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Commit f653398c authored by André Goddard Rosa's avatar André Goddard Rosa Committed by Linus Torvalds
Browse files

string: factorize skip_spaces and export it to be generally available 



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: default avatarAndré Goddard Rosa <andre.goddard@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4e62b093

include/linux/ctype.h

+1 −0
Original line number Diff line number Diff line
@@ -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

+1 −0
Original line number Diff line number Diff line
@@ -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

+15 −4
Original line number Diff line number Diff line
@@ -337,6 +337,20 @@ char *strnchr(const char *s, size_t count, int c) 
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);