Adler32 using libz

Adler32.swift

import Foundation
import zlib

extension Array where Element == UInt8 {
  func adler32() -> UInt32 {
    let a1 = zlib.adler32(0, nil, 0)
    
    let size = self.count
    
    let result = self.withUnsafeBytes { (p1: UnsafeRawBufferPointer) -> UInt32 in
      let start = p1.baseAddress!.assumingMemoryBound(to: Bytef.self)
      let adler = zlib.adler32_z(a1, start, size)
      return UInt32(adler)
    }
    return result
  }
}

extension Data {
  func adler32() -> UInt32 {
    let a1 = zlib.adler32(0, nil, 0)
    
    let _count = self.count
    
    let result = self.withUnsafeBytes { (p1: UnsafePointer<UInt8>) -> UInt32 in
      return p1.withMemoryRebound(to: Bytef.self, capacity: MemoryLayout<Bytef>.size * _count) { pBytef -> UInt32 in
        return UInt32(zlib.adler32_z(a1, pBytef, _count))
      }
    }
    
    return result
  }
}