/** Moves the cursor to a free block (either new or existing empty one). */
private void freeBlock() {
final int b = usedPages.nextFree(0);
usedPages.set(b);
readBlock(b);
++used;
++page;
}
@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;
}