Add toCharArray() method which decodes internal byte array to char[]

Author: patrickfav

CHANGELOG

@@ -3,6 +3,7 @@
 ## v1.0.0
 
 * add `append()` method supporting multiple byte arrays #26
+* add `toCharArray()` method which decodes internal byte array to char[] #27
 
 ## v0.8.0
 

src/main/java/at/favre/lib/bytes/Bytes.java

@@ -1889,6 +1889,27 @@ public double toDouble() {
         return internalBuffer().getDouble();
     }
 
+    /**
+     * Decodes the internal byte array to UTF-8 char array.
+     * This implementation will not internally create a {@link String}.
+     *
+     * @return char array
+     */
+    public char[] toCharArray() {
+        return toCharArray(StandardCharsets.UTF_8);
+    }
+
+    /**
+     * Decodes the internal byte array with given charset to a char array.
+     * This implementation will not internally create a {@link String}.
+     *
+     * @param charset to use for decoding
+     * @return char array
+     */
+    public char[] toCharArray(Charset charset) {
+        return Util.byteToCharArray(internalArray(), charset);
+    }
+
     /**
      * Compares this bytes instance to another.
      * <p>

src/main/java/at/favre/lib/bytes/Util.java

@@ -21,28 +21,14 @@
 
 package at.favre.lib.bytes;
 
-import java.io.ByteArrayOutputStream;
-import java.io.DataInput;
-import java.io.File;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.RandomAccessFile;
+import java.io.*;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.CharBuffer;
+import java.nio.charset.CharacterCodingException;
 import java.nio.charset.Charset;
 import java.nio.file.Files;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-import java.util.NoSuchElementException;
-import java.util.Objects;
-import java.util.Random;
-import java.util.UUID;
+import java.util.*;
 
 /**
  * Common Util methods to convert or modify byte arrays
@@ -438,9 +424,36 @@ static byte[] charToByteArray(char[] charArray, Charset charset, int offset, int
         }
 
         ByteBuffer bb = charset.encode(charBuffer);
-        byte[] bytes = new byte[bb.remaining()];
-        bb.get(bytes);
-        return bytes;
+        if (bb.capacity() != bb.limit()) {
+            byte[] bytes = new byte[bb.remaining()];
+            bb.get(bytes);
+            return bytes;
+        }
+        return bb.array();
+    }
+
+    /**
+     * Convert given byte array in given encoding to char array
+     *
+     * @param bytes   as data source
+     * @param charset of the byte array
+     * @return char array
+     */
+    static char[] byteToCharArray(byte[] bytes, Charset charset) {
+        Objects.requireNonNull(bytes, "bytes must not be null");
+        Objects.requireNonNull(charset, "charset must not be null");
+
+        try {
+            CharBuffer charBuffer = charset.newDecoder().decode(ByteBuffer.wrap(bytes));
+            if (charBuffer.capacity() != charBuffer.limit()) {
+                char[] compacted = new char[charBuffer.remaining()];
+                charBuffer.get(compacted);
+                return compacted;
+            }
+            return charBuffer.array();
+        } catch (CharacterCodingException e) {
+            throw new IllegalStateException(e);
+        }
     }
 
     /**

src/test/java/at/favre/lib/bytes/BytesConstructorTests.java

@@ -26,11 +26,7 @@
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 
-import java.io.ByteArrayInputStream;
-import java.io.DataInput;
-import java.io.DataInputStream;
-import java.io.File;
-import java.io.FileOutputStream;
+import java.io.*;
 import java.math.BigInteger;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
@@ -299,6 +295,35 @@ public void fromCharArray() {
         assertArrayEquals(Bytes.empty().array(), Bytes.from(CharBuffer.allocate(0)).array());
     }
 
+    @Test
+    public void toCharArray() {
+        String unicodeString = "|µ€@7é8ahslishalsdalöskdḼơᶉëᶆ ȋṕšᶙṁ ḍỡḽǭᵳ ʂǐť ӓṁệẗ, ĉṓɲṩḙċ";
+        assertArrayEquals(Bytes.from(unicodeString.toCharArray()).array(), Bytes.from(Bytes.from(unicodeString).toCharArray()).array());
+
+        checkToCharArray(unicodeString, StandardCharsets.UTF_8);
+        checkToCharArray(unicodeString, StandardCharsets.UTF_16);
+        checkToCharArray(unicodeString, StandardCharsets.UTF_16BE);
+
+        String asciiString = "asciiASCIIString1234$%&";
+
+        checkToCharArray(asciiString, StandardCharsets.UTF_8);
+        checkToCharArray(asciiString, StandardCharsets.UTF_16);
+        checkToCharArray(asciiString, StandardCharsets.US_ASCII);
+        checkToCharArray(asciiString, StandardCharsets.ISO_8859_1);
+    }
+
+    private void checkToCharArray(String string, Charset charset) {
+        byte[] b0 = String.valueOf(string.toCharArray()).getBytes(charset);
+        char[] charArray = Bytes.from(b0).toCharArray(charset);
+        assertEquals(string, new String(charArray));
+        assertArrayEquals(string.toCharArray(), Bytes.from(string.toCharArray(), charset).toCharArray(charset));
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void toCharArrayShouldThroughNullPointer() {
+        Bytes.allocate(4).toCharArray(null);
+    }
+
     @Test
     public void fromMultipleBytes() {
         assertArrayEquals(new byte[]{0x01, 0x02, 0x03}, Bytes.from(Bytes.from((byte) 0x01), Bytes.from((byte) 0x02), Bytes.from((byte) 0x03)).array());