CommandLineToolkit

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import AtomicModels
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import Dispatch
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import Foundation
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public final class BlockingArrayBasedJSONStream: AppendableJSONStream {
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    private let readLock = NSLock()
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    private let writeLock = DispatchSemaphore(value: 0)
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    private let storage = AtomicValue<[UInt8]>([])
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    private var willProvideMoreData = true
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    public init() {}
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    public func append(bytes: [UInt8]) {
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        storage.withExclusiveAccess {
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            $0.insert(contentsOf: bytes.reversed(), at: 0)
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        }
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        onNewData()
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    }
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    // MARK: - JSONStream
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    public func touch() -> UInt8? {
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        return lastByte(delete: false)
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    }
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    public func read() -> UInt8? {
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        return lastByte(delete: true)
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    }
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    public func close() {
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        willProvideMoreData = false
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        onStreamClose()
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    }
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    private func lastByte(delete: Bool) -> UInt8? {
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        readLock.lock()
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        defer {
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            readLock.unlock()
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        }
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        if storage.currentValue().isEmpty {
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            if willProvideMoreData {
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                waitForNewDataOrStreamCloseEvent()
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            } else {
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                return nil
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            }
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        }
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        return storage.withExclusiveAccess {
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            if delete {
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                return $0.popLast()
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            } else {
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                return $0.last
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            }
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        }
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    }
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    private func waitForNewDataOrStreamCloseEvent() {
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        writeLock.waitForUnblocking()
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    }
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    private func onNewData() {
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        writeLock.unblock()
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    }
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    private func onStreamClose() {
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        writeLock.unblock()
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    }
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}
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extension DispatchSemaphore {
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    func waitForUnblocking() {
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        wait()
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        signal()
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    }
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    func unblock() {
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        signal()
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        wait()
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    }
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}
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