crc32 implemented in Swift

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
  jloup@gzip.org          madler@alumni.caltech.edu
*/

import Foundation

/**
Table of CRC-32's of all single-byte values (made by make_crc_table)
*/
private 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: NSData?) -> UInt32 {
	guard let data = data else {
		return crc32(0, buffer: nil, length: 0)
	}
	return crc32(crc, buffer: UnsafePointer<UInt8>(data.bytes), length: data.length)
}

/**
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 {
	if buffer == nil {
		return 0
	}
	var crc1 = crc ^ 0xffffffff
	var len = length
	var buf = buffer
	func DO1() {
		let toBuf = buf.memory
		buf++
		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()
		} 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 {
	private var initialized = false
	private(set) var crc: UInt32 = 0
	
	var hashValue: Int {
		return Int(crc)
	}
	
	init() {}
	
	convenience init(data: NSData) {
		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: NSData) {
		crc = crc32(crc, data: data)
		initialized = true
	}
}

Line 122 needs a parenthesis around crc1 ^ UInt32(toBuf)

As far as I understand in func crc... you just need to do the DO1 function len times, which is equal to:

(0..<len).forEach
{ _ in
        let toBuf = buf.memory
        buf += 1
        crc1 = crcTable[Int((crc1 ^ UInt32(toBuf)) & 0xFF)] ^ crc1 >> 8
}

May have done some small mistake, but should be more or less it.

I forked this and updated it for Swift 3: https://gist.github.com/JALsnipe/e9ad8ba24945e26f10300a18d55a2310

I recently implemented this very compact solution in Swift 5:

https://gist.github.com/antfarm/695fa78e0730b67eb094c77d53942216