[patch] Re: getfsent(3) and spaces in fstab

[Simon Barner]

Hi Terry,

> You need to add '\\' to the list of characters that can be escaped,
> or you've just traded the inability to specify '\t' or ' ' for an
> inability to speciy '\\'.

Oh yes, I have overlook this special case. I revised my patch in order
to get this right.

Simon
-------------- next part --------------
--- fstab.c.orig	Fri Aug  1 17:18:00 2003
+++ fstab.c	Mon Aug  4 01:46:55 2003
@@ -49,6 +49,7 @@
 #include <errno.h>
 #include <fstab.h>
 #include <paths.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -84,6 +85,140 @@
 	_fs_fstab.fs_spec = buf;
 }
 
+/*
+ * Get next token from string *stringp, where tokens are possibly-empty
+ * strings separated by characters from delim.
+ *
+ * Writes NULs into the string at *stringp to end tokens.
+ * delim need not remain constant from call to call.
+ * On return, *stringp points past the last NUL written (if there might
+ * be further tokens), or is NULL (if there are definitely no more tokens).
+ *
+ * If *stringp is NULL, es_strsep returns NULL.
+ *
+ * In contrast to strsep(3), es_strsep will allow escaped delimiters
+ * within a token. These escaped characters as well as the special case
+ * '\\' will be converted appropriately ('\<delim>' -> '<delim>, '\\' -> '\'
+ *
+ */
+char *
+es_strsep(char **stringp, const char *delim)
+{
+	bool	escaped=false;
+	char	*s, *t, *u;
+	int	i;
+
+
+	if (*stringp == '\0')	/* empty string */
+		return NULL;
+	s = *stringp;
+	s += strspn (s, delim);	/* skip delimiters */
+
+	if (*s == '\0')		/* string consists only of delimiters */
+		return NULL;
+	
+	/*
+	 * skip a string consisting of non-delimiters,
+	 * escapted delimiters or '\\'
+	*/
+	for (t = s; *t != '\0'; ++t) {
+		if (*t == '\\') {
+		    if (escaped) {	/* convert \\ to \ */
+			--t;
+		        u = t;
+		        escaped = false;
+		        while (u[0] != '\0') {
+		            u[0] = u[1];
+		            ++u;
+		        }
+		    } else		/* start \-Sequence */
+			escaped = true;
+		    continue;
+		}
+		
+		/* search for delimiter */
+		for (i=0; delim[i] != '\0'; ++i) {
+		    if (*t == delim[i])
+		        break;
+		}
+		
+		/* un-escaped delimiter found => end of token */
+		if (!escaped && delim[i] != '\0')
+		    break;
+		    
+		/* escaped delimiter found => remove / */
+		if (escaped) {
+    		    --t;
+	            u = t;
+                    escaped = false;
+		    while (u[0] != '\0') {
+		        u[0] = u[1];
+		        ++u;
+		    }
+		}
+	}
+
+	if (*t != '\0') {
+		*t = '\0';		/* end current token */
+		*stringp = t+1;		/* *t != '\0' => *(t+1) is valid */
+	} else
+		*stringp = 0;		/* end of string reached */	
+	
+	return s;			/* return current token */
+}
+
+/*
+ * This function converts escaped characters:
+ * '\<delim>' -> '<delim>', '\\' -> '\'
+ * 
+ * If there are unescaped delimiters, 'false' will be return to indicate
+ * an error, otherwise remove_escape returns 'true'.
+ */
+bool remove_escapes (char **s, const char* delim) {
+	bool	escaped=false;
+	char	*t, *u;
+	int	i;
+	
+	for (t = *s; *t != '\0'; ++t) {
+		if (*t == '\\') {
+		    if (escaped) {	/* convert \\ to \ */
+			--t;
+		        u = t;
+		        escaped = false;
+		        while (u[0] != '\0') {
+		            u[0] = u[1];
+		            ++u;
+		        }
+		    } else		/* start \-Sequence */
+			escaped = true;
+		    continue;
+		}
+		
+		/* search for delimiter */
+		for (i=0; delim[i] != '\0'; ++i) {
+		    if (*t == delim[i])
+		        break;
+		}
+		
+		/* un-escaped delimiter found => error */
+		if (!escaped && delim[i] != '\0')
+			return false;
+
+		/* escaped delimiter found => remove / */
+		if (escaped) {
+    		    --t;
+	            u = t;
+                    escaped = false;
+		    while (u[0] != '\0') {
+		        u[0] = u[1];
+		        ++u;
+		    }
+		}
+	}
+	
+	return true;
+}
+
 static int
 fstabscan()
 {
@@ -101,9 +236,19 @@
 		++LineNo;
 		if (*line == '#' || *line == '\n')
 			continue;
-		if (!strpbrk(p, " \t")) {
+
+		/* escapted white-spaces only are allowed in old-style format */
+		cp = p;
+		while ((cp = strpbrk(cp, " \t")) != 0 &&
+			cp != p && cp[-1] == '\\')
+			++cp;
+		if (cp == 0) {
 			_fs_fstab.fs_spec = strsep(&p, ":\n");
+			if (!remove_escapes (&_fs_fstab.fs_spec, " \t"))
+			    goto bad;
 			_fs_fstab.fs_file = strsep(&p, ":\n");
+			if (!remove_escapes (&_fs_fstab.fs_file, " \t"))
+			    goto bad;
 			fixfsfile();
 			_fs_fstab.fs_type = strsep(&p, ":\n");
 			if (_fs_fstab.fs_type) {
@@ -124,13 +269,15 @@
 			goto bad;
 		}
 /* OLD_STYLE_FSTAB */
-		while ((cp = strsep(&p, " \t\n")) != NULL && *cp == '\0')
+		while ((cp = es_strsep(&p, " \t\n")) != NULL && *cp == '\0')
 			;
 		_fs_fstab.fs_spec = cp;
 		if (!_fs_fstab.fs_spec || *_fs_fstab.fs_spec == '#')
 			continue;
-		while ((cp = strsep(&p, " \t\n")) != NULL && *cp == '\0')
+		while ((cp = es_strsep(&p, " \t\n")) != NULL && *cp == '\0')
 			;
+		if (cp == 0)
+			goto bad;
 		_fs_fstab.fs_file = cp;
 		fixfsfile();
 		while ((cp = strsep(&p, " \t\n")) != NULL && *cp == '\0')
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