Only cap the input if content length header is given

src/main/java/org/takes/rq/RqLengthAware.java

@@ -51,6 +51,10 @@
  */
 @EqualsAndHashCode(callSuper = true)
 public final class RqLengthAware extends RqWrap {
+    /**
+     * Constant for the Content-Length header.
+     */
+    private static final String CONTENT_LENGTH = "Content-Length";
 
     /**
      * Ctor.
@@ -68,14 +72,21 @@ public RqLengthAware(final Request req) {
      */
     private static InputStream cap(final Request req) throws IOException {
         final Iterator<String> hdr = new RqHeaders.Base(req)
-            .header("Content-Length").iterator();
-        InputStream body = req.body();
-        long length = (long) body.available();
+            .header(RqLengthAware.CONTENT_LENGTH).iterator();
+        final InputStream result;
         if (hdr.hasNext()) {
-            length = Long.parseLong(hdr.next());
+            final String value = hdr.next();
+            try {
+                result = new CapInputStream(req.body(), Long.parseLong(value));
+            } catch (final NumberFormatException ex) {
+                final String msg = "Invalid %s header: %s";
+                final String formated = String.format(msg, RqLengthAware.CONTENT_LENGTH, value);
+                throw new IOException(formated, ex);
+            }
+        } else {
+            result = req.body();
         }
-        body = new CapInputStream(body, length);
-        return body;
+        return result;
     }
 
 }

src/test/java/org/takes/rq/RqLengthAwareTest.java

@@ -23,6 +23,8 @@
  */
 package org.takes.rq;
 
+import java.io.ByteArrayInputStream;
+import java.io.FilterInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Arrays;
@@ -96,6 +98,32 @@ void readsByte() throws IOException {
         );
     }
 
+    @Test
+    void noContentLength() throws IOException {
+        final byte[] bytes = "test".getBytes();
+        final InputStream data = new FilterInputStream(new ByteArrayInputStream(bytes)) {
+            @Override
+            public int available() throws IOException {
+                return 1;
+            }
+        };
+        final InputStream stream = new RqLengthAware(
+            new RqFake(
+                Arrays.asList(
+                    "GET /test1",
+                    "Host: b.example.com"
+                ),
+                data
+            )
+        ).body();
+        for (final byte element : bytes) {
+            MatcherAssert.assertThat(
+                stream.read(),
+                Matchers.equalTo(element & 0xFF)
+            );
+        }
+    }
+
     @Test
     void readsByteArray() throws IOException {
         final String data = "array";