SwiftのArrayは メモリで連続だよ！

2018/5/25
京都Devかふぇ #1 〜モバイル〜

https://kyoto-dev-cafe.connpass.com/event/85513/

Transcript

1. SwiftͷArray͸ ϝϞϦͰ࿈ଓͩΑʂ ͸Δ; - LINE Fukuoka 2018/5/25 ژ౎Dev͔;͐ #1 ʙϞόΠϧʙ
2. iOS Engineer / LINE Fukuoka ͸Δ; @_ha1f ࢁޱ ஐੜ https://github.com/ha1f
3. https://github.com/koher/EasyImagy Motivation • ϐΫηϧ਺෼ͷArrayΛ༻ҙ • RGBAͷϏοτϚοϓΛඳը
4. ͳΜͩ͜Εʂ Arrayʹ͍ͭͯௐ΂ͯΈΔ
5. • Array͸͋ΔαΠζͷϝϞϦྖҬΛ֬อ͢Δ = capacity • capacityΛ௒͑ͯཁૉΛ௥Ճͨ͠ͱ͖ɺഒͷϝϞϦྖҬΛ ֬อͯ͠ɺ΋ͱͷ஋Λίϐʔ͢Δ https://developer.apple.com/documentation/swift/array Array-Growing the Size of an Array (ҙ༁)
6. ΍ͬͯΈΔ appendΛ܁Γฦͯ͠ɺ 1. capacityΛϓϩοτ 2. ΠϯλʔόϧΛϓϩοτ
7. • capacity(ॎ)ͷϓϩοτ • 0, 2, 4, 8, 16, 32, … …, 188, 380, 764, … • ઌ಄ΞυϨεΛΈΔͱɺ࣮ ࡍʹมΘ͍ͬͯΔ Append-capacity ճ਺
8. • ഒʑ͙Β͍ͷλΠϛϯάͰ εύΠΫ • ௕͍΄Ͳίϐʔ࣌ؒ↑ Append-interval ճ਺
9. ଞͷૢ࡞ͯ͠΋ ϝϞϦ্࿈ଓͳͷʁ υΩϡϝϯτݟ͔ͭΒͳ͍ͷͰɺ࣮ࡍʹࢼͯ͠ΈΔ
10. • 0..<100 ͷArray Λ༻ҙ • 50൪໨Λremove • ઌ಄ɺ50൪໨ɺ࠷ޙඌͷΞυϨεΛදࣔ REMOVE Optional(0x0000000100e30c60) Optional(0x0000000100e30df0) Optional(50) Optional(0x0000000100e30f78) Optional(0x0000000100e30c60) Optional(0x0000000100e30df0) Optional(51) Optional(0x0000000100e30f70)
11. • 0..<100 ͷArray Λ༻ҙ • 50൪໨Λremove • ઌ಄ɺ50൪໨ɺ࠷ޙඌͷΞυϨεΛදࣔ REMOVE Optional(0x0000000100e30c60) Optional(0x0000000100e30df0) Optional(50) Optional(0x0000000100e30f78) Optional(0x0000000100e30c60) Optional(0x0000000100e30df0) Optional(51) Optional(0x0000000100e30f70) ઌ಄Ґஔ͸ಉ͡ ΞυϨε͸ಉ͕ͩ͡஋͕ҧ͏ ޙΖ͸Int1ͭ෼ ζϨͯΔ
12. ࡟আͨ͠ͱ͜ΑΓޙΖଆΛશ෦ͣΒ͍ͯ͠Δ Remove લଆ ޙଆ લଆ ཁૉ ޙଆ
13. • 10ສݸͷ഑ྻ • ઌ಄࡟আ܁Γฦִͯؒ͠Λ ϓϩοτ • શମతʹԼ͕͍ͬͯ͘ • ΪβΪβͷཧ༝͸ෆ໌ REMOVE
14. • (insertඈ͹͠·͕ͨ͠) • (ఆੑతͳ࿩͔ͯ͠͠ͳ͍͚Ͳ) • SwiftͷArray͸(ૢ࡞ޙͰ΋)ϝϞϦ্Ͱ࿈ଓ (※MemoryLayout<T>.strideͷઆ໌ʹΑΓ࣮֬ͳώϯτ͕͋ͬͨ) • ಈ࡞Λҙࣝ͢Δͱ଎͘ͳΔ͔΋ʁʢreserveCapacity, …ʣ ·ͱΊ
15. THANK YOU