private ByteBuffer processAsciiCommand(ByteBuffer buffer, Cache cache) {
    CharBuffer flb = getFirstLineBuffer();
    getAsciiDecoder().reset();
    getAsciiDecoder().decode(buffer, flb, false);
    flb.flip();
    String firstLine = getFirstLine();
    String[] firstLineElements = firstLine.split(" ");

    String key = firstLineElements[1];
    int flags = Integer.parseInt(firstLineElements[2]);
    long expTime = Long.parseLong(firstLineElements[3]);
    int numBytes = Integer.parseInt(firstLineElements[4]);
    long casVersion = Long.parseLong(stripNewline(firstLineElements[5]));

    byte[] value = new byte[numBytes];
    buffer.position(firstLine.length());
    for (int i = 0; i < numBytes; i++) {
      value[i] = buffer.get();
    }

    String reply = Reply.EXISTS.toString();
    Region<Object, ValueWrapper> r = getMemcachedRegion(cache);
    ValueWrapper expected = ValueWrapper.getDummyValue(casVersion);
    if (r.replace(key, expected, ValueWrapper.getWrappedValue(value, flags))) {
      reply = Reply.STORED.toString();
    }

    return asciiCharset.encode(reply);
  }
"cas" is a check and set operation which means "store this data but only if no one else has
updated since I last fetched it."
geode-memcached/src/main/java/org/apache/geode/internal/memcached/commands/CASCommand.java