\linux-1.0\linux\include\linux\ctype.h#ifndef _LINUX_CTYPE_H
#define _LINUX_CTYPE_H#define _U 0x01 /* upper */ //大写字母
#define _L 0x02 /* lower */ //小写字母
#define _D 0x04 /* digit */ //数字
#define _C 0x08 /* cntrl */ //控制按键
#define _P 0x10 /* punct */ //
#define _S 0x20 /* white space (space/lf/tab) */
#define _X 0x40 /* hex digit */ //十六进制数
#define _SP 0x80 /* hard space (0x20) */extern unsigned char _ctype[];
extern char _ctmp;//通过设定ascii表不同的位置为什么类型， 判断时直接比较！速度很快！
#define isalnum(c) ((_ctype+1)[c]&(_U|_L|_D))
#define isalpha(c) ((_ctype+1)[c]&(_U|_L))
#define iscntrl(c) ((_ctype+1)[c]&(_C))
#define isdigit(c) ((_ctype+1)[c]&(_D))
#define isgraph(c) ((_ctype+1)[c]&(_P|_U|_L|_D))
#define islower(c) ((_ctype+1)[c]&(_L))
#define isprint(c) ((_ctype+1)[c]&(_P|_U|_L|_D|_SP))
#define ispunct(c) ((_ctype+1)[c]&(_P))
#define isspace(c) ((_ctype+1)[c]&(_S))
#define isupper(c) ((_ctype+1)[c]&(_U))
#define isxdigit(c) ((_ctype+1)[c]&(_D|_X))#define isascii(c) (((unsigned) c)<=0x7f)
#define toascii(c) (((unsigned) c)&0x7f)//2步宏，第1步赋值（防止传入值被修改），第2步 做相应的操作！
#define tolower(c) (_ctmp=c,isupper(_ctmp)?_ctmp-('A'-'a'):_ctmp)
#define toupper(c) (_ctmp=c,islower(_ctmp)?_ctmp-('a'-'A'):_ctmp)#endif
\linux-1.0\linux\include\linux\ctype.c
/** linux/lib/ctype.c** Copyright (C) 1991, 1992 Linus Torvalds*/#include <linux/ctype.h>char _ctmp;
//设定ASCII码对应的值!
unsigned char _ctype[] = {0x00, /* EOF */
_C,_C,_C,_C,_C,_C,_C,_C, /* 0-7 */
_C,_C|_S,_C|_S,_C|_S,_C|_S,_C|_S,_C,_C, /* 8-15 */
_C,_C,_C,_C,_C,_C,_C,_C, /* 16-23 */
_C,_C,_C,_C,_C,_C,_C,_C, /* 24-31 */
_S|_SP,_P,_P,_P,_P,_P,_P,_P, /* 32-39 */
_P,_P,_P,_P,_P,_P,_P,_P, /* 40-47 */
_D,_D,_D,_D,_D,_D,_D,_D, /* 48-55 */
_D,_D,_P,_P,_P,_P,_P,_P, /* 56-63 */
_P,_U|_X,_U|_X,_U|_X,_U|_X,_U|_X,_U|_X,_U, /* 64-71 */
_U,_U,_U,_U,_U,_U,_U,_U, /* 72-79 */
_U,_U,_U,_U,_U,_U,_U,_U, /* 80-87 */
_U,_U,_U,_P,_P,_P,_P,_P, /* 88-95 */
_P,_L|_X,_L|_X,_L|_X,_L|_X,_L|_X,_L|_X,_L, /* 96-103 */
_L,_L,_L,_L,_L,_L,_L,_L, /* 104-111 */
_L,_L,_L,_L,_L,_L,_L,_L, /* 112-119 */
_L,_L,_L,_P,_P,_P,_P,_C, /* 120-127 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 128-143 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 144-159 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 160-175 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 176-191 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 192-207 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 208-223 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 224-239 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; /* 240-255 */
