~file_pool() file_pool()

~file_pool ();
file_pool (int size = 40);

size specifies the number of allowed files handles to hold open at any given time.

open_file()

boost::intrusive_ptr<file> open_file (void* st, std::string const& p
      , int file_index, file_storage const& fs, int m, error_code& ec);

return an open file handle to file at file_index in the file_storage fs opened at save path p. m is the file open mode (see file::open_mode_t).

release()

void release (void* st);
void release (void* st, int file_index);

release all files belonging to the specified storage_interface (st) the overload that takes file_index releases only the file with that index in storage st.

resize()

void resize (int size);

update the allowed number of open file handles to size.

size_limit()

int size_limit () const;

returns the current limit of number of allowed open file handles held by the file_pool.

initialize()

virtual bool initialize (bool allocate_files) = 0;

This function is called when the storage is to be initialized. The default storage will create directories and empty files at this point. If allocate_files is true, it will also ftruncate all files to their target size.

Returning true indicates an error occurred.

has_any_file()

virtual bool has_any_file () = 0;

This function is called when first checking (or re-checking) the storage for a torrent. It should return true if any of the files that is used in this storage exists on disk. If so, the storage will be checked for existing pieces before starting the download.

writev() readv()

virtual int writev (file::iovec_t const* bufs, int slot, int offset, int num_bufs, int flags = file::random_access);
virtual int readv (file::iovec_t const* bufs, int slot, int offset, int num_bufs, int flags = file::random_access);

These functions should read or write the data in or to the given slot at the given offset. It should read or write num_bufs buffers sequentially, where the size of each buffer is specified in the buffer array bufs. The file::iovec_t type has the following members:

struct iovec_t
{
        void* iov_base;
        size_t iov_len;
};

The return value is the number of bytes actually read or written, or -1 on failure. If it returns -1, the error code is expected to be set to

Every buffer in bufs can be assumed to be page aligned and be of a page aligned size, except for the last buffer of the torrent. The allocated buffer can be assumed to fit a fully page aligned number of bytes though. This is useful when reading and writing the last piece of a file in unbuffered mode.

The offset is aligned to 16 kiB boundries most of the time, but there are rare exceptions when it's not. Specifically if the read cache is disabled/or full and a client requests unaligned data, or the file itself is not aligned in the torrent. Most clients request aligned data.

hint_read()

virtual void hint_read (int, int, int);

This function is called when a read job is queued. It gives the storage wrapper an opportunity to hint the operating system about this coming read. For instance, the storage may call posix_fadvise(POSIX_FADV_WILLNEED) or fcntl(F_RDADVISE).

read()

virtual int read (char* buf, int slot, int offset, int size) = 0;

negative return value indicates an error

write()

virtual int write (const char* buf, int slot, int offset, int size) = 0;

negative return value indicates an error

physical_offset()

virtual size_type physical_offset (int slot, int offset) = 0;

returns the offset on the physical storage medium for the byte at offset offset in slot slot.

sparse_end()

virtual int sparse_end (int start) const;

This function is optional. It is supposed to return the first piece, starting at start that is fully contained within a data-region on disk (i.e. non-sparse region). The purpose of this is to skip parts of files that can be known to contain zeros when checking files.

move_storage()

virtual int move_storage (std::string const& save_path, int flags) = 0;

This function should move all the files belonging to the storage to the new save_path. The default storage moves the single file or the directory of the torrent.

Before moving the files, any open file handles may have to be closed, like release_files().

returns one of: | no_error = 0 | need_full_check = -1 | fatal_disk_error = -2 | file_exist = -4

verify_resume_data()

virtual bool verify_resume_data (lazy_entry const& rd, error_code& error) = 0;

This function should verify the resume data rd with the files on disk. If the resume data seems to be up-to-date, return true. If not, set error to a description of what mismatched and return false.

The default storage may compare file sizes and time stamps of the files.

Returning false indicates an error occurred.

write_resume_data()

virtual bool write_resume_data (entry& rd) const = 0;

This function should fill in resume data, the current state of the storage, in rd. The default storage adds file timestamps and sizes.

Returning true indicates an error occurred.

move_slot()

virtual bool move_slot (int src_slot, int dst_slot) = 0;

This function should copy or move the data in slot src_slot to the slot dst_slot. This is only used in compact mode.

If the storage caches slots, this could be implemented more efficient than reading and writing the data.

Returning true indicates an error occurred.

swap_slots()

virtual bool swap_slots (int slot1, int slot2) = 0;

This function should swap the data in slot1 and slot2. The default storage uses a scratch buffer to read the data into, then moving the other slot and finally writing back the temporary slot's data

This is only used in compact mode.

Returning true indicates an error occurred.

swap_slots3()

virtual bool swap_slots3 (int slot1, int slot2, int slot3) = 0;

This function should do a 3-way swap, or shift of the slots. slot1 should move to slot2, which should be moved to slot3 which in turn should be moved to slot1.

This is only used in compact mode.

Returning true indicates an error occurred.

release_files()

virtual bool release_files () = 0;

This function should release all the file handles that it keeps open to files belonging to this storage. The default implementation just calls file_pool::release_files(this).

Returning true indicates an error occurred.

rename_file()

virtual bool rename_file (int index, std::string const& new_filename) = 0;

Rename file with index file to the thame new_name. If there is an error, true should be returned.

delete_files()

virtual bool delete_files () = 0;

This function should delete all files and directories belonging to this storage.

Returning true indicates an error occurred.

The disk_buffer_pool is used to allocate and free disk buffers. It has the following members:

struct disk_buffer_pool : boost::noncopyable
{
        char* allocate_buffer(char const* category);
        void free_buffer(char* buf);

        char* allocate_buffers(int blocks, char const* category);
        void free_buffers(char* buf, int blocks);

        int block_size() const { return m_block_size; }

        void release_memory();
};

disk_pool()

disk_buffer_pool* disk_pool ();

access global disk_buffer_pool, for allocating and freeing disk buffers

settings()

session_settings const& settings () const;

access global session_settings

set_error()

void set_error (std::string const& file, error_code const& ec) const;

called by the storage implementation to set it into an error state. Typically whenever a critical file operation fails.

error_file() error()

error_code const& error () const;
std::string const& error_file () const;

returns the currently set error code and file path associated with it, if set.

clear_error()

virtual void clear_error ();

reset the error state to allow continuing reading and writing to the storage

enum move_flags_t

Declared in "libtorrent/storage.hpp"