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

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
+  }
+}