SwiftDataReader

SwiftDataReader is a swift library which simplifies the work of reading values from an instance of Foundation's Data type.

Examples

var reader = DataReader(data: Data([1,2,3,4,5,6,7,8]))
let myInt: Int32 = reader.readValue()!
let myOtherInt: Int32 = reader.readValue()!

In this example, readValue(type:) infers the type and number of bytes to read from the Data object from the type of the destination variable.

If the type cannot be inferred, it can be passed as an argument to either peekValue(type:) or readValue(type:).

var reader = DataReader(data: Data([1]))
let value = reader.readValue(type: UInt8.self)!

Strings

let str = "🤞 this is a utf-8 string ⛵️"
var data = Data([UInt8(str.lengthOfBytes(using: .utf8)),0,0,0]) // str count
data.append(str.data(using: .utf8)!) // the string to be read back

var reader = DataReader(data: data)

let strLen: UInt32 = reader.readValue()!
let testStr: String = reader.readValue(count: Int(strLen))!

Arrays

let reader = DataReader(data: Data([1,0,0,0, 2,0,0,0, 3,0,0,0, 4,0,0,0]))
let value: [Int32] = reader.peekValue(count: 3)!

Enums

Enums that conform to RawRepresentable can be read directly.

enum MyEnum: UInt8 {
  case ten = 10
  case twenty = 20
}

let reader = DataReader(data: Data([10, 20]))
let value = reader.peekValue(type: MyEnum.self)! // => .ten

Custom Types

Some, but not all custom types can be read directly. Notably, structs which contain enums that conform to RawRepresentable cannot be read directly if the raw values of enums are not contiugous and 0-based. This is a reminder that in the end, the success or failure of a read operation is highly dependent on how the compiler chooses to represent a given type in memory and whether the data being read is already in that form.

It is likely that such in-memory representations could change between compiler versions and should not be relied upon. For this reason it is better to stick with reading individual scalar values.

struct Foo: DefaultInitializable, Equatable {
  var x: Int32 = 0
  var y: Int32 = 0
}
var reader = DataReader(data: Data([1,0,0,0,2,0,0,0]))
let f:Foo = reader.readValue()!