Sequence, Collection and Array in Swift

My talk at COSCUP 20 about how Swift constructs its collection data structure architecture using protocols.

Also a quick guide to Swift source code building and overall understanding.

Transcript

1. Sequence, Collection and Array in Swift Pofat @ COSCUP 2020
2. Hi, I am Pofat Podcaster @ [weak self] @weak_self iOS Developer @PofatTseng pofat
3. Swift
4. About Swift • Goal: Safe, fast and expressive with modern approach • Apache 2.0 license with a Runtime Library Exception • Swift project is governed by a core team that drives the strategic direction by working with the community.
5. Swift Projects • Swift compiler: https://swift.org/compiler-stdlib/ • The standard library bundled as part of the language • Core libraries that provide higher-level functionality: https://swift.org/core- libraries/ • The LLDB Debugger with Swift REPL: https://swift.org/lldb/ • Swift Package Manager: https://swift.org/package-manager/ • Xcode playground support
6. Platform Support • Apple: iOS, macOS, watchOS, iPadOS and tvOS • Linux: Ubuntu, CentOS, Amazon Linux2 and etc..
7. Swift Evolution • Manifesto: Describe the proposed roadmap and goal for major projects. • Proposal: Describe the design proposal for new features or changes • Status of proposals can be traces at https://apple.github.io/swift-evolution/
8. Build Swift!
9. Requirement • Ninja/cmake • Xcode • Power • Env: Swift 5.2.4-RELEASE
10. Build Swift
11. GYB Tuple.swift.gyb
12. Tuple.swift
13. Swift-Doc • https://github.com/SwiftDocOrg/swift-doc •
14. VS Code Setup for Swift Install Xcode • Install Xcode (The correct way to install Xcode)
15. VS Code Setup for Swift Install VS Code and NPM • Install VS Code • Install VS Code command line tool • Install node and npm
16. VS Code Setup for Swift Build and install SourceKit-LSP for VS Code
17. Happy Tracing
18. Debug Swift Using VS Code • Open cloned Swift source code root folder • Create configuration launch.json
20. Standard Library
21. Fundamental Architecture Swift Standard library Foundation
22. Standard Library Core • Standard library: Core, Runtime and SDK overlays • Definitions of all data types, protocol, functions, etc. • All written in Swift • Use GYB for repetitive codes
23. Standard Library Core • Data types: Int, Optional, Bool, Array, … • Protocols: Sequence, Hashable, CustomStringConvertible, … • Functions: +, +=, …
24. += Is a function IntegerTypes.swift
26. Compile Swift Swift Frontend IRGen LLVM Swift code SIL LLVM IR Machine code
27. BuiltIn BuiltIn LLVM IR Standard Library Type Method BuiltIn.Type BuiltIn.Method
28. Attributes • @inlinable : Make it inline when compile with -O • @_transparent : Must be inline even when compile with -None • @usableFromInline : Temporary change scope during inline stage • @_fixed_layout : Processed at SIL stage. It tells compiler that access properties by offset is possible without looking up metadata. • @frozen : Only allowed in library evolution mode. Marked enum or struct can’t change their declaration by adding, removing, or reordering an enumeration’s cases or a structure’s stored instance properties.
29. Example: Bool
30. Protocol-Oriented Programming
31. Why Protocol? • Contract of interfaces • Cross-cutting concern • Better way to share code than inheritance
32. Protocol Hashable.swift
33. Protocols in Standard Library • Identity: Sequence, Collection, … • Ability: Hashable, Equatable, … • Able to convert to: CustomStringConvertible, …
34. Sequence
35. Sequence • Definition: A sequence is a list of values that you can step through one at a time. • Iterator step through the whole sequence
36. Sequence Protocol Sequence.swift
37. IteratorProtocol Sequence.swift
38. Sequence Protocol Hierarchy
39. Reduce SequenceAlgorithms.swift
40. Map by Reduce
41. FlatMap SequenceAlgorithms.swift
42. What if the sequence is infinite in length?
43. Map a large sequence will lead to…
44. Lazy Sequence LazySequence.swift
45. LazySequenceProtocol LazySequence.swift Map.swift
46. LazyMapSequence Map.swift
47. Being Lazy Map.swift
48. Revise FileSequenceHandler
49. Collection
50. Collection Collection.swift
51. IndexingIterator Collection.swift
52. IndexingIterator Collection.swift
53. Collection Families
54. Collection Algorithms Shuffle CollectionAlgorithms.swift
55. Array
56. Array Sequence Collection MutableCollection BidirectionalCollection RangeReplaceableCollection RandomAccessCollection Array
57. Array ContinuousArray struct Array _buffer struct _ArrayBuffer struct _BridgeStorage _storage _rawValue BuiltIn.BridgeObject
58. Copy On Write Array.swift
59. Copy Array Array.swift
60. Copy Array If buffer is full ArrayShared.swift
61. Copy Array Grow strategy ArrayShared.swift
62. How Array Grows Exactly Double…? ܻ㺔氂ࣁ蝡螲 薹朰ஃ蝡螲
63. String
64. Let’s Read String!
65. String String.swift
66. String Conformance • Protocol hierarchy
67. String Hierarchy String _guts: _StringGuts _StringGuts _object: StringObject _StringObject _countAndFlagBits: UInt64 _object: Builtin.BridgeObject rawBits: RawBitPattern discriminatedObjectRawBits: UInt64 _StringStorage _realCapacityAndFlags: UInt64 _countAnd ags: CountAnd ags _ShardStringStorage _countAnd ags: CountAnd ags Maybe Maybe
68. _StringStorage StringStorage.swift
69. _StringStorage Creation StringStorage.swift
70. _StringStorage Creation Flow • String.init(decoding:as:) -> • String._fromCodeUnits(codeUnits:encoding:) -> • String._slowFromCodeUnits(_:encoding:repair:) StringStorage.swift
71. StringCreate.swift
72. StringCreate.swift
73. StringCreate.swift
74. Real Creation of UTF8 String StringCreate.swift
75. _SmallString SmallString.swift
76. _SmallString SmallString.swift RawBitPattern.0 RawBitPattern.1 0 1 2 3 4 5 6 7 8 9 A B C D E F Discriminator UTF8 Code Point 56 57 58 59 60 61 62 63 Used Count isForeign 0 isSmall 1 ASCII 0/1 isImmortal 1
77. String Initialize Small String String _StringGuts _StringObject _SmallString Raw bytes after transcode Init with buffer Return smallString smallString Init with smallString Init with _StringObject Return _StringObject Return _StringGuts Init with guts
78. String Equatable StringComparable.swift
79. String Equatable String Compare StringComparison.swift
80. String Equatable String Guts StringGuts.swift StringObject.swift
81. Exercises • What’s the flow of initializing a large string • How does String mutation work? (e.g. append)
82. String Index • String index is not Int, but StringIndex. A position of a character or code unit. StringIndex.swift
83. String Index A closer look
84. String.count O(n) • String is only BidirectionalCollection, not RandomAccessCollection. StringCharacterView.swift
85. String.count distance(from:to:) BidirectionalCollection.swift
86. String.count formIndex StringCharacterView.swift
87. Exercises • How can we make String conform to RandomAccessCollection?
88. Guts _Storage Native Small/Large
89. ๜茐֢ኧPofat Tseng蕣֢牧犥獺አCC নݷ秂纈 4.0 㾴褬 ദ稗礿稠朰ڊ牐 Thank you!