shithub: mc

ref: ee50a71ce18d4721e868e575d26d894bc8f13e37
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
}