Commit f653398c86a1c104f0992bd788dd4bb065449be4
Committed by
Linus Torvalds
Linus Torvalds
1 parent
4e62b09302
Exists in
master
and in
7 other branches
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: André Goddard Rosa <andre.goddard@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Showing 3 changed files with 17 additions and 4 deletions Side-by-side Diff
include/linux/ctype.h
| ... | ... | @@ -27,6 +27,7 @@ |
| 27 | 27 | #define islower(c) ((__ismask(c)&(_L)) != 0) |
| 28 | 28 | #define isprint(c) ((__ismask(c)&(_P|_U|_L|_D|_SP)) != 0) |
| 29 | 29 | #define ispunct(c) ((__ismask(c)&(_P)) != 0) |
| 30 | +/* Note: isspace() must return false for %NUL-terminator */ | |
| 30 | 31 | #define isspace(c) ((__ismask(c)&(_S)) != 0) |
| 31 | 32 | #define isupper(c) ((__ismask(c)&(_U)) != 0) |
| 32 | 33 | #define isxdigit(c) ((__ismask(c)&(_D|_X)) != 0) |
include/linux/string.h
| ... | ... | @@ -62,6 +62,7 @@ |
| 62 | 62 | #ifndef __HAVE_ARCH_STRRCHR |
| 63 | 63 | extern char * strrchr(const char *,int); |
| 64 | 64 | #endif |
| 65 | +extern char * __must_check skip_spaces(const char *); | |
| 65 | 66 | extern char * __must_check strstrip(char *); |
| 66 | 67 | #ifndef __HAVE_ARCH_STRSTR |
| 67 | 68 | extern char * strstr(const char *,const char *); |
lib/string.c
| ... | ... | @@ -338,6 +338,20 @@ |
| 338 | 338 | #endif |
| 339 | 339 | |
| 340 | 340 | /** |
| 341 | + * skip_spaces - Removes leading whitespace from @s. | |
| 342 | + * @s: The string to be stripped. | |
| 343 | + * | |
| 344 | + * Returns a pointer to the first non-whitespace character in @s. | |
| 345 | + */ | |
| 346 | +char *skip_spaces(const char *str) | |
| 347 | +{ | |
| 348 | + while (isspace(*str)) | |
| 349 | + ++str; | |
| 350 | + return (char *)str; | |
| 351 | +} | |
| 352 | +EXPORT_SYMBOL(skip_spaces); | |
| 353 | + | |
| 354 | +/** | |
| 341 | 355 | * strstrip - Removes leading and trailing whitespace from @s. |
| 342 | 356 | * @s: The string to be stripped. |
| 343 | 357 | * |
| ... | ... | @@ -360,10 +374,7 @@ |
| 360 | 374 | end--; |
| 361 | 375 | *(end + 1) = '\0'; |
| 362 | 376 | |
| 363 | - while (*s && isspace(*s)) | |
| 364 | - s++; | |
| 365 | - | |
| 366 | - return s; | |
| 377 | + return skip_spaces(s); | |
| 367 | 378 | } |
| 368 | 379 | EXPORT_SYMBOL(strstrip); |
| 369 | 380 |