os2: implement the iterator based read directory

core/os/os2/dir_posix.odin

@@ -2,70 +2,77 @@
 //+build darwin, netbsd, freebsd, openbsd
 package os2
 
-import "base:runtime"
-
 import "core:sys/posix"
 
-@(private)
-_read_directory :: proc(f: ^File, n: int, allocator: runtime.Allocator) -> (files: []File_Info, err: Error) {
-	if f == nil || f.impl == nil {
-		err = .Invalid_File
+Read_Directory_Iterator_Impl :: struct {
+	dir:      posix.DIR,
+	idx:      int,
+
+	// NOTE: could there be paths bigger than this, maybe, probably, but why does it exist then?
+	fullpath: [posix.PATH_MAX]byte,
+}
+
+@(require_results)
+_read_directory_iterator :: proc(it: ^Read_Directory_Iterator) -> (fi: File_Info, index: int, ok: bool) {
+	index = it.impl.idx
+	it.impl.idx += 1
+
+	entry := posix.readdir(it.impl.dir)
+	if entry == nil {
+		// NOTE(laytan): would be good to have an `error` field on the `Read_Directory_Iterator`
+		// There isn't a way to now know if it failed or if we are at the end.
 		return
 	}
 
-	n := n
-	if n == 0 {
+	cname := cstring(raw_data(entry.d_name[:]))
+
+	// NOTE: these shouldn't be given back, but how?
+	// if cname == "." || cname == ".." {
+	//     continue
+	// }
+
+	stat: posix.stat_t
+	if posix.fstatat(posix.dirfd(it.impl.dir), cname, &stat, { .SYMLINK_NOFOLLOW }) != .OK {
+		// NOTE(laytan): would be good to have an `error` field on the `Read_Directory_Iterator`
+		// There isn't a way to now know if it failed or if we are at the end.
 		return
 	}
 
-	impl := (^File_Impl)(f)
+	fimpl := (^File_Impl)(it.f.impl)
 
-	dir := posix.fdopendir(impl.fd)
-	if dir == nil {
-		err = _get_platform_error()
+	n := copy(it.impl.fullpath[:],  fimpl.name)
+	n += copy(it.impl.fullpath[n:], "/")
+	n += copy(it.impl.fullpath[n:], string(cname))
+
+	fi = internal_stat(stat, string(it.impl.fullpath[:n]))
+	ok = true
+	return
+}
+
+@(require_results)
+_read_directory_iterator_create :: proc(f: ^File) -> (iter: Read_Directory_Iterator, err: Error) {
+	if f == nil || f.impl == nil {
+		err = .Invalid_File
 		return
 	}
-	defer posix.closedir(dir)
+	iter.f = f
+	iter.impl.idx = 0
 
-	dfiles: [dynamic]File_Info
-	dfiles.allocator = allocator
-	defer if err != nil {
-		file_info_slice_delete(dfiles[:], allocator)
-	}
+	impl := (^File_Impl)(f.impl)
 
-	for {
-		posix.set_errno(.NONE)
-		entry := posix.readdir(dir)
-		if entry == nil {
-			if errno := posix.errno(); errno != .NONE {
-				err = _get_platform_error()
-				return
-			} else {
-				break
-			}
-		}
-
-		cname := cstring(raw_data(entry.d_name[:]))
-		if cname == "." || cname == ".." {
-			continue
-		}
-
-		stat: posix.stat_t
-		if posix.fstatat(posix.dirfd(dir), cname, &stat, { .SYMLINK_NOFOLLOW }) != .OK {
-			err = _get_platform_error()
-			return
-		}
-
-		fullpath := concatenate({impl.name, "/", string(cname)}, allocator) or_return
-		fi := internal_stat(stat, fullpath)
-		append(&dfiles, fi) or_return
-
-		n -= 1
-		if n == 0 {
-			break
-		}
+	iter.impl.dir = posix.fdopendir(impl.fd)
+	if iter.impl.dir == nil {
+		err = _get_platform_error()
+		return
 	}
 
-	files = dfiles[:]
 	return
 }
+
+_read_directory_iterator_destroy :: proc(it: ^Read_Directory_Iterator) {
+	if it == nil || it.impl.dir == nil {
+		return
+	}
+
+	posix.closedir(it.impl.dir)
+}