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Working With Binary Data in Swift
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JP Simard
October 29, 2015
Programming
4
1.2k
Working With Binary Data in Swift
Presented at Swift Summit SF 2015.
Source available here:
https://github.com/jpsim/talks
JP Simard
October 29, 2015
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Transcript
Working with Binary Data in Swift
JP Simard @ Realm
None
Options → NSData → [UInt8] → withUnsafePointer() → ???
Layout-Aligned Structs
func encode<T>(var value: T) -> NSData { return withUnsafePointer(&value) {
p in NSData(bytes: p, length: sizeofValue(value)) } } func decode<T>(data: NSData) -> T { let pointer = UnsafeMutablePointer<T>.alloc(sizeof(T)) data.getBytes(pointer, length: sizeof(T)) return pointer.move() }
enum Either<T> { case Left(T) case Right(T) } let value
= Either.Left("Swift Summit") let data = encode(value) data // => <NSData> let decoded: Either<String> = decode(data) decoded // => Either.Left("Swift Summit")
None
None
Get SourceKit syntax map struct A { subscript(index: Int) ->
() { return () } }
Result 00 00 00 00 00 00 00 00 30
00 00 00 00 00 00 00 40 4c 81 01 01 00 00 00 00 00 00 00 0c 00 00 00 78 4c 81 01 01 00 00 00 07 00 00 00 14 00 00 00 b0 4c 81 01 01 00 00 00 12 00 00 00 1e 00 00 00 00
Result 00 00 00 00 00 00 00 00 30
00 00 00 00 00 00 00 --------16 bytes------- --------16 bytes------- 40 4c 81 01 01 00 00 00 00 00 00 00 0c 00 00 00 --------16 bytes------- --------16 bytes------- 78 4c 81 01 01 00 00 00 07 00 00 00 14 00 00 00 --------16 bytes------- --------16 bytes------- b0 4c 81 01 01 00 00 00 12 00 00 00 1e 00 00 00 --------16 bytes------- --------16 bytes------- 00
!
struct SyntaxToken { let type: String let offset: Int let
length: Int }
Strideable
tokens = 16.stride(through: numberOfTokens * 16, by: 16).map { parserOffset
in . }
tokens = 16.stride(through: numberOfTokens * 16, by: 16).map { parserOffset
in var uid = UInt64(0), offset = 0, length = 0 data.getBytes(&uid, range: NSRange(location: parserOffset, length: 8)) data.getBytes(&offset, range: NSRange(location: 8 + parserOffset, length: 4)) data.getBytes(&length, range: NSRange(location: 12 + parserOffset, length: 4)) }
tokens = 16.stride(through: numberOfTokens * 16, by: 16).map { parserOffset
in var uid = UInt64(0), offset = 0, length = 0 data.getBytes(&uid, range: NSRange(location: parserOffset, length: 8)) data.getBytes(&offset, range: NSRange(location: 8 + parserOffset, length: 4)) data.getBytes(&length, range: NSRange(location: 12 + parserOffset, length: 4)) return SyntaxToken( type: stringForSourceKitUID(uid) ?? "unknown", offset: offset, length: length >> 1 ) }
Collection of Bytes → Making our own → Conforming to
ExtensibleCollectionType → What Index type should we use? Int?
Just end up with [UInt8]
Links → SourceKittenFramework SyntaxMap → Convert structs and enums to
NSData → robnapier.net/nsdata → Simon Lewis on parsing OLE/COM → github.com/realm/jazzy → realm.io
try! ask(...) struct Question { let value: String let canJPAnswer:
Bool } func ask<S: SequenceType where S.Generator.Element == Question>(questions: S) throws { // excercise for attendees }