crc32 implemented in Swift (Swift 3)

crc32.swift

//
//  crc32.swift
//  SuperSFV
//
//  Created by C.W. Betts on 8/23/15.
//
//
/* crc32.swift -- compute the CRC-32 of a data stream
 Copyright (C) 1995-1998 Mark Adler
 Copyright (C) 2015 C.W. "Madd the Sane" Betts
 
 This software is provided 'as-is', without any express or implied
 warranty.  In no event will the authors be held liable for any damages
 arising from the use of this software.
 
 Permission is granted to anyone to use this software for any purpose,
 including commercial applications, and to alter it and redistribute it
 freely, subject to the following restrictions:
 
 1. The origin of this software must not be misrepresented; you must not
 claim that you wrote the original software. If you use this software
 in a product, an acknowledgment in the product documentation would be
 appreciated but is not required.
 2. Altered source versions must be plainly marked as such, and must not be
 misrepresented as being the original software.
 3. This notice may not be removed or altered from any source distribution.
 
 Jean-loup Gailly        Mark Adler
 [email protected]          [email protected]
 */

// Migrated to Swift 3 by Josh Lieberman

import Foundation

/**
 Table of CRC-32's of all single-byte values (made by make_crc_table)
 */
fileprivate let crcTable: [UInt32] = [
    0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
    0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
    0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
    0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
    0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
    0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
    0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
    0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
    0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
    0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
    0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
    0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
    0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
    0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
    0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
    0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
    0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
    0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
    0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
    0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
    0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
    0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
    0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
    0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
    0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
    0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
    0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
    0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
    0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
    0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
    0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
    0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
    0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
    0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
    0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
    0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
    0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
    0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
    0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
    0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
    0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
    0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
    0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
    0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
    0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
    0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
    0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
    0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
    0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
    0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
    0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
    0x2d02ef8d]

func crc32(_ crc: UInt32, data: Data?) -> UInt32 {
    guard let data = data else {
        return crc32(0, buffer: nil, length: 0)
    }
    
    return data.withUnsafeBytes({
        crc32(0, buffer: $0, length: data.count)
    })
}

/**
 Update a running crc with the bytes buf[0..len-1] and return the updated
 crc. If buf is `nil`, this function returns the required initial value
 for the crc. Pre- and post-conditioning (one's complement) is performed
 within this function so it shouldn't be done by the application.<br>
 Usage example:
 
 Var crc: UInt32 = crc32(0, nil, 0);
 
 while (read_buffer(buffer, length) != EOF) {
 crc = crc32(crc, buffer: buffer, length: length)
 }
 if (crc != original_crc) error();
 */
func crc32(_ crc: UInt32, buffer: UnsafePointer<UInt8>?, length: Int) -> UInt32 {
    
    guard let buffer = buffer else {
        return 0
    }
    
    var crc1 = crc ^ 0xffffffff
    var len = length
    var buf = buffer
    func DO1() {
        let toBuf = buf.pointee
        buf += 1
        crc1 = crcTable[Int((crc1 ^ UInt32(toBuf)) & 0xFF)] ^ crc1 >> 8
    }
    func DO2() { DO1(); DO1(); }
    func DO4() { DO2(); DO2(); }
    func DO8() { DO4(); DO4(); }
    
    while len >= 8 {
        DO8()
        len -= 8
    }
    if len != 0 {
        repeat {
            DO1()
            len -= 1
        } while len != 0
    }
    
    return crc1 ^ 0xffffffff;
}

func ==(lhs: CRC32, rhs: CRC32) -> Bool {
    return lhs.initialized == rhs.initialized && lhs.crc == rhs.crc
}

final class CRC32: Hashable {
    fileprivate var initialized = false
    fileprivate(set) var crc: UInt32 = 0
    
    var hashValue: Int {
        return Int(crc)
    }
    
    init() {}
    
    convenience init(data: Data) {
        self.init()
        crc = crc32(crc, data: data)
        initialized = true
    }
    
    func run(buffer buffer: UnsafePointer<UInt8>, length: Int) {
        crc = crc32(crc, buffer: buffer, length: length)
        initialized = true
    }
    
    func run(data data: Data) {
        crc = crc32(crc, data: data)
        initialized = true
    }
}

You should update the run functions at the bottom of the file to not have duplicated argument labels like so:

func run(buffer: UnsafePointer<UInt8>, length: Int) {
    crc = crc32(crc, buffer: buffer, length: length)
    initialized = true
}

func run(data: Data) {
    crc = crc32(crc, data: data)
    initialized = true
}

Alternative:

extension Data {
    func crc32(_ initial: UInt32) -> UInt32 {
        let value = reduce(initial ^ 0xffffffff, { (value, byte) -> UInt32 in
            return crc32Table[Int(UInt8(value & 0xff) ^ byte)] ^ (value >> 8)
        })
        return value ^ 0xffffffff
    }
}

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, without any restrictions.

Just a heads up, in line 58 you are converting a UInt32 to a Int32 or Int64, depending on the platform it runs on. On a 32-bit iPhone 5, half of the times, the conversion to Int32 will crash because it can't fit.

And the crc32 function should be fixed:

func crc32(_ crc: UInt32, data: Data?) -> UInt32 {
    guard let data = data else {
        return crc32(0, buffer: nil, length: 0)
    }
    
    return data.withUnsafeBytes({
        crc32(crc, buffer: $0, length: data.count)
    })
}

Note how the last call to crc32 take "crc" as first parameter, which is otherwise never used in the function.

On 2nd thought, the first call should also have "crc" instead of "0".