Add a new sysfs_streq() string comparison function

Add a new sysfs_streq() string comparison function, which ignores the trailing newlines found in sysfs inputs. By example: sysfs_streq("a", "b") ==> false sysfs_streq("a", "a") ==> true sysfs_streq("a", "a\n") ==> true sysfs_streq("a\n", "a") ==> true This is intended to simplify parsing of sysfs inputs, letting them avoid the need to manually strip off newlines from inputs. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Acked-by: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Add a new sysfs_streq() string comparison function
Add a new sysfs_streq() string comparison function, which ignores the trailing newlines found in sysfs inputs. By example: sysfs_streq("a", "b") ==> false sysfs_streq("a", "a") ==> true sysfs_streq("a", "a\n") ==> true sysfs_streq("a\n", "a") ==> true This is intended to simplify parsing of sysfs inputs, letting them avoid the need to manually strip off newlines from inputs. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Acked-by: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
David Brownell · Linus Torvalds
1 parent 7dffa3c673
Showing 2 changed files with 29 additions and 0 deletions Side-by-side Diff
include/linux/string.h
lib/string.c
@@ -109,6 +109,8 @@
 extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
 extern void argv_free(char **argv);
  
+extern bool sysfs_streq(const char *s1, const char *s2);
+
 #endif
 #endif /* _LINUX_STRING_H_ */
@@ -493,6 +493,33 @@
 EXPORT_SYMBOL(strsep);
 #endif
  
+/**
+ * sysfs_streq - return true if strings are equal, modulo trailing newline
+ * @s1: one string
+ * @s2: another string
+ *
+ * This routine returns true iff two strings are equal, treating both
+ * NUL and newline-then-NUL as equivalent string terminations.  It's
+ * geared for use with sysfs input strings, which generally terminate
+ * with newlines but are compared against values without newlines.
+ */
+bool sysfs_streq(const char *s1, const char *s2)
+{
+	while (*s1 && *s1 == *s2) {
+		s1++;
+		s2++;
+	}
+
+	if (*s1 == *s2)
+		return true;
+	if (!*s1 && *s2 == '\n' && !s2[1])
+		return true;
+	if (*s1 == '\n' && !s1[1] && !*s2)
+		return true;
+	return false;
+}
+EXPORT_SYMBOL(sysfs_streq);
+
 #ifndef __HAVE_ARCH_MEMSET
 /**
  * memset - Fill a region of memory with the given value
...	...	@@ -109,6 +109,8 @@
109	109	extern char *argv_split(gfp_t gfp, const char str, int *argcp);
110	110	extern void argv_free(char **argv);
111	111
	112	+extern bool sysfs_streq(const char s1, const char s2);
	113	+
112	114	#endif
113	115	#endif /* _LINUX_STRING_H_ */
...	...	@@ -493,6 +493,33 @@
493	493	EXPORT_SYMBOL(strsep);
494	494	#endif
495	495
	496	+/**
	497	+ * sysfs_streq - return true if strings are equal, modulo trailing newline
	498	+ * @s1: one string
	499	+ * @s2: another string
	500	+ *
	501	+ * This routine returns true iff two strings are equal, treating both
	502	+ * NUL and newline-then-NUL as equivalent string terminations. It's
	503	+ * geared for use with sysfs input strings, which generally terminate
	504	+ * with newlines but are compared against values without newlines.
	505	+ */
	506	+bool sysfs_streq(const char s1, const char s2)
	507	+{
	508	+ while (s1 && s1 == *s2) {
	509	+ s1++;
	510	+ s2++;
	511	+ }
	512	+
	513	+ if (s1 == s2)
	514	+ return true;
	515	+ if (!s1 && s2 == '\n' && !s2[1])
	516	+ return true;
	517	+ if (s1 == '\n' && !s1[1] && !s2)
	518	+ return true;
	519	+ return false;
	520	+}
	521	+EXPORT_SYMBOL(sysfs_streq);
	522	+
496	523	#ifndef __HAVE_ARCH_MEMSET
497	524	/**
498	525	* memset - Fill a region of memory with the given value