~ sonar: fixed some 'bugs'

src/main/java/com/kasisoft/libs/common/datatypes/GzipFileType.java

@@ -19,7 +19,7 @@ public int getMinSize() {
     @Override
     public boolean test(byte[] data) {
         if (getMinSize() <= data.length) {
-            return (((data[1] << 8) | data[0]) & 0x0000FFFF) == GZIPInputStream.GZIP_MAGIC;
+            return (((data[1] << 8) | (data[0] & 0xFF)) & 0x0000FFFF) == GZIPInputStream.GZIP_MAGIC;
         }
         return false;
     }

src/main/java/com/kasisoft/libs/common/io/IoFunctions.java

@@ -249,7 +249,12 @@ public static Optional<Path> findNewTempFile(String prefix, String suffix) {
     public static void skip(InputStream input, @Min(0) long size) {
         if (size > 0) {
             try {
-                input.skip(size);
+                long remaining = size;
+                long skipped   = input.skip(remaining);
+                while (remaining > 0) {
+                    remaining -= skipped;
+                    skipped    = input.skip(remaining);
+                }
             } catch (Exception ex) {
                 throw KclException.wrap(ex);
             }

src/main/java/com/kasisoft/libs/common/io/impl/FileIoSupport.java

@@ -21,7 +21,7 @@
  */
 public class FileIoSupport implements IoSupport<File> {
 
-    private static final long MB_16 = 16 * 1024 * 1024;
+    private static final long MB_16 = 16L * 1024 * 1024;
 
     @Override
     public InputStream newInputStreamImpl(File source) throws Exception {

src/main/java/com/kasisoft/libs/common/io/impl/PathIoSupport.java

@@ -21,7 +21,7 @@
  */
 public class PathIoSupport implements IoSupport<Path> {
 
-    private static final long MB_16 = 16 * 1024 * 1024;
+    private static final long MB_16 = 16L * 1024 * 1024;
 
     @Override
     public InputStream newInputStreamImpl(Path source) throws Exception {

src/main/java/com/kasisoft/libs/common/utils/Encryptor.java

@@ -124,20 +124,22 @@ private String setupSecret(String secret) {
         return result;
     }
 
+    @NotNull
     private KeyGenerator keyGenerator() {
         try {
             return KeyGenerator.getInstance(algorithm);
         } catch (NoSuchAlgorithmException ex) {
-            // won't happen as it had been tested before
+            // won't happen as it had been tested before (see #verify)
             return null;
         }
     }
 
+    @NotNull
     private Cipher cipher() {
         try {
             return Cipher.getInstance(cipher);
         } catch (NoSuchAlgorithmException | NoSuchPaddingException ex) {
-            // won't happen as it had been tested before
+            // won't happen as it had been tested before (see #verify)
             return null;
         }
     }