Add -audioPlayer:didSeek:toFrame: delegate method

Sources/CSFBAudioEngine/Player/AudioPlayer.h

@@ -261,10 +261,12 @@ class AudioPlayer final {
         started = 1,
         /// Decoding complete
         complete = 2,
+        /// Seek
+        seek = 3,
         /// Decoder canceled by user or aborted due to error
-        canceled = 3,
+        canceled = 4,
         /// Decoding error
-        error = 4,
+        error = 5,
     };
 
     /// Render block events
@@ -288,6 +290,9 @@ class AudioPlayer final {
     /// Reads and processes a decoding complete event from `decodingEvents_`
     bool processDecodingCompleteEvent() noexcept;
 
+    /// Reads and processes a decoder seek event from `decodingEvents_`
+    bool processDecoderSeekEvent() noexcept;
+
     /// Reads and processes a decoder canceled event from `decodingEvents_`
     bool processDecoderCanceledEvent() noexcept;
 

Sources/CSFBAudioEngine/Player/AudioPlayer.mm

@@ -1232,6 +1232,15 @@ Flags clearFlags(Flags flags, std::memory_order order = std::memory_order_acq_re
                     decoderState->setFlags(DecoderState::Flags::cancelRequested);
                     continue;
                 }
+
+                if (const auto frame = decoderState->framesDecoded_.load(std::memory_order_acquire);
+                    decodingEvents_.writeAll(DecodingEventCommand::seek, nextEventIdentificationNumber(),
+                                             decoderState->sequenceNumber_, frame)) {
+                    eventSemaphore_.signal();
+                } else {
+                    os_log_fault(log_, "Error writing decoder seek event");
+                }
+
                 ringBufferStale = true;
 
                 if (bits::is_set(flags, DecoderState::Flags::decodingComplete)) {
@@ -1722,6 +1731,9 @@ Flags clearFlags(Flags flags, std::memory_order order = std::memory_order_acq_re
     case DecodingEventCommand::complete:
         return processDecodingCompleteEvent();
 
+    case DecodingEventCommand::seek:
+        return processDecoderSeekEvent();
+
     case DecodingEventCommand::canceled:
         return processDecoderCanceledEvent();
 
@@ -1804,6 +1816,36 @@ Flags clearFlags(Flags flags, std::memory_order order = std::memory_order_acq_re
     return true;
 }
 
+bool sfb::AudioPlayer::processDecoderSeekEvent() noexcept {
+    uint64_t sequenceNumber;
+    int64_t frame;
+    if (!decodingEvents_.readAll(sequenceNumber, frame)) {
+        os_log_error(log_, "Missing decoder sequence number or frame position for decoder seek event");
+        return false;
+    }
+
+    Decoder decoder = nil;
+    {
+        std::lock_guard lock{activeDecodersMutex_};
+
+        if (const auto iter = std::ranges::find(activeDecoders_, sequenceNumber, &DecoderState::sequenceNumber_);
+            iter != activeDecoders_.cend()) {
+            decoder = (*iter)->decoder_;
+        } else {
+            os_log_error(log_, "Decoder state with sequence number %llu missing for decoder seek event",
+                         sequenceNumber);
+            return false;
+        }
+    }
+
+    if (__strong id<SFBAudioPlayerDelegate> delegate = player_.delegate;
+        delegate != nil && [delegate respondsToSelector:@selector(audioPlayer:didSeek:toFrame:)]) {
+        [delegate audioPlayer:player_ didSeek:decoder toFrame:frame];
+    }
+
+    return true;
+}
+
 bool sfb::AudioPlayer::processDecoderCanceledEvent() noexcept {
     uint64_t sequenceNumber;
     if (!decodingEvents_.read(sequenceNumber)) {

Sources/CSFBAudioEngine/include/SFBAudioEngine/SFBAudioPlayer.h

@@ -52,12 +52,13 @@ typedef NS_ENUM(NSUInteger, SFBAudioPlayerPlaybackState) {
 ///  7. Now playing changed
 ///  8. Playback state changed
 ///  9. End of audio
-///  10. Decoder canceled by user
-///  11. Decoding aborted due to error
-///  12. Asynchronous error encountered
-///  13. Processing graph format change with custom nodes present
-///  14. `AVAudioEngineConfigurationChange` notification received
-///  15. `AVAudioSessionInterruption` notification received
+///  10. Seek complete
+///  11. Decoder canceled by user
+///  12. Decoding aborted due to error
+///  13. Asynchronous error encountered
+///  14. Processing graph format change with custom nodes present
+///  15. `AVAudioEngineConfigurationChange` notification received
+///  16. `AVAudioSessionInterruption` notification received
 ///
 /// The dispatch queue on which delegate messages are sent is not specified.
 NS_SWIFT_NAME(AudioPlayer)
@@ -367,6 +368,14 @@ NS_SWIFT_NAME(AudioPlayer.Delegate)
 /// Called to notify the delegate when rendering is complete for all available decoders
 /// - parameter audioPlayer: The `SFBAudioPlayer` object
 - (void)audioPlayerEndOfAudio:(SFBAudioPlayer *)audioPlayer NS_SWIFT_NAME(audioPlayerEndOfAudio(_:));
+/// Called to notify the delegate after performing a user-initiated seek in a decoder
+/// - warning: Do not change any properties of `decoder`
+/// - parameter audioPlayer: The `SFBAudioPlayer` object processing `decoder`
+/// - parameter decoder: The decoder that performed the seek
+/// - parameter frame: The new frame position in `decoder`
+- (void)audioPlayer:(SFBAudioPlayer *)audioPlayer
+            didSeek:(id<SFBPCMDecoding>)decoder
+            toFrame:(AVAudioFramePosition)frame;
 /// Called to notify the delegate that the decoding and rendering processes for a decoder have been canceled by a
 /// user-initiated request
 /// - warning: Do not change any properties of `decoder`