524 lines
16 KiB
ReStructuredText
524 lines
16 KiB
ReStructuredText
=================
|
|
creating torrents
|
|
=================
|
|
|
|
:Author: Arvid Norberg, arvid@rasterbar.com
|
|
:Version: 0.16.1
|
|
|
|
.. contents:: Table of contents
|
|
:depth: 2
|
|
:backlinks: none
|
|
|
|
overview
|
|
========
|
|
|
|
This section describes the functions and classes that are used
|
|
to create torrent files. It is a layered API with low level classes
|
|
and higher level convenience functions. A torrent is created in 4
|
|
steps:
|
|
|
|
1. first the files that will be part of the torrent are determined.
|
|
2. the torrent properties are set, such as tracker url, web seeds,
|
|
DHT nodes etc.
|
|
3. Read through all the files in the torrent, SHA-1 all the data
|
|
and set the piece hashes.
|
|
4. The torrent is bencoded into a file or buffer.
|
|
|
|
If there are a lot of files and or deep directoy hierarchies to
|
|
traverse, step one can be time consuming.
|
|
|
|
Typically step 3 is by far the most time consuming step, since it
|
|
requires to read all the bytes from all the files in the torrent.
|
|
|
|
All of these classes and functions are declared by including
|
|
``libtorrent/create_torrent.hpp``.
|
|
|
|
high level example
|
|
==================
|
|
|
|
::
|
|
|
|
file_storage fs;
|
|
|
|
// recursively adds files in directories
|
|
add_files(fs, "./my_torrent");
|
|
|
|
create_torrent t(fs);
|
|
t.add_tracker("http://my.tracker.com/announce");
|
|
t.set_creator("libtorrent example");
|
|
|
|
// reads the files and calculates the hashes
|
|
set_piece_hashes(t, ".");
|
|
|
|
ofstream out("my_torrent.torrent", std::ios_base::binary);
|
|
bencode(std::ostream_iterator<char>(out), t.generate());
|
|
|
|
add_files
|
|
=========
|
|
|
|
::
|
|
|
|
template <class Pred>
|
|
void add_files(file_storage& fs, std::string const& path, Pred p
|
|
, boost::uint32_t flags = 0);
|
|
template <class Pred>
|
|
void add_files(file_storage& fs, std::wstring const& path, Pred p
|
|
, boost::uint32_t flags = 0);
|
|
|
|
void add_files(file_storage& fs, std::string const& path
|
|
, boost::uint32_t flags = 0);
|
|
void add_files(file_storage& fs, std::wstring const& path
|
|
, boost::uint32_t flags = 0);
|
|
|
|
Adds the file specified by ``path`` to the ``file_storage`` object. In case ``path``
|
|
refers to a diretory, files will be added recursively from the directory.
|
|
|
|
If specified, the predicate ``p`` is called once for every file and directory that
|
|
is encountered. files for which ``p`` returns true are added, and directories for
|
|
which ``p`` returns true are traversed. ``p`` must have the following signature::
|
|
|
|
bool Pred(std::string const& p);
|
|
|
|
and for the wide string version::
|
|
|
|
bool Pred(std::wstring const& p);
|
|
|
|
The path that is passed in to the predicate is the full path of the file or
|
|
directory. If no predicate is specified, all files are added, and all directories
|
|
are traveresed.
|
|
|
|
The ".." directory is never traversed.
|
|
|
|
The ``flags`` argument should be the same as the flags passed to the `create_torrent`_
|
|
constructor.
|
|
|
|
set_piece_hashes()
|
|
==================
|
|
|
|
::
|
|
|
|
template <class Fun>
|
|
void set_piece_hashes(create_torrent& t, std::string const& p, Fun f);
|
|
template <class Fun>
|
|
void set_piece_hashes(create_torrent& t, std::wstring const& p, Fun f);
|
|
template <class Fun>
|
|
void set_piece_hashes(create_torrent& t, std::string const& p, Fun f
|
|
, error_code& ec);
|
|
template <class Fun>
|
|
void set_piece_hashes(create_torrent& t, std::wstring const& p, Fun f
|
|
, error_code& ec);
|
|
|
|
void set_piece_hashes(create_torrent& t, std::string const& p);
|
|
void set_piece_hashes(create_torrent& t, std::wstring const& p);
|
|
void set_piece_hashes(create_torrent& t, std::string const& p
|
|
, error_code& ec);
|
|
void set_piece_hashes(create_torrent& t, std::wstring const& p
|
|
, error_code& ec);
|
|
|
|
This function will assume that the files added to the torrent file exists at path
|
|
``p``, read those files and hash the content and set the hashes in the ``create_torrent``
|
|
object. The optional function ``f`` is called in between every hash that is set. ``f``
|
|
must have the following signature::
|
|
|
|
void Fun(int);
|
|
|
|
The overloads that don't take an ``error_code&`` may throw an exception in case of a
|
|
file error, the other overloads sets the error code to reflect the error, if any.
|
|
|
|
file_storage
|
|
============
|
|
|
|
The ``file_storage`` class represents a file list and the piece
|
|
size. Everything necessary to interpret a regular bittorrent storage
|
|
file structure. Its synopsis::
|
|
|
|
class file_storage
|
|
{
|
|
public:
|
|
|
|
bool is_valid() const;
|
|
|
|
enum flags_t
|
|
{
|
|
pad_file = 1,
|
|
attribute_hidden = 2,
|
|
attribute_executable = 4
|
|
};
|
|
|
|
void add_file(file_entry const& e);
|
|
void add_file(std::string const& p, size_type size, int flags = 0);
|
|
void add_file(std::wstring const& p, size_type size, int flags = 0);
|
|
void rename_file(int index, std::string const& new_filename);
|
|
void rename_file(int index, std::wstring const& new_filename);
|
|
|
|
std::vector<file_slice> map_block(int piece, size_type offset
|
|
, int size) const;
|
|
peer_request map_file(int file, size_type offset, int size) const;
|
|
|
|
typedef std::vector<internal_file_entry>::const_iterator iterator;
|
|
typedef std::vector<internal_file_entry>::const_reverse_iterator reverse_iterator;
|
|
|
|
iterator begin() const;
|
|
iterator end() const;
|
|
reverse_iterator rbegin();
|
|
reverse_iterator rend() const;
|
|
int num_files() const;
|
|
|
|
file_entry at(int index) const;
|
|
|
|
size_type total_size() const;
|
|
void set_num_pieces(int n);
|
|
int num_pieces() const;
|
|
void set_piece_length(int l);
|
|
int piece_length() const;
|
|
int piece_size(int index) const;
|
|
|
|
sha1_hash const& hash(int index) const;
|
|
std::string const& symlink(int index) const;
|
|
time_t mtime(int index) const;
|
|
int file_index(int index) const;
|
|
size_type file_base(int index) const;
|
|
void set_file_base(int index, size_type off);
|
|
|
|
void set_name(std::string const& n);
|
|
void set_name(std::wstring const& n);
|
|
const std::string& name() const;
|
|
|
|
void swap(file_storage& ti);
|
|
}
|
|
|
|
add_file()
|
|
----------
|
|
|
|
::
|
|
|
|
void add_file(file_entry const& e);
|
|
void add_file(std::string const& p, size_type size, int flags = 0);
|
|
void add_file(std::wstring const& p, size_type size, int flags = 0);
|
|
|
|
Adds a file to the file storage. The ``flags`` argument sets attributes on the file.
|
|
The file attributes is an extension and may not work in all bittorrent clients.
|
|
The possible arreibutes are::
|
|
|
|
pad_file
|
|
attribute_hidden
|
|
attribute_executable
|
|
|
|
If more files than one are added, certain restrictions to their paths apply.
|
|
In a multi-file file storage (torrent), all files must share the same root directory.
|
|
|
|
That is, the first path element of all files must be the same.
|
|
This shared path element is also set to the name of the torrent. It
|
|
can be changed by calling ``set_name``.
|
|
|
|
The built in functions to traverse a directory to add files will
|
|
make sure this requirement is fulfilled.
|
|
|
|
hash() symlink() mtime() file_index()
|
|
-------------------------------------
|
|
|
|
::
|
|
|
|
sha1_hash hash(int index) const;
|
|
std::string const& symlink(int index) const;
|
|
time_t mtime(int index) const;
|
|
int file_index(int index) const;
|
|
|
|
These functions are used to query the symlink, file hash,
|
|
modification time and the file-index from a file index.
|
|
|
|
The file hash is a sha-1 hash of the file, or 0 if none was
|
|
provided in the torrent file. This can potentially be used to
|
|
join a bittorrent network with other file sharing networks.
|
|
|
|
The modification time is the posix time when a file was last
|
|
modified when the torrent was created, or 0 if it was not provided.
|
|
|
|
The file index of a file is simply a 0 based index of the
|
|
file as they are ordered in the torrent file.
|
|
|
|
file_base() set_file_base()
|
|
---------------------------
|
|
|
|
::
|
|
|
|
size_type file_base(int index) const;
|
|
void set_file_base(int index, size_type off);
|
|
|
|
The file base of a file is the offset within the file on the filsystem
|
|
where it starts to write. For the most part, this is always 0. It's
|
|
possible to map several files (in the torrent) into a single file on
|
|
the filesystem by making them all point to the same filename, but with
|
|
different file bases, so that they don't overlap.
|
|
``torrent_info::remap_files`` can be used to use a new file layout.
|
|
|
|
create_torrent
|
|
==============
|
|
|
|
The ``create_torrent`` class has the following synopsis::
|
|
|
|
|
|
struct create_torrent
|
|
{
|
|
enum {
|
|
optimize = 1
|
|
, merkle = 2
|
|
, modification_time = 4
|
|
, symlink = 8
|
|
, calculate_file_hashes = 16
|
|
};
|
|
create_torrent(file_storage& fs, int piece_size = 0, int pad_size_limit = -1
|
|
, int flags = optimize);
|
|
create_torrent(torrent_info const& ti);
|
|
|
|
entry generate() const;
|
|
|
|
file_storage const& files() const;
|
|
|
|
void set_comment(char const* str);
|
|
void set_creator(char const* str);
|
|
void set_hash(int index, sha1_hash const& h);
|
|
void set_file_hash(int index, sha1_hash const& h);
|
|
void add_url_seed(std::string const& url);
|
|
void add_http_seed(std::string const& url);
|
|
void add_node(std::pair<std::string, int> const& node);
|
|
void add_tracker(std::string const& url, int tier = 0);
|
|
void set_root_cert(std::string const& pem);
|
|
void set_priv(bool p);
|
|
|
|
int num_pieces() const;
|
|
int piece_length() const;
|
|
int piece_size(int i) const;
|
|
bool priv() const;
|
|
};
|
|
|
|
create_torrent()
|
|
----------------
|
|
|
|
::
|
|
|
|
enum {
|
|
optimize = 1
|
|
, merkle = 2
|
|
, modification_time = 4
|
|
, symlink = 8
|
|
, calculate_file_hashes = 16
|
|
};
|
|
create_torrent(file_storage& fs, int piece_size = 0, int pad_size_limit = -1
|
|
, int flags = optimize);
|
|
create_torrent(torrent_info const& ti);
|
|
|
|
The ``piece_size`` is the size of each piece in bytes. It must
|
|
be a multiple of 16 kiB. If a piece size of 0 is specified, a
|
|
piece_size will be calculated such that the torrent file is roughly 40 kB.
|
|
|
|
If a ``pad_size_limit`` is specified (other than -1), any file larger than
|
|
the specified number of bytes will be preceeded by a pad file to align it
|
|
with the start of a piece. The pad_file_limit is ignored unless the
|
|
``optimize`` flag is passed. Typically it doesn't make sense to set this
|
|
any lower than 4kiB.
|
|
|
|
The overload that takes a ``torrent_info`` object will make a verbatim
|
|
copy of its info dictionary (to preserve the info-hash). The copy of
|
|
the info dictionary will be used by ``generate()``. This means
|
|
that none of the member functions of create_torrent that affects
|
|
the content of the info dictionary (such as ``set_hash()``), will
|
|
have any affect.
|
|
|
|
The ``flags`` arguments specifies options for the torrent creation. It can
|
|
be any combination of the following flags:
|
|
|
|
optimize
|
|
This will insert pad files to align the files to piece boundaries, for
|
|
optimized disk-I/O.
|
|
|
|
merkle
|
|
This will create a merkle hash tree torrent. A merkle torrent cannot
|
|
be opened in clients that don't specifically support merkle torrents.
|
|
The benefit is that the resulting torrent file will be much smaller and
|
|
not grow with more pieces. When this option is specified, it is
|
|
recommended to have a fairly small piece size, say 64 kiB.
|
|
When creating merkle torrents, the full hash tree is also generated
|
|
and should be saved off separately. It is accessed through the
|
|
``merkle_tree()`` function.
|
|
|
|
modification_time
|
|
This will include the file modification time as part of the torrent.
|
|
This is not enabled by default, as it might cause problems when you
|
|
create a torrent from separate files with the same content, hoping to
|
|
yield the same info-hash. If the files have different modification times,
|
|
with this option enabled, you would get different info-hashes for the
|
|
files.
|
|
|
|
symlink
|
|
If this flag is set, files that are symlinks get a symlink attribute
|
|
set on them and their data will not be included in the torrent. This
|
|
is useful if you need to reconstruct a file hierarchy which contains
|
|
symlinks.
|
|
|
|
calculate_file_hashes
|
|
If this is set, the `set_piece_hashes()`_ function will, as it calculates
|
|
the piece hashes, also calculate the file hashes and add those associated
|
|
with each file. Note that unless you use the `set_piece_hashes()`_ function,
|
|
this flag will have no effect.
|
|
|
|
generate()
|
|
----------
|
|
|
|
::
|
|
|
|
entry generate() const;
|
|
|
|
This function will generate the .torrent file as a bencode tree. In order to
|
|
generate the flat file, use the bencode() function.
|
|
|
|
It may be useful to add custom entries to the torrent file before bencoding it
|
|
and saving it to disk.
|
|
|
|
If anything goes wrong during torrent generation, this function will return
|
|
an empty ``entry`` structure. You can test for this condition by querying the
|
|
type of the entry::
|
|
|
|
file_storage fs;
|
|
// add file ...
|
|
create_torrent t(fs);
|
|
// add trackers and piece hashes ...
|
|
e = t.generate();
|
|
|
|
if (e.type() == entry::undefined_t)
|
|
{
|
|
// something went wrong
|
|
}
|
|
|
|
For instance, you cannot generate a torrent with 0 files in it. If you don't add
|
|
any files to the ``file_storage``, torrent generation will fail.
|
|
|
|
set_comment()
|
|
-------------
|
|
|
|
::
|
|
|
|
void set_comment(char const* str);
|
|
|
|
Sets the comment for the torrent. The string ``str`` should be utf-8 encoded.
|
|
The comment in a torrent file is optional.
|
|
|
|
set_creator()
|
|
-------------
|
|
|
|
::
|
|
|
|
void set_creator(char const* str);
|
|
|
|
Sets the creator of the torrent. The string ``str`` should be utf-8 encoded.
|
|
This is optional.
|
|
|
|
set_hash()
|
|
----------
|
|
|
|
::
|
|
|
|
void set_hash(int index, sha1_hash const& h);
|
|
|
|
This sets the SHA-1 hash for the specified piece (``index``). You are required
|
|
to set the hash for every piece in the torrent before generating it. If you have
|
|
the files on disk, you can use the high level convenience function to do this.
|
|
See `set_piece_hashes()`_.
|
|
|
|
set_file_hash()
|
|
---------------
|
|
|
|
::
|
|
|
|
void set_file_hash(int index, sha1_hash const& h);
|
|
|
|
This sets the sha1 hash for this file. This hash will end up under the key ``sha1``
|
|
associated with this file (for multi-file torrents) or in the root info dictionary
|
|
for single-file torrents.
|
|
|
|
add_url_seed() add_http_seed()
|
|
------------------------------
|
|
|
|
::
|
|
|
|
void add_url_seed(std::string const& url);
|
|
void add_http_seed(std::string const& url);
|
|
|
|
This adds a url seed to the torrent. You can have any number of url seeds. For a
|
|
single file torrent, this should be an HTTP url, pointing to a file with identical
|
|
content as the file of the torrent. For a multi-file torrent, it should point to
|
|
a directory containing a directory with the same name as this torrent, and all the
|
|
files of the torrent in it.
|
|
|
|
The second function, ``add_http_seed()`` adds an HTTP seed instead.
|
|
|
|
add_node()
|
|
----------
|
|
|
|
::
|
|
|
|
void add_node(std::pair<std::string, int> const& node);
|
|
|
|
This adds a DHT node to the torrent. This especially useful if you're creating a
|
|
tracker less torrent. It can be used by clients to bootstrap their DHT node from.
|
|
The node is a hostname and a port number where there is a DHT node running.
|
|
You can have any number of DHT nodes in a torrent.
|
|
|
|
add_tracker()
|
|
-------------
|
|
|
|
::
|
|
|
|
void add_tracker(std::string const& url, int tier = 0);
|
|
|
|
Adds a tracker to the torrent. This is not strictly required, but most torrents
|
|
use a tracker as their main source of peers. The url should be an http:// or udp://
|
|
url to a machine running a bittorrent tracker that accepts announces for this torrent's
|
|
info-hash. The tier is the fallback priority of the tracker. All trackers with tier 0 are
|
|
tried first (in any order). If all fail, trackers with tier 1 are tried. If all of those
|
|
fail, trackers with tier 2 are tried, and so on.
|
|
|
|
set_root_cert()
|
|
---------------
|
|
|
|
::
|
|
|
|
void set_root_cert(std::string const& pem);
|
|
|
|
This function sets an X.509 certificate in PEM format to the torrent. This makes the
|
|
torrent an *SSL torrent*. An SSL torrent requires that each peer has a valid certificate
|
|
signed by this root certificate. For SSL torrents, all peers are connecting over SSL
|
|
connections. For more information on SSL torrents, see the manual_.
|
|
|
|
The string is not the path to the cert, it's the actual content of the certificate,
|
|
loaded into a std::string.
|
|
|
|
.. _manual: manual.html#ssl-torrents
|
|
|
|
set_priv() priv()
|
|
-----------------
|
|
|
|
::
|
|
|
|
void set_priv(bool p);
|
|
bool priv() const;
|
|
|
|
Sets and queries the private flag of the torrent.
|
|
|
|
merkle_tree()
|
|
-------------
|
|
|
|
::
|
|
|
|
std::vector<sha1_hash> const& merkle_tree() const;
|
|
|
|
This function returns the merkle hash tree, if the torrent was created as a merkle
|
|
torrent. The tree is created by ``generate()`` and won't be valid until that function
|
|
has been called. When creating a merkle tree torrent, the actual tree itself has to
|
|
be saved off separately and fed into libtorrent the first time you start seeding it,
|
|
through the ``torrent_info::set_merkle_tree()`` function. From that point onwards, the
|
|
tree will be saved in the resume data.
|
|
|
|
|
|
|