private <T> T mergeObjectEncodedAsGroup(T value, final Schema<T> schema) throws IOException {
        if (value == null) {
            value = schema.newMessage();
        }
        schema.mergeFrom(this, value);
        if (!schema.isInitialized(value)) {
            throw new UninitializedMessageException(value, schema);
        }
        // handling is in #readFieldNumber
        checkLastTagWas(0);
        return value;
    }
Read an {@code sint64} field value from the internal buffer.
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/serialization/impl/protostuff/io/NioBufInput.java