Seed a Hasher at runtime instead of through an environment variable

Hasher+Seedable.swift

extension Hasher {
    static func randomSeed() -> [UInt8] {
        Array(unsafeUninitializedCapacity: 32) { pointer, initializedCount in
            for i in 0..<32 {
                pointer[i] = UInt8(arc4random())
            }
            
            initializedCount = 32
        }
    }
    
    init(seed: [UInt8]) {
        guard seed.count == 32 else {
            preconditionFailure("Seed must be exactly 32 bytes")
        }
        
        let buffer = UnsafeMutableRawBufferPointer.allocate(byteCount: MemoryLayout<Hasher>.size, alignment: MemoryLayout<Hasher>.alignment)
        
        for index in 0..<8 {
            buffer[index] = 0
        }
        
        for index in 8..<40 {
            buffer[index] = seed[index - 8]
        }
        
        for index in 40..<72 {
            buffer[index] = 0
        }
        
        self = buffer.bindMemory(to: Hasher.self).baseAddress!.pointee
    }
}