Swift 中结构数组的 SHA1 hash

Question

I need to produce an SHA1 hash of an array of custom structs in Swift. The app receives the array from an external source at periodic intervals. The objective is to be able to tell if the data changed after last update, without holding a full copy of the data.

How can I do this?

struct Person {
    let firstName: String
    let lastName: String
}

let people = [
    Person(firstName: "John", lastName: "Appleseed"),
    Person(firstName: "Mike", lastName: "Doe")
]

// Produce an SHA1 digest of `people` here?

Answer 1

One way to do this could be using JSON with sorted keys:

struct Person: Encodable {
    let firstName: String
    let lastName: String
}

let people = [
    Person(firstName: "John", lastName: "Appleseed"),
    Person(firstName: "Mike", lastName: "Doe")
]

let encoder = JSONEncoder()
encoder.outputFormatting = .sortedKeys
let data = try! encoder.encode(people)

var digest = [UInt8](repeating: 0, count: Int(CC_SHA1_DIGEST_LENGTH))
data.withUnsafeBytes { ptr in
    CC_SHA1(ptr.baseAddress, CC_LONG(data.count), &digest)
}