Move methods for decode hex dump into StringUtil

Motivation:

PR netty#6811 introduced a public utility methods to decode hex dump and its parts, but they are not visible from netty-common.

Modifications:

1. Move the `decodeHexByte`, `decodeHexDump` and `decodeHexNibble` methods into `StringUtils`.
2. Apply these methods where applicable.
3. Remove similar methods from other locations (e.g. `HpackHex` test class).

Result:

Less code duplication.

buffer/src/main/java/io/netty/buffer/ByteBufUtil.java

@@ -21,7 +21,6 @@
 import io.netty.util.Recycler;
 import io.netty.util.Recycler.Handle;
 import io.netty.util.concurrent.FastThreadLocal;
-import io.netty.util.internal.EmptyArrays;
 import io.netty.util.internal.PlatformDependent;
 import io.netty.util.internal.StringUtil;
 import io.netty.util.internal.SystemPropertyUtil;
@@ -129,21 +128,21 @@ public static String hexDump(byte[] array, int fromIndex, int length) {
      * Decode a 2-digit hex byte from within a string.
      */
     public static byte decodeHexByte(CharSequence s, int pos) {
-        return HexUtil.decodeHexByte(s, pos);
+        return StringUtil.decodeHexByte(s, pos);
     }
 
     /**
      * Decodes a string generated by {@link #hexDump(byte[])}
      */
     public static byte[] decodeHexDump(CharSequence hexDump) {
-        return HexUtil.decodeHexDump(hexDump, 0, hexDump.length());
+        return StringUtil.decodeHexDump(hexDump, 0, hexDump.length());
     }
 
     /**
      * Decodes part of a string generated by {@link #hexDump(byte[])}
      */
     public static byte[] decodeHexDump(CharSequence hexDump, int fromIndex, int length) {
-        return HexUtil.decodeHexDump(hexDump, fromIndex, length);
+        return StringUtil.decodeHexDump(hexDump, fromIndex, length);
     }
 
     /**
@@ -891,55 +890,6 @@ private static String hexDump(ByteBuf buffer, int fromIndex, int length) {
             return new String(buf);
         }
 
-        /**
-         * Helper to decode half of a hexadecimal number from a string.
-         * @param c The ASCII character of the hexadecimal number to decode.
-         * Must be in the range {@code [0-9a-fA-F]}.
-         * @return The hexadecimal value represented in the ASCII character
-         * given, or {@code -1} if the character is invalid.
-         */
-        private static int decodeHexNibble(final char c) {
-            // Character.digit() is not used here, as it addresses a larger
-            // set of characters (both ASCII and full-width latin letters).
-            if ('0' <= c && c <= '9') {
-                return c - '0';
-            }
-            if ('a' <= c && c <= 'f') {
-                return c - 'a' + 0xA;
-            }
-            if ('A' <= c && c <= 'F') {
-                return c - 'A' + 0xA;
-            }
-            return -1;
-        }
-
-        private static byte decodeHexByte(CharSequence s, int pos) {
-            int hi = decodeHexNibble(s.charAt(pos));
-            int lo = decodeHexNibble(s.charAt(pos + 1));
-            if (hi == -1 || lo == -1) {
-                throw new IllegalArgumentException(String.format(
-                        "invalid hex byte '%s' at index %d of '%s'", s.subSequence(pos, pos + 2), pos, s));
-            }
-            return (byte) ((hi << 4) + lo);
-        }
-
-        private static byte[] decodeHexDump(CharSequence hexDump, int fromIndex, int length) {
-            if (length < 0 || (length & 1) != 0) {
-                throw new IllegalArgumentException("length: " + length);
-            }
-            if (length == 0) {
-                return EmptyArrays.EMPTY_BYTES;
-            }
-
-            byte[] bytes = new byte[length >>> 1];
-
-            for (int i = 0; i < length; i += 2) {
-                bytes[i >>> 1] = decodeHexByte(hexDump, fromIndex + i);
-            }
-
-            return bytes;
-        }
-
         private static String hexDump(byte[] array, int fromIndex, int length) {
             if (length < 0) {
               throw new IllegalArgumentException("length: " + length);

codec-http/src/main/java/io/netty/handler/codec/http/QueryStringDecoder.java

@@ -33,7 +33,6 @@
 
 import static io.netty.util.internal.ObjectUtil.*;
 import static io.netty.util.internal.StringUtil.*;
-import static io.netty.buffer.ByteBufUtil.decodeHexByte;
 
 /**
  * Splits an HTTP query string into a path string and key-value parameter pairs.

codec-http2/src/test/java/io/netty/handler/codec/http2/HpackDecoderTest.java

@@ -33,6 +33,7 @@
 
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
+import io.netty.util.internal.StringUtil;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -55,11 +56,11 @@ public class HpackDecoderTest {
     private Http2Headers mockHeaders;
 
     private static String hex(String s) {
-        return HpackHex.encodeHexString(s.getBytes());
+        return StringUtil.toHexString(s.getBytes());
     }
 
     private void decode(String encoded) throws Http2Exception {
-        byte[] b = HpackHex.decodeHex(encoded.toCharArray());
+        byte[] b = StringUtil.decodeHexDump(encoded);
         ByteBuf in = Unpooled.wrappedBuffer(b);
         try {
             hpackDecoder.decode(0, in, mockHeaders);
@@ -79,7 +80,7 @@ public void testDecodeULE128IntMax() throws Http2Exception {
         byte[] input = {(byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0xFF, (byte) 0x07};
         ByteBuf in = Unpooled.wrappedBuffer(input);
         try {
-            assertEquals(Integer.MAX_VALUE, decodeULE128(in, 0));
+            assertEquals(MAX_VALUE, decodeULE128(in, 0));
         } finally {
             in.release();
         }
@@ -224,7 +225,7 @@ public void testLiteralHuffmanEncodedWithPaddingNotCorrespondingToMSBThrows() th
 
     @Test(expected = Http2Exception.class)
     public void testIncompleteIndex() throws Http2Exception {
-        byte[] compressed = HpackHex.decodeHex("FFF0".toCharArray());
+        byte[] compressed = StringUtil.decodeHexDump("FFF0");
         ByteBuf in = Unpooled.wrappedBuffer(compressed);
         try {
             hpackDecoder.decode(0, in, mockHeaders);

codec-http2/src/test/java/io/netty/handler/codec/http2/HpackTestCase.java

@@ -41,8 +41,8 @@
 import com.google.gson.JsonParseException;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
+import io.netty.util.internal.StringUtil;
 
-import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.lang.reflect.Type;
@@ -71,11 +71,11 @@ final class HpackTestCase {
     private HpackTestCase() {
     }
 
-    static HpackTestCase load(InputStream is) throws IOException {
+    static HpackTestCase load(InputStream is) {
         InputStreamReader r = new InputStreamReader(is);
         HpackTestCase hpackTestCase = GSON.fromJson(r, HpackTestCase.class);
         for (HeaderBlock headerBlock : hpackTestCase.headerBlocks) {
-            headerBlock.encodedBytes = HpackHex.decodeHex(headerBlock.getEncodedStr().toCharArray());
+            headerBlock.encodedBytes = StringUtil.decodeHexDump(headerBlock.getEncodedStr());
         }
         return hpackTestCase;
     }
@@ -92,7 +92,7 @@ void testCompress() throws Exception {
             if (!Arrays.equals(actual, headerBlock.encodedBytes)) {
                 throw new AssertionError(
                         "\nEXPECTED:\n" + headerBlock.getEncodedStr() +
-                                "\nACTUAL:\n" + HpackHex.encodeHexString(actual));
+                                "\nACTUAL:\n" + StringUtil.toHexString(actual));
             }
 
             List<HpackHeaderField> actualDynamicTable = new ArrayList<HpackHeaderField>();

common/src/main/java/io/netty/util/NetUtil.java

@@ -17,6 +17,7 @@
 
 import io.netty.util.internal.PlatformDependent;
 import io.netty.util.internal.SocketUtils;
+import io.netty.util.internal.StringUtil;
 import io.netty.util.internal.SystemPropertyUtil;
 import io.netty.util.internal.logging.InternalLogger;
 import io.netty.util.internal.logging.InternalLoggerFactory;
@@ -381,25 +382,6 @@ public static byte[] createByteArrayFromIpAddressString(String ipAddressString)
         return null;
     }
 
-    /**
-     * Convert ASCII hexadecimal character to the {@code int} value.
-     * Unlike {@link Character#digit(char, int)}, returns {@code 0} if character is not a HEX-represented.
-     */
-    private static int getIntValue(char c) {
-        if (c >= '0' && c <= '9') {
-            return c - '0';
-        }
-        if (c >= 'A' && c <= 'F') {
-            // 0xA - a start value in sequence 'A'..'F'
-            return c - 'A' + 0xA;
-        }
-        if (c >= 'a' && c <= 'f') {
-            // 0xA - a start value in sequence 'a'..'f'
-            return c - 'a' + 0xA;
-        }
-        return 0;
-    }
-
     private static int decimalDigit(String str, int pos) {
         return str.charAt(pos) - '0';
     }
@@ -808,7 +790,7 @@ private static byte[] getIPv6ByName(CharSequence ip, boolean ipv4Mapped) {
                 // at most 4 consecutive bytes we can use bit shifting to accomplish this.
                 // The most significant byte will be encountered first, and reside in the right most
                 // position of the following integer
-                value += getIntValue(c) << ((i - begin) << 2);
+                value += StringUtil.decodeHexNibble(c) << ((i - begin) << 2);
                 break;
             }
         }