Use NSDataSequence by SHA

CryptoSwift/SHA1.swift

@@ -29,9 +29,7 @@ final class SHA1 : HashProtocol {
         
         // Process the message in successive 512-bit chunks:
         let chunkSizeBytes = 512 / 8 // 64
-        var leftMessageBytes = tmpMessage.length
-        for var i = 0; i < tmpMessage.length; i = i + chunkSizeBytes, leftMessageBytes -= chunkSizeBytes {
-            let chunk = tmpMessage.subdataWithRange(NSRange(location: i, length: min(chunkSizeBytes,leftMessageBytes)))
+        for chunk in NSDataSequence(chunkSize: chunkSizeBytes, data: tmpMessage) {
             // break chunk into sixteen 32-bit words M[j], 0 ≤ j ≤ 15, big-endian
             // Extend the sixteen 32-bit words into eighty 32-bit words:
             var M:[UInt32] = [UInt32](count: 80, repeatedValue: 0)

CryptoSwift/SHA2.swift

@@ -133,9 +133,7 @@ final class SHA2 : HashProtocol {
         
         // Process the message in successive 512-bit chunks:
         let chunkSizeBytes = 512 / 8 // 64
-        var leftMessageBytes = tmpMessage.length
-        for var i = 0; i < tmpMessage.length; i = i + chunkSizeBytes, leftMessageBytes -= chunkSizeBytes {
-            let chunk = tmpMessage.subdataWithRange(NSRange(location: i, length: min(chunkSizeBytes,leftMessageBytes)))
+        for chunk in NSDataSequence(chunkSize: chunkSizeBytes, data: tmpMessage) {
             // break chunk into sixteen 32-bit words M[j], 0 ≤ j ≤ 15, big-endian
             // Extend the sixteen 32-bit words into sixty-four 32-bit words:
             var M:[UInt32] = [UInt32](count: variant.k.count, repeatedValue: 0)