Fix unmanaged self retain missing corrisponding release (caused memory leak)

Author: exPHAT

Sources/SwiftWhisper/Whisper.swift

@@ -3,6 +3,7 @@ import whisper_cpp
 
 public class Whisper {
     private let whisperContext: OpaquePointer
+    private var unmanagedSelf: Unmanaged<Whisper>?
 
     public var delegate: WhisperDelegate?
     public var params: WhisperParams
@@ -14,17 +15,13 @@ public class Whisper {
     public init(fromFileURL fileURL: URL, withParams params: WhisperParams = .default) {
         self.whisperContext = fileURL.relativePath.withCString { whisper_init_from_file($0) }
         self.params = params
-
-        prepareCallbacks()
     }
 
     public init(fromData data: Data, withParams params: WhisperParams = .default) {
         var copy = data // Need to copy memory so we can gaurentee exclusive ownership over pointer
 
         self.whisperContext = copy.withUnsafeMutableBytes { whisper_init_from_buffer($0.baseAddress!, data.count) }
         self.params = params
-
-        prepareCallbacks()
     }
 
     deinit {
@@ -38,8 +35,11 @@ public class Whisper {
 
          We can unwrap that and obtain a copy of self inside the callback.
          */
-        params.new_segment_callback_user_data = Unmanaged.passRetained(self).toOpaque()
-        params.encoder_begin_callback_user_data = Unmanaged.passRetained(self).toOpaque()
+        cleanupCallbacks()
+        let unmanagedSelf = Unmanaged.passRetained(self)
+        self.unmanagedSelf = unmanagedSelf
+        params.new_segment_callback_user_data = unmanagedSelf.toOpaque()
+        params.encoder_begin_callback_user_data = unmanagedSelf.toOpaque()
 
         // swiftlint:disable line_length
         params.new_segment_callback = { (ctx: OpaquePointer?, _: OpaquePointer?, newSegmentCount: Int32, userData: UnsafeMutableRawPointer?) in
@@ -94,32 +94,45 @@ public class Whisper {
         }
     }
 
+    private func cleanupCallbacks() {
+        guard let unmanagedSelf else { return }
+
+        unmanagedSelf.release()
+        self.unmanagedSelf = nil
+    }
+
     public func transcribe(audioFrames: [Float], completionHandler: @escaping (Result<[Segment], Error>) -> Void) {
+        prepareCallbacks()
+
+        let wrappedCompletionHandler: (Result<[Segment], Error>) -> Void = { result in
+            self.cleanupCallbacks()
+            completionHandler(result)
+        }
+
         guard !inProgress else {
-            completionHandler(.failure(WhisperError.instanceBusy))
+            wrappedCompletionHandler(.failure(WhisperError.instanceBusy))
             return
         }
         guard audioFrames.count > 0 else {
-            completionHandler(.failure(WhisperError.invalidFrames))
+            wrappedCompletionHandler(.failure(WhisperError.invalidFrames))
             return
         }
 
         inProgress = true
         frameCount = audioFrames.count
 
-        DispatchQueue.global(qos: .userInitiated).async { [unowned self] in
-
-            whisper_full(whisperContext, params.whisperParams, audioFrames, Int32(audioFrames.count))
+        DispatchQueue.global(qos: .userInitiated).async {
+            whisper_full(self.whisperContext, self.params.whisperParams, audioFrames, Int32(audioFrames.count))
 
-            let segmentCount = whisper_full_n_segments(whisperContext)
+            let segmentCount = whisper_full_n_segments(self.whisperContext)
 
             var segments: [Segment] = []
             segments.reserveCapacity(Int(segmentCount))
 
             for index in 0..<segmentCount {
-                guard let text = whisper_full_get_segment_text(whisperContext, index) else { continue }
-                let startTime = whisper_full_get_segment_t0(whisperContext, index)
-                let endTime = whisper_full_get_segment_t1(whisperContext, index)
+                guard let text = whisper_full_get_segment_text(self.whisperContext, index) else { continue }
+                let startTime = whisper_full_get_segment_t0(self.whisperContext, index)
+                let endTime = whisper_full_get_segment_t1(self.whisperContext, index)
 
                 segments.append(
                     .init(
@@ -130,20 +143,20 @@ public class Whisper {
                 )
             }
 
-            if let cancelCallback {
+            if let cancelCallback = self.cancelCallback {
                 DispatchQueue.main.async {
                     // Should cancel callback be called after delegate and completionHandler?
                     cancelCallback()
 
                     let error = WhisperError.cancelled
 
                     self.delegate?.whisper(self, didErrorWith: error)
-                    completionHandler(.failure(error))
+                    wrappedCompletionHandler(.failure(error))
                 }
             } else {
                 DispatchQueue.main.async {
                     self.delegate?.whisper(self, didCompleteWithSegments: segments)
-                    completionHandler(.success(segments))
+                    wrappedCompletionHandler(.success(segments))
                 }
             }