acd.c

操作系统源代码

				name= allocate(name, (n*= 2) * sizeof(char));
			getdesc();
		} while (extalnum(dch));
	} else {
		/* $* */
		name[i++]= dch;
		getdesc();
	}
	name[i++]= 0;
	name= allocate(name, i * sizeof(char));
	tok->type= SUBST;
	tok->subst= newcell();
	tok->subst->type= WORD;
	tok->subst->name= name;
	tok->subst= inc(tok->subst);
	return inc(tok);
}

typedef enum how { SUPERFICIAL, PARTIAL, FULL, EXPLODE, IMPLODE } how_t;

cell_t *explode(cell_t *p, how_t how);

cell_t *get_string(cell_t **pp)
/* Get a string: A series of letters and substs.  Special tokens '=', '+', '-'
 * and '*' are also recognized if on their own.  A finished string is "exploded"
 * to a word if it consists of letters only.
 */
{
	cell_t *p= *pp, *s= nil, **ps= &s;
	int quoted= 0;

	while (p != nil) {
		switch (p->type) {
		case STRING:
			quoted= 1;
			dec(p);
			break;
		case EQUALS:
		case PLUS:
		case MINUS:
		case STAR:
		case SUBST:
		case LETTER:
			*ps= cons(STRING, p);
			ps= &(*ps)->cdr;
			break;
		default:
			goto got_string;
		}
		p= get_token();
	}
    got_string:
	*pp= p;

	/* A single special token must be folded up. */
	if (!quoted && s != nil && s->cdr == nil) {
		switch (s->car->type) {
		case EQUALS:
		case PLUS:
		case MINUS:
		case STAR:
		case SUBST:
			return go(s, s->car);
		}
	}

	/* Go over the string changing '=', '+', '-', '*' to letters. */
	for (p= s; p != nil; p= p->cdr) {
		int c= 0;

		switch (p->car->type) {
		case EQUALS:
			c= '='; break;
		case PLUS:
			c= '+'; break;
		case MINUS:
			c= '-'; break;
		case STAR:
			c= '*'; break;
		}
		if (c != 0) {
			dec(p->car);
			p->car= newcell();
			p->car->type= LETTER;
			p->car->letter= c;
			p->car= inc(p->car);
		}
	}
	return explode(s, SUPERFICIAL);
}

cell_t *get_list(cell_t **pp, type_t stop)
/* Read a series of tokens upto a token of type "stop". */
{
	cell_t *p= *pp, *l= nil, **pl= &l;

	while (p != nil && p->type != stop
				&& !(stop == EOLN && p->type == SEMI)) {
		switch (p->type) {
		case WHITE:
		case COMMENT:
		case SEMI:
		case EOLN:
			dec(p);
			p= get_token();
			break;
		case OPEN:
			/* '(' words ')'. */
			dec(p);
			p= get_token();
			*pl= cons(CELL, get_list(&p, CLOSE));
			pl= &(*pl)->cdr;
			dec(p);
			p= get_token();
			break;
		case CLOSE:
			/* Unexpected closing parenthesis. (*/
			fprintf(stderr, "\"%s\", line %u: unmatched ')'\n",
				descr, lineno);
			action= 0;
			dec(p);
			p= get_token();
			break;
		case INPUT:
		case OUTPUT:
			*pl= cons(CELL, p);
			pl= &(*pl)->cdr;
			p= get_token();
			break;
		case STRING:
		case EQUALS:
		case PLUS:
		case MINUS:
		case STAR:
		case LETTER:
		case SUBST:
			*pl= cons(CELL, get_string(&p));
			pl= &(*pl)->cdr;
			break;
		default:
			assert(0);
		}
	}

	if (p == nil && stop == CLOSE) {
		/* Couldn't get the closing parenthesis. */
		fprintf(stderr, "\"%s\", lines %u-%u: unmatched '('\n",	/*)*/
			descr, pc->lineno, lineno);
		action= 0;
	}
	*pp= p;
	return l;
}

program_t *get_line(cell_t *file)
{
	program_t *l;
	cell_t *p;
	static keep_indent= 0;
	static unsigned old_indent= 0;

	/* Skip leading whitespace to determine the indentation level. */
	indent= 0;
	while ((p= get_token()) != nil && p->type == WHITE) dec(p);

	if (p == nil) return nil;		/* EOF */

	if (p->type == EOLN) indent= old_indent;	/* Empty line. */

	/* Make a program line. */
	pc= l= allocate(nil, sizeof(*l));

	l->next= nil;
	l->file= inc(file);
	l->indent= keep_indent ? old_indent : indent;
	l->lineno= lineno;

	l->line= get_list(&p, EOLN);

	/* If the line ended in a semicolon then keep the indentation level. */
	keep_indent= (p != nil && p->type == SEMI);
	old_indent= l->indent;

	dec(p);

	if (verbose >= 4) {
		if (l->line == nil)
			fputc('\n', stdout);
		else {
			printf("%*s", (int) l->indent, "");
			prin2n(l->line);
		}
	}
	return l;
}

program_t *get_prog(void)
/* Read the description file into core. */
{
	cell_t *file;
	program_t *prog, **ppg= &prog;

	descr= copystr(descr);

	if (descr[0] == '-' && descr[1] == 0) {
		/* -descr -: Read from standard input. */
		deallocate(descr);
		descr= copystr("stdin");
		dfp= stdin;
	} else {
		char *d= descr;

		if (*d == '.' && *++d == '.') d++;
		if (*d != '/') {
			/* -descr name: Read /usr/lib/<name>/descr. */

			d= allocate(nil, sizeof(LIB) +
					(strlen(descr) + 7) * sizeof(*d));
			sprintf(d, "%s/%s/descr", LIB, descr);
			deallocate(descr);
			descr= d;
		}
		if ((dfp= fopen(descr, "r")) == nil) fatal(descr);
	}
	file= findword(descr);
	deallocate(descr);
	descr= file->name;

	/* Preread the first character. */
	dch= 0;
	lineno= 1;
	indent= 0;
	getdesc();

	while ((*ppg= get_line(file)) != nil) ppg= &(*ppg)->next;

	if (dfp != stdin) (void) fclose(dfp);
	dec(file);

	return prog;
}

void makenames(cell_t ***ppr, cell_t *s, char **name, size_t i, size_t *n)
/* Turn a string of letters and lists into words.  A list denotes a choice
 * between several paths, like a search on $PATH.
 */
{
	cell_t *p, *q;
	size_t len;

	/* Simply add letters, skip empty lists. */
	while (s != nil && (s->car == nil || s->car->type == LETTER)) {
		if (s->car != nil) {
			if (i == *n) *name= allocate(*name,
						(*n *= 2) * sizeof(**name));
			(*name)[i++]= s->car->letter;
		}
		s= s->cdr;
	}

	/* If the end is reached then make a word out of the result. */
	if (s == nil) {
		**ppr= cons(CELL, findnword(*name, i));
		*ppr= &(**ppr)->cdr;
		return;
	}

	/* Elements of a list must be tried one by one. */
	p= s->car;
	s= s->cdr;

	while (p != nil) {
		if (p->type == WORD) {
			q= p; p= nil;
		} else {
			assert(p->type == CELL);
			q= p->car; p= p->cdr;
			assert(q != nil);
			assert(q->type == WORD);
		}
		len= strlen(q->name);
		if (i + len > *n) *name= allocate(*name,
					(*n += i + len) * sizeof(**name));
		memcpy(*name + i, q->name, len);

		makenames(ppr, s, name, i+len, n);
	}
}

int constant(cell_t *p)
/* See if a string has been partially evaluated to a constant so that it
 * can be imploded to a word.
 */
{
	while (p != nil) {
		switch (p->type) {
		case CELL:
		case STRING:
			if (!constant(p->car)) return 0;
			p= p->cdr;
			break;
		case SUBST:
			return 0;
		default:
			return 1;
		}
	}
	return 1;
}

cell_t *evaluate(cell_t *p, how_t how);

cell_t *explode(cell_t *s, how_t how)
/* Explode a string with several choices to just one list of choices. */
{
	cell_t *t, *r= nil, **pr= &r;
	size_t i, n;
	char *name;
	struct stat st;

	if (how >= PARTIAL) {
		/* Evaluate the string, expanding substitutions. */
		while (s != nil) {
			assert(s->type == STRING);
			t= inc(s->car);
			s= go(s, s->cdr);

			t= evaluate(t, how == IMPLODE ? EXPLODE : how);

			/* A list of one element becomes that element. */
			if (t != nil && t->type == CELL && t->cdr == nil)
				t= go(t, t->car);

			/* Append the result, trying to flatten it. */
			*pr= t;

			/* Find the end of what has just been added. */
			while ((*pr) != nil) {
				*pr= append(STRING, *pr);
				pr= &(*pr)->cdr;
			}
		}
		s= r;
	}

	/* Is the result a simple string of constants? */
	if (how <= PARTIAL && !constant(s)) return s;

	/* Explode the string to all possible choices, by now the string is
	 * a series of characters, words and lists of words.
	 */
	r= nil; pr= &r;
	name= allocate(nil, (n= 16) * sizeof(char));
	i= 0;

	makenames(&pr, s, &name, i, &n);
	deallocate(name);
	assert(r != nil);
	dec(s);
	s= r;

	/* "How" may specify that a choice must be made. */
	if (how == IMPLODE) {
		if (s->cdr != nil) {
			/* More than one choice, find the file. */
			do {
				assert(s->car->type == WORD);
				if (stat(s->car->name, &st) >= 0)
					return go(r, s->car);	/* Found. */
			} while ((s= s->cdr) != nil);
		}
		/* The first name is the default if nothing is found. */
		return go(r, r->car);
	}

	/* If the result is a list of one word then return that word, otherwise
	 * turn it into a string again unless this explode has been called
	 * by another explode.  (Exploding a string inside a string, the joys
	 * of recursion.)
	 */
	if (s->cdr == nil) return go(s, s->car);

	return how >= EXPLODE ? s : cons(STRING, s);
}

void modify(cell_t **pp, cell_t *p, type_t mode)
/* Add or remove the element p from the list *pp. */
{
	while (*pp != nil) {
		*pp= append(CELL, *pp);

		if ((*pp)->car == p) {
			/* Found it, if adding then exit, else remove. */
			if (mode == PLUS) break;
			*pp= go(*pp, (*pp)->cdr);
		} else
			pp= &(*pp)->cdr;
	}

	if (*pp == nil && mode == PLUS) {
		/* Not found, add it. */
		*pp= cons(CELL, p);
	} else
		dec(p);
}

int tainted(cell_t *p)
/* A variable is tainted (must be substituted) if either it is marked as a
 * local variable, or some subst in its value is.
 */
{
	if (p == nil) return 0;

	switch (p->type) {
	case CELL:
	case STRING:
		return tainted(p->car) || tainted(p->cdr);
	case SUBST:
		return p->subst->flags & W_LOCAL || tainted(p->subst->value);
	default:
		return 0;
	}
}

cell_t *evaluate(cell_t *p, how_t how)
/* Evaluate an expression, usually the right hand side of an assignment. */
{
	cell_t *q, *t, *r= nil, **pr= &r;
	type_t mode;

	if (p == nil) return nil;

	switch (p->type) {
	case CELL:
		break;	/* see below */
	case STRING:
		return explode(p, how);
	case SUBST:
		if (how >= FULL || tainted(p))
			p= evaluate(go(p, p->subst->value), how);
		return p;
	case EQUALS:
		fprintf(stderr,
			"\"%s\", line %u: Can't do nested assignments\n",
			descr, pc->lineno);
		action= 0;
		dec(p);
		return nil;
	case LETTER:
	case WORD:
	case INPUT:
	case OUTPUT:
	case PLUS:
	case MINUS:
		return p;
	default:
		assert(0);
	}

	/* It's a list, see if there is a '*' there forcing a full expansion,
	 * or a '+' or '-' forcing an implosive expansion.  (Yeah, right.)
	 * Otherwise evaluate each element.
	 */
	q = inc(p);
	while (p != nil) {
		if ((t= p->car) != nil) {
			if (t->type == STAR) {
				if (how < FULL) how= FULL;
				dec(q);
				*pr= evaluate(go(p, p->cdr), how);
				return r;
			}
			if (how>=FULL && (t->type == PLUS || t->type == MINUS))
				break;
		}

		t= evaluate(inc(t), how);
		assert(p->type == CELL);
		p= go(p, p->cdr);

		if (how >= FULL) {
			/* Flatten the list. */
			*pr= t;
		} else {
			/* Keep the nested list structure. */
			*pr= cons(CELL, t);
		}

		/* Find the end of what has just been added. */
		while ((*pr) != nil) {
			*pr= append(CELL, *pr);
			pr= &(*pr)->cdr;
		}
	}

	if (p == nil) {
		/* No PLUS or MINUS: done. */
		dec(q);
		return r;
	}

	/* A PLUS or MINUS, reevaluate the original list implosively. */
	if (how < IMPLODE) {
		dec(r);
		dec(p);
		return evaluate(q, IMPLODE);
	}
	dec(q);

	/* Execute the PLUSes and MINUSes. */
	while (p != nil) {
		t= inc(p->car);
		p= go(p, p->cdr);

		if (t != nil && (t->type == PLUS || t->type == MINUS)) {
			/* Change the add/subtract mode. */
			mode= t->type;
			dec(t);
			continue;
		}

		t= evaluate(t, IMPLODE);

		/* Add or remove all elements of t to/from r. */
		while (t != nil) {
			if (t->type == CELL) {
				modify(&r, inc(t->car), mode);
			} else {
				modify(&r, t, mode);
				break;
			}
			t= go(t, t->cdr);
		}
	}
	return r;
}

/* An ACD program can be in three phases: Initialization (the first run
 * of the program), argument scanning, and compilation.
 */
typedef enum phase { INIT, SCAN, COMPILE } phase_t;

phase_t phase;

typedef struct rule {		/* Transformation rule. */
	struct rule	*next;
	char		type;		/* arg, transform, combine */
	char		flags;
	unsigned short	npaths;		/* Number of paths running through. */
#	define	match	from		/* Arg matching strings. */
	cell_t		*from;		/* Transformation source suffixe(s) */
	cell_t		*to;		/* Destination suffix. */
	cell_t		*wait;		/* Files waiting to be transformed. */
	program_t	*prog;		/* Program to execute. */
	struct rule	*path;		/* Transformation path. */
} rule_t;

typedef enum ruletype { ARG, PREFER, TRANSFORM, COMBINE } ruletype_t;

#define R_PREFER	0x01		/* A preferred transformation. */

rule_t *rules= nil;

void newrule(ruletype_t type, cell_t *from, cell_t *to)
/* Make a new rule cell. */
{
	rule_t *r= nil, **pr= &rules;

	/* See if there is a rule with the same suffixes, probably a matching
	 * transform and prefer, or a re-execution of the same arg command.
	 */
	while ((r= *pr) != nil) {
		if (r->from == from && r->to == to) break;
		pr= &r->next;
	}

	if (*pr == nil) {
		/* Add a new rule. */
		*pr= r= allocate(nil, sizeof(*r));

		r->next= nil;
		r->type= type;
		r->flags= 0;
		r->from= r->to= r->wait= nil;
		r->path= nil;
	}
	if (type == TRANSFORM) r->type= TRANSFORM;
	if (type == PREFER) r->flags|= R_PREFER;
	if (type != PREFER) r->prog= pc;
	dec(r->from); r->from= from;
	dec(r->to); r->to= to;
}

int talk(void)
/* True if verbose and if so indent what is to come. */
{
	if (verbose < 3) return 0;
	printf("%*s", (int) pc->indent, "");
	return 1;
}

void unix_exec(cell_t *c)
/* Execute the list of words p as a UNIX command. */
{
	cell_t *v, *a;
	int fd[2];
	int *pf;
	char **argv;
	int i, n;
	int r, pid, status;

	if (action == 0) return;	/* Error mode. */

	if (talk() || verbose >= 2) prin2n(c);

	fd[0]= fd[1]= -1;

	argv= allocate(nil, (n= 16) * sizeof(*argv));
	i= 0;

	/* Gather argv[] and scan for I/O redirection. */
	for (v= c; v != nil; v= v->cdr) {
		a= v->car;
		pf= nil;
		if (a->type == INPUT) pf= &fd[0];
		if (a->type == OUTPUT) pf= &fd[1];

		if (pf == nil) {
			/* An argument. */
			argv[i++]= a->name;
			if (i==n) argv= allocate(argv, (n*= 2) * sizeof(*argv));
			continue;
		}
		/* I/O redirection. */
		if ((v= v->cdr) == nil || (a= v->car)->type != WORD) {
			fprintf(stderr,
			"\"%s\", line %u: I/O redirection without a file\n",
				descr, pc->lineno);
			action= 0;
			if (v == nil) break;
		}
		if (*pf >= 0) close(*pf);

		if (action >= 2
			&& (*pf= open(a->name, pf == &fd[0] ? O_RDONLY
				: O_WRONLY | O_CREAT | O_TRUNC, 0666)) < 0
		) {
			report(a->name);
			action= 0;
		}
	}
	argv[i]= nil;

	if (i >= 0 && action > 0 && verbose == 1) {
		char *name= strrchr(argv[0], '/');

		if (name == nil) name= argv[0]; else name++;

		printf("%s\n", name);
	}
	if (i >= 0 && action >= 2) {
		/* Really execute the command. */
		fflush(stdout);
		switch (pid= fork()) {
		case -1:
			fatal("fork()");
		case 0:
			if (fd[0] >= 0) { dup2(fd[0], 0); close(fd[0]); }
			if (fd[1] >= 0) { dup2(fd[1], 1); close(fd[1]); }