Add construction from DataInput

Author: patrickfav

CHANGELOG

@@ -3,8 +3,10 @@
 ## v0.4.2
 
 * add check method if transformer supports inplace
-* adds contains method
-* adds Iterable interface
+* add contains method
+* add Iterable interface
+* add setByteAt
+* add construction from DataInput
 
 ## v0.4.1
 

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

@@ -21,10 +21,7 @@
 
 package at.favre.lib.bytes;
 
-import java.io.ByteArrayInputStream;
-import java.io.File;
-import java.io.InputStream;
-import java.io.Serializable;
+import java.io.*;
 import java.math.BigInteger;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
@@ -329,6 +326,17 @@ public static Bytes from(InputStream stream) {
         return wrap(Util.readFromStream(stream));
     }
 
+    /**
+     * Reads given {@link DataInput} and creates a new instance from read data
+     *
+     * @param dataInput to read from
+     * @param length    how many bytes should be read
+     * @return new instance
+     */
+    public static Bytes from(DataInput dataInput, int length) {
+        return wrap(Util.readFromDataInput(dataInput, length));
+    }
+
     /**
      * Reads given file and returns the byte content. Be aware that the whole file content will be loaded to
      * memory, so be careful what to read in.

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

@@ -21,10 +21,7 @@
 
 package at.favre.lib.bytes;
 
-import java.io.ByteArrayOutputStream;
-import java.io.File;
-import java.io.IOException;
-import java.io.InputStream;
+import java.io.*;
 import java.nio.ByteBuffer;
 import java.nio.file.Files;
 import java.util.*;
@@ -272,6 +269,24 @@ static byte[] readFromStream(InputStream inputStream) {
         }
     }
 
+    /**
+     * Read all bytes until length from given byte array.
+     *
+     * @param dataInput to read from
+     * @return all bytes from the dataInput
+     */
+    static byte[] readFromDataInput(DataInput dataInput, int length) {
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        try {
+            for (int i = 0; i < length; i++) {
+                out.write(dataInput.readUnsignedByte());
+            }
+            return out.toByteArray();
+        } catch (Exception e) {
+            throw new IllegalStateException("could not read from data input", e);
+        }
+    }
+
     /**
      * Combines a single argument with a vararg to a single array
      *

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

@@ -27,6 +27,7 @@
 import org.junit.rules.TemporaryFolder;
 
 import java.io.ByteArrayInputStream;
+import java.io.DataInputStream;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.math.BigInteger;
@@ -234,6 +235,25 @@ private void checkInputStream(byte[] array) {
         assertArrayEquals(array, Bytes.from(new ByteArrayInputStream(array)).array());
     }
 
+    @Test
+    public void fromDataInput() throws Exception {
+        checkDataInput(example_bytes_one);
+        checkDataInput(example_bytes_two);
+        checkDataInput(example_bytes_four);
+        checkDataInput(example_bytes_seven);
+        checkDataInput(example_bytes_eight);
+        checkDataInput(example_bytes_sixteen);
+    }
+
+    private void checkDataInput(byte[] array) {
+        assertArrayEquals(array, Bytes.from(new DataInputStream(new ByteArrayInputStream(array)), array.length).array());
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void fromDataInputShouldThrowException() throws Exception {
+        Bytes.from(new DataInputStream(new ByteArrayInputStream(example_bytes_one)), 2);
+    }
+
     @Test
     public void fromList() throws Exception {
         checkList(example_bytes_one);