// stores all strings as UTF8 (typically half as big)
static class CondensedStrings2 extends AbstractList<S> implements RandomAccess {
  byte[] data;
  int[] indices;

  *() {} // only for serialisation
  
  *(L<S> l) {
    long totalLength = 0;
    for (S s : l) totalLength += l(toUtf8(s));
    int len = (int) totalLength;
    if (len != totalLength) fail("TOO BIG!!!!!! " + totalLength);
    data = new byte[len];
    int n = l(l);
    indices = new int[n];
    int idx = 0;
    for (int i = 0; i < n; i++) {
      S s = l.get(i);
      try {
        byte[] x = toUtf8(s);
        System.arraycopy(x, 0, data, idx, l(x));
        indices[i] = idx;
        idx += l(x);
      } catch (RuntimeException e) {
        print("idx=" + idx + ", s=" + s + ", i=" + i +", n=" + n + ", len=" + len);
        throw e;
      }
    }
  }
  
  public S get(int i) ctex {
    int idx1 = indices[i];
    int idx2 = i+1 < indices.length ? indices[i+1] : data.length;
    ret fastu_fromUtf8(data, idx1, idx2-idx1);
  }
  
  public int size() {
    ret indices.length;
  }
  
  int totalSize() {
    ret data.length;
  }
}

Began life as a copy of #1002526