remove the concept of slots, and just talk about pieces (since we don't do compact allocation anymore). Remove the section about compact allocation
This commit is contained in:
arvidn
parent
9bed3d1dd5
commit
cec6748e0c
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@ -394,10 +394,6 @@ The file format is a bencoded dictionary containing the following fields:
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| | means it is free, that there's no piece there. If it is -1, |
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| | means the slot isn't allocated on disk yet. The pieces have |
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| | to meet the following requirement: |
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| | |
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| | If there's a slot at the position of the piece index, |
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| | the piece must be located in that slot. |
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| | |
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+--------------------------+--------------------------------------------------------------+
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| ``total_uploaded`` | integer. The number of bytes that have been uploaded in |
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| | total for this torrent. |
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@ -579,61 +575,6 @@ The benefits of this mode are:
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* No risk of a download failing because of a full disk during download, once
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all files have been created.
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compact allocation
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------------------
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.. note::
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Support for compact allocation has been removed from libttorrent
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The compact allocation will only allocate as much storage as it needs to keep
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the pieces downloaded so far. This means that pieces will be moved around to be
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placed at their final position in the files while downloading (to make sure the
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completed download has all its pieces in the correct place). So, the main
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drawbacks are:
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* More disk operations while downloading since pieces are moved around.
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* Potentially more fragmentation in the filesystem.
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* Cannot be used while having files with priority 0.
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The benefits though, are:
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* No startup delay, since the files don't need allocating.
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* The download will not use unnecessary disk space.
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* Disk caches perform much better than in full allocation and raises the
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download speed limit imposed by the disk.
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* Works well on filesystems that don't support sparse files.
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The algorithm that is used when allocating pieces and slots isn't very
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complicated. For the interested, a description follows.
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storing a piece:
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1. let **A** be a newly downloaded piece, with index **n**.
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2. let **s** be the number of slots allocated in the file we're
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downloading to. (the number of pieces it has room for).
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3. if **n** >= **s** then allocate a new slot and put the piece there.
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4. if **n** < **s** then allocate a new slot, move the data at
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slot **n** to the new slot and put **A** in slot **n**.
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allocating a new slot:
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1. if there's an unassigned slot (a slot that doesn't
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contain any piece), return that slot index.
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2. append the new slot at the end of the file (or find an unused slot).
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3. let **i** be the index of newly allocated slot
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4. if we have downloaded piece index **i** already (to slot **j**) then
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1. move the data at slot **j** to slot **i**.
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2. return slot index **j** as the newly allocated free slot.
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5. return **i** as the newly allocated slot.
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HTTP seeding
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============
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@ -7,7 +7,7 @@
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v
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+--------------------------+
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| "piece_manager" |
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| "(maps pieces to slots)" |
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| "disk job fence logic" |
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+--------------------------+
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^
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@ -15,13 +15,13 @@
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/----------------------------\ +-------------------+
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| "storage" |<---->| "file_pool" |
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| | | "open file cache" |
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| "(maps slots to file and" | +-------------------+
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| "(maps pieces to file and" | +-------------------+
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| "offset. reads and writes" |
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| "to disk)" | +--------------------+
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| "to disk)" | +---------------------+
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| |<-----+ "file_storage" |
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\----------------------------/ | "standard slot to" |
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\----------------------------/ | "standard piece to" |
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^ | "file mapping" |
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| +--------------------+
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| +---------------------+
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v
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+--------------------------+
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| "file" |
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@ -90,9 +90,9 @@ POSSIBILITY OF SUCH DAMAGE.
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// temp_storage(file_storage const& fs) : m_files(fs) {}
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// virtual bool initialize(storage_error& se) { return false; }
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// virtual bool has_any_file() { return false; }
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// virtual int read(char* buf, int slot, int offset, int size)
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// virtual int read(char* buf, int piece, int offset, int size)
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// {
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// std::map<int, std::vector<char> >::const_iterator i = m_file_data.find(slot);
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// std::map<int, std::vector<char> >::const_iterator i = m_file_data.find(piece);
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// if (i == m_file_data.end()) return 0;
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// int available = i->second.size() - offset;
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// if (available <= 0) return 0;
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@ -100,9 +100,9 @@ POSSIBILITY OF SUCH DAMAGE.
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// memcpy(buf, &i->second[offset], available);
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// return available;
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// }
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// virtual int write(const char* buf, int slot, int offset, int size)
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// virtual int write(const char* buf, int piece, int offset, int size)
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// {
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// std::vector<char>& data = m_file_data[slot];
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// std::vector<char>& data = m_file_data[piece];
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// if (data.size() < offset + size) data.resize(offset + size);
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// std::memcpy(&data[offset], buf, size);
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// return size;
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@ -114,15 +114,15 @@ POSSIBILITY OF SUCH DAMAGE.
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// , std::vector<std::string> const* links
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// , storage_error& error) { return false; }
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// virtual bool write_resume_data(entry& rd) const { return false; }
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// virtual boost::int64_t physical_offset(int slot, int offset)
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// { return slot * m_files.piece_length() + offset; };
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// virtual sha1_hash hash_for_slot(int slot, partial_hash& ph, int piece_size)
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// virtual boost::int64_t physical_offset(int piece, int offset)
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// { return piece * m_files.piece_length() + offset; };
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// virtual sha1_hash hash_for_slot(int piece, partial_hash& ph, int piece_size)
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// {
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// int left = piece_size - ph.offset;
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// assert(left >= 0);
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// if (left > 0)
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// {
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// std::vector<char>& data = m_file_data[slot];
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// std::vector<char>& data = m_file_data[piece];
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// // if there are padding files, those blocks will be considered
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// // completed even though they haven't been written to the storage.
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// // in this case, just extend the piece buffer to its full size
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@ -202,9 +202,10 @@ namespace libtorrent
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// but modifies some particular behavior, for instance encrypting the data
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// before it's written to disk, and decrypting it when it's read again.
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//
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// The storage interface is based on slots, each slot is 'piece_size' number
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// The storage interface is based on pieces. Avery read and write operation
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// happens in the piece-space. Each piece fits 'piece_size' number
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// of bytes. All access is done by writing and reading whole or partial
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// slots. One slot is one piece in the torrent.
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// pieces.
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//
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// libtorrent comes with two built-in storage implementations;
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// ``default_storage`` and ``disabled_storage``. Their constructor functions
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@ -466,7 +467,7 @@ namespace libtorrent
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};
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void delete_one_file(std::string const& p, error_code& ec);
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int readwritev(file::iovec_t const* bufs, int slot, int offset
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int readwritev(file::iovec_t const* bufs, int piece, int offset
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, int num_bufs, fileop const& op, storage_error& ec);
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void need_partfile();
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@ -477,7 +478,7 @@ namespace libtorrent
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// in order to avoid calling stat() on each file multiple times
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// during startup, cache the results in here, and clear it all
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// out once the torrent starts (to avoid getting stale results)
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// each slot represents the size and timestamp of the file
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// each entry represents the size and timestamp of the file
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mutable stat_cache m_stat_cache;
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// helper function to open a file in the file pool with the right mode
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@ -714,12 +714,12 @@ namespace libtorrent
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}
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}
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int default_storage::sparse_end(int slot) const
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int default_storage::sparse_end(int piece) const
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{
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TORRENT_ASSERT(slot >= 0);
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TORRENT_ASSERT(slot < files().num_pieces());
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TORRENT_ASSERT(piece >= 0);
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TORRENT_ASSERT(piece < files().num_pieces());
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boost::int64_t file_offset = boost::int64_t(slot) * files().piece_length();
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boost::int64_t file_offset = boost::int64_t(piece) * files().piece_length();
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int file_index = 0;
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for (;;)
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@ -734,7 +734,7 @@ namespace libtorrent
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error_code ec;
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file_handle handle = open_file_impl(file_index, file::read_only, ec);
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if (ec) return slot;
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if (ec) return piece;
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boost::int64_t data_start = handle->sparse_end(file_offset);
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return int((data_start + files().piece_length() - 1) / files().piece_length());
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@ -1096,7 +1096,7 @@ namespace libtorrent
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}
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int default_storage::readv(file::iovec_t const* bufs, int num_bufs
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, int slot, int offset, int flags, storage_error& ec)
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, int piece, int offset, int flags, storage_error& ec)
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{
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fileop op = { &file::readv
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, file::read_only | flags };
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@ -1104,15 +1104,15 @@ namespace libtorrent
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boost::thread::sleep(boost::get_system_time()
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+ boost::posix_time::milliseconds(1000));
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#endif
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return readwritev(bufs, slot, offset, num_bufs, op, ec);
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return readwritev(bufs, piece, offset, num_bufs, op, ec);
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}
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int default_storage::writev(file::iovec_t const* bufs, int num_bufs
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, int slot, int offset, int flags, storage_error& ec)
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, int piece, int offset, int flags, storage_error& ec)
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{
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fileop op = { &file::writev
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, file::read_write | flags };
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return readwritev(bufs, slot, offset, num_bufs, op, ec);
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return readwritev(bufs, piece, offset, num_bufs, op, ec);
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}
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// much of what needs to be done when reading and writing
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@ -1121,12 +1121,12 @@ namespace libtorrent
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// is a template, and the fileop decides what to do with the
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// file and the buffers.
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int default_storage::readwritev(file::iovec_t const* const bufs
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, const int slot, const int offset
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, const int piece, const int offset
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, const int num_bufs, fileop const& op, storage_error& ec)
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{
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TORRENT_ASSERT(bufs != 0);
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TORRENT_ASSERT(slot >= 0);
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TORRENT_ASSERT(slot < m_files.num_pieces());
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TORRENT_ASSERT(piece >= 0);
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TORRENT_ASSERT(piece < m_files.num_pieces());
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TORRENT_ASSERT(offset >= 0);
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TORRENT_ASSERT(num_bufs > 0);
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@ -1135,7 +1135,7 @@ namespace libtorrent
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TORRENT_ASSERT(files().is_loaded());
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// find the file iterator and file offset
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boost::uint64_t torrent_offset = slot * boost::uint64_t(m_files.piece_length()) + offset;
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boost::uint64_t torrent_offset = piece * boost::uint64_t(m_files.piece_length()) + offset;
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int file_index = files().file_index_at_offset(torrent_offset);
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TORRENT_ASSERT(torrent_offset >= files().file_offset(file_index));
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TORRENT_ASSERT(torrent_offset < files().file_offset(file_index) + files().file_size(file_index));
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@ -1229,13 +1229,13 @@ namespace libtorrent
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// the fileop object.
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// write
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bytes_transferred = m_part_file->writev(tmp_bufs, num_tmp_bufs
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, slot, offset, e);
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, piece, offset, e);
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}
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else
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{
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// read
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bytes_transferred = m_part_file->readv(tmp_bufs, num_tmp_bufs
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, slot, offset, e);
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, piece, offset, e);
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}
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if (e)
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{
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