+The root hash is built by hashing all the piece hashes pair-wise, until they all collapse +down to the root.
+
+
+The root hash is built by hashing all the piece hashes pair-wise, until they all collapse +down to the root.
+
+libtorrent's storage implementation is customizable. That means a special purpose bittorrent +client can replace the default way to store files on disk.
+When implementing a bittorrent cache, it doesn't matter how the data is stored on disk, as +long as it can be retrieved and seeded. In that case a new storage class can be implemented +(inheriting from the storage_interface class) that avoids the unnecessary step of mapping +slots to files and offsets. The storage can ignore the file boundaries and just store the +entire torrent in a single file (which will end up being all the files concatenated). The main +advantage of this, other than a slight cpu performance gain, is that all file operations would +be page (and sector) aligned. This enables efficient unbuffered I/O, and can potentially +lead to more efficient read caching (using the built in disk cache rather than relying on the +operating system's disk cache).
+The storage interface supports operating systems where you can ask for sparse regions +(such as Windows and Solaris). The advantage of this is that when checking files, the regions +that are known to be sparse can be skipped, which can reduce the time to check a torrent +significantly.
+One of the design goals of the libtorrent API is to make common operations simple, but still +have it possible to do complicated and advanced operations. This is best illustrated by example +code to implement a simple bittorrent client:
+
+#include <iostream>
+#include "libtorrent/session.hpp"
+
+// usage a.out [torrent-file]
+int main(int argc, char* argv[]) try
+{
+ using namespace libtorrent;
+
+ session s;
+ s.listen_on(std::make_pair(6881, 6889));
+ add_torrent_params p;
+ p.save_path = "./";
+ p.ti = new torrent_info(argv[1]);
+ s.add_torrent(p);
+
+ // wait for the user to end
+ char a;
+ std::cin.unsetf(std::ios_base::skipws);
+ std::cin >> a;
+ return 0;
+}
+catch (std::exception& e)
+{
+ std::cerr << ec.what() << std::endl;
+ return 1;
+}
+
+This client doesn't give the user any status information or progress about the torrent, but +it is fully functional.
+libtorrent also comes with python bindings for easy access for python developers.