shithub: mc

ref: e70d7196737e825c0b884572de64c699c482c939
dir: /lib/std/pathjoin.myr/

use "alloc.use"
use "extremum.use"
use "strjoin.use"
use "strsplit.use"
use "sleq.use"
use "sljoin.use"
use "sldup.use"
use "slcp.use"
use "die.use"
use "fmt.use"

pkg std =
	const pathcat	: (a : byte[:], b : byte[:] -> byte[:])
	const pathjoin	: (p : byte[:][:] -> byte[:])
	const pathnorm	: (p : byte[:] -> byte[:])
;;

const pathcat = {a, b
	-> pathjoin([a, b][:])
}

const pathjoin = {l
	var p, i, q

	for i = 0; i < l.len; i++
		if l[i].len != 0
			break
		;;
	;;
	p = strjoin(l[i:], "/")
	q = pathnorm(p)
	slfree(p)
	-> q
}

const pathnorm = {p
	var comps
	var i, del, dst
	var s, ret

	comps = strsplit(p, "/")
	/* 
	"." is a no-op component, so we drop it. In order
	to drop a component, we set it to the empty string,
	and remove it later on in the code.
	*/
	for i = 0; i < comps.len; i++
		if sleq(comps[i], ".")
			comps[i] = ""
		;;
	;;

	/*
	then, resolve '..' by cancelling out previous components. Scan
	backwards in the component list for the first real component,
	and delete both it and the '..' that lead to it.
	
	Leave in extra '..' components, so that, eg, ../foo doesn't
	get mangled.
	*/
	for i = 0; i < comps.len; i++
		if !sleq(comps[i], "..")
			continue
		;;
		for del = 1; del <= i; del++
			if comps[i - del].len > 0 && !sleq(comps[i-del], "..")
				comps[i - del] = ""
				comps[i] = ""
				break
			;;
		;;
	;;

	/* clear out the path nodes we decided to drop */
	dst = 0
	for i = 0; i < comps.len; i++
		if comps[i].len > 0
			comps[dst++] = comps[i]
		;;
	;;
	comps = comps[:dst]

	/*
	and reassemble. If we have an absolute path,
	make it absolute. If we have an empty path, return
	".". Otherwise, just return the path.
	*/
	if p.len > 0 && sleq(p[:1], "/")
		for i = 0; i < comps.len; i++
			if !sleq(comps[i], "..")
				break
			;;
		;;
		s = strjoin(comps[i:], "/")
		ret = fmt("/{}", s)
		slfree(s)
	elif comps.len == 0
		ret = sldup(".")
	else
		ret = strjoin(comps, "/")
	;;
	slfree(comps)
	-> ret
}