Pointer と向き合う / Facing the Pointer

登壇者名：Masatoshi Tsushima
登壇したイベント：Swift Expands! #2 ~組み込みシステムに挑戦してみよう~
　　　　　　　　　（https://bitkey.connpass.com/event/317143/）
登壇したイベントの登壇者URL：https://www.youtube.com/live/krNTPlRP8kc?feature=shared

Transcript

1. Copyright © Bitkey Inc. All rights reserved. Pointer ͱ޲͖߹͏ Swift Expands! #2 Masatoshi Tsushima
2. Copyright © Bitkey Inc. All rights reserved. ௡ౡ խढ़ Masatoshi Tsushima 2004 ιϑτ΢ΣΞ։ൃͱͷग़ձ͍ WebαΠτ΍ܞଳΞϓϦΛ࡞ͬͯ༡ΜͰ͍·ͨ͠ 2018ळ Bitkeyʹࢀը ౰ॳ͸bitkey platformͷ։ൃΛ୲౰ ओʹGoͰαʔόαΠυΛ։ൃ 2019ळ ϑΝʔϜ΢ΣΞνʔϜΛ্ཱͪ͛ bitlock LITEͷϑΝʔϜ΢ΣΞΛ಺੡Խ ݱࡏʹଓ͘։ൃελΠϧΛߏங 2020Ն ୈೋੈ୅ϩοΫσόΠεͷ։ൃ ಺੡Λલఏͱͨ͠ϑΝʔϜ΢ΣΞ։ൃ 2021य़ϦϦʔε 2022Ն Individual contributor (?) Android/iOS/FlutterɺσόΠεQA༻ΞϓϦɺࣾ಺ ࢓༷ͷඪ४ԽɺMakefile৬ਓɺCI͓͡͞Μ
3. Copyright © Bitkey Inc. All rights reserved. ૊ࠐΈͰόάͷݪҼͱ͍͑͹
4. Copyright © Bitkey Inc. All rights reserved. p = &var
5. Copyright © Bitkey Inc. All rights reserved. p++
6. Copyright © Bitkey Inc. All rights reserved. *p
7. Copyright © Bitkey Inc. All rights reserved. ෳࡶͳૢ࡞ͰόάΔ
8. Copyright © Bitkey Inc. All rights reserved. ͦͯ͠ͳ͔ͥಈ͘
9. Copyright © Bitkey Inc. All rights reserved. ͱࢥͬͨΒ ϦϦʔεϏϧυͰಈ͔ͳ͍
10. Copyright © Bitkey Inc. All rights reserved. C Ҏ֎Ͱݟͳ͍ͩΖͱࢥͬͯ·ͨ͠ ૊ࠐΈ͔Β iOS ։ൃʹҟಈ͢Δ·Ͱ͸ var x = 1 let p = UnsafePointer(&x) print("\(p.pointee), \(p)")
11. Copyright © Bitkey Inc. All rights reserved. ·͓ͨલ͔
12. Copyright © Bitkey Inc. All rights reserved. Pointer ͱ޲͖߹͏
13. Copyright © Bitkey Inc. All rights reserved. Q: ࣮ࡍͷॴϙΠϯλͬͯԿʹ࢖͏ͷʁ A: ओʹόΠτྻͷૢ࡞ • C ݴޠͷ഑ྻ • Swift ͷ Array/Data ಡΈସ͑ɾॻ͖׵͑ɾసૹɾಠࣗͷ؅ཧ…
14. Copyright © Bitkey Inc. All rights reserved. Data ͔Β Int ʹ͍ͨ͠ ݕࡧ͢ΔͱΑ͘ग़ͯ͘Δ΍ͭ import Foundation let data = Data([1, 2, 3, 4]) let x = data.withUnsafeBytes { $0.load(as: UInt16.self) } print(x) // Output: 513
15. Copyright © Bitkey Inc. All rights reserved. Data ͔Β Int ʹ͍ͨ͠ load ͷ୅ΘΓʹ OpaquePointer Λܦ༝ͤͯ͞Έͨ import Foundation let data = Data([1, 2, 3, 4]) let x = data.withUnsafeBytes { UnsafePointer<UInt16>(OpaquePointer($0.baseAddress!)).pointee } print(x) // Output: 513 खݩͰ͸ -O -emit-assembly Ͱಉ݁͡Ռ
16. Copyright © Bitkey Inc. All rights reserved. ͪͳΈʹ: Swift ͷΤϯσΟΞϯͷૢ࡞ λʔήοτͱҟͳΔͳΒٯॱʹ͢Δ print(x) // Apple Silicon ͸ 513 print(x.bigEndian) // 258 print(x.littleEndian) // 513 print(x.bigEndian.bigEndian) // 513 print(x.littleEndian.littleEndian) // 513
17. Copyright © Bitkey Inc. All rights reserved. Struct ͸Ͳ͏ͳͷʁ ಉ͡ΞʔΩςΫνϟؒͳΒେৎ෉Έ͍ͨ Alignment Λௐ੔͢Δखஈʹ͚ܽΔ
18. Copyright © Bitkey Inc. All rights reserved. ༷ʑͳܕ • UnsafePointer<T> • UnsafeMutablePointer<T> • UnsafeRawPointer • UnsafeMutableRawPointer • UnsafeBufferPointer<T> • UnsafeMutableBufferPointer<T> • UnsafeRawBufferPointer • UnsafeMutableRawBufferPointer Mutable ॻ͖׵͑Մೳ Buffer ௕͞ (count) ෇͖ Raw ૯শܕ (<T>) ແ͠
19. Copyright © Bitkey Inc. All rights reserved. Unsafe ͱ͸ʁ • UnsafePointer<T> • UnsafeMutablePointer<T> • UnsafeRawPointer • UnsafeMutableRawPointer • UnsafeBufferPointer<T> • UnsafeMutableBufferPointer<T> • UnsafeRawBufferPointer • UnsafeMutableRawBufferPointer
20. Copyright © Bitkey Inc. All rights reserved. C ͷͱ͖Λࢥ͍ग़ͯ͠ΈΔ ࡾେҙຯෆ໌ͳڍಈ͢ΔόάͷݪҼ • ະ֬อ ◦ ࢦࣔ͢͠ઌ͕֬อ͞Ε͍ͯͳ͍͔΋ • ະॳظԽ ◦ ॳظԽ͞Ε͍ͯͳ͍͔΋ • ະ։์ ◦ ։์͞Εͳ͍͔΋
21. Copyright © Bitkey Inc. All rights reserved. ະ֬อ ֬อͤͣʹ࢖͏ var x: Int = 10 let p = UnsafePointer<Int>(&x) print(p.advanced(by: 10).pointee)
22. Copyright © Bitkey Inc. All rights reserved. ະ֬อ ֬อͤͣʹ࢖͏ var x: Int = 10 let p = UnsafePointer<Int>(&x) print(p.advanced(by: 10).pointee) ਖ਼ৗऴྃͪ͠Ό͏Μͩͳ͜Ε͕…
23. Copyright © Bitkey Inc. All rights reserved. ະ֬อ ֬อͤͣʹ࢖͏ ಈ͔͢۩߹ʹΑͬͯ͸ͪΌΜͱࢮ͵
24. Copyright © Bitkey Inc. All rights reserved. ະ֬อ ൣғ֎ʹΞΫηε͢Δ
25. Copyright © Bitkey Inc. All rights reserved. ະ֬อ ൣғ֎ʹΞΫηε͢Δ import Foundation let data = Data([1, 2, 3, 4]) let x = data.withUnsafeBytes { let op = OpaquePointer($0.baseAddress!.advanced(by: 10)) return UnsafePointer<UInt16>(op).pointee } print(x) load ͷ count νΣοΫΛආ͚Δͱਖ਼ৗऴྃ͢Δ
26. Copyright © Bitkey Inc. All rights reserved. ະॳظԽ initialize ͠ͳ͍
27. Copyright © Bitkey Inc. All rights reserved. ະ։์ deallocate ͠ͳ͍ for _ in 1...1_000_000 { let _ = UnsafeMutablePointer<Int> .allocate(capacity: 1_000) }
28. Copyright © Bitkey Inc. All rights reserved. ະ։์ 8 GiB ֬อͨ͠͸ͣͰ͸…ʁ
29. Copyright © Bitkey Inc. All rights reserved. ؀ڥม਺ MallocScribble=1 ֬อͨ͠ϝϞϦʹॻ͖ࠐΉ ։์͞Εͨ஋ʹґଘ͠ͳ͍Α͏ʹ ద౰ͳ஋ (0x55) Λॻ͖ࠐΉ
30. Copyright © Bitkey Inc. All rights reserved. ະ։์ 7.67 × 10243 = 8,235,599,790
31. Copyright © Bitkey Inc. All rights reserved. ·ͱΊ: Swift ͷ Pointer • Data ͱ Int ͷ૬ޓม׵͕୅දྫ • Ͳͷ͋ͨΓ͕ Unsafe ʁ ◦ ະ֬อ: ࢦࣔ͢͠ઌ͕֬อ͞Ε͍ͯͳ͍͔΋ ◦ ະॳظԽ: ॳظԽ͞Ε͍ͯͳ͍͔΋ ◦ ະ։์: ։์͞Εͳ͍͔΋ • ਖ਼͘͠࢖Θͳ͍ͱͲ͏ͳΔʁ ◦ ίϯύΠϧ͸௨Δ ◦ Ϋϥογϡͨ͠Γ͠ͳ͔ͬͨΓϝϞϦΛ৯͍ͭͿͨ͠Γ͢Δ
32. Copyright © Bitkey Inc. All rights reserved. ࢀߟจݙ • Safely manage pointers in Swift - WWWDC20 • [Swift] IntͱDataͷ૬ޓม׵ #Swift - Qiita • ʲSwift5ʳDataΛInt΍DoubleͳͲͱ૬ޓม׵͢Δํ๏ – Ώ͖ͬͿΖ͙ • ios - how to convert Data to Int in swift - Stack Overflow • ૉ੖Β͍͠SwiftͷϙΠϯλܕͷղઆ #Swift - Qiita
33. Copyright © Bitkey INC. All rights reserved.