Initial implementation of APKINDEX, fetching, reading, parsing, & merging

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)"
+    }
+  }
+}