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//
// OperationCache.swift
//
// Created by Indragie Karunaratne on 8/3/15.
//
import Foundation
public struct Expirable<ValueType> {
public let expiryDate: NSDate
public let value: ValueType
public var expired: Bool {
return NSDate().compare(expiryDate) == .OrderedDescending
}
}
public func ==<ValueType: Equatable>(lhs: Expirable<ValueType>, rhs: Expirable<ValueType>) -> Bool {
return lhs.expiryDate == rhs.expiryDate && lhs.value == rhs.value
}
/// Swift port of https://github.com/odeke-em/cache/blob/master/cache.go
///
/// Lockless & thread safe with support for multiple concurrent readers
/// and a single writer.
public class OperationCache<KeyType: Hashable, ValueType> {
public typealias ExpirableType = Expirable<ValueType>
private let queue = dispatch_queue_create("com.indragie.OperationCache", DISPATCH_QUEUE_CONCURRENT)
private var storage = [KeyType: ExpirableType]()
public var snapshot: Zip2Sequence<[KeyType], [ExpirableType]> {
var sequence: Zip2Sequence<[KeyType], [ExpirableType]>? = nil
dispatch_sync(queue) {
sequence = zip(self.storage.keys.array, self.storage.values.array)
}
return sequence!
}
public subscript(key: KeyType) -> Expirable<ValueType>? {
get {
var value: ExpirableType?
dispatch_sync(queue) { value = self.storage[key] }
if let value = value where value.expired {
self[key] = nil
return nil
}
return value
}
set {
dispatch_barrier_async(queue) { self.storage[key] = newValue }
}
}
}
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