/** 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 synchronized void flush() throws IOException {
for (final Buffer b : bm.all()) if (b.dirty) writeBlock(b);
if (!dirty) return;
try (final DataOutput out = new DataOutput(meta.dbfile(DATATBL + 'i'))) {
out.writeNum(blocks);
out.writeNum(used);
// due to legacy issues, number of blocks is written several times
out.writeNum(blocks);
for (int a = 0; a < blocks; a++) out.writeNum(fpres[a]);
out.writeNum(blocks);
for (int a = 0; a < blocks; a++) out.writeNum(pages[a]);
out.writeLongs(usedPages.toArray());
}
dirty = false;
}
@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;
}
@Override
public void delete(final int pre, final int nr) {
if (nr == 0) return;
dirty();
// get first block
cursor(pre);
// some useful variables to make code more readable
int from = pre - fpre;
final int last = pre + nr;
// check if all entries are in current block: handle and return
if (last - 1 < npre) {
final Buffer bf = bm.current();
copy(bf.data, from + nr, bf.data, from, npre - last);
updatePre(nr);
// if whole block was deleted, remove it from the index
if (npre == fpre) {
// mark the block as empty
usedPages.clear(pages[page]);
Array.move(fpres, page + 1, -1, used - page - 1);
Array.move(pages, page + 1, -1, used - page - 1);
--used;
readPage(page);
}
return;
}
// handle blocks whose entries are to be deleted entirely
// first count them
int unused = 0;
while (npre < last) {
if (from == 0) {
++unused;
// mark the blocks as empty; range clear cannot be used because the
// blocks may not be consecutive
usedPages.clear(pages[page]);
}
setPage(page + 1);
from = 0;
}
// if the last block is empty, clear the corresponding bit
readBlock(pages[page]);
final Buffer bf = bm.current();
if (npre == last) {
usedPages.clear((int) bf.pos);
++unused;
if (page < used - 1) readPage(page + 1);
else ++page;
} else {
// delete entries at beginning of current (last) block
copy(bf.data, last - fpre, bf.data, 0, npre - last);
}
// now remove them from the index
if (unused > 0) {
Array.move(fpres, page, -unused, used - page);
Array.move(pages, page, -unused, used - page);
used -= unused;
page -= unused;
}
// update index entry for this block
fpres[page] = pre;
fpre = pre;
updatePre(nr);
}