strtok.c

Many C samples. It is a good sample for students to learn C language.

/*  File   : strtok.c
    Author : Richard A. O'Keefe.
    Updated: 11 April 1984
    Defines: istrtok(), strtok()

    strtok(src, set)
	skips over initial characters of src[] which occur in set[].
	The result is a pointer to the first character of src[]
	which does not occur in set[].  It then skips until it finds
	a character which does occur in set[], and changes it to NUL.
	If src is NullS, it is as if you had specified the place
	just after the last NUL was written.  If src[] contains no
	characters which are not in set[] (e.g. if src == "") the
	result is NullS.

	To read a sequence of words separated by spaces you might write
	p = strtok(sequence, " ");
	while (p) {process_word(p); p = strtok(NullS, " ");}
	This is unpleasant, so there is also a function

    istrtok(src, set)
	which builds the set and notes the source string for future
	reference.  With this function, you can write

	for (istrtok(wordlist, " \t"); p = strtok(NullS, NullS); )
	    process_word(p);
*/

#include "strings.h"
#include "_str2set.h"

static	char	*oldSrc = "";

void istrtok(src, set)
    char *src, *set;
    {
	_str2set(set);
	if (src != NullS) oldSrc = src;
    }


char *strtok(src, set)
    register char *src;
    char *set;
    {
	char *save;

	_str2set(set);
	if (src == NullS) src = oldSrc;
	while (_set_vec[*src] == _set_ctr) src++;
	if (!*src) return NullS;
	save = src;
	while (_set_vec[*++src] != _set_ctr) ;
	*src++ = NUL;
	oldSrc = src;
	return save;
    }