Пример #1
0
 @Override
 public boolean lock(final boolean lock) {
   try {
     if (lock) {
       if (exclusiveLock()) return true;
       if (sharedLock()) return false;
     } else {
       if (sharedLock()) return true;
     }
   } catch (final IOException ex) {
     Util.stack(ex);
   }
   throw Util.notExpected((lock ? "Exclusive" : "Shared") + " lock could not be acquired.");
 }
Пример #2
0
 /**
  * Searches for the block containing the entry for the specified pre value. Reads the block and
  * returns its offset inside the block.
  *
  * @param pre pre of the entry to search for
  * @return offset of the entry in the block
  */
 private int cursor(final int pre) {
   int fp = fpre;
   int np = npre;
   if (pre < fp || pre >= np) {
     final int last = used - 1;
     int l = 0;
     int h = last;
     int m = page;
     while (l <= h) {
       if (pre < fp) h = m - 1;
       else if (pre >= np) l = m + 1;
       else break;
       m = h + l >>> 1;
       fp = fpre(m);
       np = m == last ? meta.size : fpre(m + 1);
     }
     if (l > h)
       throw Util.notExpected(
           "Data Access out of bounds:"
               + "\n- pre value: "
               + pre
               + "\n- #used blocks: "
               + used
               + "\n- #total locks: "
               + blocks
               + "\n- access: "
               + m
               + " ("
               + l
               + " > "
               + h
               + ']');
     readPage(m);
   }
   return pre - fpre << IO.NODEPOWER;
 }
Пример #3
0
  @Override
  public void insert(final int pre, final byte[] entries) {
    final int nnew = entries.length;
    if (nnew == 0) return;
    dirty();

    // number of records to be inserted
    final int nr = nnew >>> IO.NODEPOWER;

    int split = 0;
    if (used == 0) {
      // special case: insert new data into first block if database is empty
      readPage(0);
      usedPages.set(0);
      ++used;
    } else if (pre > 0) {
      // find the offset within the block where the new records will be inserted
      split = cursor(pre - 1) + IO.NODESIZE;
    } else {
      // all insert operations will add data after first node.
      // i.e., there is no "insert before first document" statement
      throw Util.notExpected("Insertion at beginning of populated table.");
    }

    // number of bytes occupied by old records in the current block
    final int nold = npre - fpre << IO.NODEPOWER;
    // number of bytes occupied by old records which will be moved at the end
    final int moved = nold - split;

    // special case: all entries fit in the current block
    Buffer bf = bm.current();
    if (nold + nnew <= IO.BLOCKSIZE) {
      Array.move(bf.data, split, nnew, moved);
      System.arraycopy(entries, 0, bf.data, split, nnew);
      bf.dirty = true;

      // increment first pre-values of blocks after the last modified block
      for (int i = page + 1; i < used; ++i) fpres[i] += nr;
      // update cached variables (fpre is not changed)
      npre += nr;
      meta.size += nr;
      return;
    }

    // append old entries at the end of the new entries
    final byte[] all = new byte[nnew + moved];
    System.arraycopy(entries, 0, all, 0, nnew);
    System.arraycopy(bf.data, split, all, nnew, moved);

    // fill in the current block with new entries
    // number of bytes which fit in the first block
    int nrem = IO.BLOCKSIZE - split;
    if (nrem > 0) {
      System.arraycopy(all, 0, bf.data, split, nrem);
      bf.dirty = true;
    }

    // number of new required blocks and remaining bytes
    final int req = all.length - nrem;
    int needed = req / IO.BLOCKSIZE;
    final int remain = req % IO.BLOCKSIZE;

    if (remain > 0) {
      // check if the last entries can fit in the block after the current one
      if (page + 1 < used) {
        final int o = occSpace(page + 1) << IO.NODEPOWER;
        if (remain <= IO.BLOCKSIZE - o) {
          // copy the last records
          readPage(page + 1);
          bf = bm.current();
          System.arraycopy(bf.data, 0, bf.data, remain, o);
          System.arraycopy(all, all.length - remain, bf.data, 0, remain);
          bf.dirty = true;
          // reduce the pre value, since it will be later incremented with nr
          fpres[page] -= remain >>> IO.NODEPOWER;
          // go back to the previous block
          readPage(page - 1);
        } else {
          // there is not enough space in the block - allocate a new one
          ++needed;
        }
      } else {
        // this is the last block - allocate a new one
        ++needed;
      }
    }

    // number of expected blocks: existing blocks + needed block - empty blocks
    final int exp = blocks + needed - (blocks - used);
    if (exp > fpres.length) {
      // resize directory arrays if existing ones are too small
      final int ns = Math.max(fpres.length << 1, exp);
      fpres = Arrays.copyOf(fpres, ns);
      pages = Arrays.copyOf(pages, ns);
    }

    // make place for the blocks where the new entries will be written
    Array.move(fpres, page + 1, needed, used - page - 1);
    Array.move(pages, page + 1, needed, used - page - 1);

    // write the all remaining entries
    while (needed-- > 0) {
      freeBlock();
      nrem += write(all, nrem);
      fpres[page] = fpres[page - 1] + IO.ENTRIES;
      pages[page] = (int) bm.current().pos;
    }

    // increment all fpre values after the last modified block
    for (int i = page + 1; i < used; ++i) fpres[i] += nr;

    meta.size += nr;

    // update cached variables
    fpre = fpres[page];
    npre = page + 1 < used && fpres[page + 1] < meta.size ? fpres[page + 1] : meta.size;
  }