52 lines
2.9 KiB
Swift
52 lines
2.9 KiB
Swift
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// Callbacks — the C function pointers passed to `vc_callbacks`. These are the Swift
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// equivalent of the C# client's `[UnmanagedCallersOnly]` static methods (NativeCallbacks.cs).
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//
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// The critical patterns (carried over from the proven C# implementation):
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// 1. `@convention(c)` closures — plain C function pointers, NOT GC/ARC-managed closures.
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// A @convention(c) closure cannot capture context, which is why the `user` pointer is
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// used to resolve back to the VoiceCatClient instance (the C# version uses GCHandle for
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// the same thing; Swift uses Unmanaged).
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// 2. `Unmanaged.passUnretained(self).toOpaque()` as the `user` context — a stable raw
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// pointer to the Swift object WITHOUT incrementing the retain count. This is safe
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// because `deinit` calls `vc_client_destroy` (which synchronously joins every internal
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// thread) BEFORE the object's memory is freed — so no callback can fire after the object
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// is gone. (The C# equivalent: GCHandle.Alloc + GCHandle.Free in Dispose.)
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// 3. Copy `ev.text` to a Swift `String` INSIDE `onEvent` (via `VoiceCatEvent.from(_:)`)
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// before returning — the raw pointer is dangling after the callback returns. This is
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// the #1 lifetime rule from voicecat.h's vc_event doc comment.
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import VoiceCatC
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import Foundation
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/// Internal: builds the `vc_callbacks` struct wired to VoiceCatClient's C function pointers.
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/// The `user` context is an Unmanaged-passUnretained pointer to the client — resolved back
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/// to the client inside `onEvent`/`onLevel` below.
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internal enum Callbacks {
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/// The `on_event` C function pointer. Non-capturing @convention(c) closure — resolves
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/// the VoiceCatClient from `user` and enqueues a safe copy of the event.
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static let onEvent: @convention(c) (
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UnsafeMutableRawPointer?, UnsafePointer<vc_event>?
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) -> Void = { user, ev in
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guard let user, let ev else { return }
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let client = Unmanaged<VoiceCatClient>.fromOpaque(user).takeUnretainedValue()
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// Copy the event (including text) to a Swift value NOW — the raw vc_event is
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// invalid after this callback returns.
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client.enqueueEvent(VoiceCatEvent.from(ev.pointee))
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}
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/// The `on_level` C function pointer. Coalesces to "latest sample per stream_id"
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/// (intermediate values are visually irrelevant — same as C#'s ConcurrentDictionary).
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static let onLevel: @convention(c) (
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UnsafeMutableRawPointer?, UInt32, Float
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) -> Void = { user, streamId, rms in
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guard let user else { return }
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let client = Unmanaged<VoiceCatClient>.fromOpaque(user).takeUnretainedValue()
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client.enqueueLevel(streamId, rms)
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}
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/// Construct the vc_callbacks struct for a given client.
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static func make(user: UnsafeMutableRawPointer) -> vc_callbacks {
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vc_callbacks(on_event: onEvent, on_level: onLevel, user: user)
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}
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}
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