Swiftで高速にCRC32を求める。

CRC32.swift

import Foundation
import zlib

struct CRC32: Equatable, ExpressibleByIntegerLiteral, CustomStringConvertible {
    typealias IntegerLiteralType = UInt32
    
    let value: UInt32
    var description: String { String(format: "%08X", value) }

    init(data: Data) {
        value = data.withUnsafeBytes {
            UInt32(crc32(0, $0.bindMemory(to: UInt8.self).baseAddress, numericCast(data.count)))
        }
    }
    
    init?<T: DataProtocol>(data: T) {
        guard let value = data.withContiguousStorageIfAvailable({
            UInt32(crc32(0, $0.baseAddress, numericCast(data.count)))
        }) else {
            return nil
        }
        self.value = value
    }
    
    init(value: UInt32) {
        self.value = value
    }

    init(integerLiteral value: UInt32) {
        self.value = value
    }

    static func ~=(crc32: CRC32, value: UInt32) -> Bool {
        crc32.value == value
    }
}