/***
*strspn.c - find length of initial substring of chars from a control string
*
*       Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       defines strspn() - finds the length of the initial substring of
*       a string consisting entirely of characters from a control string.
*
*       defines strcspn()- finds the length of the initial substring of
*       a string consisting entirely of characters not in a control string.
*
*       defines strpbrk()- finds the index of the first character in a string
*       that is not in a control string
*
*******************************************************************************/


/***
*int strspn(string, control) - find init substring of control chars
*
*Purpose:
*       Finds the index of the first character in string that does belong
*       to the set of characters specified by control.  This is
*       equivalent to the length of the initial substring of string that
*       consists entirely of characters from control.  The '\0' character
*       that terminates control is not considered in the matching process.
*
*Entry:
*       char *string - string to search
*       char *control - string containing characters not to search for
*
*Exit:
*       returns index of first char in string not in control
*
*Exceptions:
*
*******************************************************************************/

#include <string.h> /* size_t */

size_t strspn(const char *string, const char *control)
{
	const unsigned char *str = (unsigned char *)string;
	const unsigned char *ctrl = (unsigned char *)control;

	unsigned char map[32];
	int count;

	/* Clear out bit map */
	for(count=0; count<32; count++)
		map[count] = 0;

	/* Set bits in control map */
	while(*ctrl)
	{
		map[*ctrl >> 3] |= (1 << (*ctrl & 7));
		ctrl++;
	}

	/* 1st char NOT in control map stops search */
	if(*str)
	{
		count=0;
		while(map[*str >> 3] & (1 << (*str & 7)))
		{
			count++;
			str++;
		}
		
		return count;
	}
	
	return 0;
}
