static <T> void mergeFrom(InputStream in, byte[] buf, T message, Schema<T> schema,
            boolean decodeNestedMessageAsGroup) throws IOException
    {
        final CodedInput input = new CodedInput(in, buf, decodeNestedMessageAsGroup);
        schema.mergeFrom(input, message);
        input.checkLastTagWas(0);
    }
Merges the {@code message} from the {@link InputStream} with the supplied {@code buf} to use.
protostuff-core/src/main/java/io/protostuff/IOUtil.java