# swift-extras-json

**Repository Path**: R2Jinx/swift-extras-json

## Basic Information

- **Project Name**: swift-extras-json
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: Apache-2.0
- **Default Branch**: main
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2022-05-11
- **Last Updated**: 2022-05-11

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# swift-extras-json

[![Swift 5.1](https://img.shields.io/badge/Swift-5.1-blue.svg)](https://swift.org/download/)
[![github-actions](https://github.com/swift-extras/swift-extras-json/workflows/CI/badge.svg)](https://github.com/swift-extras/swift-extras-json/actions)
[![codecov](https://codecov.io/gh/swift-extras/swift-extras-json/branch/main/graph/badge.svg)](https://codecov.io/gh/swift-extras/swift-extras-json)

This package provides a json encoder and decoder in Swift (without the use of Foundation or any other dependency). 
The implementation is [RFC8259](https://tools.ietf.org/html/rfc8259) compliant. It offers a significant performance improvement compared to the Foundation implementation on Linux.

If you like the idea of using Swift without any dependencies, you might also like our reimplementation of Base64 in Swift: [`swift-extras-base64`](https://github.com/swift-extras/swift-extras-base64)

## Goals

- [x] does not use Foundation at all
- [x] does not use `unsafe` Swift syntax
- [x] no external dependencies, only the Swift stdlib required
- [x] faster than Foundation implementation

#### Currently not supported

- custom encoder and decoder for [ `Data` and `Date`](#what-about-date-and-data)
- parsing/decoding of [UTF-16 and UTF-32 encoded json](#utf-16-and-utf-32)
- transforming `CodingKey`s to camelCase or snake_case (I want to look into this)

#### Alternatives

- [IkigaJSON](https://github.com/autimatisering/IkigaJSON) super fast encoding and decoding especially for server side Swift code. Depends on `SwiftNIO`.
- [Foundation Coding](https://github.com/apple/swift-corelibs-foundation/blob/main/Sources/Foundation/JSONEncoder.swift)

## Usage

Add `swift-extras-json` as dependency to your `Package.swift`:

```swift
  dependencies: [
    .package(url: "https://github.com/swift-extras/swift-extras-json.git", .upToNextMajor(from: "0.6.0")),
  ],
```

Add `ExtrasJSON` to the target you want to use it in.

```swift
  targets: [
    .target(name: "MyFancyTarget", dependencies: [
      .product(name: "ExtrasJSON", package: "swift-extras-json"),
    ])
  ]
```

Use it as you would use the Foundation encoder and decoder.

```swift
import ExtrasJSON

let bytesArray  = try XJSONEncoder().encode(myEncodable)
let myDecodable = try XJSONDecoder().decode(MyDecodable.self, from: bytes)
```

### Use with SwiftNIO ByteBuffer

For maximal performance create an `[UInt8]` from your `ByteBuffer`, even though `buffer.readableBytesView` would technically work as well.

```swift
let result = try XJSONDecoder().decode(
  [SampleStructure].self,
  from: buffer.readBytes(length: buffer.readableBytes)!)
```

```swift
let bytes = try XJSONEncoder().encode(encodable)
var buffer = byteBufferAllocator.buffer(capacity: bytes.count)
buffer.writeBytes(bytes)
```


### Use with Vapor 4

Increase the performance of your Vapor 4 API by using `swift-extras-json` instead of the default Foundation implementation. First you'll need to implement the conformance to Vapor's `ContentEncoder` and `ContentDecoder` as described in the [Vapor docs](https://docs.vapor.codes/4.0/content/#custom-coders).

```swift
import Vapor
import ExtrasJSON

extension XJSONEncoder: ContentEncoder {
  public func encode<E: Encodable>(
    _ encodable: E,
    to body: inout ByteBuffer,
    headers: inout HTTPHeaders) throws
  {
    headers.contentType = .json
    let bytes = try self.encode(encodable)
    // the buffer's storage is resized in case its capacity is not sufficient
    body.writeBytes(bytes)
  }
}

extension XJSONDecoder: ContentDecoder {
  public func decode<D: Decodable>(
    _ decodable: D.Type,
    from body: ByteBuffer,
    headers: HTTPHeaders) throws -> D
  {
    guard headers.contentType == .json || headers.contentType == .jsonAPI else {
      throw Abort(.unsupportedMediaType)
    }
    var body = body
    return try self.decode(D.self, from: body.readBytes(length: body.readableBytes)!)
  }
}
```

Next, register the encoder and decoder for use in Vapor:

```swift
let decoder = XJSONDecoder()
ContentConfiguration.global.use(decoder: decoder, for: .json)

let encoder = XJSONEncoder()
ContentConfiguration.global.use(encoder: encoder, for: .json)
```


## Performance

All tests have been run on a 2019 MacBook Pro (16" – 2,4 GHz 8-Core Intel Core i9). You can run the tests yourself
by cloning this repo and

```bash
# change dir to perf tests
$ cd PerfTests

# compile and run in release mode - IMPORTANT ‼️
$ swift run -c release
```

#### Encoding

|  | macOS Swift 5.1 | macOS Swift 5.2 | Linux Swift 5.1 | Linux Swift 5.2 |
|:--|:--|:--|:--|:--|
| Foundation   | 2.61s | 2.62s | 13.03s | 12.52s |
| ExtrasJSON | 1.23s | 1.25s | 1.13s | 1.05s |
| Speedup | ~2x | ~2x | **~10x** | **~10x** |


#### Decoding

|  | macOS Swift 5.1 | macOS Swift 5.2 | Linux Swift 5.1 | Linux Swift 5.2 |
|:--|:--|:--|:--|:--|
| Foundation   | 2.72s | 3.04s | 10.27s | 10.65s |
| ExtrasJSON | 1.70s | 1.72s | 1.39s | 1.16s |
| Speedup | ~1.5x | ~1.5x | **~7x** | **~8x** |

## Workarounds

### What about `Date` and `Data`?

Date and Data are particular cases for encoding and decoding. They do have default implementations that are kind off special:

- Date will be encoded as a float

    Example: `2020-03-17 16:36:58 +0000` will be encoded as `606155818.503831`
    
- Data will be encoded as a numeric array.

    Example: `0, 1, 2, 3, 255` will be encoded as: `[0, 1, 2, 3, 255]`
    
Yes, that is the default implementation. Only Apple knows why it is not [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601) and [Base64](https://en.wikipedia.org/wiki/Base64). 🙃
Since I don't want to link against Foundation, it is not possible to implement default encoding and decoding strategies for `Date` and `Data` like the Foundation implementation does. That's why, if you want to use another encoding/decoding strategy than the default, you need to overwrite `encode(to: Encoder)` and `init(from: Decoder)`.

This could look like this:

```swift
struct MyEvent: Decodable {

  let eventTime: Date
  
  enum CodingKeys: String, CodingKey {
    case eventTime
  }

  init(from decoder: Decoder) {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    let dateString = try container.decode(String.self, forKey: .eventTime)
    guard let timestamp = MyEvent.dateFormatter.date(from: dateString) else {
      let dateFormat = String(describing: MyEvent.dateFormatter.dateFormat)
      throw DecodingError.dataCorruptedError(forKey: .eventTime, in: container, debugDescription:
        "Expected date to be in format `\(dateFormat)`, but `\(dateString) does not fulfill format`")
    }
    self.eventTime = timestamp
  }
  
  private static let dateFormatter: DateFormatter = MyEvent.createDateFormatter()
  private static func createDateFormatter() -> DateFormatter {
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"
    formatter.timeZone   = TimeZone(secondsFromGMT: 0)
    formatter.locale     = Locale(identifier: "en_US_POSIX")
    return formatter
  }
}
```

You can find more information about [encoding and decoding custom types in Apple's documentation](https://developer.apple.com/documentation/foundation/archives_and_serialization/encoding_and_decoding_custom_types).

Of course you can use `@propertyWrapper`s to make this more elegant:

```swift
import Foundation

@propertyWrapper
struct DateStringCoding: Decodable {
  var wrappedValue: Date
  
  init(wrappedValue: Date) {
    self.wrappedValue = wrappedValue
  }

  init(from decoder: Decoder) throws {
    let container = try decoder.singleValueContainer()
    let dateString = try container.decode(String.self)
    guard let date = Self.dateFormatter.date(from: dateString) else {
      let dateFormat = String(describing: Self.dateFormatter.dateFormat)
      throw DecodingError.dataCorruptedError(in: container, debugDescription:
            "Expected date to be in format `\(dateFormat)`, but `\(dateString) does not fulfill format`")
    }
    self.wrappedValue = date
  }

  private static let dateFormatter: DateFormatter = Self.createDateFormatter()
  private static func createDateFormatter() -> DateFormatter {
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"
    formatter.timeZone   = TimeZone(secondsFromGMT: 0)
    formatter.locale     = Locale(identifier: "en_US_POSIX")
    return formatter
  }
}

struct MyEvent: Decodable {
  @DateStringCoding
  var eventTime: Date
}
```

Checkout a full example in the test file [DateCodingTests](https://github.com/swift-extras/swift-extras-json/blob/main/Tests/ExtrasJSONTests/DateCodingTests.swift).

### UTF-16 and UTF-32

If your input is [UTF-16](https://en.wikipedia.org/wiki/UTF-16) or [UTF-32](https://en.wikipedia.org/wiki/UTF-32) encoded, you can easily convert it to UTF-8: 

```swift
let utf16 = UInt16[]() // your utf-16 encoded data
let utf8  = Array(String(decoding: utf16, as: Unicode.UTF16.self).utf8)
```

```swift
let utf32 = UInt32[]() // your utf-32 encoded data
let utf8  = Array(String(decoding: utf32, as: Unicode.UTF32.self).utf8)
```

## Contributing

Please feel welcome and encouraged to contribute to `swift-extras-json`. This is a very young endeavour and help is always welcome.

If you've found a bug, have a suggestion, or need help getting started, please open an Issue or a PR. If you use this package, I'd be grateful for sharing your experience.

Focus areas for the time being:

- ensuring safe use of nested containers while encoding and decoding
- supporting camelCase and snakeCase aka [`KeyEncodingStrategy`](https://developer.apple.com/documentation/foundation/jsonencoder/keyencodingstrategy)

## Credits

- [@weissi](https://github.com/weissi) thanks for answering all my questions and for opening tickets [SR-12125](https://bugs.swift.org/browse/SR-12125) and [SR-12126](https://bugs.swift.org/browse/SR-12126)
- [@dinhhungle](https://github.com/dinhhungle) thanks for your quality assurance. It helped a lot! 
- [@Ro-M](https://github.com/Ro-M) thanks for checking my README.md
- [@Trzyipolkostkicukru](https://github.com/Trzyipolkostkicukru) thanks for your advice on `@propertyWrappers` and for finding typos.