Added function which calculates crc32.

2026-06-23 14:56:41 +00:00 · 2016-12-18 14:16:16 +03:00
parent b4766be618
commit bc64ce44b1
1 changed files with 39 additions and 0 deletions
@@ -0,0 +1,39 @@
+//
+//  CheckSums.swift
+//  SWCompression
+//
+//  Created by Timofey Solomko on 18.12.16.
+//  Copyright © 2016 tsolomko. All rights reserved.
+//
+
+import Foundation
+
+struct CheckSums {
+
+    static let crc32table: [UInt32] = {
+        var table: [UInt32] = Array(repeating: 0, count: 256)
+        let crc32poly = 0xEDB88320
+        var r = 0
+        var j = 0
+        for i in 0..<256 {
+            r = i
+            j = 8
+            while j > 0 {
+                r = r & 1 > 0 ? (r >> 1) ^ crc32poly : r >> 1
+                j -= 1
+            }
+            table[i] = UInt32(r)
+        }
+        return table
+    }()
+
+    static func crc32(_ array: [UInt8]) -> Int {
+        var crc: UInt32 = ~0
+        for i in 0..<array.count {
+            let index = (Int(crc) & 0xFF) ^ (array[i].toInt())
+            crc = CheckSums.crc32table[index] ^ (crc >> 8)
+        }
+        return Int(~crc)
+    }
+    
+}