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

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)
+    }
+  }
+}