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Recovering data from multi-disk ZIP archives

2024-12-13T00:00:00Z

Last year, I wrote about how I had recently been imaging and archiving my old 3.5-inch floppy disks from the late '80s to mid-'90s. Quite a number of those disks contain multi-disk ZIP archives, made by the original PKZIP.

This post is a short one about the steps I figured out to extract them using zip and unzip from the Info-ZIP package. (The unzip and zip that are installed by default on macOS.)

To extract files from multi-part ZIP archives (the ones with volume labels like PKBACK# 001, etc), perform the following steps:

Rename the original zip files (from the individual disk volumes) to <name>.z01, <name>.z02, etc.
Run: zip -FF <name>.z01 --out <name>.zip
1. Answer n when it asks: Is this a single-disk archive? (y/n):
2. Answer e (end) when it complains that it could not find <name>.z0n (where n is one higher than the last file number).
Run unzip <name>.zip

You should now have all the files in the combined archive.

Fixing stuck macOS Local Network permissions

2024-12-04T00:00:00Z

TL;DR

macOS permissions can become stuck in a state where the UI shows them turned on, but the system behaves as though they are turned off. The workaround is to reset the permission with tccutil, then find and delete every copy of the app with the same Bundle ID, and maybe restart.

The Scene

Apple added a yet another new permission prompt in macOS 15 Sequoia; they brought Local Network permission over from iOS. Now when an app needs to access another device (like a server) on the same local network (over Ethernet or Wi-Fi), the system will throw up a permission dialog on first access, then fail local network access until the user gives the app permission.

That's all well-and-good; until it's not. Shortly after the first beta release of Sequoia, I was working on one of my personal apps that accesses a service on a local server. At this point I'd already given the app Local Network permission, and things had been working smoothly.

The Problem

As part of the changes I was making to the app, I was renaming it from All-the-Things to Omni. Suddenly Omni was unable to access my server, as though I'd denied Local Network access. Checking System Settings > Privacy & Security > Local Network showed Omni in there, under the new name, and with access turned on. There may even have been two entries in there (it was 6 months ago, after all).

Michael and I ended up spending half the day trying to get the Local Network permission dialog to appear. It seems that once you’ve approved access for a given Bundle ID, if you change something about the built app, such as the target name, you will be silently denied Local Network access.

The Workaround

In the end, the workaround is to:

Use tccutil to remove all permissions for your app's bundle id.
```
tccutil reset All your.bundle.id
```
Then, remove all copies of the app that the system can see. Don't forget to find all the builds of your app that are inside your Developer folder. I'm not sure if you need to remove builds that are inside your Xcode Archives (.xcarchive). Also, you probably need to empty the Trash.
```
find /Applications -name 'YourApp.app' -type d
find ~ -name 'YourApp.app' -type d
```

If you’re lucky, the app will be gone from the System Settings page. If it’s not gone, just missing its icon, a reboot might fix that. Once it’s gone from Settings, the next launch of the app (after re-building it) should show the permission dialog again.

Open Questions

Exactly how extensively to you need to remove copies of your app? Maybe the system is only looking in a couple of these places. For example is it looking in the .xcarchive folders?
Is this bug limited to just the Local Network permission, or does it affect all the TCC-controlled permissions?

Epilogue

A couple of days ago Michael called me, asking me what the steps were to get out of this situation. The app he's writing had suddenly fallen into the same state. I dug up my old notes, read them out to him, then he used find to locate and delete all copies of his app. After a restart, the permission dialog appeared again. At that point we decided I should write this up for other people to find.

Also, I just looked at my Local Network permissions page, and saw the same problem waiting to bite me 😳:

Restoring old DOS backups in 2023

2023-04-28T00:00:00Z

Recently, as part of an ongoing effort to preserve old work, and to free up physical storage space, I went through the process of imaging all my 3.5-inch floppy disks. I’ve been using my Kryoflux board to save off a .img file for each floppy.

While most of the disks contained .zip files, or multi-disk .zip archives (something for another post), there were several multi-disk backup sets created by some version of DOS Backup in the mid-nineties.

Each of these backup disks contained a single file with names like KK50306D.001. Looking at these files in a hex editor, we can see that they contain the string NORTON Ver 1E in their header. Apparently Microsoft licensed Norton Backup for inclusion in versions of DOS at around that time.

I fondly imagined that someone had written an open source tool for restoring these; I didn’t find one. I briefly thought about doing that myself.

Here are the steps I ended up taking to restore my backup sets:

It looked as though the only option was using the original DOS restore functionality. But which version of DOS?
Research led to DOS 6, 6.2, or 6.22 (see DoubleSpace vs DriveSpace and the Stac Electronics patent).
I installed DOS 6.22 in a VirtualBox VM and tried its version of msbackup. It couldn’t reconstruct the catalog from my disk images.
Some mucking around and it reconstructed the catalog from specially-named directories on disk, but when I tried to restore, it skipped all the files without explaining why.
So I installed Windows 3.11 and tried the Windows version of backup, mwbackup.
mwbackup told me that this backup was made by DOS 6 or 6.20, and pointed me to the DOS readme file, which explained that I could install the DOS 6 or 6.20 versions of msbackup over the 6.22 ones.
After accidentally trashing my VM, I rebuilt DOS 6.22 and installed the DOS 6 msbackup over the top.
This version was happy to reconstruct the catalog from floppy images, and I was able to restore all my backup sets.
The backups include the drive letter that the original files were backed up from. You can choose to restore to a different drive letter, however msbackup will prompt with an "Are you sure?" message for each new directory it needs to create. To avoid that, I used the DOS subst command to map my drive as the drive letter from the original backups, then picked the msbackup option to restore to the original drive letter.

Some links which helped me through this:

SwiftUI errors with any View vs some View

2022-08-25T00:00:00Z

When writing SwiftUI code, Xcode sometimes complains with an error much like this:

Generic struct 'List' requires that 'some AccessibilityRotorContent' conform to 'View'
Initializer 'init(content:)' requires that 'some AccessibilityRotorContent' conform to 'View'
Struct 'ViewBuilder' requires that 'some AccessibilityRotorContent' conform to 'View'

When this happens, it turns out that I've just written something like this:

struct ContentView: View {
    var body: some View {
        List {
            ForEach(0..<10, id: \.self) { _ in
                MyView()
                    .myNewModifier()
            }
        }
    }
}

struct MyView: View {
    var body: some View {
        Text("MyView")
    }
    
    func myNewModifier() -> any View {
        self.foregroundColor(.red)
    }
}

The subtle error is that the signature of myNewModifier should have looked like this:

func myNewModifier() -> some View

Note the some vs the any in my non-compiling code.

Postscript

I was going to put this down to inattention on my part, but as I was writing this post, I noticed what the sequence of events is:

I write a function signature like
```
func myNewModifier() -> View
```

Xcode responds with the following error and Fix-it:

Use of protocol 'View' as a type must be written 'any View'
Replace 'View' with 'any View'  [Fix]

I click Fix, and the scene is set for me to run around like a headless chook, looking for the mystery error.

SceneKit: first steps — Part 1: Just a box

2016-05-11T00:00:00Z

Background

In the spirit of #showyourwork, and learning in the open, I've decided to document my journey as I teach myself about SceneKit on iOS and OS X, and modern 3D APIs.

Early 1980s

My first foray into 3D was sometime in the early 1980s, when I played with drawing a 3D model of the earth. My inspiration was most likely Robert Tinney's cover for the May 1979 issue of BYTE magazine:

Unfortunately inspiration didn't equal reality on my home-brewed TRS-80 clone. Its 128×48 graphics mode was a bit limiting, and state-of-the-art 3D on that platform looked like subLogic Flight Simulator:

Mid 1990s

In the mid 1990s I was experimenting with projecting from 3D to 2D, then drawing directly to Windows' GDI API. Later, I played around with Microsoft's WinG API, then Direct3D.

Early 2000s

By about 2000, my inspiration was the movie Toy Story, and the game Train Simulator (fuelled by my then two-year-old son's train obsession). I still have a bunch of books with titles like OpenGL Programming Guide (the "red book"), Advanced RenderMan, Real-Time Rendering, and Advanced Animation and Rendering Techniques.

At the time I played around with modelling the front of a locomotive, in code, and rendering it with OpenGL.

Now

Today's inspiration are games like The Witness and Monument Valley:

Getting started

Enough history. Let's get started!

Through this series, I'm being guided by Apple's SceneKit documentation, David Rönnqvist's SceneKit article from objc.io, and his excellent iBooks book 3D Graphics with Scene Kit.

I'll be doing all of these steps in a simple single-view application. The scene is presented in an SCNView that completly covers the app's main view. The SCNView from the storyboard is accessed through an @IBOutlet called sceneView. The complete listing for the view controller can be found at the bottom of this post.

An empty scene

The first step is to create an empty scene. Note that I set the scence view's background color to black, for that super-spooky look (and to make sure that the simple lighting looks realistic). I also get a reference to the scene's root node, as a convenience for later:

let scene = SCNScene()
sceneView.scene = scene
sceneView.debugOptions = [] // [.ShowLightExtents, .ShowBoundingBoxes]
sceneView.backgroundColor = UIColor.blackColor()
sceneView.allowsCameraControl = true  // allow dragging the camera around
let rootNode = scene.rootNode

An actor

Next up we need something to look at. In this first test, it's going to be a 1 × 1 × 1 cube with rounded edges. SceneKit provides the SCNBox class which creates some geometry in the shape of a rounded box. Add one of those to a node, and add that node to the root node of the scene, and we have our boxy actor:

func createBoxNode() -> SCNNode {
    // make a 1×1×1 box
    let box = SCNBox(width: 1, height: 1, length: 1, chamferRadius: 0.1)
    let boxNode = SCNNode(geometry: box)
    return boxNode
}

…

let boxNode = createBoxNode()
rootNode.addChildNode(boxNode)

Camera

At this point the scene will render, but with a default light and camera. The position of the default camera means that the cube will fill the entire viewport. To fix that we need our own camera.

func createCameraNode(lookingAt target: SCNNode) -> SCNNode {
    let lookAt = SCNLookAtConstraint(target: target)
    lookAt.gimbalLockEnabled = true

    let camera = SCNCamera()
    camera.xFov = 60.0;

    let cameraNode = SCNNode()
    cameraNode.camera = camera
    cameraNode.constraints = [lookAt]
    return cameraNode
}

…

let cameraNode = createCameraNode(lookingAt: boxNode)
cameraNode.position = SCNVector3(x: 2, y: 1.5, z: 2.5)
rootNode.addChildNode(cameraNode)

Here I've setup a camera with a field-of-view of 60º in the x-axis (xFov), a constraint that keeps the camera looking at the box, and with gimbal-lock enabled to keep the horizon level if the camera moves.

With the camera moved into place, here's what we can see (remember that we're still using the default light source):

Lights

So, things don't look great with the default lighting. Let's replace the defaults with our own light:

func createOmniDirectionalLightNode() -> SCNNode {
    let omniLight = SCNLight()
    omniLight.type = SCNLightTypeOmni
    omniLight.color = UIColor.init(red: 1, green: 0.75, blue: 0.75, alpha: 1)
    omniLight.attenuationStartDistance = 1;
    omniLight.attenuationEndDistance = 10;

    let omniLightNode = SCNNode()
    omniLightNode.light = omniLight
    return omniLightNode
}

…

let omniLightNode = createOmniDirectionalLightNode()
omniLightNode.position = SCNVector3(x: 1, y: 1.5, z: 1)
rootNode.addChildNode(omniLightNode)

I've placed a light pink (rose gold!) omnidirectional light to the right, above, and in-front of the box. I've also used attenuationStartDistance and attenuationEndDistance to make sure that the brightness falls off with distance from the light. Here's what it looks like now:

The cube is starting to look better, but some better materials and texture could definitely spruce things up. Next time I'll look at adding some of those.

ViewController.swift

class ViewController: UIViewController {
    @IBOutlet weak var sceneView: SCNView!

    override func viewDidLoad() {
        super.viewDidLoad()

        // create a brand-new scene
        let scene = SCNScene()
        let rootNode = scene.rootNode

        let boxNode = createBoxNode()
        rootNode.addChildNode(boxNode)

        let omniLightNode = createOmniDirectionalLightNode()
        omniLightNode.position = SCNVector3(x: 1, y: 1.5, z: 1)
        rootNode.addChildNode(omniLightNode)

        let cameraNode = createCameraNode(lookingAt: boxNode)
        cameraNode.position = SCNVector3(x: 2, y: 1.5, z: 2.5)
        rootNode.addChildNode(cameraNode)

        sceneView.pointOfView = cameraNode
        sceneView.scene = scene
    }

    func createBoxNode() -> SCNNode {
        // make a 1x1x1 box
        let box = SCNBox(width: 1, height: 1, length: 1, chamferRadius: 0.1)

        let boxNode = SCNNode(geometry: box)
        return boxNode
    }

    func createOmniDirectionalLightNode() -> SCNNode {
        let omniLight = SCNLight()
        omniLight.type = SCNLightTypeOmni
        omniLight.color = UIColor.init(red: 1, green: 0.75, blue: 0.75, alpha: 1)
        omniLight.attenuationStartDistance = 1;
        omniLight.attenuationEndDistance = 10;

        let omniLightNode = SCNNode()
        omniLightNode.light = omniLight
        return omniLightNode
    }

    func createCameraNode(lookingAt target: SCNNode) -> SCNNode {
        let lookAt = SCNLookAtConstraint(target: target)
        let camera = SCNCamera()

        let cameraNode = SCNNode()
        cameraNode.camera = camera
        cameraNode.constraints = [lookAt]
        return cameraNode
    }
}

A fix for cwRsync ignoring --delete

2016-05-03T00:00:00Z

I was just helping Michael set up a Windows rsync-based solution to sync/backup his symbolic-linked game saves to a central folder (for subsequent syncing with BitTorrent Sync). We installed cwRsync, then used a command-line like this:

rsync -aL /cygdrive/C/Users/michael/GameSaves/ /cygdrive/C/Users/michael/Backups/

Copying worked without a hitch, but then we added --delete to the command-line. This should delete any files from the Backups folder that have been deleted from the GameSaves folder since the last sync:

rsync -aL --delete /cygdrive/C/Users/michael/GameSaves/ /cygdrive/C/Users/michael/Backups/

Unlike the copying, this proved difficult to get working. After longer than I care to admit, I listened to my Spidey-sense, and switched the upper-case drive letters to lower-case. Suddenly the deletes started working! The final command-line looked like this:

rsync -aL --delete /cygdrive/c/Users/michael/GameSaves/ /cygdrive/c/Users/michael/Backups/

So, it seems that cwRsync (and possibly a full Cygwin rsync installation) doesn't like upper-cased drive letters in its paths.

Fixing 'could not find symbol value for runtime.buildVersion' Delve debugger error

2015-09-13T02:40:00Z

TL;DR

If you're trying to debug Go code using the Delve debugger, or the Go plug-in for IntelliJ (which uses Delve), and you get the following error:

could not launch process: Could not determine version number:
	could not find symbol value for runtime.buildVersion

you should upgrade your go environment to a newer version.

Details

Yesterday, I decided I needed a better way to debug Go code than using fmt.Println. I discovered that there's a work-in-progress Go plug-in for IntelliJ. After installing the latest IntelliJ IDEA Community Edition, and installing the plug-in, I was dissapointed to be greeted with the could not find symbol value for runtime.buildVersion error when I tried to debug.

After searching through the Delve code, I decided that the most likely fix was to upgrade my go installation. At that point I was running version 1.3.3. After upgrading to 1.5.1, I can now happily go about my debugging.

This time it’s personal

2015-05-06T10:00:00Z

A developer’s initial Apple Watch impressions

I've been building software, in one form or another, for the best part of 40 years. Starting with an 8-bit microprocessor with 256 bytes of RAM, through to several generations of Macs, iPhones, and now Apple Watch, I've written code for almost every programmable platform I've owned. (Fun fact: The Apple Watch has 2 million times more RAM than that first machine.) Invariably I write one-or-more programs that are for my (or my family's) personal use on those devices.

Here's the thing: The more personal a device is, the more motivated I am to write personally meaningful software for it.

I've had 6 modern-era Macs, from a PowerBook G4, to my current Retina MacBook Pro. During that time, I've written many Python and Ruby scripts to do tasks like photo-management, but I've never written a native Cocoa app that was more than an experiment; nothing that was a personal experience.
The iPhone has been my constant companion for the last seven years. During that time, I've written several apps that I personally interact with multiple times each day (none on the App Store, but I'm working on it :-) ). I love my iPhone, and I want to extend it for my own ends.
My Apple Watch arrived at lunchtime on launch day. By evening I had one of my most used apps up-and-running on the watch. Since then I've continued to refine that app, and I'm working with my son on another. The tools, and some of the interactions on the watch, still seem a little rough around the edges. Despite that, having my own code, right on my wrist, is empowering. The Apple Watch gives me the chance to build tiny dashboards of actionable personal information, and I'm loving it.

It seems that the more personal (intimate, in Apple's words) the hardware is, the more eager I am to build personally useful software for it. Hopefully I'll be super-keen to code for my Apple ContactLens in 2025!

Network Not Starting on Migrated Virtual Machines

2013-12-09T23:22:19Z

If you've recently migrated a Ubuntu virtual machine file from one computer to another, or from one virtualization product to another, you might have discovered that networking inside the VM was no longer working.

As described in this Parallels KB article, what's probably happened is that the random MAC address generated by the virtualization host has changed. The file: /etc/udev/rules.d/70-persistent-net.rules contains a record of the matching MAC address from the previous host. When Ubuntu networking starts, a new interface, perhaps eth1 gets created, but is not listed to start automatically.

The fix is to edit /etc/udev/rules.d/70-persistent-net.rules to contain the MAC address from the new virtualization host's virtual network hardware.

Snowflakes on a Razer Blade

2013-12-09T22:50:05Z

The magnificent set of snowflake photos by Russian photographer Alexey Kljatov (recently featured by kottke.org) make for some wonderful desktop images. Michael and I have both just recently updated our desktop images to these snowflake macros.

Michael's Razer Blade features an 800x640 display as the trackpad. A resized snowflake makes an ideal trackpad background.

Pro Tip: If you're trying to turn one of these images into a 16:9 or 16:10 wallpaper, Photoshop's Content-aware Fill (Shift+F5) is your best friend.