Add HEX string convertion

Author: Artem Labazin

CHANGELOG.md

@@ -12,6 +12,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Add more tests.
 - Add `JavaDoc`.
 
+## [1.16.1](https://github.com/appulse-projects/utils-java/releases/tag/1.16.1) - 2019-04-26
+
+### Added
+
+- `HexUtil` to/from HEX string and byte array converter methods.
+
 ## [1.16.0](https://github.com/appulse-projects/utils-java/releases/tag/1.16.0) - 2019-04-24
 
 ### Added

pom.xml

@@ -24,7 +24,7 @@ limitations under the License.
 
   <groupId>io.appulse</groupId>
   <artifactId>utils-java</artifactId>
-  <version>1.16.0</version>
+  <version>1.16.1</version>
   <packaging>jar</packaging>
 
   <properties>
@@ -66,7 +66,7 @@ limitations under the License.
     <url>https://github.com/appulse-projects/utils-java</url>
     <connection>scm:git:https://github.com/appulse-projects/utils-java.git</connection>
     <developerConnection>scm:git:https://github.com/appulse-projects/utils-java.git</developerConnection>
-    <tag>1.16.0</tag>
+    <tag>1.16.1</tag>
   </scm>
 
   <distributionManagement>

src/main/java/io/appulse/utils/HexUtil.java

@@ -45,6 +45,62 @@ public final class HexUtil {
     NEW_LINE = newLine;
   }
 
+  private static final char[] HEX_CODES = "0123456789ABCDEF".toCharArray();
+
+  /**
+   * Converts an array of bytes into a string.
+   *
+   * @param bytes an array of bytes
+   *
+   * @return a string containing a lexical representation of HEX binary
+   *
+   * @throws NullpointerException if {@code bytes} is null.
+   *
+   * @since 1.16.1
+   */
+  public static String toHexString (@NonNull byte[] bytes) {
+    val result = new StringBuilder(bytes.length * 2);
+    for (val value : bytes) {
+      result.append(HEX_CODES[(value >> 4) & 0xF]);
+      result.append(HEX_CODES[value & 0xF]);
+    }
+    return result.toString();
+  }
+
+  /**
+   * Converts the string argument into an array of bytes.
+   *
+   * @param string a string containing lexical representation of HEX binary.
+   *
+   * @return an array of bytes represented by the string argument.
+   *
+   * @throws NullpointerException if {@code string} is null.
+   *
+   * @throws IllegalArgumentException if string parameter does not conform to lexical
+   *                                  value space defined for HEX binary.
+   *
+   * @since 1.16.1
+   */
+  public static byte[] toByteArray (@NonNull String string) {
+    val length = string.length();
+    if (length % 2 != 0) {
+      val msg = String.format(ENGLISH, "hexBinary needs to be even-length: %s", string);
+      throw new IllegalArgumentException(msg);
+    }
+
+    val result = new byte[length / 2];
+    for (int index = 0; index < length; index += 2) {
+      int hight = hexToBin(string.charAt(index));
+      int low = hexToBin(string.charAt(index + 1));
+      if (hight == -1 || low == -1) {
+        val msg = String.format(ENGLISH, "contains illegal character for hexBinary: %s", string);
+        throw new IllegalArgumentException(msg);
+      }
+      result[index / 2] = (byte) (hight * 16 + low);
+    }
+    return result;
+  }
+
   /**
    * Converts an integer value into two-chars string with leading 0.
    *
@@ -133,10 +189,9 @@ public static String prettyHexDump (@NonNull Bytes buffer, int offset, int lengt
       for (int index = 0; index < limit; index++) {
         val value = buffer.getUnsignedByte(rowStartIndex + index);
 
-        val hex = byteToHex(value);
         val hexIndex = 1 + 3 * index;
-        hexDump.setCharAt(hexIndex, hex.charAt(0));
-        hexDump.setCharAt(hexIndex + 1, hex.charAt(1));
+        hexDump.setCharAt(hexIndex, HEX_CODES[(value >> 4) & 0xF]);
+        hexDump.setCharAt(hexIndex + 1, HEX_CODES[value & 0xF]);
 
         asciiDump.setCharAt(index, byteToChar(value));
       }
@@ -150,6 +205,17 @@ public static String prettyHexDump (@NonNull Bytes buffer, int offset, int lengt
         .toString();
   }
 
+  private static int hexToBin (char character) {
+    if (Character.isDigit(character)) {
+      return character - '0';
+    }
+
+    val letter = Character.toUpperCase(character);
+    return 'A' <= letter && letter <= 'F'
+           ? letter - 'A' + 10
+           : -1;
+  }
+
   private HexUtil () {
     throw new UnsupportedOperationException();
   }

src/test/java/io/appulse/utils/HexUtilTests.java

@@ -16,6 +16,8 @@
 
 package io.appulse.utils;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 import io.netty.util.internal.ThreadLocalRandom;
 import lombok.val;
 import org.junit.jupiter.api.Test;
@@ -39,4 +41,20 @@ void test2 () {
     val prettyPrint = HexUtil.prettyHexDump(bytes);
     System.out.println(prettyPrint);
   }
+
+  @Test
+  void toHexToByteArray () {
+    val bytes = new byte[] {
+        (byte) 0xDB, (byte) 0x68, (byte) 0xFE, (byte) 0x74, (byte) 0x59,
+        (byte) 0x7A, (byte) 0x9A, (byte) 0xC1, (byte) 0xCF, (byte) 0x27,
+        (byte) 0xCE, (byte) 0x65, (byte) 0x64, (byte) 0x08, (byte) 0xC8
+    };
+
+    val string = HexUtil.toHexString(bytes);
+    assertThat(string)
+        .isEqualTo("DB68FE74597A9AC1CF27CE656408C8");
+
+    assertThat(HexUtil.toByteArray(string))
+        .isEqualTo(bytes);
+  }
 }