/**
* Finds the multichunks that need to be downloaded for the given file version -- using the local
* database and given winners database. Returns a set of multichunk identifiers.
*/
private Collection<MultiChunkId> determineMultiChunksToDownload(
FileVersion fileVersion, MemoryDatabase winnersDatabase) {
Set<MultiChunkId> multiChunksToDownload = new HashSet<MultiChunkId>();
// First: Check if we know this file locally!
List<MultiChunkId> multiChunkIds = localDatabase.getMultiChunkIds(fileVersion.getChecksum());
if (multiChunkIds.size() > 0) {
multiChunksToDownload.addAll(multiChunkIds);
} else {
// Second: We don't know it locally; must be from the winners database
FileContent winningFileContent = winnersDatabase.getContent(fileVersion.getChecksum());
boolean winningFileHasContent = winningFileContent != null;
if (winningFileHasContent) { // File can be empty!
List<ChunkChecksum> fileChunks = winningFileContent.getChunks();
// TODO [medium] Instead of just looking for multichunks to download here, we should look
// for chunks in local files as well
// and return the chunk positions in the local files ChunkPosition (chunk123 at file12,
// offset 200, size 250)
Map<ChunkChecksum, MultiChunkId> checksumsWithMultiChunkIds =
localDatabase.getMultiChunkIdsByChecksums(fileChunks);
for (ChunkChecksum chunkChecksum : fileChunks) {
MultiChunkId multiChunkIdForChunk = checksumsWithMultiChunkIds.get(chunkChecksum);
if (multiChunkIdForChunk == null) {
multiChunkIdForChunk = winnersDatabase.getMultiChunkIdForChunk(chunkChecksum);
if (multiChunkIdForChunk == null) {
throw new RuntimeException("Cannot find multichunk for chunk " + chunkChecksum);
}
}
if (!multiChunksToDownload.contains(multiChunkIdForChunk)) {
logger.log(
Level.INFO,
" + Adding multichunk " + multiChunkIdForChunk + " to download list ...");
multiChunksToDownload.add(multiChunkIdForChunk);
}
}
}
}
return multiChunksToDownload;
}
