Algorithms¶

Word indexing¶

Theses steps are valid independently of the language.

1. Each file is split in word, there is a set of characters which will use as delimiter between the word like [' ', '#', '.', '?',..].
2. Some character are replaced by a another, for example : ['é', 'ë',..] => 'e'. The goal is to remove all accent.

Searching¶

For a functional description see here : Functional definition

This schema depicts how the results are sorted from one peer. Each peer result are then merged.

Peer ID¶

Each peer owns a peer id which is unique and generated during the first start. This ID is used to identify a peer, it's better than the previous usage of peer IP, considering this situation :

• A put in queue a file entry f from B, B doesn't know the hashes of this file entry.
• B change his IP address.
• A want to download f, it can ask B for the hashes even B's IP changed.

Core threads¶

There are three kind of threads in the core in addition to the main thread :

• Downloading thread : DownloadManager::ChunkDownloader
• Uploading thread : UploadManager::Uploader
• Updating file cache thread : FileManager::FileUpdater

Updating the file cache (Obsolete, must be rewritten after the seventh prototype ended)¶

Here is the algorithm for the thread (FileManager::FileUpdater) which will periodically update the file cache and persist it.

D : The set of shared directories
T : Time during the hashes are computed (for example 30s)
F : A set of file initialy empty

- Add a watcher to the shared directories

// First synchronize (at start)
For each d in D (recursively) :
   - Synchronize physical folders and files with d content
   - Add in F the files which doesn't have computed hashes

Loop :   
   t : Time.now
   For each f in F :
      - Compute the unknown hash of files f
      - Remove f from F
      If (Time.now - t) > T : break
   - Wait T - (Time.now - t)
   - Wait for changes for a period of P
      - When a modification occurs synchronise the file/folder
      - Add each new file in F
   - Persist the entire cache in a file (only every ~30min)

Downloading¶

See here : Protocol_core-core