sclass LineCompReader {
  new LS literals;
  int[] literalOffsets; // where they start in file
  new L<IntPair> pairs;
  new LinkedHashMap<S, L<Int>> versions;
  bool byteMode;
  
  *() {}
  
  // takes text or gzipped input file
  *(File f) {
    temp BufferedReader reader = rawByteReader_possiblyGZipped(f);
    load(reader);
  }
  
  *(InputStream in) { load(rawBytesReader(in)); }
  *(BufferedReader reader) { load(reader); }
  
  void load(BufferedReader reader) ctex {
    S s = readLineIgnoreCR(reader);
    int ofs = l(s)+1;
    new Matches m;
    if (startsWith(s, "BYTECOMP ", m)) set byteMode;
    else if (!startsWith(s, "LINECOMP ", m))
      fail("Not a LINECOMP file");
    int nLiterals = parseInt(m.rest());
    new IntBuffer offsets;
    for i to nLiterals: {
      S line = readLineIgnoreCR(reader);
      assertNotNull(line);
      literals.add(byteMode ? str(charFromHex(line)) : line);
      offsets.add(ofs);
      ofs += l(line)+1;
    }
    offsets.add(ofs);
    literalOffsets = offsets.toArray();
    while licensed {
      s = readLineIgnoreCR(reader);
      if (s == null || contains(s, "=")) break;
      try {
        pairs.add(assertNotNull(listToIntPair(parseInts(splitAtSpace(s)))));
      } on fail {
        print("On line " + (nLiterals + l(pairs)));
      }
    }
    while (contains(s, "=")) {
      int i = indexOf(s, '=');
      versions.put(takeFirst(s, i), compactIntList(parseInts(splitAtSpace(substring(s, i+1)))));
      s = readLineIgnoreCR(reader);
    }
  }
  
  Set<S> versions() { ret keys(versions); }
  
  S getText(S version) { ret textForVersion(version); }
  S textForVersion(S version) {
    L<Int> encoded = versions.get(version);
    if (encoded == null) null;
    new LS buf;
    for (int idx : encoded)
      decode(idx, buf);
    ret myFromLines(buf);
  }
  
  // name of first (or only) file
  S firstFile() { ret first(versions()); }
  
  // text for first (or only) file
  S text() { ret getText(firstFile()); }
  
  L<Int> encoding() { ret versions.get(firstFile()); }
  
  S myFromLines(LS l) {
    ret byteMode
      ? join(l)
      : fromLines_rtrim(l);
  }
  
  void decode(int idx, LS buf) {
    if (idx < l(literals))
      buf.add(literals.get(idx));
    else {
      IntPair p = pairs.get(idx-l(literals));
      decode(p.a, buf);
      decode(p.b, buf);
    }
  }
  
  // That was it! The rest of this file is just for calculating some stats.
  
  new Map<Int> lineCountsForPairs;
  new Map<Int, Long> byteCountsForPairs;

  int lineCountForPointer(int idx) {
    ret idx < l(literals) ? 1 : lineCountForPair(idx);
  }
  
  long byteCountForPointer(int idx) {
    ret idx < l(literals) ? l(literals.get(idx))+1 : byteCountForPair(idx);
  }
  
  int lineCountForPair(int idx) {
    Int c = lineCountsForPairs.get(idx);
    if (c == null) {
      IntPair p = pairs.get(idx-l(literals));
      c = lineCountForPointer(p.a) + lineCountForPointer(p.b);
      lineCountsForPairs.put(idx, c);
    }
    ret c;
  }
  
  long byteCountForPair(int idx) {
    Long c = byteCountsForPairs.get(idx);
    if (c == null) {
      IntPair p = pairs.get(idx-l(literals));
      c = byteCountForPointer(p.a) + byteCountForPointer(p.b);
      byteCountsForPairs.put(idx, c);
    }
    ret c;
  }
  
  int lineCountForVersion(S version) {
    L<Int> encoded = versions.get(version);
    if (encoded == null) ret 0;
    int n = 0;
    for (int i : encoded) n += lineCountForPointer(i);
    ret n;
  }
  
  long byteCountForVersion(S version) {
    L<Int> encoded = versions.get(version);
    if (encoded == null) ret 0;
    long n = 0;
    for (int i : encoded) n += byteCountForPointer(i);
    ret max(0, n-1);
  }
  
  long totalByteCount() {
    ret longSum(lambdaMap byteCountForVersion(versions()));
  }
  
  // now we can also save again
  
  void save(PrintWriter out) {
    out.println((byteMode ? "BYTECOMP " : "LINECOMP ") + l(literals));
    for (S s : literals)
      out.println(byteMode ? charToHex(first(s)) : s);
    for (IntPair p : pairs)
      out.println(p.a + " " + p.b);
    for (S id, L<Int> l : versions)
      out.println(id + "=" + joinWithSpace(l));
  }  
}

Began life as a copy of #1028182