Added ReadableFile#size()

main/filesystem-inmemory/src/main/java/org/cryptomator/filesystem/inmem/InMemoryReadableFile.java

@@ -55,6 +55,11 @@ class InMemoryReadableFile implements ReadableFile {
 		}
 	}
 
+	@Override
+	public long size() throws UncheckedIOException {
+		return contentGetter.get().limit();
+	}
+
 	@Override
 	public void position(long position) throws UncheckedIOException {
 		assert position < Integer.MAX_VALUE : "Can not use that big in-memory files.";

main/filesystem-inmemory/src/test/java/org/cryptomator/filesystem/inmem/InMemoryFileSystemTest.java

@@ -103,6 +103,11 @@ public class InMemoryFileSystemTest {
 		}
 		Assert.assertTrue(fooFile.exists());
 
+		// check if size = 11 bytes
+		try (ReadableFile readable = fooFile.openReadable()) {
+			Assert.assertEquals(11, readable.size());
+		}
+
 		// copy foo to bar
 		File barFile = fs.file("bar.txt");
 		try (WritableFile writable = barFile.openWritable()) {