siddhu wrote:
>
As I know strtok_r is re-entrant version of strtok.
strtok_r() is called with s1(lets say) as its first parameter.
Remaining tokens from s1 are obtained by calling strtok_r() with
a null pointer for the first parameter. My confusion is that
this behavior is same as strtok. So I assume strtok_r must also
be using any function static variable to keep the information
about s1. If this is the case then how strtok_r is re- entrant?
Otherwise how it keeps the information about s1?
There is no such standard C function as strtok_r(). To discuss
such a function you have to give its source, in standard C.
However, I just happen to have a suitable replacement function
lying about, whose source follows:
/* ------- file tknsplit.c ----------*/
#include "tknsplit.h "
/* copy over the next tkn from an input string, after
skipping leading blanks (or other whitespace?). The
tkn is terminated by the first appearance of tknchar,
or by the end of the source string.
The caller must supply sufficient space in tkn to
receive any tkn, Otherwise tkns will be truncated.
Returns: a pointer past the terminating tknchar.
This will happily return an infinity of empty tkns if
called with src pointing to the end of a string. Tokens
will never include a copy of tknchar.
A better name would be "strtkn", except that is reserved
for the system namespace. Change to that at your risk.
released to Public Domain, by C.B. Falconer.
Published 2006-02-20. Attribution appreciated.
Revised 2006-06-13 2007-05-26 (name)
*/
const char *tknsplit(const char *src, /* Source of tkns */
char tknchar, /* tkn delimiting char */
char *tkn, /* receiver of parsed tkn */
size_t lgh) /* length tkn can receive */
/* not including final '\0' */
{
if (src) {
while (' ' == *src) src++;
while (*src && (tknchar != *src)) {
if (lgh) {
*tkn++ = *src;
--lgh;
}
src++;
}
if (*src && (tknchar == *src)) src++;
}
*tkn = '\0';
return src;
} /* tknsplit */
#ifdef TESTING
#include <stdio.h>
#define ABRsize 6 /* length of acceptable tkn abbreviations */
/* ---------------- */
static void showtkn(int i, char *tok)
{
putchar(i + '1'); putchar(':');
puts(tok);
} /* showtkn */
/* ---------------- */
int main(void)
{
char teststring[] = "This is a test, ,, abbrev, more";
const char *t, *s = teststring;
int i;
char tkn[ABRsize + 1];
puts(teststring );
t = s;
for (i = 0; i < 4; i++) {
t = tknsplit(t, ',', tkn, ABRsize);
showtkn(i, tkn);
}
puts("\nHow to detect 'no more tkns' while truncating");
t = s; i = 0;
while (*t) {
t = tknsplit(t, ',', tkn, 3);
showtkn(i, tkn);
i++;
}
puts("\nUsing blanks as tkn delimiters");
t = s; i = 0;
while (*t) {
t = tknsplit(t, ' ', tkn, ABRsize);
showtkn(i, tkn);
i++;
}
return 0;
} /* main */
#endif
/* ------- end file tknsplit.c ----------*/
/* ------- file tknsplit.h ----------*/
#ifndef H_tknsplit_h
# define H_tknsplit_h
# ifdef __cplusplus
extern "C" {
# endif
#include <stddef.h>
/* copy over the next tkn from an input string, after
skipping leading blanks (or other whitespace?). The
tkn is terminated by the first appearance of tknchar,
or by the end of the source string.
The caller must supply sufficient space in tkn to
receive any tkn, Otherwise tkns will be truncated.
Returns: a pointer past the terminating tknchar.
This will happily return an infinity of empty tkns if
called with src pointing to the end of a string. Tokens
will never include a copy of tknchar.
released to Public Domain, by C.B. Falconer.
Published 2006-02-20. Attribution appreciated.
revised 2007-05-26 (name)
*/
const char *tknsplit(const char *src, /* Source of tkns */
char tknchar, /* tkn delimiting char */
char *tkn, /* receiver of parsed tkn */
size_t lgh); /* length tkn can receive */
/* not including final '\0' */
# ifdef __cplusplus
}
# endif
#endif
/* ------- end file tknsplit.h ----------*/
--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net>
--
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