Kudos

• Adam Catley AirTag - Extremely useful Air tag breakdown with information compiled by Adam Catley
• bluetooth assigned-numbers lists - Bluetooth.com assigned numbers list, used for resolving Company UUIDs

Objective

FindMy Device Scanner: Shows you what Apple Find my devices have been in your vecinity for a length of time.

Application is tested on Windows, Linux, and mac and works on both.
Windows has an annoying flicker. I'm not sure what a good method of dealing with the screen buffering is.

Bluetooth device scanner in two routines

• scanner routine
  • Detects and maintains a list of local Bluetooth devices and sorts and passes down an ingest path.
• screen-writer routine.
  • Receives pre sorted list of devices on the ingest path, and prints them to a table.

Screenshot

Below is an AI generated breakdown of how this code works.

Purpose

Displays the output of the Bluetooth scanner in a neatly formatted table on the terminal screen. It does this by:

1. Receiving device data: Reads the stream of scanned device data from a channel.
2. Formatting the data: Prepares data rows for a table, including resolving company names and marking "Find My" devices.
3. Table Management: Uses the go-pretty/table library to create, style, and render the table.
4. Clearing the Screen: Ensures a clean display for each update.

Types

• screenWriter struct: Represents the component responsible for writing to the screen.
  • wg: WaitGroup for coordination.
  • ptab: A table.Writer instance from the go-pretty/table library.
  • header: The table's header row.
  • quit: Channel to signal stopping the writer.
  • readPath: Channel from which it receives device data

Functions

• newWriter(...) Constructor for creating a screenWriter. Initializes the table writer and other settings.

• startWriter(...) Bootstraps the screen writer process. Creates a screenWriter and starts its execution loop.

• execute() The main loop of the screenWriter:

  • Waits for signals on the quit channel to stop.
  • Waits for device data on the readPath channel.
  • Calls Write to update the table when data arrives.

• Write(devs []devContent) Handles the table updates:

  • Iterates over the received device data.
  • Calls helper functions like resolveCompanyIdent and isFindMyDevice to process device information.
  • Appends new rows to the table.
  • Clears the screen with clearScreen (you'll need to implement this function).
  • Renders the updated table.
  • Resets the table rows for the next update.

• Helper Functions

• resolveCompanyIdent(c *CorpIdentMap, t uint16) string:

  • Takes a pointer to the CorpIdentMap (c) and a company identifier (t).
  • Looks up the identifier in the map.
  • Returns the corresponding company name if found, or "Unknown" if not.

• ingestCorpDevices(loc string) CorpIdentMap:

  1. Opens the YAML file at the given location (company_identifiers.yaml).
  2. Defines structs to model the YAML data.
  3. Uses a YAML decoder to read the file contents into the CompanyIdentifiers struct.
  4. Iterates over the decoded data, populating the CorpIdentMap.
  5. Returns the filled CorpIdentMap.

• isFindMyDevice(b map[uint16][]byte) bool:

  • Takes the device's manufacturer data (b).
  • Iterates through the manufacturer data, checking if the first byte of any entry matches the "Find My" ID.
  • Returns true if a match is found, otherwise false.

• getCompanyIdent(md manData) uint16:

  • Takes the device's manufacturer data (md).
  • If the data isn't empty, it simply returns the first manufacturer ID found (assumes that's how the company ID is embedded).

This code implements a Bluetooth Low Energy (BLE) device scanner. Its essential functions are:

1. Scanning for BLE Devices: Discovers nearby BLE devices and gathers their data.
2. Storing Device Information: Maintains a list of discovered devices along with information like their addresses, manufacturer data, and the time they were last seen.
3. Transmitting Device Data: Regularly sends the collected device data downstream for further processing.
4. Managing Old Devices: Removes devices from the list if they haven't been seen within a specified time threshold.

Package and Imports

• main: The main package for the executable program.
• fmt: Standard input/output (I/O) formatting.
• log: Simple logging.
• reflect: Runtime type inspection.
• sort: Sorting.
• sync: Synchronization primitives (e.g., WaitGroup).
• time: Time-related functions.
• tinygo.org/x/bluetooth: Bluetooth library (assumed to be TinyGo-specific).

Constants

Defines time intervals and buffer sizes for the scanning and data processing:

• scanRate: How often to start a new scan.
• scanBufferSize: Capacity of the channel receiving scan results.
• scanLength: How long each scan lasts.
• writeTime: How often to send the collected devices to the ingest path.
• trimTime: How often to remove old devices from the storage.
• oldestDevice: Maximum age for devices in storage.

Types

• scanner struct: Represents the BLE scanner object.
  • wg: WaitGroup for coordination.
  • adptr: Bluetooth adapter.
  • devices: Map storing device data (Key: UUID, Value: map[UUID]devContent)
  • count: Count of discovered devices.
  • start: Timestamp of when the scan began.
  • quit: Channel to signal stopping the scan.
  • ingPath: Channel to send device data.
• DevContentList: A sortable slice of devContent structs.
• ingestPath: A channel for transmitting the discovered device data.
• devContent struct:** Represents information about a single BLE device
  • id: UUID of the device.
  • manufacturerData: Raw manufacturer data.
  • localName: Device's advertised name.
  • companyIdent: Company identifier extracted from manufacturer data.
  • lastSeen: Timestamp when the device was last observed.

Functions

• scan(returnPath chan bluetooth.ScanResult): The core scanning function. Performs repeated scans and sends results on the returnPath channel.
• newScanner(...): A constructor to create a new scanner object.
• startScan(): Starts the scanner's main loop (scanning, writing data, and trimming).
• startBleScanner(wg *sync.WaitGroup, ingPath ingestPath, q chan any): Bootstraps the scanner, sets up the Bluetooth adapter, and starts the scanning process.
• scanlog(s string): Simple logging function.
• TrimMap(): Removes stale device entries from the devices map.
• sortAndPass(): Sorts the devices by ID and sends them on the ingPath.