Add more to readme and read from file

Author: patrickfav

README.md

@@ -61,7 +61,7 @@ Initializing **empty arrays** of arbitrary length:
 
 ```java
 Bytes.allocate(16);
-Bytes.allocate(4,(byte) 1); //fill with 0x01
+Bytes.allocate(4, (byte) 1); //fill with 0x01
 ```
 
 Creating **random** byte arrays for e.g. testing:
@@ -85,6 +85,7 @@ Bytes.from(byteInputStream); //any inputStream
 Bytes.from(byteList); //List<Byte> byteList = ...
 Bytes.from(myBitSet); //BitSet myBitSet = ...
 Bytes.from(bigInteger);
+Bytes.from(file); //reads bytes from any java.io.File
 ```
 
 For parsing binary-text-encoded strings, see below.
@@ -180,6 +181,8 @@ Bytes.from(array).encodeOctal(); //1124517677707527755
 Bytes.from(array).encodeBase36(); //5qpdvuwjvu5
 ```
 
+### Utility Methods
+
 ### Validation
 
 A simple validation framework which can be used to check the internal byte array:

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

@@ -22,6 +22,7 @@
 package at.favre.lib.bytes;
 
 import java.io.ByteArrayInputStream;
+import java.io.File;
 import java.io.InputStream;
 import java.math.BigInteger;
 import java.nio.ByteBuffer;
@@ -295,6 +296,19 @@ public static Bytes from(InputStream stream) {
         return wrap(Util.readFromStream(stream));
     }
 
+    /**
+     * 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.
+     *
+     * @param file to read from
+     * @return new instance
+     * @throws IllegalArgumentException if file does not exist
+     * @throws IllegalStateException    if file could not be read
+     */
+    public static Bytes from(File file) {
+        return wrap(Util.readFromFile(file));
+    }
+
     /**
      * Creates a new instance from given utf-8 encoded string
      *
@@ -985,7 +999,6 @@ private ByteBuffer internalBuffer() {
     }
 
 
-
     /**
      * Returns a mutable version of this instance with sharing the same underlying byte-array.
      * If you want the mutable version to be a copy, call {@link #copy()} first.

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

@@ -22,7 +22,10 @@
 package at.favre.lib.bytes;
 
 import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.IOException;
 import java.io.InputStream;
+import java.nio.file.Files;
 import java.util.*;
 
 /**
@@ -232,6 +235,25 @@ static byte[] concatVararg(byte firstByte, byte[] moreBytes) {
         }
     }
 
+    /**
+     * Reads all bytes from a file
+     *
+     * @param file the file to read
+     * @return byte content
+     */
+    static byte[] readFromFile(File file) {
+        if (file == null || !file.exists() || !file.isFile()) {
+            throw new IllegalArgumentException("file must not be null, has to exist and must be a file (not a directory) " + file);
+        }
+
+        try {
+            return Files.readAllBytes(file.toPath());
+        } catch (IOException e) {
+            throw new IllegalStateException("could not read from file", e);
+        }
+
+    }
+
     /*
     =================================================================================================
      Copyright 2011 Twitter, Inc.

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

@@ -21,9 +21,13 @@
 
 package at.favre.lib.bytes;
 
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
 
 import java.io.ByteArrayInputStream;
+import java.io.File;
+import java.io.FileOutputStream;
 import java.math.BigInteger;
 import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
@@ -36,6 +40,8 @@
 import static org.junit.Assert.*;
 
 public class BytesConstructorTests extends ABytesTest {
+    @Rule
+    public TemporaryFolder testFolder = new TemporaryFolder();
 
     @Test
     public void wrapTest() throws Exception {
@@ -255,4 +261,16 @@ public void fromPartByte() throws Exception {
         assertArrayEquals(new byte[]{example_bytes_four[1]}, Bytes.from(example_bytes_four, 1, 1).array());
         assertArrayEquals(new byte[]{example_bytes_eight[4], example_bytes_eight[5], example_bytes_eight[6]}, Bytes.from(example_bytes_eight, 4, 3).array());
     }
+
+    @Test
+    public void fromFile() throws Exception {
+        File tempFile = testFolder.newFile("out-test.txt");
+        Bytes randomBytes = Bytes.random(500);
+
+        try (FileOutputStream stream = new FileOutputStream(tempFile)) {
+            stream.write(randomBytes.array());
+        }
+
+        assertArrayEquals(randomBytes.array(), Bytes.from(tempFile).array());
+    }
 }