expand.c

操作系统源代码

	struct strlist *sp;
	char *start;
	register char *p;
	char *q;
	char *ifs;

	start = string;
	if (ifslastp != NULL) {
		ifsp = &ifsfirst;
		do {
			p = string + ifsp->begoff;
			ifs = ifsp->nulonly? nullstr : ifsval();
			while (p < string + ifsp->endoff) {
				q = p;
				if (*p == CTLESC)
					p++;
				if (strchr(ifs, *p++)) {
					if (q > start || *ifs != ' ') {
						*q = '\0';
						sp = (struct strlist *)stalloc(sizeof *sp);
						sp->text = start;
						*arglist->lastp = sp;
						arglist->lastp = &sp->next;
					}
					if (*ifs == ' ') {
						for (;;) {
							if (p >= string + ifsp->endoff)
								break;
							q = p;
							if (*p == CTLESC)
								p++;
							if (strchr(ifs, *p++) == NULL) {
								p = q;
								break;
							}
						}
					}
					start = p;
				}
			}
		} while ((ifsp = ifsp->next) != NULL);
		if (*start || (*ifs != ' ' && start > string)) {
			sp = (struct strlist *)stalloc(sizeof *sp);
			sp->text = start;
			*arglist->lastp = sp;
			arglist->lastp = &sp->next;
		}
	} else {
		sp = (struct strlist *)stalloc(sizeof *sp);
		sp->text = start;
		*arglist->lastp = sp;
		arglist->lastp = &sp->next;
	}
}



/*
 * Expand shell metacharacters.  At this point, the only control characters
 * should be escapes.  The results are stored in the list exparg.
 */

char *expdir;


STATIC void
expandmeta(str)
	struct strlist *str;
	{
	char *p;
	struct strlist **savelastp;
	struct strlist *sp;
	char c;

	while (str) {
		if (fflag)
			goto nometa;
		p = str->text;
#if UDIR
		if (p[0] == '/' && p[1] == 'u' && p[2] == '/')
			str->text = p = expudir(p);
#endif
#if TILDE
		if (p[0] == '~')
			str->text = p = expudir(p);
#endif
		for (;;) {			/* fast check for meta chars */
			if ((c = *p++) == '\0')
				goto nometa;
			if (c == '*' || c == '?' || c == '[' || c == '!')
				break;
		}
		savelastp = exparg.lastp;
		INTOFF;
		if (expdir == NULL)
			expdir = ckmalloc(1024); /* I hope this is big enough */
		expmeta(expdir, str->text);
		ckfree(expdir);
		expdir = NULL;
		INTON;
		if (exparg.lastp == savelastp) {
			if (! zflag) {
nometa:
				*exparg.lastp = str;
				rmescapes(str->text);
				exparg.lastp = &str->next;
			}
		} else {
			*exparg.lastp = NULL;
			*savelastp = sp = expsort(*savelastp);
			while (sp->next != NULL)
				sp = sp->next;
			exparg.lastp = &sp->next;
		}
		str = str->next;
	}
}


#if UDIR || TILDE
/*
 * UDIR: Expand /u/username into the home directory for the specified user.
 * TILDE: Expand ~username into the home directory for the specified user.
 * We hope not to use the getpw stuff here, because then we would have to load
 * in stdio and who knows what else.  With networked password files there is
 * no choice alas.
 */

#define MAXLOGNAME 32
#define MAXPWLINE 128

char *pfgets();


STATIC char *
expudir(path)
	char *path;
	{
	register char *p, *q, *r;
	char name[MAXLOGNAME];
	char line[MAXPWLINE];
	int i;
#if USEGETPW
	struct passwd *pw;
#endif

	r = path;				/* result on failure */
	p = r + (*r == '~' ? 1 : 3);	/* the 1 skips "~", 3 skips "/u/" */
	q = name;
	while (*p && *p != '/') {
		if (q >= name + MAXLOGNAME - 1)
			return r;		/* fail, name too long */
		*q++ = *p++;
	}
	*q = '\0';

#if TILDE
	if (*name == 0 && *r == '~') {
		/* null name, use $HOME */
		if ((q = lookupvar("HOME")) == NULL)
			return r;		/* fail, home not set */
		i = strlen(q);
		r = stalloc(i + strlen(p) + 1);
		scopy(q, r);
		scopy(p, r + i);
		TRACE(("expudir converts %s to %s\n", path, r));
		didudir = 1;
		path = r;
		return r;
	}
#endif
#if !USEGETPW	/* can do without the bloat */
	setinputfile("/etc/passwd", 1);
	q = line + strlen(name);
	while (pfgets(line, MAXPWLINE) != NULL) {
		if (line[0] == name[0] && prefix(name, line) && *q == ':') {
			/* skip to start of home directory */
			i = 4;
			do {
				while (*++q && *q != ':');
			} while (--i > 0);
			if (*q == '\0')
				break;		/* fail, corrupted /etc/passwd */
			q++;
			for (r = q ; *r && *r != '\n' && *r != ':' ; r++);
			*r = '\0';		/* nul terminate home directory */
			i = r - q;		/* i = strlen(q) */
			r = stalloc(i + strlen(p) + 1);
			scopy(q, r);
			scopy(p, r + i);
			TRACE(("expudir converts %s to %s\n", path, r));
			didudir = 1;
			path = r;		/* succeed */
			break;
		}
	}
	popfile();
#else
	if ((pw = getpwnam(name)) != NULL) {
		/* user exists */
		q = pw->pw_dir;
		i = strlen(q);
		r = stalloc(i + strlen(p) + 1);
		scopy(q, r);
		scopy(p, r + i);
		TRACE(("expudir converts %s to %s\n", path, r));
		didudir = 1;
		path = r;
	}
	endpwent();
#endif /* USEGETPW */

	return r;
}
#endif


/*
 * Do metacharacter (i.e. *, ?, [...]) expansion.
 */

STATIC void
expmeta(enddir, name)
	char *enddir;
	char *name;
	{
	register char *p;
	char *q;
	char *start;
	char *endname;
	int metaflag;
	struct stat statb;
	DIR *dirp;
	struct dirent *dp;
	int atend;
	int matchdot;

	metaflag = 0;
	start = name;
	for (p = name ; ; p++) {
		if (*p == '*' || *p == '?')
			metaflag = 1;
		else if (*p == '[') {
			q = p + 1;
			if (*q == '!')
				q++;
			for (;;) {
				if (*q == CTLESC)
					q++;
				if (*q == '/' || *q == '\0')
					break;
				if (*++q == ']') {
					metaflag = 1;
					break;
				}
			}
		} else if (*p == '!' && p[1] == '!'	&& (p == name || p[-1] == '/')) {
			metaflag = 1;
		} else if (*p == '\0')
			break;
		else if (*p == CTLESC)
			p++;
		if (*p == '/') {
			if (metaflag)
				break;
			start = p + 1;
		}
	}
	if (metaflag == 0) {	/* we've reached the end of the file name */
		if (enddir != expdir)
			metaflag++;
		for (p = name ; ; p++) {
			if (*p == CTLESC)
				p++;
			*enddir++ = *p;
			if (*p == '\0')
				break;
		}
		if (metaflag == 0 || stat(expdir, &statb) >= 0)
			addfname(expdir);
		return;
	}
	endname = p;
	if (start != name) {
		p = name;
		while (p < start) {
			if (*p == CTLESC)
				p++;
			*enddir++ = *p++;
		}
	}
	if (enddir == expdir) {
		p = ".";
	} else if (enddir == expdir + 1 && *expdir == '/') {
		p = "/";
	} else {
		p = expdir;
		enddir[-1] = '\0';
	}
	if ((dirp = opendir(p)) == NULL)
		return;
	if (enddir != expdir)
		enddir[-1] = '/';
	if (*endname == 0) {
		atend = 1;
	} else {
		atend = 0;
		*endname++ = '\0';
	}
	matchdot = 0;
	if (start[0] == '.' || start[0] == CTLESC && start[1] == '.')
		matchdot++;
	while (! int_pending() && (dp = readdir(dirp)) != NULL) {
		if (dp->d_name[0] == '.' && ! matchdot)
			continue;
		if (patmatch(start, dp->d_name)) {
			if (atend) {
				scopy(dp->d_name, enddir);
				addfname(expdir);
			} else {
				char *q;
				for (p = enddir, q = dp->d_name ; *p++ = *q++ ;);
				p[-1] = '/';
				expmeta(p, endname);
			}
		}
	}
	closedir(dirp);
	if (! atend)
		endname[-1] = '/';
}


/*
 * Add a file name to the list.
 */

STATIC void
addfname(name)
	char *name;
	{
	char *p;
	struct strlist *sp;

	p = stalloc(strlen(name) + 1);
	scopy(name, p);
	sp = (struct strlist *)stalloc(sizeof *sp);
	sp->text = p;
	*exparg.lastp = sp;
	exparg.lastp = &sp->next;
}


/*
 * Sort the results of file name expansion.  It calculates the number of
 * strings to sort and then calls msort (short for merge sort) to do the
 * work.
 */

STATIC struct strlist *
expsort(str)
	struct strlist *str;
	{
	int len;
	struct strlist *sp;

	len = 0;
	for (sp = str ; sp ; sp = sp->next)
		len++;
	return msort(str, len);
}


STATIC struct strlist *
msort(list, len)
	struct strlist *list;
	{
	struct strlist *p, *q;
	struct strlist **lpp;
	int half;
	int n;

	if (len <= 1)
		return list;
	half = len >> 1;      
	p = list;
	for (n = half ; --n >= 0 ; ) {
		q = p;
		p = p->next;
	}
	q->next = NULL;			/* terminate first half of list */
	q = msort(list, half);		/* sort first half of list */
	p = msort(p, len - half);		/* sort second half */
	lpp = &list;
	for (;;) {
		if (strcmp(p->text, q->text) < 0) {
			*lpp = p;
			lpp = &p->next;
			if ((p = *lpp) == NULL) {
				*lpp = q;
				break;
			}
		} else {
			*lpp = q;
			lpp = &q->next;
			if ((q = *lpp) == NULL) {
				*lpp = p;
				break;
			}
		}
	}
	return list;
}



/*
 * Returns true if the pattern matches the string.
 */

int
patmatch(pattern, string)
	char *pattern;
	char *string;
	{
	if (pattern[0] == '!' && pattern[1] == '!')
		return 1 - pmatch(pattern + 2, string);
	else
		return pmatch(pattern, string);
}


STATIC int
pmatch(pattern, string)
	char *pattern;
	char *string;
	{
	register char *p, *q;
	register char c;

	p = pattern;
	q = string;
	for (;;) {
		switch (c = *p++) {
		case '\0':
			goto breakloop;
		case CTLESC:
			if (*q++ != *p++)
				return 0;
			break;
		case '?':
			if (*q++ == '\0')
				return 0;
			break;
		case '*':
			c = *p;
			if (c != CTLESC && c != '?' && c != '*' && c != '[') {
				while (*q != c) {
					if (*q == '\0')
						return 0;
					q++;
				}
			}
			do {
				if (pmatch(p, q))
					return 1;
			} while (*q++ != '\0');
			return 0;
		case '[': {
			char *endp;
			int invert, found;
			char chr;

			endp = p;
			if (*endp == '!')
				endp++;
			for (;;) {
				if (*endp == '\0')
					goto dft;		/* no matching ] */
				if (*endp == CTLESC)
					endp++;
				if (*++endp == ']')
					break;
			}
			invert = 0;
			if (*p == '!') {
				invert++;
				p++;
			}
			found = 0;
			chr = *q++;
			c = *p++;
			do {
				if (c == CTLESC)
					c = *p++;
				if (*p == '-' && p[1] != ']') {
					p++;
					if (*p == CTLESC)
						p++;
					if (chr >= c && chr <= *p)
						found = 1;
					p++;
				} else {
					if (chr == c)
						found = 1;
				}
			} while ((c = *p++) != ']');
			if (found == invert)
				return 0;
			break;
		}
dft:	    default:
			if (*q++ != c)
				return 0;
			break;
		}
	}
breakloop:
	if (*q != '\0')
		return 0;
	return 1;
}



/*
 * Remove any CTLESC characters from a string.
 */

void
rmescapes(str)
	char *str;
	{
	register char *p, *q;

	p = str;
	while (*p != CTLESC) {
		if (*p++ == '\0')
			return;
	}
	q = p;
	while (*p) {
		if (*p == CTLESC)
			p++;
		*q++ = *p++;
	}
	*q = '\0';
}



/*
 * See if a pattern matches in a case statement.
 */

int
casematch(pattern, val)
	union node *pattern;
	char *val;
	{
	struct stackmark smark;
	int result;
	char *p;

	setstackmark(&smark);
	argbackq = pattern->narg.backquote;
	STARTSTACKSTR(expdest);
	ifslastp = NULL;
	/* Preserve any CTLESC characters inserted previously, so that
	   we won't expand reg exps which are inside strings.  */
	argstr(pattern->narg.text, 1);
	STPUTC('\0', expdest);
	p = grabstackstr(expdest);
	result = patmatch(p, val);
	popstackmark(&smark);
	return result;
}