Existing ctype checks are implemented using a 256 byte lookup table, allowing each character to be in any of 8 character classes. Since there are 8 existing character classes without the blank class, I implemented isblank without using the lookup table. Since there are only two blank characters - tab and space - this is a more reasonable approach than doubling the size of the lookup table to accommodate one more class.
Signed-off-by: Jason Hobbs jason.hobbs@calxeda.com --- new in v4
changes in v5: - none
include/linux/ctype.h | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/include/linux/ctype.h b/include/linux/ctype.h index 6dec944..42f9305 100644 --- a/include/linux/ctype.h +++ b/include/linux/ctype.h @@ -31,6 +31,12 @@ extern const unsigned char _ctype[]; #define isupper(c) ((__ismask(c)&(_U)) != 0) #define isxdigit(c) ((__ismask(c)&(_D|_X)) != 0)
+/* + * Rather than doubling the size of the _ctype lookup table to hold a 'blank' + * flag, just check for space or tab. + */ +#define isblank(c) (c == ' ' || c == '\t') + #define isascii(c) (((unsigned char)(c))<=0x7f) #define toascii(c) (((unsigned char)(c))&0x7f)