--- title: NS Prefix 外伝 … Copy-On-Write #関モバ tags: #関モバ #swift author: [熊谷友宏](https://www.docswell.com/user/es_kumagai) site: [Docswell](https://www.docswell.com/) thumbnail: https://bcdn.docswell.com/page/LJLPQ82PER.jpg?width=480 description: Swift 3 の変化のひとつに Foundation での NS プレフィックス削除があります。その中でも、とりわけ "新しい値型" の新設に伴って、値型とクラス型をブリッジする選択が取られた型の、そのパフォーマンスの最適化に注目してみました。 ※ Docswell での公開に移行する直前の Slideshare での閲覧数は 3,693 でした。 published: October 27, 16 canonical: https://www.docswell.com/s/es_kumagai/KMXL9W-copy-on-write-161026175442 --- # Page. 1 ![Page Image](https://bcdn.docswell.com/page/LJLPQ82PER.jpg) /41SFGJY֎఻ $PQZ0O8SJUF ؔ੢ϞόΠϧΞϓϦ‫ڀݚ‬ձ ʜ &;/&5‫۽‬୩༑޺ IUUQF[OFUKQ 4XJGU # Page. 2 ![Page Image](https://bcdn.docswell.com/page/47M41682EW.jpg) ‫۽‬୩༑޺ 5PNPIJSP,VNBHBJ ⾣ 4XJGU‫͕ޠݴ‬௒େ޷͖Ͱ͢ʂ ⾣ ΈΜͳͰָ͠Ήษ‫ڧ‬ձ͕େ޷͖Ͱ͢ʂ ⾣ ϓϩάϥϛϯάͷָ͠͞Λ఻͍͖͍͑ͯͨɻ !FT@LVNBHBJ UPNPIJSPLVNBHBJ $PEF1JFDFGPSNBD04 IUUQF[OFUKQ 9DPEFపఈղઆ # Page. 3 ![Page Image](https://bcdn.docswell.com/page/P7RWLP55E9.jpg) ษ‫ڧ‬ձΛ։࠵͍ͯ͠·͢ɻ Θ͍Θ͍ɺָ͘͠ɺ ΈΜͳͰ‫ޠ‬Β͑Δ৔ॴΛ໨ࢦͯ͠ ԣ඿J1IPOF։ൃऀษ‫ڧ‬ձ ୈճ໨͸݄೔ͷ։࠵ ΧδϡΞϧ4XJGUษ‫ڧ‬ձ ୈճ໨Λ݄ʹ։࠵ʢ‫ݕ‬౼தʣ ΈΜͳͰ4XJGU ෮शձ ୈճ໨Λ݄தʹ։࠵ʢ‫ݕ‬౼தʣ ZJEFW ˏԣ඿ɾഅंಓ IUUQTBUOEPSHHSPVQTZJEFW DTXJGU !ԣ඿ɾ੨༿୆ IUUQTBUOEPSHHSPVQTDTXJGU NJOOB@EF@TXJGU ˏौ୩ IUUQDTXJGUDPOOQBTTDPN # Page. 4 ![Page Image](https://bcdn.docswell.com/page/PJXPW3KXEX.jpg) NPPLNPPLSBEJP Ќ൛ ϜοΫϜοΫϥδΦ ‫۽‬୩ͱ៸໘͕ϓϩάϥϛϯάίʔυͷ಺͔Β ௌ͑ͯ͘͜Δ੠ʹࣖΛ܏ָ͚ͯ͠ΉϥδΦ ຖ݄ୈ̎ɾୈ̐ ݄༵೔ ʹ഑৴ IUUQNPPLNPPLSBEJPDPNB ⾣ ୈ̒࿩ ʢ݄೔ʹ഑৴༧ఆʣ ⾣ ୈ̑࿩ ʰΞΫηείϯτϩʔϧʱ ⾣ ୈ̐࿩ ʰίϝϯτͷଓ͖ˍ੔਺‫ܕ‬ʱ ⾣ ୈ̏࿩ ʰίϝϯτʱ ⾣ ୈ̎࿩ ʰྻ‫ܕڍ‬ʱ # Page. 5 ![Page Image](https://bcdn.docswell.com/page/3JKDVY597D.jpg) %SPQ/41SFGJY JO4XJGU'PVOEBUJPO # Page. 6 ![Page Image](https://bcdn.docswell.com/page/LE3RM9K975.jpg) %SPQ/41SFpYJO4XJGU'PVOEBUJPO /41SFpY ⾣ ফ͑Ώ͘΋ͷ ⾣ ࢒Δ΋ͷ ⾣ ‫ڞ‬ଘ͢Δ΋ͷ # Page. 7 ![Page Image](https://bcdn.docswell.com/page/8EDY6G38EG.jpg) /41SFpY ‫ڞ‬ଘ͢Δ΋ͷ ⾣ ஋‫ܕ‬૬౰ͷΫϥεͰɺ஋‫৽͕ܕ‬ઃ͞Εͨ΋ͷ ⾣ /4෇͖ͷΫϥε‫ͱܕ‬ɺ/4ͳ͠ͷ஋‫ڞ͕ͱܕ‬ଘ ͨͱ͑͹ʜ • NSString, String • NSData, Data • NSArray, Array<Element> # Page. 8 ![Page Image](https://bcdn.docswell.com/page/V7P6Y34WJ8.jpg) /FX7BMVF5ZQFT JO4XJGU'PVOEBUJPO # Page. 9 ![Page Image](https://bcdn.docswell.com/page/2JV3G4X9EQ.jpg) /FX7BMVF5ZQFT ஋‫ʹܕ‬૬౰͢ΔΫϥεʹண໨ ⾣ ಉ౳ͷ஋‫ܕ‬Λɺߏ଄ମͰ ৽‫ ن‬௥Ճʜ/41SFpYͳ͠ ⾣ ‫ط‬ଘͷΫϥε‫ܕ‬͸ɺͦͷ·· ଘଓ ʜ/41SFpY͋Γ ⾣ ஋‫ͱܕ‬Ϋϥε‫ܕ‬Λ૬‫ ʹޓ‬ϒϦοδ ⾣ ஋‫ܕ‬Λओମʹѻ͏͜ͱͰɺ4XJGUͷྑ͞Λಋग़ ⾣ ஋‫ͱܕ‬Ϋϥε‫Ͱܕ‬ɺ‫ػ‬ೳ͕΍΍ҟͳΔ৔߹΋͋Δ # Page. 10 ![Page Image](https://bcdn.docswell.com/page/5EG381V47L.jpg) /FX7BMVF5ZQFT *NNVUBCMF⁶/4*NNVUBCMF ⾣ ಉ౳ͷߏ଄ମΛ'PVOEBUJPOʹ௥Ճ ⾣ ૒ํͱ΋ɺੑ࣭͸WBS΋MFU΋*NNVUBCMFѻ͍ TUSVDU66*% DMBTT/466*% # Page. 11 ![Page Image](https://bcdn.docswell.com/page/4JQ59D6R7P.jpg) /FX7BMVF5ZQFT .VUBCMF⁶/4.VUBCMF ⾣ ಉ౳ͷߏ଄ମΛ'PVOEBUJPOʹ௥Ճ ⾣ ஋‫Ͱܕ‬͸ɺੑ࣭͕WBS͔MFU͔ͰมԽ TUSVDU"⒏OF5SBOTGPSN DMBTT/4"⒏OF5SBOTGPSN TUSVDU%BUF DMBTT/4%BUF TUSVDU%BUF$PNQPOFOUT DMBTT/4%BUF$PNQPOFOUT TUSVDU1FSTPO/BNF$PNQPOFOUT DMBTT/41FSTPO/BNF$PNQPOFOUT TUSVDU63- DMBTT/463- TUSVDU63-$PNQPOFOUT DMBTT/463-$PNQPOFOUT # Page. 12 ![Page Image](https://bcdn.docswell.com/page/K749XZ4QE1.jpg) /FX7BMVF5ZQFT .VUBCMF⁶/4*NNVUBCMF ⾣ ಉ౳ͷߏ଄ମΛ'PVOEBUJPOʹ௥Ճ ⾣ ஋‫͚ͩܕ‬NVUBUJOHͳੑ࣭Λ࣋ͭ TUSVDU*OEFY1BUI DMBTT/4*OEFY1BUI TUSVDU/PUJpDBUJPO DMBTT/4/PUJpDBUJPO TUSVDU63-2VFSZ*UFN DMBTT/463-2VFSZ*UFN # Page. 13 ![Page Image](https://bcdn.docswell.com/page/LJ1KNR4L7G.jpg) /FX7BMVF5ZQFT .VUBCMF⁶/4 *NNVUBCMF .VUBCMF ⾣ ஋‫ܕ‬ͷߏ଄ମΛ'PVOEBUJPOʹ௥Ճ ⾣ ஋‫*ͱܕ‬NNVUBCMFΛϒϦοδɺΫϥεؒ͸Ωϟετ TUSVDU$IBSBDUFS4FU DMBTT/4$IBSBDUFS4FU DMBTT/4.VUBCMF$IBSBDUFS4FU TUSVDU%BUB DMBTT/4%BUB DMBTT/4.VUBCMF%BUB TUSVDU*OEFY4FU DMBTT/4*OEFY4FU DMBTT/4.VUBCMF*OEFY4FU # Page. 14 ![Page Image](https://bcdn.docswell.com/page/GJWD41XQ72.jpg) 7BMVF5ZQFT # Page. 15 ![Page Image](https://bcdn.docswell.com/page/4EZG2P63J3.jpg) 7BMVF5ZQFT ஋‫ࢀͱܕ‬র‫ܕ‬ ⾣ ஋‫  ܕ‬ʜσʔλΛίϐʔ ⾣ ࢀর‫ ܕ‬ʜΠϯελϯεΛ‫ڞ‬༗ # Page. 16 ![Page Image](https://bcdn.docswell.com/page/Y76YVM2ZEV.jpg) ࠓ·Ͱࢀর‫ͨͬͩܕ‬ͷΛ ஋‫ͯ͠ʹܕ‬ɺॏ͘ͳΒͳ͍ͷʁ # Page. 17 ![Page Image](https://bcdn.docswell.com/page/G75GDZ2974.jpg) 0QUJNJ[BUJPO # Page. 18 ![Page Image](https://bcdn.docswell.com/page/9J2Y8R45JR.jpg) 0QUJNJ[BUJPO 3FGFSFODF$POWFSUJCMF ⾣ Ͳͷࢀর‫ʹܕ‬ϒϦοδͰ͖Δ͔Λද‫ݱ‬ ⾣ ϒϦοδର৅ͷࢀর‫ܕ‬͸lίϐʔՄೳzͱ‫ن‬ఆ // 要所だけ抜粋 protocol ReferenceConvertible : _ObjectiveCBridgeable { // 参照型は Objective-C 互換で、コピー可能 associatedtype ReferenceType : NSObject, NSCopying } # Page. 19 ![Page Image](https://bcdn.docswell.com/page/DEYG6DM6EM.jpg) -BSHFS7BMVF5ZQFT # Page. 20 ![Page Image](https://bcdn.docswell.com/page/VJNGZ63178.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT $PQZ0O8SJUF ⾣ ΫϥεΠϯελϯεͷࢀরΛ಺แ͠ɺ‫ڞ‬༗ ⾣ ॻ͖ࠐΈ࣌ʹॳΊͯɺσʔλΛෳ੡ ஋ 8SJUF Ϋϥε Ϋϥε #SJEHF ʷ ࣮ମ ࣮ମ $PQZ # Page. 21 ![Page Image](https://bcdn.docswell.com/page/YE9WZL9YE3.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT $PQZ0O8SJUFͷಛ௃ ⾣ ίϐʔͷ‫ݪ‬ଇΛӡ༻ͰΧόʔʢ҉໧తʣ ⾣ ඞཁʹͳΔ·Ͱɺσʔλͷෳ੡ίετΛճආ ⾣ ࢀরΧ΢ϯτपΓͷ؅ཧίετ͸૿Ճ # Page. 22 ![Page Image](https://bcdn.docswell.com/page/GE8N1X9K7D.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT -BSHFS7BMVF5ZQFT  $IBSBDUFS4FU  %BUF$PNQPOFOUT  %BUB  *OEFY4FU  *OEFY1BUI  1FSTPO/BNF$PNQPOFOUT  63-  63-$PNQPOFOUT  63-2VFSZ*UFN  66*% # Page. 23 ![Page Image](https://bcdn.docswell.com/page/LELPQ8WP7R.jpg) %BUBͷ࣮ࡍ # Page. 24 ![Page Image](https://bcdn.docswell.com/page/4JM416927W.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT %BUBͷ࣮ࡍ ⾣ /4%BUB΁ͷϒϦοδΛ૝ఆ ⾣ ࢀরΛ@4XJGU/4%BUBͰ#PYJOH public struct Data : ReferenceConvertible, _MutablePairBoxing { // NSData とのブリッジ public typealias ReferenceType = NSData // 参照をラップ (Boxing) する internal var _wrapped : _SwiftNSData # Page. 25 ![Page Image](https://bcdn.docswell.com/page/PJRWLPG579.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT %BUBͷ࣮ࡍ#PYJOH ⾣ /4%BUBͱ/4.VUBCMF%BUBΛ۠ผͯ͠؅ཧ ⾣ /4%BUBͱϝϞϦϨϕϧͰ‫׵ޓ‬ੑ͕͋ΔΒ͍͠ internal final class _SwiftNSData { // NSData と NSMutableData とを管理するラッパー var __wrapped : _MutableUnmanagedWrapper< NSData, NSMutableData> # Page. 26 ![Page Image](https://bcdn.docswell.com/page/PEXPW3XX7X.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT %BUBͷ࣮ࡍ#PYJOHৄࡉ ⾣ *NNVUBCMF·ͨ͸.VUBCMFͷͲͪΒ͔ ⾣ /PO"3$ͰࢀরΛ؅ཧ internal enum _MutableUnmanagedWrapper< ImmutableType, MutableType> { case Immutable(Unmanaged<ImmutableType>) case Mutable(Unmanaged<MutableType>) } # Page. 27 ![Page Image](https://bcdn.docswell.com/page/3EKDVYW9JD.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT %BUBͷ࣮ࡍΠϯελϯεԽ ⾣ ಺෦σʔλΛɺΫϥε‫ܕ‬ͷࢀরͰ࣋ͭ ⾣ Ұൠʹɺ*NNVUBCMFͳΠϯελϯεͰੜ੒ public init(bytes: UnsafeRawPointer, count: Int) { _wrapped = _SwiftNSData(immutableObject: NSData(bytes: bytes, length: count)) } # Page. 28 ![Page Image](https://bcdn.docswell.com/page/L73RM919J5.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT %BUBͷ࣮ࡍฤू ⾣ *NNVUBCMFͳΒɺແ৚݅ͰNVUBCMF$PQZ ⾣ .VUBCMFͳΒɺඇ6OJRVF࣌ͷΈNVUBCMF$PQZ public mutating func append(_ other: Data) { // ここで mutableCopy の必要性を判断・実施 _applyUnmanagedMutation { $0.append(other) } } # Page. 29 ![Page Image](https://bcdn.docswell.com/page/87DY6GX87G.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT %BUBͷ࣮ࡍॻ͖ࠐΈେલఏͷੜ੒ ⾣ ಺෦σʔλΛɺଈ࠲ʹ.VUBCMFͰੜ੒͢Δ͜ͱ΋ ⾣ ॳճॻࠐ࣌ͷNVUBCMF$PQZΛ࡟‫ݮ‬ public init(capacity: Int) { if let d = NSMutableData(capacity: capacity) { _wrapped = _SwiftNSData(mutableObject: d) } else { } } fatalError("Unable to allocate data of the requested capacity") # Page. 30 ![Page Image](https://bcdn.docswell.com/page/VJP6Y3PWE8.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT %BUBͷ࣮ࡍࢀর‫΁ܕ‬ͷม‫׵‬ ⾣ 4XJGU/4%BUBͰอ࣋ͨ͠ࢀরΛ‫੍ڧ‬Ωϟετ ⾣ ‫ڍͳີݫ‬ಈ͸௫Ίͣʜߴ଎ಈ࡞ʹ͸‫ظ‬଴ public func _bridgeToObjectiveC() -> NSData { // NSData.self は 8 Byte return unsafeBitCast(_wrapped, to: NSData.self) } # Page. 31 ![Page Image](https://bcdn.docswell.com/page/2EV3G4297Q.jpg) 0QUJNJ[BUJPOGPS-BSHFS7BMVF5ZQFT %BUBͷ࣮ࡍࢀর‫͔ܕ‬Βͷม‫׵‬ ⾣ ࢀর‫͔ܕ‬Βͷม‫׵‬͸ɺ஋‫ܕ‬ͷΠχγϟϥΠβʔͰ ⾣ /4.VUBCMF%BUBʹඋ͑DPQZΛऔಘͯ͠#PYJOH public static func _forceBridgeFromObjectiveC( _ input: NSData, result: inout Data?) { result = Data(referencing: input) } public init(referencing reference: NSData) { _wrapped = _SwiftNSData(immutableObject: reference.copy() as AnyObject) } # Page. 32 ![Page Image](https://bcdn.docswell.com/page/57G381R4JL.jpg) 4NBMM7BMVF5ZQFT # Page. 33 ![Page Image](https://bcdn.docswell.com/page/4EQ59DVRJP.jpg) 0QUJNJ[BUJPOGPS4NBMM7BMVF5ZQFT $PQZ*NNFEJBUFMZ ⾣ ߏ଄ମͷσʔλͱͯ࣋ͪ͠ɺϒϦοδ࣌ʹଈෳ੡ ⾣ ͦͷ‫ޙ‬΋ɺผม਺΁୅ೖ͢ΔͨͼʹσʔλΛෳ੡ ஋ 8SJUF Ϋϥε σʔλ #SJEHF $PQZ ࣮ମ σʔλ # Page. 34 ![Page Image](https://bcdn.docswell.com/page/KJ49XZMQ71.jpg) 0QUJNJ[BUJPOGPS4NBMM7BMVF5ZQFT ଈ࣌ίϐʔͷಛ௃ ⾣ ίϐʔͷ‫ݪ‬ଇʹ஧࣮ ⾣ ୅ೖ΍ϒϦοδͰɺσʔλ෼ͷෳ੡ίετ͕ൃੜ ⾣ ࢀরΧ΢ϯτपΓͷ؅ཧίετͷ࡟আ # Page. 35 ![Page Image](https://bcdn.docswell.com/page/LE1KNR8LJG.jpg) 0QUJNJ[BUJPOGPS4NBMM7BMVF5ZQFT 4NBMM7BMVF5ZQFT  "⒏OF5SBOTGPSN  %BUF  /PUJpDBUJPO # Page. 36 ![Page Image](https://bcdn.docswell.com/page/GEWD41ZQJ2.jpg) %BUFͷ࣮ࡍ # Page. 37 ![Page Image](https://bcdn.docswell.com/page/47ZG2P13E3.jpg) 0QUJNJ[BUJPOGPS4NBMM7BMVF5ZQFT %BUFͷ࣮ࡍ ⾣ /4%BUF΁ͷϒϦοδΛ૝ఆ ⾣ /4%BUF΁ͷࢀর͸࣋ͨͣɺσʔλΛ௚઀อ࣋ public struct Date : ReferenceConvertible { // NSDate とのブリッジ public typealias ReferenceType = NSDate // データを TimeInterval (Double) で直接保持 fileprivate var _time : TimeInterval # Page. 38 ![Page Image](https://bcdn.docswell.com/page/YJ6YVMLZ7V.jpg) 0QUJNJ[BUJPOGPS4NBMM7BMVF5ZQFT %BUFͷ࣮ࡍΠϯελϯεԽ ⾣ ಺෦σʔλΛɺσʔλͱͯ͠௚઀࣋ͭ ⾣ /4%BUF͸ؔ༩͠ͳ͍ public init(timeIntervalSinceReferenceDate ti: TimeInterval) { _time = ti } # Page. 39 ![Page Image](https://bcdn.docswell.com/page/GJ5GDZ19J4.jpg) 0QUJNJ[BUJPOGPS4NBMM7BMVF5ZQFT %BUFͷ࣮ࡍฤू ⾣ ಺෦σʔλΛॻ͖‫͑׵‬Δ ⾣ ࣗ෼ઐ༻ͷσʔλͳͷͰɺࢀরͳͲ͸ߟྀෆཁ public mutating func addTimeInterval( _ timeInterval: TimeInterval) { self += timeInterval } # Page. 40 ![Page Image](https://bcdn.docswell.com/page/LE3RM91275.jpg) 0QUJNJ[BUJPOGPS4NBMM7BMVF5ZQFT %BUFͷ࣮ࡍࢀর‫΁ܕ‬ͷϒϦοδ ⾣ ಺෦σʔλ͔Β/4%BUBΛੜ੒ ⾣ ૉ௚͔ͭ࠷୹‫Ͱ཭ڑ‬ͷϒϦοδ public func _bridgeToObjectiveC() -> NSDate { return NSDate(timeIntervalSinceReferenceDate: _time) } # Page. 41 ![Page Image](https://bcdn.docswell.com/page/8EDY6GX6EG.jpg) 0QUJNJ[BUJPOGPS4NBMM7BMVF5ZQFT %BUFͷ࣮ࡍࢀর‫͔ܕ‬ΒͷϒϦοδ ⾣ /4%BUBͷ౰֘৘ใ͔ΒΠϯελϯεΛੜ੒ ⾣ ࢀর؅ཧ͔ΒಠཱʢࢀরΧ΢ϯτΛ‫ڞ‬༗͠ͳ͍ʣ public static func _conditionallyBridgeFromObjectiveC( _ x: NSDate, result: inout Date?) -> Bool { result = Date(timeIntervalSinceReferenceDate: x.timeIntervalSinceReferenceDate) return true } # Page. 42 ![Page Image](https://bcdn.docswell.com/page/V7P6Y3KZJ8.jpg) ஋‫Ͱܕ‬΋ɺ ύϑΥʔϚϯεΛ‫ͨ͠ʹؾ‬ઃ‫ܭ‬ # Page. 43 ![Page Image](https://bcdn.docswell.com/page/2JV3G4VMEQ.jpg) /FX7BMVF5ZQFT ҆৺ͯ͠࢖ͬͯɺେৎ෉ͦ͏ɻ # Page. 44 ![Page Image](https://bcdn.docswell.com/page/5EG381LX7L.jpg) &OKPZ4XJGU 5IBOLZPV /41SFpY֎఻ $PQZ0O8SJUF &;/&5‫۽‬୩༑޺ IUUQF[OFUKQ ⾣ /FX7BMVF5ZQFT ⾣ 0QUJNJ[BUJPO ⾣ %BUBͷ࣮ࡍɺ%BUFͷ࣮ࡍ