("c = %c (%d)\n", c, c);
#endif
	return c;
}

static int
is_predicate(int z)
{	char c, c_prev = z;
	char want = (z == '{') ? '}' : ')';
	int i = 0, j, nesting = 0;
	char peek_buf[512];

	c = tl_peek(i++);	/* look ahead without changing position */
	while ((c != want || nesting > 0) && c != -1 && i < 2047)
	{	if (islower((int) c) || c == '_')
		{	peek_buf[0] = c;
			j = 1;
			while (j < (int) sizeof(peek_buf)
			&&    (isalnum((int)(c = tl_peek(i))) || c == '_'))
			{	peek_buf[j++] = c;
				i++;
			}
			c = 0;	/* make sure we don't match on z or want on the peekahead */
			if (j >= (int) sizeof(peek_buf))
			{	peek_buf[j-1] = '\0';
				fatal("name '%s' in ltl formula too long", peek_buf);
			}
			peek_buf[j] = '\0';
			if (strcmp(peek_buf, "always") == 0
			||  strcmp(peek_buf, "equivalent") == 0
			||  strcmp(peek_buf, "eventually") == 0
			||  strcmp(peek_buf, "until") == 0
			||  strcmp(peek_buf, "next") == 0
			||  strcmp(peek_buf, "c_expr") == 0)
			{	return 0;
			}
		} else
		{	int c_nxt = tl_peek(i);
			if (((c == 'U' || c == 'V' || c == 'X')
			&& !isalnum_(c_prev)
			&& (c_nxt == -1 || !isalnum_(c_nxt)))
			||  (c == '<' && c_nxt == '>')
			||  (c == '<' && c_nxt == '-')
			||  (c == '-' && c_nxt == '>')
			||  (c == '[' && c_nxt == ']'))
			{	return 0;
		}	}

		if (c == z)
		{	nesting++;
		}
		if (c == want)
		{	nesting--;
		}
		c_prev = c;
		c = tl_peek(i++);
	}
	return 1;
}

static void
read_upto_closing(int z)
{	char c, want = (z == '{') ? '}' : ')';
	int i = 0, nesting = 0;

	c = tl_Getchar();
	while ((c != want || nesting > 0) && c != -1 && i < 2047) /* yytext is 2048 */
	{	yytext[i++] = c;
		if (c == z)
		{	nesting++;
		}
		if (c == want)
		{	nesting--;
		}
		c = tl_Getchar();
	}
	yytext[i] = '\0';
}

static int
tl_lex(void)
{	int c;

	do {
		c = tl_Getchar();
		yytext[0] = (char ) c;
		yytext[1] = '\0';

		if (c <= 0)
		{	Token(';');
		}

	} while (c == ' ');	/* '\t' is removed in tl_main.c */

	if (c == '{' || c == '(')	/* new 6.0.0 */
	{	if (is_predicate(c))
		{	read_upto_closing(c);
			tl_yylval = tl_nn(PREDICATE,ZN,ZN);
			if (!tl_yylval)
			{	fatal("unexpected error 4", (char *) 0);
			}
			tl_yylval->sym = tl_lookup(yytext);
			return PREDICATE;
	}	}

	if (c == '}')
	{	tl_yyerror("unexpected '}'");
	}
	if (islower(c))
	{	tl_getword(c, isalnum_);
		if (strcmp("true", yytext) == 0)
		{	Token(TRUE);
		}
		if (strcmp("false", yytext) == 0)
		{	Token(FALSE);
		}
		if (strcmp("always", yytext) == 0)
		{	Token(ALWAYS);
		}
		if (strcmp("eventually", yytext) == 0)
		{	Token(EVENTUALLY);
		}
		if (strcmp("until", yytext) == 0)
		{	Token(U_OPER);
		}
#ifdef NXT
		if (strcmp("next", yytext) == 0)
		{	Token(NEXT);
		}
#endif
		if (strcmp("c_expr", yytext) == 0)
		{	Token(CEXPR);
		}
		if (strcmp("not", yytext) == 0)
		{	Token(NOT);
		}
		tl_yylval = tl_nn(PREDICATE,ZN,ZN);
		if (!tl_yylval)
		{	fatal("unexpected error 5", (char *) 0);
		}
		tl_yylval->sym = tl_lookup(yytext);
		return PREDICATE;
	}

	if (c == '<')
	{	c = tl_Getchar();
		if (c == '>')
		{	Token(EVENTUALLY);
		}
		if (c != '-')
		{	tl_UnGetchar();
			tl_yyerror("expected '<>' or '<->'");
		}
		c = tl_Getchar();
		if (c == '>')
		{	Token(EQUIV);
		}
		tl_UnGetchar();
		tl_yyerror("expected '<->'");
	}

	switch (c) {
	case '/' : c = tl_follow('\\', AND, '/'); break;
	case '\\': c = tl_follow('/', OR, '\\'); break;
	case '&' : c = tl_follow('&', AND, '&'); break;
	case '|' : c = tl_follow('|', OR, '|'); break;
	case '[' : c = tl_follow(']', ALWAYS, '['); break;
	case '-' : c = tl_follow('>', IMPLIES, '-'); break;
	case '!' : c = NOT; break;
	case 'U' : c = U_OPER; break;
	case 'V' : c = V_OPER; break;
#ifdef NXT
	case 'X' : c = NEXT; break;
#endif
	default  : break;
	}
	Token(c);
}

Symbol *
tl_lookup(char *s)
{	Symbol *sp;
	unsigned int h = hash(s);

	for (sp = symtab[h]; sp; sp = sp->next)
		if (strcmp(sp->name, s) == 0)
			return sp;

	sp = (Symbol *) tl_emalloc(sizeof(Symbol));
	sp->name = (char *) tl_emalloc((int) strlen(s) + 1);
	strcpy(sp->name, s);
	sp->next = symtab[h];
	symtab[h] = sp;

	return sp;
}

Symbol *
getsym(Symbol *s)
{	Symbol *n = (Symbol *) tl_emalloc(sizeof(Symbol));

	n->name = s->name;
	return n;
}