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use "types.use"
use "option.use"

pkg std =
	const strfind	: (haystack : byte[:], needle : byte[:] -> option(size))
	const strrfind	: (haystack : byte[:], needle : byte[:] -> option(size))
	const strhas	: (haystack : byte[:], needle : byte[:]	-> bool)
;;

const strfind = {haystack, needle
	-> strfindin(haystack, needle, 0, haystack.len)
}

const strrfind = {haystack, needle
	-> strfindin(haystack, needle, haystack.len - 1, -1)
}

const strfindin = {haystack, needle, start, end
	var i, j, inc : size

	inc = 1
	if start > end
		inc = -1
	;;
	for i = start; i != end; i += inc
		/* 
		if we knew the direction we could terminate early,
		but we allow the start and end to be passed in.
		*/
		if i + needle.len > haystack.len
			continue
		;;
		if haystack[i] == needle[0]
			for j = 0; j < needle.len; j++
				if haystack[i + j] != needle[j]
					goto nextiter
				;;
			;;
			-> `Some i
		;;
:nextiter
	;;
	-> `None
}

const strhas = {haystack, needle
	match strfind(haystack, needle)
	| `Some _:	-> true
	| `None:	-> false
	;;
}