42 lines
1.7 KiB
Swift
42 lines
1.7 KiB
Swift
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extension Sound {
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/// A source that produces audio by calling back into Swift.
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public final class CallbackSource: Source {
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let callback: Callback
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/// Every callback source is kept alive here while the C side may
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/// still invoke its trampoline: from creation until it is removed
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/// with `Sound.removeSource`/`Channel.removeSource`, or until its
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/// owning channel is freed.
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nonisolated(unsafe) static var live: [CallbackSource] = []
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/// Releases the registration added by `adopt(pointer:)`.
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static func release(_ source: Source) {
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live.removeAll { $0 === source }
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}
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init(callback: @escaping Callback) {
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self.callback = callback
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super.init(pointer: nil, isOwned: false)
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}
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var contextPointer: UnsafeMutableRawPointer {
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Unmanaged.passUnretained(self).toOpaque()
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}
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static let trampoline: @convention(c) (UnsafeMutableRawPointer?, UnsafeMutablePointer<Int16>?,
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UnsafeMutablePointer<Int16>?, Int32) -> Int32 = { context, left, right, length in
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guard let context, let left else { return 0 }
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let source = Unmanaged<CallbackSource>.fromOpaque(context).takeUnretainedValue()
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let leftBuffer = UnsafeMutableBufferPointer(start: left, count: Int(length))
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let rightBuffer = right.map { UnsafeMutableBufferPointer(start: $0, count: Int(length)) }
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return source.callback(leftBuffer, rightBuffer) ? 1 : 0
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}
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/// Attaches the C object created for this source.
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func adopt(pointer: OpaquePointer) {
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self.pointer = pointer
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CallbackSource.live.append(self)
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}
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}
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}
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