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

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)
+    }
+  }
+}