dirReadHaiku

fn dirReadHaiku(userdata: ?*anyopaque, dr: *Dir.Reader, buffer: []Dir.Entry) Dir.Reader.Error!usize {
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;
    var buffer_index: usize = 0;
    while (buffer.len - buffer_index != 0) {
        if (dr.end - dr.index == 0) {
            // Refill the buffer, unless we've already created references to
            // buffered data.
            if (buffer_index != 0) break;
            if (dr.state == .reset) {
                const syscall: Syscall = try .start();
                while (true) {
                    const rc = posix.system._kern_rewind_dir(dr.dir.handle);
                    switch (@as(posix.E, @fromBackingInt(@intCast(@min(rc, 0))))) {
                        .SUCCESS => {
                            syscall.finish();
                            break;
                        },
                        .INTR => {
                            try syscall.checkCancel();
                            continue;
                        },
                        else => |e| {
                            syscall.finish();
                            switch (e) {
                                else => |err| return posix.unexpectedErrno(err),
                            }
                        },
                    }
                }
                dr.state = .reading;
            }
            const syscall: Syscall = try .start();
            const n: usize = while (true) {
                const rc = posix.system._kern_read_dir(dr.dir.handle, dr.buffer.ptr, dr.buffer.len, @truncate(dr.buffer.len / @sizeOf(posix.system.DirEnt)));
                switch (@as(posix.E, @fromBackingInt(@intCast(@min(rc, 0))))) {
                    .SUCCESS => {
                        syscall.finish();
                        break @intCast(rc);
                    },
                    .INTR => {
                        try syscall.checkCancel();
                        continue;
                    },
                    else => |e| {
                        syscall.finish();
                        switch (e) {
                            else => |err| return posix.unexpectedErrno(err),
                        }
                    },
                }
            };
            if (n == 0) {
                dr.state = .finished;
                return 0;
            }
            dr.index = 0;
            // _kern_read_dir returns entry count, but Dir.Reader is designed for byte count
            dr.end = 0;
            var i: usize = 0;
            while (i < n) : (i += 1) {
                const entry = @as(*align(1) posix.system.DirEnt, @ptrCast(&dr.buffer[dr.end]));
                dr.end += entry.reclen;
            }
        }
        const entry = @as(*align(1) posix.system.DirEnt, @ptrCast(&dr.buffer[dr.index]));
        const next_index = dr.index + entry.reclen;
        dr.index = next_index;

        const name = std.mem.sliceTo(@as([*:0]u8, @ptrCast(&entry.name)), 0);
        if (std.mem.eql(u8, name, ".") or std.mem.eql(u8, name, "..") or entry.ino == 0) continue;

        // haiku dirent doesn't expose type, so we have to call stat to get it.
        var stat: std.c.Stat = undefined;
        {
            const syscall: Syscall = try .start();
            while (true) {
                const rc = posix.system._kern_read_stat(dr.dir.handle, name, false, &stat, @sizeOf(std.c.Stat));
                switch (@as(posix.E, @fromBackingInt(@intCast(@min(rc, 0))))) {
                    .SUCCESS => {
                        syscall.finish();
                        break;
                    },
                    .INTR => {
                        try syscall.checkCancel();
                        continue;
                    },
                    else => |e| {
                        syscall.finish();
                        switch (e) {
                            else => |err| return posix.unexpectedErrno(err),
                        }
                    },
                }
            }
        }

        const entry_kind: File.Kind = switch (stat.mode & posix.S.IFMT) {
            posix.S.IFBLK => .block_device,
            posix.S.IFCHR => .character_device,
            posix.S.IFDIR => .directory,
            posix.S.IFIFO => .named_pipe,
            posix.S.IFLNK => .sym_link,
            posix.S.IFREG => .file,
            else => .unknown,
        };
        buffer[buffer_index] = .{
            .name = name,
            .kind = entry_kind,
            .inode = entry.ino,
        };
        buffer_index += 1;
    }
    return buffer_index;
}