- 论坛徽章:
- 0
|
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
/*mystrtok is the same as the function "strtok" in string.h*/
char *mystrtok(register char *s, register const char *delim);
int main(void) {
printf("---mystrtok---\n");
char myinput[16] = "abcde,fgh";
char *s;
s = mystrtok(myinput, "c,h");
printf("%s\n", s);
s = mystrtok(NULL, "c,h");
if (s)
printf("%s\n", s);
s = mystrtok(NULL, ",");
if (s)
printf("%s\n", s);
printf("%s\n", myinput);
return EXIT_SUCCESS;
}
char *mystrtok(register char *s, register const char *delim) {
static char *last;
char *tok;
char *ucdelim;
/*(1)s为空，并且上次剩余值也为空，则直接返回NULL，否则s为last或当前值中有值的一方*/
/*if (s == NULL && (s = last) == NULL)
return NULL;*/
/*(2)以上内容与下面等价：
下面意为：如果s==NULL的时候，s则为last（上次执行该项的时候的剩余值）；
若这时候s还为空（即上次没有剩余），则返回NULL。
*/
if (s == NULL)
s = last;
if(s == NULL)
return NULL;
/*(3)也意为：若后续值为NULL则不进行操作，否则继续操作。
其中，后续值的界定方法为: 若last不为空的时候，则s为last，否则为输入值
* */
/*
if(last != NULL)
s = last;
else if(s == NULL)
return NULL;*/
tok = s;
int found = 0;
while (!found && *s != '\0') {
ucdelim = (char *) delim;
while (*ucdelim) {
if (*s == *ucdelim) {
found = 1;
*s = '\0';
last = s + 1;
break;
}
ucdelim++;
}
if (!found)
s++;
}
return tok;
}
/*********************************************************************/
/***
*strtok.c - tokenize a string with given delimiters
*
* Copyright (c) Microsoft Corporation. All rights reserved.
*
*Purpose:
* defines strtok() - breaks string into series of token
* via repeated calls.
*
*******************************************************************************/
#include <cruntime.h>
#include <string.h>
#ifdef _SECURE_VERSION
#include <internal.h>
#else /* _SECURE_VERSION */
#include <mtdll.h>
#endif /* _SECURE_VERSION */
/***
*char *strtok(string, control) - tokenize string with delimiter in control
*
*Purpose:
* strtok considers the string to consist of a sequence of zero or more
* text tokens separated by spans of one or more control chars. the first
* call, with string specified, returns a pointer to the first char of the
* first token, and will write a null char into string immediately
* following the returned token. subsequent calls with zero for the first
* argument (string) will work thru the string until no tokens remain. the
* control string may be different from call to call. when no tokens remain
* in string a NULL pointer is returned. remember the control chars with a
* bit map, one bit per ascii char. the null char is always a control char.
*
*Entry:
* char *string - string to tokenize, or NULL to get next token
* char *control - string of characters to use as delimiters
*
*Exit:
* returns pointer to first token in string, or if string
* was NULL, to next token
* returns NULL when no more tokens remain.
*
*Uses:
*
*Exceptions:
*
*******************************************************************************/
#ifdef _SECURE_VERSION
#define _TOKEN *context
#else /* _SECURE_VERSION */
#define _TOKEN ptd->_token
#endif /* _SECURE_VERSION */
#ifdef _SECURE_VERSION
char * __cdecl strtok_s (
char * string,
const char * control,
char ** context
)
#else /* _SECURE_VERSION */
char * __cdecl strtok (
char * string,
const char * control
)
#endif /* _SECURE_VERSION */
{
unsigned char *str;
const unsigned char *ctrl = control;
unsigned char map[32];
int count;
#ifdef _SECURE_VERSION
/* validation section */
_VALIDATE_RETURN(context != NULL, EINVAL, NULL);
_VALIDATE_RETURN(string != NULL || *context != NULL, EINVAL, NULL);
_VALIDATE_RETURN(control != NULL, EINVAL, NULL);
/* no static storage is needed for the secure version */
#else /* _SECURE_VERSION */
_ptiddata ptd = _getptd();
#endif /* _SECURE_VERSION */
/* Clear control map */
for (count = 0; count < 32; count++)
map[count] = 0;
/* Set bits in delimiter table */
do {
map[*ctrl >> 3] |= (1 << (*ctrl & 7));
} while (*ctrl++);
/* Initialize str */
/* If string is NULL, set str to the saved
* pointer (i.e., continue breaking tokens out of the string
* from the last strtok call) */
if (string)
str = string;
else
str = _TOKEN;
/* Find beginning of token (skip over leading delimiters). Note that
* there is no token iff this loop sets str to point to the terminal
* null (*str == '\0') */
while ( (map[*str >> 3] & (1 << (*str & 7))) && *str )
str++;
string = str;
/* Find the end of the token. If it is not the end of the string,
* put a null there. */
for ( ; *str ; str++ )
if ( map[*str >> 3] & (1 << (*str & 7)) ) {
*str++ = '\0';
break;
}
/* Update nextoken (or the corresponding field in the per-thread data
* structure */
_TOKEN = str;
/* Determine if a token has been found. */
if ( string == str )
return NULL;
else
return string;
}
[ 本帖最后由 rq8y 于 2008-9-9 07:46 编辑 ] |
|
免费注册
发表于 2005-10-27 12:52
{
[/quote]