code: private static void set32x64Bits(int[] table, int start, int limit) {
          assert (64 == table.length);
          int lead = start >> 6;  // Named for UTF-8 2-byte lead byte with upper 5 bits.
          int trail = start & 0x3f;  // Named for UTF-8 2-byte trail byte with lower 6 bits.
  
          // Set one bit indicating an all-one block.
          int bits = 1 << lead;
          if ((start + 1) == limit) { // Single-character shortcut.
              table[trail] |= bits;
              return;
          }
  
          int limitLead = limit >> 6;
          int limitTrail = limit & 0x3f;
  
          if (lead == limitLead) {
              // Partial vertical bit column.
              while (trail < limitTrail) {
                  table[trail++] |= bits;
              }
          } else {
              // Partial vertical bit column,
              // followed by a bit rectangle,
              // followed by another partial vertical bit column.
              if (trail > 0) {
                  do {
                      table[trail++] |= bits;
                  } while (trail < 64);
                  ++lead;
              }
              if (lead < limitLead) {
                  bits = ~((1 << lead) - 1);
                  if (limitLead < 0x20) {
                      bits &= (1 << limitLead) - 1;
                  }
                  for (trail = 0; trail < 64; ++trail) {
                      table[trail] |= bits;
                  }
              }
              // limit<=0x800. If limit==0x800 then limitLead=32 and limitTrail=0.
              // In that case, bits=1<<limitLead == 1<<0 == 1
              // (because Java << uses only the lower 5 bits of the shift operand)
              // but the bits value is not used because trail<limitTrail is already false.
              bits = 1 << limitLead;
              for (trail = 0; trail < limitTrail; ++trail) {
                  table[trail] |= bits;
              }
          }
      }
docs: Set bits in a bit rectangle in "vertical" bit organization. start<limit<=0x800