public int selectBestBlockForDownload(Friend remoteFriend) throws IOException {
if (T.t) {
T.debug("Selecting best block for download. Remote: " + remoteFriend);
}
BlockMask bm = blockMasks.get(remoteFriend.getGuid());
if (bm == null) {
if (T.t) {
T.info("Ehh. Don't know anything about this friends block mask. Can't download.");
}
return -1;
}
BitSet interestingBlocks = getInterestingBlocks(bm);
// remove bocks in progress from interesting blocks:
BlockFile bf = storage.getBlockFile(root);
BitSet blocksInProgress = bf == null ? new BitSet() : bf.getBlocksInProgress();
blocksInProgress.flip(0, fd.getNumberOfBlocks());
blocksInProgress.and(interestingBlocks);
if (blocksInProgress.cardinality() > 0) {
// there are blocks of interest that are NOT in progress. Take one of these
interestingBlocks = blocksInProgress;
} // else there are only blocks in progress. Use any of them
int highestBlockNumber = 0;
if (bf != null) {
highestBlockNumber = bf.getHighestCompleteBlock();
}
highestBlockNumber += manager.getCore().getSettings().getInternal().getMaxfileexpandinblocks();
// we prefer to load blocks below highestBlockNumber
if (interestingBlocks.nextSetBit(0) < highestBlockNumber) {
// we're good - there are interesting blocks below the highest block number.
// remove all blocks above highest block number:
if (highestBlockNumber + 1 < fd.getNumberOfBlocks()) {
interestingBlocks.clear(highestBlockNumber + 1, fd.getNumberOfBlocks());
}
}
// select a random block of the ones we're interested in - change this to rarest first in the
// future
int c = interestingBlocks.cardinality();
int n = (int) (Math.random() * c);
for (int i = interestingBlocks.nextSetBit(0), j = 0;
i >= 0;
i = interestingBlocks.nextSetBit(i + 1), j++) {
if (j == n) {
return i;
}
}
if (T.t) {
T.trace("Can't find any block to download from " + remoteFriend);
}
return -1;
}
