diff --git a/.gitignore b/.gitignore
index 47bd4c1..e86b8c2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,7 +3,6 @@
 /Packages
 xcuserdata/
 DerivedData/
-.swiftpm/configuration/registries.json
-.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
+.swiftpm/
 .netrc
 Package.resolved
diff --git a/Package.swift b/Package.swift
index 8c083aa..63f4947 100644
--- a/Package.swift
+++ b/Package.swift
@@ -3,13 +3,24 @@ import PackageDescription
 
 let package = Package(
   name: "darwin-apk",
+  platforms: [
+    .macOS(.v13),
+  ],
   dependencies: [
     .package(url: "https://github.com/apple/swift-argument-parser", from: "1.5.0"),
+    .package(url: "https://github.com/tsolomko/SWCompression", from: "4.8.6"),
   ],
   targets: [
+    .target(
+      name: "darwin-apk",
+      dependencies: [
+        .product(name: "SWCompression", package: "SWCompression"),
+      ],
+      path: "Sources/apk"),
     .executableTarget(
       name: "dpk",
       dependencies: [
+        "darwin-apk",
         .product(name: "ArgumentParser", package: "swift-argument-parser"),
       ],
       path: "Sources/dpk-cli"
diff --git a/Sources/apk/Index/ApkIndex.swift b/Sources/apk/Index/ApkIndex.swift
new file mode 100644
index 0000000..4ec800a
--- /dev/null
+++ b/Sources/apk/Index/ApkIndex.swift
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: Apache-2.0
+
+struct ApkIndex {
+  let packages: [ApkIndexPackage]
+}
+
+extension ApkIndex {
+  func first(name: String) -> ApkIndexPackage? {
+    self.packages.first {
+      $0.name == name
+    }
+  }
+}
+
+extension ApkIndex {
+  static func merge<S: Sequence>(_ tables: S) -> Self where S.Element == Self {
+    Self.init(packages: tables.flatMap(\.packages))
+  }
+
+  static func merge(_ tables: Self...) -> ApkIndex {
+    Self.init(packages: tables.flatMap(\.packages))
+  }
+}
+
+extension ApkIndex {
+  init(raw: ApkRawIndex) throws {
+    self.packages = try raw.packages.map {
+      try ApkIndexPackage(raw: $0)
+    }
+  }
+}
diff --git a/Sources/apk/Index/ApkIndexDownloader.swift b/Sources/apk/Index/ApkIndexDownloader.swift
new file mode 100644
index 0000000..b08139c
--- /dev/null
+++ b/Sources/apk/Index/ApkIndexDownloader.swift
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import Foundation
+
+struct ApkIndexDownloader {
+  func downloadFile(remote remoteURL: URL, destination destLocalURL: URL) {
+    let sem = DispatchSemaphore.init(value: 0)
+    let downloadTask = URLSession.shared.downloadTask(with: remoteURL) { url, response, error in
+      if let localURL = url {
+        do {
+          // Replace existing APKINDEX.tar.gz files
+          if FileManager.default.fileExists(atPath: destLocalURL.path()) {
+            try FileManager.default.removeItem(at: destLocalURL)
+          }
+          // Move temporary to the new location
+          try FileManager.default.moveItem(at: localURL, to: destLocalURL)
+        } catch {
+          print("Download error: \(error.localizedDescription)")
+        }
+      }
+      sem.signal()
+    }
+    downloadTask.resume()
+    sem.wait()
+  }
+}
diff --git a/Sources/apk/Index/ApkIndexPackage.swift b/Sources/apk/Index/ApkIndexPackage.swift
new file mode 100644
index 0000000..98892c4
--- /dev/null
+++ b/Sources/apk/Index/ApkIndexPackage.swift
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import Foundation
+
+struct ApkIndexPackage {
+  let indexChecksum: String  //TODO: Decode cus why not
+  let name: String
+  let version: String
+  let architecture: String?
+  let packageSize: UInt64
+  let installedSize: UInt64
+  let packageDescription: String
+  let url: String
+  let license: String
+  let origin: String?
+  let maintainer: String?
+  let buildTime: Date?
+  let commit: String?
+  let providerPriority: UInt16?
+  let dependencies: [String]  //TODO: stuff
+  let provides: [String]  //TODO: stuff
+  let installIf: [String]  //TODO: stuff
+
+  var downloadFilename: String { "\(self.name)-\(version).apk" }
+
+  //TODO: Implementation
+  //lazy var semanticVersion: (Int, Int, Int) = (0, 0, 0)
+}
+
+extension ApkIndexPackage {
+  init(raw rawEntry: ApkRawIndexEntry) throws(Self.ParseError) {
+    // Required fields
+    var indexChecksum: String? = nil
+    var name: String? = nil
+    var version: String? = nil
+    var description: String? = nil
+    var url: String? = nil
+    var license: String? = nil
+    var packageSize: UInt64? = nil
+    var installedSize: UInt64? = nil
+
+    var dependencies = [String]()
+    var provides = [String]()
+    var installIf = [String]()
+
+    // Optional fields
+    var architecture: String? = nil
+    var origin: String? = nil
+    var maintainer: String? = nil
+    var buildTime: Date? = nil
+    var commit: String? = nil
+    var providerPriority: UInt16? = nil
+
+    // Read all the raw records for this entry
+    for record in rawEntry.fields {
+      switch record.key {
+      case "P":
+        name = record.value
+      case "V":
+        version = record.value
+      case "T":
+        description = record.value
+      case "U":
+        url = record.value
+      case "L":
+        license = record.value
+      case "A":
+        architecture = record.value
+      case "D":
+        dependencies = record.value.components(separatedBy: " ")
+      case "C":
+        indexChecksum = record.value  // base64-encoded SHA1 hash prefixed with "Q1"
+      case "S":
+        guard let value = UInt64(record.value, radix: 10) else {
+          throw .badValue(key: record.key)
+        }
+        packageSize = value
+      case "I":
+        guard let value = UInt64(record.value, radix: 10) else {
+          throw .badValue(key: record.key)
+        }
+        installedSize = value
+      case "p":
+        provides = record.value.components(separatedBy: " ")
+      case "i":
+        installIf = record.value.components(separatedBy: " ")
+      case "o":
+        origin = record.value
+      case "m":
+        maintainer = record.value
+      case "t":
+        guard let timet = UInt64(record.value, radix: 10),
+            let timetInterval = TimeInterval(exactly: timet) else {
+          throw .badValue(key: record.key)
+        }
+        buildTime = Date(timeIntervalSince1970: timetInterval)
+      case "c":
+        commit = record.value
+      case "k":
+        guard let value = UInt64(record.value, radix: 10),
+            (0..<UInt64(UInt16.max)).contains(value) else {
+          throw .badValue(key: record.key)
+        }
+        providerPriority = UInt16(truncatingIfNeeded: value)
+      case "F", "M", "R", "Z", "r", "q", "a", "s", "f":
+        break // installed db entries
+      default:
+        // Safe to ignore
+        guard record.key.isLowercase else {
+          throw .badValue(key: record.key)
+        }
+      }
+    }
+
+    self.indexChecksum = try indexChecksum.unwrap(or: Self.ParseError.required(key: "C"))
+    self.name = try name.unwrap(or: Self.ParseError.required(key: "P"))
+    self.version = try version.unwrap(or: Self.ParseError.required(key: "V"))
+    self.packageDescription = try description.unwrap(or: Self.ParseError.required(key: "T"))
+    self.url = try url.unwrap(or: Self.ParseError.required(key: "U"))
+    self.license = try license.unwrap(or: Self.ParseError.required(key: "L"))
+    self.packageSize = try packageSize.unwrap(or: Self.ParseError.required(key: "S"))
+    self.installedSize = try installedSize.unwrap(or: Self.ParseError.required(key: "I"))
+
+    self.architecture = architecture
+    self.origin = origin
+    self.maintainer = maintainer
+    self.buildTime = buildTime
+    self.commit = commit
+    self.providerPriority = providerPriority
+
+    self.dependencies = dependencies
+    self.provides = provides
+    self.installIf = installIf
+  }
+
+  public enum ParseError: Error, LocalizedError {
+    case badValue(key: Character)
+    case unexpectedKey(key: Character)
+    case required(key: Character)
+
+    public var errorDescription: String? {
+      switch self {
+      case .badValue(let key):      "Bad value for key \"\(key)\""
+      case .unexpectedKey(let key): "Unexpected key \"\(key)\""
+      case .required(let key):      "Missing required key \"\(key)\""
+      }
+    }
+  }
+}
+
+extension ApkIndexPackage: CustomStringConvertible {
+  var description: String { "pkg(\(self.name))" }
+}
+
+fileprivate extension Optional {
+  func unwrap<E: Error>(or error: @autoclosure () -> E) throws(E) -> Wrapped {
+    switch self {
+    case .some(let v):
+      return v
+    case .none:
+      throw error()
+    }
+  }
+}
diff --git a/Sources/apk/Index/ApkIndexUpdate.swift b/Sources/apk/Index/ApkIndexUpdate.swift
new file mode 100644
index 0000000..d5cd989
--- /dev/null
+++ b/Sources/apk/Index/ApkIndexUpdate.swift
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import Foundation
+import SWCompression
+import CryptoKit
+
+public struct ApkIndexUpdater {
+  var repositories: [String]
+  var architectures: [String]
+
+  public init() {
+    self.repositories = [
+      "https://dl-cdn.alpinelinux.org/alpine/v3.21/main",
+      "https://dl-cdn.alpinelinux.org/alpine/edge/community"
+    ]
+    // other archs: "armhf", "armv7", "loongarch64", "ppc64le", "riscv64", "s390x", "x86"
+    self.architectures = [ "aarch64", "x86_64" ]
+  }
+
+  public func update() {
+    let repositories = self.repositories.flatMap { repo in
+      self.architectures.map { arch in
+        Repository(name: repo, arch: arch)
+      }
+    }
+
+    let downloader = ApkIndexDownloader()
+    for repo in repositories {
+      let localIndex = URL(filePath: repo.localName)
+#if false
+      let shouldDownload = true
+#else
+      let shouldDownload = !FileManager.default.fileExists(atPath: localIndex.path())
+#endif
+      if shouldDownload {
+        print("Fetching index for \"\(repo.name)\"")
+        downloader.downloadFile(remote: repo.url, destination: localIndex)
+      }
+    }
+
+    let index: ApkIndex
+    do {
+      let tables = try repositories.map { try readIndex(URL(filePath: $0.localName)) }
+      index = ApkIndex.merge(tables)
+    } catch {
+      fatalError(error.localizedDescription)
+    }
+
+    for package in index.packages {
+      print(package)
+    }
+  }
+
+  private func readIndex(_ indexURL: URL) throws -> ApkIndex {
+    let tarSignature: [TarReader.Entry]
+    let tarRecords: [TarReader.Entry]
+
+    let tars = try GzipArchive.multiUnarchive(  // Slow...
+      archive: Data(contentsOf: indexURL))
+    assert(tars.count >= 2)
+
+    var signatureStream = MemoryInputStream(buffer: tars[0].data)
+    tarSignature = try TarReader.read(&signatureStream)
+    var recordsStream = MemoryInputStream(buffer: tars[1].data)
+    tarRecords = try TarReader.read(&recordsStream)
+
+    guard case .file(let signatureName, _) = tarSignature.first
+    else { fatalError("Missing signature") }
+    print(signatureName)
+    guard let apkIndexFile = tarRecords.firstFile(name: "APKINDEX")
+    else { fatalError("APKINDEX missing") }
+    guard let description = tarRecords.firstFile(name: "DESCRIPTION")
+    else { fatalError("DESCRIPTION missing") }
+
+    let reader = TextInputStream(binaryStream: MemoryInputStream(buffer: apkIndexFile))
+    return try ApkIndex(raw:
+      try ApkRawIndex(lines: reader.lines))
+  }
+}
+
+extension ApkIndexUpdater {
+  struct Repository {
+    let name: String
+    let arch: String
+    let discriminator: String
+
+    private static func resolveApkIndex(_ repo: String, _ arch: String)
+      -> String { "\(repo)/\(arch)/APKINDEX.tar.gz" }
+    var url: URL { URL(string: Self.resolveApkIndex(self.name, self.arch))! }
+    var localName: String { "APKINDEX.\(discriminator).tar.gz" }
+
+    init(name repo: String, arch: String) {
+      self.name = repo
+      self.arch = arch
+
+      let urlSHA1Digest = Data(Insecure.SHA1.hash(data: Data(Self.resolveApkIndex(repo, arch).utf8)))
+      self.discriminator = urlSHA1Digest.subdata(in: 0..<3).map { String(format: "%02x", $0) }.joined()
+    }
+  }
+}
diff --git a/Sources/apk/Index/ApkRawIndex.swift b/Sources/apk/Index/ApkRawIndex.swift
new file mode 100644
index 0000000..9064699
--- /dev/null
+++ b/Sources/apk/Index/ApkRawIndex.swift
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import Foundation
+
+struct ApkRawIndex {
+  let packages: [ApkRawIndexEntry]
+
+  init(lines: any Sequence<String>) throws {
+    var packages = [ApkRawIndexEntry]()
+
+    var recordLines = [String]()
+    recordLines.reserveCapacity(15)
+
+    for line in lines {
+      if line.trimmingCharacters(in: .whitespaces).isEmpty {
+        if !recordLines.isEmpty {
+          packages.append(try .init(parsingEntryLines: recordLines))
+          recordLines.removeAll(keepingCapacity: true)
+        }
+      } else {
+        recordLines.append(line)
+      }
+    }
+    if !recordLines.isEmpty {
+      packages.append(try .init(parsingEntryLines: recordLines))
+    }
+
+    self.packages = packages
+  }
+}
+
+struct ApkRawIndexEntry {
+  let fields: [Record]
+
+  struct Record {
+    let key: Character
+    let value: String
+  }
+}
+
+extension ApkRawIndexEntry {
+  init(parsingEntryLines lines: any Sequence<String>) throws {
+    self.fields = try lines.map { line in
+      guard let splitIdx = line.firstIndex(of: ":"),
+          line.distance(from: line.startIndex, to: splitIdx) == 1 else {
+        throw ApkRawIndexError.badPair
+      }
+      return Record(
+        key:   line.first!,
+        value: String(line[line.index(after: splitIdx)...]))
+    }
+  }
+
+  func toMap() -> [Character: String] {
+    Dictionary(uniqueKeysWithValues: self.fields.map { $0.pair })
+  }
+
+  func lookup(_ key: Character) -> String? {
+    fields.first(where: { $0.key == key })?.value
+  }
+}
+
+extension ApkRawIndexEntry.Record {
+  var pair: (Character, String) {
+    (self.key, self.value)
+  }
+}
+
+enum ApkRawIndexError: Error, LocalizedError {
+  case badPair
+
+  var errorDescription: String? {
+    switch self {
+    case .badPair: "Malformed raw key-value pair"
+    }
+  }
+}
diff --git a/Sources/apk/Utility/FileInputStream.swift b/Sources/apk/Utility/FileInputStream.swift
new file mode 100644
index 0000000..e3e0d6e
--- /dev/null
+++ b/Sources/apk/Utility/FileInputStream.swift
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import Foundation
+
+public struct FileInputStream: InputStream {
+  private var _hnd: FileHandle
+
+  public init(_ fileURL: URL) throws {
+    self._hnd = try FileHandle(forReadingFrom: fileURL)
+  }
+
+  public mutating func seek(_ whence: StreamWhence) throws(StreamError) {
+    let applyOffset = { (position: UInt64, offset: Int) throws(StreamError) -> UInt64 in
+      if offset < 0 {
+        let (newPosition, overflow) = position.subtractingReportingOverflow(UInt64(-offset))
+        if overflow { throw .seekRange }
+        return newPosition
+      } else {
+        let (newPosition, overflow) = position.addingReportingOverflow(UInt64(offset))
+        if overflow { throw .overflow }
+        return newPosition
+      }
+    }
+
+    switch whence {
+    case .set(let position):
+      if position < 0 { throw .seekRange }
+      do { try self._hnd.seek(toOffset: UInt64(truncatingIfNeeded: position)) }
+      catch {
+        throw .fileHandleError(error)
+      }
+    case .current(let offset):
+      do { try self._hnd.seek(toOffset: try applyOffset(try self._hnd.offset(), offset)) }
+      catch {
+        if error is StreamError {
+          throw error as! StreamError
+        } else {
+          throw .fileHandleError(error)
+        }
+      }
+    case .end(let offset):
+      do { try self._hnd.seek(toOffset: applyOffset(try self._hnd.seekToEnd(), offset)) }
+      catch {
+        if error is StreamError {
+          throw error as! StreamError
+        } else {
+          throw .fileHandleError(error)
+        }
+      }
+    }
+  }
+
+  public var tell: Int {
+    get throws(StreamError) {
+      let offset: UInt64
+      do { offset = try self._hnd.offset() }
+      catch {
+        throw .fileHandleError(error)
+      }
+      if offset > Int.max { throw .overflow }
+      return Int(truncatingIfNeeded: offset)
+    }
+  }
+
+  public mutating func read(_ count: Int) throws(StreamError) -> Data {
+    do {
+      return try self._hnd.read(upToCount: count) ?? Data()
+    } catch {
+      throw .fileHandleError(error)
+    }
+  }
+}
diff --git a/Sources/apk/Utility/InputStream.swift b/Sources/apk/Utility/InputStream.swift
new file mode 100644
index 0000000..c8ce16c
--- /dev/null
+++ b/Sources/apk/Utility/InputStream.swift
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import Foundation
+
+public protocol InputStream: Stream, IteratorProtocol {
+  associatedtype Element = UInt8
+
+  mutating func read(_ count: Int) throws(StreamError) -> Data
+}
+
+public extension InputStream {
+  mutating func read(_ size: Int, items: Int) throws(StreamError) -> Data {
+    try self.read(size * items)
+  }
+}
+
+public extension InputStream {
+  mutating func next() -> UInt8? {
+    try? self.read(1).first
+  }
+}
diff --git a/Sources/apk/Utility/MemoryInputStream.swift b/Sources/apk/Utility/MemoryInputStream.swift
new file mode 100644
index 0000000..3c820eb
--- /dev/null
+++ b/Sources/apk/Utility/MemoryInputStream.swift
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import Foundation
+
+public struct MemoryInputStream: InputStream {
+  private var _buf: [UInt8]! = nil
+  private let _sli: ArraySlice<UInt8>
+  private let _len: Int
+  private var _idx = 0
+
+  public init(buffer: Data) {
+    self._len = buffer.count
+    self._buf = [UInt8](repeating: 0, count: self._len)
+    self._buf.withUnsafeMutableBytes { _ = buffer.copyBytes(to: $0) }
+    self._sli = self._buf[...]
+  }
+
+  public init(view: ArraySlice<UInt8>) {
+    self._sli = view
+    self._len = view.count
+  }
+
+  public mutating func seek(_ whence: StreamWhence) throws(StreamError) {
+    let (position, overflow) = switch whence {
+    case .set(let position):   (position, false)
+    case .current(let offset): self._idx.addingReportingOverflow(offset)
+    case .end(let offset):     self._len.addingReportingOverflow(offset)
+    }
+    if overflow {
+      throw .overflow
+    } else if position < 0 {
+      throw .seekRange
+    } else {
+      self._idx = position
+    }
+  }
+
+  public var tell: Int {
+    get throws(StreamError) {
+      self._idx
+    }
+  }
+
+  public mutating func read(_ count: Int) throws(StreamError) -> Data {
+    let beg = min(self._idx, self._len)
+    let end = min(self._idx + count, self._len)
+    let bytes = Data(self._sli[beg..<end])
+    self._idx += beg.distance(to: end)
+    return bytes
+  }
+
+  public mutating func next() -> UInt8? {
+    if self._idx < self._len {
+      let byte = self._sli[self._idx]
+      self._idx += 1
+      return byte
+    } else {
+      return nil
+    }
+  }
+}
diff --git a/Sources/apk/Utility/Stream.swift b/Sources/apk/Utility/Stream.swift
new file mode 100644
index 0000000..52ffd75
--- /dev/null
+++ b/Sources/apk/Utility/Stream.swift
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import Foundation
+
+public protocol Stream {
+  mutating func seek(_ whence: StreamWhence) throws(StreamError)
+  var tell: Int { get throws(StreamError) }
+}
+
+public enum StreamWhence {
+  case set(_ position: Int)
+  case current(_ offset: Int)
+  case end(_ offset: Int)
+}
+
+public enum StreamError: Error, LocalizedError {
+  case unsupported
+  case seekRange
+  case overflow
+  case fileHandleError(_ error: any Error)
+
+  public var errorDescription: String? {
+    switch self {
+    case .unsupported: "Unsupported operation"
+    case .seekRange: "Seek out of range"
+    case .overflow: "Stream position overflowed"
+    case .fileHandleError(let error): "Error from file handle: \(error.localizedDescription)"
+    }
+  }
+}
diff --git a/Sources/apk/Utility/TarMemoryReader.swift b/Sources/apk/Utility/TarMemoryReader.swift
new file mode 100644
index 0000000..88e00a8
--- /dev/null
+++ b/Sources/apk/Utility/TarMemoryReader.swift
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import Foundation
+
+public struct TarReader {
+  private static let tarBlockSize  = 512
+  private static let tarTypeOffset = 156
+  private static let tarNameOffset =   0
+  private static let tarNameSize   = 100
+  private static let tarSizeOffset = 124
+  private static let tarSizeSize   =  12
+
+  public enum Entry {
+    case file(name: String, data: Data)
+    case directory(name: String)
+  }
+
+  public static func read<S: InputStream>(_ stream: inout S) throws -> [Entry] {
+    var entries = [Entry]()
+
+    while true {
+      let tarBlock = try stream.read(Self.tarBlockSize)
+      if tarBlock.isEmpty { break }
+      if tarBlock.count < Self.tarBlockSize { throw TarError.unexpectedEndOfStream }
+
+      let type = UnicodeScalar(tarBlock[Self.tarTypeOffset])
+      switch type {
+      case "0":  // Regular file
+        // Read metadata
+        let name = try Self.readName(tarBlock)
+        let size = try Self.readSize(tarBlock)
+
+        // Read file data
+        var data = Data()
+        var bytesRemaining = size, readAmount = 0
+        while bytesRemaining > 0 {
+          //FIXME: just read the whole thing at once tbh
+          readAmount = min(bytesRemaining, Self.tarBlockSize)
+          let block = try stream.read(readAmount)
+          if block.count < readAmount { throw TarError.unexpectedEndOfStream }
+          data += block
+          bytesRemaining -= readAmount
+        }
+        entries.append(.file(name: name, data: data))
+
+        // Seek to next block
+        let seekAmount = Self.tarBlockSize - readAmount
+        if seekAmount > 0 {
+          try stream.seek(.current(seekAmount))
+        }
+      case "5":
+        // Directory
+        let name = try Self.readName(tarBlock)
+        entries.append(.directory(name: name))
+      case "\0":
+        // Null block, might also be a legacy regular file
+        break
+      case "x":
+        // Extended header block
+        try stream.seek(.current(Self.tarBlockSize))
+      // Symlink, Reserved, Character, Block, FIFO, Reserved, Global, ignore all these
+      case "1", "2", "3", "4", "6", "7", "g":
+        let size = try self.readSize(tarBlock)
+        let blockCount = (size - 1) / Self.tarBlockSize + 1  // Compute blocks to skip
+        try stream.seek(.current(Self.tarBlockSize * blockCount))
+      default: throw TarError.invalidType(type: type)  // Not a TAR type
+      }
+    }
+    return entries
+  }
+
+  private static func readName(_ tar: Data, offset: Int = Self.tarNameOffset) throws (TarError) -> String {
+    var nameSize = Self.tarNameSize
+    for i in 0...Self.tarNameSize {
+      if tar[offset + i] == 0 {
+        nameSize = i
+        break
+      }
+    }
+    let data = tar.subdata(in: offset..<offset + nameSize)
+    guard let name = String(data: data, encoding: .utf8) else { throw TarError.badNameField }
+    return name
+  }
+
+  private static func readSize(_ tar: Data, offset: Int = Self.tarSizeOffset) throws (TarError) -> Int {
+    let sizeData = tar.subdata(in: offset..<offset + Self.tarSizeSize)
+    let sizeEnd = sizeData.firstIndex(of: 0) ?? sizeData.endIndex  // Find the null terminator
+    guard
+      let sizeString = String(data: sizeData[..<sizeEnd], encoding: .ascii),
+      let result = Int(sizeString, radix: 0o10) else { throw TarError.badSizeField }
+    return result
+  }
+}
+
+public enum TarError: Error, LocalizedError {
+  case unexpectedEndOfStream
+  case invalidType(type: UnicodeScalar)
+  case badNameField, badSizeField
+
+  public var errorDescription: String? {
+    switch self {
+    case .unexpectedEndOfStream: "Stream unexpectedly ended early"
+    case .invalidType(let type): "Invalid block type \(type) found"
+    case .badNameField: "Bad name field"
+    case .badSizeField: "Bad size field"
+    }
+  }
+}
+
+public extension Array<TarReader.Entry> {
+  func firstFile(name firstNameMatch: String) -> Data? {
+    for entry in self {
+      if case .file(let name, let data) = entry {
+        if name == firstNameMatch {
+          return data
+        }
+      }
+    }
+    return nil
+  }
+}
diff --git a/Sources/apk/Utility/TextInputStream.swift b/Sources/apk/Utility/TextInputStream.swift
new file mode 100644
index 0000000..cfb386a
--- /dev/null
+++ b/Sources/apk/Utility/TextInputStream.swift
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: Apache-2.0
+
+//FIXME: I don't like this, also SLOWWW
+struct TextInputStream<InStream: InputStream> where InStream.Element == UInt8 {
+  private var _stream: InStream
+
+  public init(binaryStream: InStream) {
+    _stream = binaryStream
+  }
+
+  public var lines: LineSequence {
+    LineSequence(_stream: self._stream)
+  }
+
+  public struct LineSequence: Sequence {
+    public typealias Element = String
+
+    fileprivate var _stream: InStream
+
+    public struct Iterator: IteratorProtocol where InStream.Element == UInt8 {
+      public typealias Element = String
+
+      fileprivate init(stream: InStream) {
+        self._stream = stream
+      }
+
+      private var _stream: InStream
+      private var _utf8Decoder = UTF8()
+      private var _scalars = [Unicode.Scalar]()
+      private var _lastChar: UnicodeScalar = "\0"
+      private var _eof = false
+
+      private mutating func decodeScalarsLine() {
+        Decode: while true {
+          switch self._utf8Decoder.decode(&self._stream) {
+          case .scalarValue(let value):
+            if value == "\n" {
+              if self._lastChar == "\n" { break }
+              else { break Decode }
+            } else if value == "\r" {
+              break Decode
+            }
+            self._scalars.append(value)
+            self._lastChar = value
+          case .emptyInput:
+            self._eof = true
+            break Decode
+          case .error:
+            break Decode
+            //FIXME: repair like the stdlib does
+            //scalars.append(UTF8.encodedReplacementCharacter)
+            //lastChar = UTF8.encodedReplacementCharacter
+          }
+        }
+      }
+
+      public mutating func next() -> String? {
+        // Return early if we already hit the end of the stream
+        guard !self._eof else {
+          return nil
+        }
+
+        // Decode a line of scalars
+        self.decodeScalarsLine()
+        defer {
+          self._scalars.removeAll(keepingCapacity: true)
+        }
+
+        // Ignore the final empty newline
+        guard !self._eof || !self._scalars.isEmpty else {
+          return nil
+        }
+
+        // Convert to string and return
+        var string = String()
+        string.unicodeScalars.append(contentsOf: self._scalars)
+        return string
+      }
+    }
+
+    public func makeIterator() -> Iterator {
+      Iterator(stream: self._stream)
+    }
+  }
+}
diff --git a/Sources/dpk-cli/CommandLine.swift b/Sources/dpk-cli/CommandLine.swift
index f508b80..89e86fd 100644
--- a/Sources/dpk-cli/CommandLine.swift
+++ b/Sources/dpk-cli/CommandLine.swift
@@ -8,68 +8,9 @@ struct DarwinApkCLI: ParsableCommand {
     commandName: "dpk",
     abstract: "Command-line interface for managing packages installed via darwin-apk.",
     subcommands: [
-      Install.self,
-      Remove.self,
-      Update.self,
-      Upgrade.self
+      DpkInstallCommand.self,
+      DpkRemoveCommand.self,
+      DpkUpdateCommand.self,
+      DpkUpgradeCommand.self
     ])
 }
-
-extension DarwinApkCLI {
-  struct Install: ParsableCommand {
-    static let configuration = CommandConfiguration(
-      commandName: "add",
-      abstract: "Install package(s) to the system.",
-      aliases: [ "install", "i", "a" ])
-
-    @Argument(help: "One or more package names to install to the system.")
-    var packages: [String]
-
-    func run() throws {
-      print("installing \"\(packages.joined(separator: "\", \""))\"")
-    }
-  }
-
-  struct Remove: ParsableCommand {
-    static let configuration = CommandConfiguration(
-      commandName: "remove",
-      abstract: "Remove specified package(s) from the system.",
-      aliases: [ "uninstall", "del", "rem", "r" ])
-
-    @Argument(help: "One or more package names to uninstall from the system.")
-    var packages: [String]
-
-    func run() throws {
-      print("uninstalling \"\(packages.joined(separator: "\", \""))\"")
-    }
-  }
-
-  struct Update: ParsableCommand {
-    static let configuration = CommandConfiguration(
-      commandName: "update",
-      abstract: "Update the system package repositories.",
-      aliases: [ "u" ])
-
-    func run() throws {
-      print("updating package repositories")
-    }
-  }
-
-  struct Upgrade: ParsableCommand {
-    static let configuration = CommandConfiguration(
-      commandName: "upgrade",
-      abstract: "Upgrade installed packages.",
-      aliases: [ "U" ])
-
-    @Argument(help: "Optionally specify packages to upgrade. Otherwise upgrade all packages installed on the system.")
-    var packages: [String] = []
-
-    func run() throws {
-      if packages.isEmpty {
-        print("upgrading system")
-      } else {
-        print("upgrading invidual packages: \"\(packages.joined(separator: "\", \""))\"")
-      }
-    }
-  }
-}
diff --git a/Sources/dpk-cli/Subcommands/DpkInstallCommand.swift b/Sources/dpk-cli/Subcommands/DpkInstallCommand.swift
new file mode 100644
index 0000000..1dc1746
--- /dev/null
+++ b/Sources/dpk-cli/Subcommands/DpkInstallCommand.swift
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import ArgumentParser
+
+struct DpkInstallCommand: ParsableCommand {
+  static let configuration = CommandConfiguration(
+    commandName: "add",
+    abstract: "Install package(s) to the system.",
+    aliases: [ "a", "install" ])
+
+  @Argument(help: "One or more package names to install to the system.")
+  var packages: [String]
+
+  func run() throws {
+    print("installing \"\(packages.joined(separator: "\", \""))\"")
+  }
+}
diff --git a/Sources/dpk-cli/Subcommands/DpkRemoveCommand.swift b/Sources/dpk-cli/Subcommands/DpkRemoveCommand.swift
new file mode 100644
index 0000000..750d1e4
--- /dev/null
+++ b/Sources/dpk-cli/Subcommands/DpkRemoveCommand.swift
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import ArgumentParser
+
+struct DpkRemoveCommand: ParsableCommand {
+  static let configuration = CommandConfiguration(
+    commandName: "remove",
+    abstract: "Remove specified package(s) from the system.",
+    aliases: [ "r", "rem", "del", "uninstall" ])
+
+  @Argument(help: "One or more package(s) to uninstall from the system.")
+  var packages: [String]
+
+  func run() throws {
+    print("uninstalling \"\(packages.joined(separator: "\", \""))\"")
+  }
+}
diff --git a/Sources/dpk-cli/Subcommands/DpkUpdateCommand.swift b/Sources/dpk-cli/Subcommands/DpkUpdateCommand.swift
new file mode 100644
index 0000000..aaae988
--- /dev/null
+++ b/Sources/dpk-cli/Subcommands/DpkUpdateCommand.swift
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import Foundation
+import ArgumentParser
+import darwin_apk
+
+struct DpkUpdateCommand: ParsableCommand {
+  static let configuration = CommandConfiguration(
+    commandName: "update",
+    abstract: "Update the system package repositories.",
+    aliases: [ "u" ])
+
+  func run() throws {
+    print("Updating package repositories")
+    var updater = ApkIndexUpdater()
+    updater.update()
+  }
+}
diff --git a/Sources/dpk-cli/Subcommands/DpkUpgradeCommand.swift b/Sources/dpk-cli/Subcommands/DpkUpgradeCommand.swift
new file mode 100644
index 0000000..8a15fd1
--- /dev/null
+++ b/Sources/dpk-cli/Subcommands/DpkUpgradeCommand.swift
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: Apache-2.0
+
+import ArgumentParser
+
+struct DpkUpgradeCommand: ParsableCommand {
+  static let configuration = CommandConfiguration(
+    commandName: "upgrade",
+    abstract: "Upgrade installed packages.",
+    aliases: [ "U" ])
+
+  @Argument(help: "Optionally specify packages to upgrade. Otherwise upgrade all packages installed on the system.")
+  var packages: [String] = []
+
+  func run() throws {
+    if packages.isEmpty {
+      print("upgrading system")
+    } else {
+      print("upgrading invidual packages: \"\(packages.joined(separator: "\", \""))\"")
+    }
+  }
+}