index.c

来自「speech signal process tools」· C语言 代码 · 共 32 行

/* static char Sccsid[]="@(#)index.c	1.2 12/8/89 ESI, ATT"; */
/*
	If `s2' is a substring of `s1' return the offset of the first
	occurrence of `s2' in `s1',
	else return -1.
*/

int 
index(as1,as2)
char *as1,*as2;
{
	register char *s1,*s2,c;
	int offset;

	s1 = as1;
	s2 = as2;
	c = *s2;

	while (*s1)
		if (*s1++ == c) {
			offset = s1 - as1 - 1;
			s2++;
			while ((c = *s2++) == *s1++ && c) ;
			if (c == 0)
				return(offset);
			s1 = offset + as1 + 1;
			s2 = as2;
			c = *s2;
		}
	 return(-1);
}