Make BaseEncoding.encodingStream().close() idempotent.

guava-tests/test/com/google/common/io/BaseEncodingTest.java

@@ -558,6 +558,17 @@ private static void testStreamingDecodes(BaseEncoding encoding, String encoded,
     }
   }
 
+  @GwtIncompatible // Writer
+  public void testEncodingStream_closeIsIdempotent() throws IOException {
+    StringWriter writer = new StringWriter();
+    OutputStream encodingStream = base64().encodingStream(writer);
+    encodingStream.write(0);
+    encodingStream.close();
+    assertThat(writer.toString()).isEqualTo("AA==");
+    encodingStream.close();
+    assertThat(writer.toString()).isEqualTo("AA==");
+  }
+
   public void testToString() {
     assertThat(base64().toString()).isEqualTo("BaseEncoding.base64().withPadChar('=')");
     assertThat(base32Hex().omitPadding().toString())

guava/src/com/google/common/io/BaseEncoding.java

@@ -646,6 +646,7 @@ public OutputStream encodingStream(Writer out) {
         int bitBuffer = 0;
         int bitBufferLength = 0;
         int writtenChars = 0;
+        boolean closed = false;
 
         @Override
         public void write(int b) throws IOException {
@@ -667,6 +668,10 @@ public void flush() throws IOException {
 
         @Override
         public void close() throws IOException {
+          if (closed) {
+            return;
+          }
+          closed = true;
           if (bitBufferLength > 0) {
             int charIndex = (bitBuffer << (alphabet.bitsPerChar - bitBufferLength)) & alphabet.mask;
             out.write(alphabet.encode(charIndex));
@@ -677,6 +682,7 @@ public void close() throws IOException {
                 writtenChars++;
               }
             }
+            bitBufferLength = 0;
           }
           out.close();
         }