projects/linux·commit f653398c

string: factorize skip_spaces and export it to be generally available

f653398c · André Goddard Rosa <[email protected]> · 2009-12-14 18:01:04 -08:00

On the following sentence:
    while (*s && isspace(*s))
        s++;

If *s == 0, isspace() evaluates to ((_ctype[*s] & 0x20) != 0), which
evaluates to ((0x08 & 0x20) != 0) which equals to 0 as well.
If *s == 1, we depend on isspace() result anyway. In other words,
"a char equals zero is never a space", so remove this check.

Also, *s != 0 is most common case (non-null string).

Fixed const return as noticed by Jan Engelhardt and James Bottomley.
Fixed unnecessary extra cast on strstrip() as noticed by Jan Engelhardt.

Signed-off-by: André Goddard Rosa <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Commit
f653398c86a1c104f0992bd788dd4bb065449be4
Parents
4e62b093

Changes

3 files changed · +17 −4

FileStatusAddDelContent
include/linux/ctype.hmodified+1−0View file
include/linux/string.hmodified+1−0View file
lib/string.cmodified+15−4View file

include/linux/ctype.h

View file
diff --git a/include/linux/ctype.h b/include/linux/ctype.h
index 6dec944..a3d6ee0 100644
--- a/include/linux/ctype.h
+++ b/include/linux/ctype.h
@@ -27,6 +27,7 @@ extern const unsigned char _ctype[];
#define islower(c) ((__ismask(c)&(_L)) != 0)
#define isprint(c) ((__ismask(c)&(_P|_U|_L|_D|_SP)) != 0)
#define ispunct(c) ((__ismask(c)&(_P)) != 0)
+/* Note: isspace() must return false for %NUL-terminator */
#define isspace(c) ((__ismask(c)&(_S)) != 0)
#define isupper(c) ((__ismask(c)&(_U)) != 0)
#define isxdigit(c) ((__ismask(c)&(_D|_X)) != 0)

include/linux/string.h

View file
diff --git a/include/linux/string.h b/include/linux/string.h
index b850886..168dad1 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -62,6 +62,7 @@ extern char * strnchr(const char *, size_t, int);
#ifndef __HAVE_ARCH_STRRCHR
extern char * strrchr(const char *,int);
#endif
+extern char * __must_check skip_spaces(const char *);
extern char * __must_check strstrip(char *);
#ifndef __HAVE_ARCH_STRSTR
extern char * strstr(const char *,const char *);

lib/string.c

View file
diff --git a/lib/string.c b/lib/string.c
index e96421a..3a912a4 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -338,6 +338,20 @@ EXPORT_SYMBOL(strnchr);
#endif
/**
+ * skip_spaces - Removes leading whitespace from @s.
+ * @s: The string to be stripped.
+ *
+ * Returns a pointer to the first non-whitespace character in @s.
+ */
+char *skip_spaces(const char *str)
+{
+ while (isspace(*str))
+ ++str;
+ return (char *)str;
+}
+EXPORT_SYMBOL(skip_spaces);
+
+/**
* strstrip - Removes leading and trailing whitespace from @s.
* @s: The string to be stripped.
*
@@ -360,10 +374,7 @@ char *strstrip(char *s)
end--;
*(end + 1) = '\0';
- while (*s && isspace(*s))
- s++;
-
- return s;
+ return skip_spaces(s);
}
EXPORT_SYMBOL(strstrip);