72 lines
3.0 KiB
Swift
72 lines
3.0 KiB
Swift
import PromiseKit
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import YapDatabase
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// Some important notes about YapDatabase:
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//
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// • Connections are thread-safe.
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// • Executing a write transaction from within a write transaction is NOT allowed.
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@objc(LKStorage)
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public final class Storage : NSObject {
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public static let serialQueue = DispatchQueue(label: "Storage.serialQueue", qos: .userInitiated)
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private static var owsStorage: OWSPrimaryStorageProtocol { SNUtilitiesKitConfiguration.shared.owsPrimaryStorage }
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@objc public static let shared = Storage()
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// MARK: Reading
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// Some important points regarding reading from the database:
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//
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// • Background threads should use `OWSPrimaryStorage`'s `dbReadConnection`, whereas the main thread should use `OWSPrimaryStorage`'s `uiDatabaseConnection` (see the `YapDatabaseConnectionPool` documentation for more information).
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// • Multiple read transactions can safely be executed at the same time.
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@objc(readWithBlock:)
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public static func read(with block: @escaping (YapDatabaseReadTransaction) -> Void) {
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owsStorage.dbReadConnection.read(block)
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}
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// MARK: Writing
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// Some important points regarding writing to the database:
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//
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// • There can only be a single write transaction per database at any one time, so all write transactions must use `OWSPrimaryStorage`'s `dbReadWriteConnection`.
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// • Executing a write transaction from within a write transaction causes a deadlock and must be avoided.
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@discardableResult
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@objc(writeWithBlock:)
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public static func objc_write(with block: @escaping (YapDatabaseReadWriteTransaction) -> Void) -> AnyPromise {
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return AnyPromise.from(write(with: block) { })
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}
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@discardableResult
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public static func write(with block: @escaping (YapDatabaseReadWriteTransaction) -> Void) -> Promise<Void> {
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return write(with: block) { }
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}
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@discardableResult
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@objc(writeWithBlock:completion:)
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public static func objc_write(with block: @escaping (YapDatabaseReadWriteTransaction) -> Void, completion: @escaping () -> Void) -> AnyPromise {
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return AnyPromise.from(write(with: block, completion: completion))
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}
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@discardableResult
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public static func write(with block: @escaping (YapDatabaseReadWriteTransaction) -> Void, completion: @escaping () -> Void) -> Promise<Void> {
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let (promise, seal) = Promise<Void>.pending()
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serialQueue.async {
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owsStorage.dbReadWriteConnection.readWrite { transaction in
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transaction.addCompletionQueue(DispatchQueue.main, completionBlock: completion)
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block(transaction)
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}
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seal.fulfill(())
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}
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return promise
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}
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/// Blocks the calling thread until the write has finished.
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@objc(writeSyncWithBlock:)
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public static func writeSync(with block: @escaping (YapDatabaseReadWriteTransaction) -> Void) {
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try! write(with: block, completion: { }).wait() // The promise returned by write(with:completion:) never rejects
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}
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}
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