711 lines
19 KiB
Plaintext
711 lines
19 KiB
Plaintext
===============================================================================
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= =
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= Ocarina 6.0 =
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= =
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===============================================================================
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My main goal for Ocarina 6.x is to plan out all of my actions before writing
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code. In the past I was adding features as I thought of them before thinking
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out how everything works together, and this made Ocarina difficult to maintain
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because I had no overall plan. This document aims to fix that.
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I will also create unit tests as I add features so bugs can be found faster.
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Unit tests will be created for each module (file) in my backend library code.
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Files:
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$HOME/.ocarina{-debug}/
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album.db
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artist.db
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genre.db
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groups.idx
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library.db
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playlists.lst
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track.db
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/usr/bin/
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ocarina
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/usr/lib/ocarina/
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ocarina/
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design.txt
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ocarina/include/
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audio.h
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database.h
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database.hpp
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file.h
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filter.h
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groups.h
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idle.h
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index.h
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library.h
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playlist.h
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prefs.h
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print.h
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version.h
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ocarina/lib/
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audio.cpp
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database.cpp
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file.cpp
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filter.cpp
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groups.cpp
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idle.cpp
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index.cpp
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library.cpp
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playlist.cpp
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prefs.cpp
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Install:
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Ocarina will be compiled into a single executable placed under
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/usr/bin/. Any extra files needed to run will be placed under
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/usr/lib/ocarina/.
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Printing: (include/print.h>
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Sometimes text needs to be printed to the screen so users (or debuggers)
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know what is going on.
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API:
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void print(string fmt, ...)
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Print text to the screen
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void dprint(string fmt, ...)
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Print text to the screen when debugging is enabled
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Versioning: (include/version.h)
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This file contains a simple function for returning a string stating
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the current version.
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API:
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const char *get_version();
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Returns a string describing the current version.
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Audio: (lib/audio.cpp)
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This file will introduce an "audio" namespace containing all of the
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functions interacting with gstreamer. This will create a wrapper
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namespace that will be easier to work with than using raw gstreamer
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functions.
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The audio layer will also control the "pause after N tracks" feature
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so songs can be loaded without neeting to pass in a "begin playback"
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flag every time.
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- Internal:
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Set up a message bus to look for end-of-stream and error messages so
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the next song can be played. This function should call the play
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function after loading a track and after checking the "pause after N"
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count.
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- API:
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audio :: init(argc, argv)
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Initialize the gstreamer layer and reload the track that was
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last loaded before shutdown. Please only pass --gst-* options
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for argv.
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audio :: load_file(filepath)
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Loads a file path but does not begin playback.
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audio :: play()
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Begin playback
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audio :: pause()
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Pause playback
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audio :: seek_to(X)
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Seek to a position X seconds into the track
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audio :: stop()
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pause()
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seek_to(0)
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audio :: pause_after(N)
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Pause after N tracks, pass a negative number to disable.
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audio :: position()
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Return the number of seconds that the song has played
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audio :: duration()
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Return the duration of the current song in seconds
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On-disk files: (lib/file.cpp)
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Data will be stored in the user's home directory according to the
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XDG / freedesktop.org specification. This means storing data in
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$XDG_DATA_HOME/ocarina{-debug|-test}/ and storing configuration in
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$XDG_CONFIG_HOME/ocarina{-debug|-test}/. In addition, I will support
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importing data from Ocarina 5.10 for conversion to the new format.
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In theory my file format will not change often, so it should be
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possible to use multiple Ocarina versions with the same data. However,
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should the format need to change I will only support forward
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compatibility. This means that downgrades will not be possible after
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a file format change. To keep the code even cleaner, I will only
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support updating from the previous file format version. This means
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that legacy support will be removed after the first file format change.
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Items should be written to a file with either a space or new line
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separating multiple values.
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- Notation:
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File << aaaaa << bbbbb << endl is translated into "aaaaa bbbbb\n"
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- File version:
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#define FILE_VERSION 0
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- Hint where the file is located:
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enum FileLocHint {
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FILE_TYPE_CONFIG,
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FILE_TYPE_DATA,
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FILE_TYPE_LEGACY,
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}
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- Open mode:
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enum OpenMode {
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OPEN_READ,
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OPEN_WRITE,
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NOT_OPEN,
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}
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- File:
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class File : std::fstream {
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private:
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unsigned int version;
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OpenMode mode;
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FileLocHint hint;
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string filepath;
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public:
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File(string, FileLocHint);
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~File();
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const char *get_filepath();
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const unsigned int get_version();
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bool exists();
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bool open(OpenMode);
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bool close();
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string getline();
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}
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- File format:
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File << FILE_VERSION << endl;
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File << <OTHER_DATA>;
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- API:
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File : File(string filepath, FileLocHint hint)
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Resolve filepath to one of:
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XDG_{CONFIG|DATA}_HOME/ocarina/filepath
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XDG_{CONFIG|DATA}_HOME/ocarina-debug/filepath
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XDG_{CONFIG|DATA}_HOME/ocarina-test/filepath
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$HOME/.ocarina/
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$HOME/.ocarina-debug/
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File : ~File()
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Close the file stream if it is open.
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const char *get_filepath()
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Return the full filepath to the file.
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const unsigned int get_version()
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Return the file version number.
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bool File : exists()
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Return true if the file exists in the filesystem.
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Return false otherwise.
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bool File : open(OpenMode mode)
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When opening a file for reading (mode == OPEN_READ),
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- Return false if the file does not exist
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- Open the file
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- Read in version from the start of the file
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- Return true
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When opening a file for writing (mode == OPEN_WRITE),
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- Return false if the file has FILE_TYPE_LEGACY set
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- Create missing directories as needed
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- Write version information to the start of the file
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- Return true
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Return false if the file is already open.
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Return false if there are any other errors.
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bool File : close()
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Close a file after IO.
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string File : getline();
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Read an entire line from the file and return it to the caller.
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In theory a return value optimization will occur so returning
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a string by value won't be a problem.
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Idle queue: (lib/idle.cpp)
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The idle queue is used to schedule tasks to run at a later time. Idle
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tasks must inherit from the IdleBase class so that multiple templated
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types can be placed on the same idle queue.
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- IdleBase:
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class IdleBase {
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IdleBase();
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~IdleBase();
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virtual void run() = 0;
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};
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- IdleTask:
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template <class T>
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class IdleTask : IdleBase {
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private:
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void (*func)(T *);
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T *data;
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public:
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IdleTask(void (*)(T *), T *);
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void run();
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};
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- Queue:
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deque(IdleTask *> idle_queue;
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float queued = 0.0
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float serviced = 0.0
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- API:
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template <class T>
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void idle :: schedule(void (*)(T *), T *);
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Schedule a function to run later.
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queued++
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bool idle :: run_task()
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Run the next task on the queue. Return true if a task was
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found, and false otherwise.
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scheduled++, reset to zero if idle queue is empty.
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Database: (lib/database.cpp)
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Ocarina 5.x created a different save file format for each type of
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data that needed to be stored (preferences, library paths, playlists).
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I intend to unify everything into a generic file format that can be
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accessed through a generic database interface. The database code will
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be in charge of printing the "valid" bit for each DatabaseEntry so that
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child classes do not need to call into the parent class. If valid ==
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true, the DatabaseEntry will be streamed out followed by a newline. If
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valid == false the database will print the next entry in the vector.
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Modules should inherit from the DatabasEntry class and implement their
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own read() and write() functions. The "valid" field will be stored
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before these functions are called, and the entry will be skipped if
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valid is set to false.
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The Database class is a templated class, so code could potentially
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get messy. Normal class declarations can still exist in the file
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include/database.h and member functions can be written in the file
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include/database.hpp, which will be included by database.h. Any
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function not relying on a template can be written in lib/database.cpp.
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- DatabaseEntry:
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class DatabaseEntry { /* let database modify valid flag */
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private:
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bool valid;
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public:
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virtual File &operator>>(File &) = 0;
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virtual File &operator<<(File &) = 0;
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friend class Database;
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};
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File << <CHILD_CLASS_DATA>
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- Database:
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template <class T>
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class Database {
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private:
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unsigned int _size; /* Number of valid rows */
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File filename;
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vector<T> db;
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public:
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Database::Database(filename);
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void load();
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void save();
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unsigned int insert(T);
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void delete(unsigned int);
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const unsigned int &size();
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const T &operator[](unsigned int);
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};
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File << db.size() << endl
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File << INDEX_0 << db[INDEX_0].valid << db[INDEX_0] << endl;
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File << Index_1 << db[INDEX_1].valid << db[INDEX_1] << endl;
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...
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- API:
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Database.Database(filename);
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Initializes database to use ~/.ocarina{-debug}/filename. Pass
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an empty string if you do not want this database to be saved.
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Database.load();
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Reads data from file. Call after static initialization of
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Ocarina to ensure idle tasks are configured so loading can
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happen at a later time.
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Database.save();
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Saves data to file.
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Database.insert(T &);
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Adds a new item to the db, returns the id of the item
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Database.delete(unsigned int index);
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Mark db[index] as invalid (quick deletion)
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Database.size();
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Returns number of valid rows in the database
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Database.operator[unsigned int index]
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Return a reference to db[index]
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Index: (lib/index.cpp)
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An inverted index allows me to map multiple values to a single key.
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- Index:
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class Index {
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private:
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map<string, set<int>>
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File filename;
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public:
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Index::Index(filename);
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void load();
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void save();
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void insert(key, int);
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void delete(key, int);
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void replace(key, int);
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const set<string> &keys();
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const set<int> &operator[](string);
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};
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File << key << endl;
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File << map[key].size() << int_0 << int_1 << ... << int_n << endl;
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- API:
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Index.Index(filename);
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Initializes an index using ~/.ocarina{-debug}K/filename. Pass
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an empty string if you do not want this index to be saved.
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Index.load();
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Reads data from a file. Call after static initialization of
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Ocarina to ensure idle tasks are configured
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Index.save();
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Saves data to file
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Index.insert(key, int);
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1) If key does not exist, create it.
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2) Add int to the list
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3) Index.save()
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Index.delete(key, int);
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1) Remove int from the set of values associated with key
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2) Do not delete key if set is empty
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3) Index.save()
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Index.replace(key, int)
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1) map[key].clear()
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2) insert(key, int)
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Index.keys();
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Return a set of index keys
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Index.operator[](string key);
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Return the set associated with key
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Filter: (lib/filter.cpp)
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Filtering is used to generate a subset of songs for easier searching.
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- Index:
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map<string, string> lowercase_cache;
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map<string, set<string>> substring_cache;
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Index filter_index("");
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- Parsing:
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1) Convert the provided string into a list of words, using whitespace
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and the following characters as delimiters: \/,;()_~+"
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For each word:
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2) Check the lowercase_cache to see if we have seen the word before,
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a) If we have, return the stored string
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b) Convert the string to lowercase and strip out remaining
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special characters. Add the result to the lowercase_cache;
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3) Check the substring_cache to see if we have seen the word before,
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a) If we have, use the substring set returned
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b) Break the word into substrings from the front only. For
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example: "dalek" would contain the substrings
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{d, da, dal, dale, dalek}. Add to the substring cache.
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- API:
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filter :: add(string, track_id);
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Parses the string and adds the track_id to the index.
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void filter :: search(string, set<track_id> &);
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Parse the string and fill in the set with matching tracks.
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Groups: (lib/group.cpp)
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Groups are going to be a new feature in Ocarina 6 and can compare
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directly to Gmail-style labels. Ocarina 6 will create dynamic groups
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that cannot be deleted by the user based on library status. Similar
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to the library, groups should exist in their own namespace.
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- Index:
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Index group_idx(groups.idx)
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- Default groups:
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All music
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All tracks are added to this group
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Library
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Banned Songs
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These groups are mutually exclusive. A track is either
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in the Library or the Banned Songs group
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- API
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group :: init();
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Initialize the index
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group :: list();
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return group_idx.keys();
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group :: get_tracks(name):
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return group_idx[name]
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group :: add(name, track_id)
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group_idx.insert(name, track_id);
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group :: del(name, track_id)
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grou_idx.delete(name, track_id)
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Library: (lib/library.cpp)
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The library manages databases containing track information added by the
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user. Ocarina 6 splits the library into multiple database tables for
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storing content. The library will exist in a library namespace to
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to make functions and classes more unique.
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When a library : Track is created, it should be added to the "Library"
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group if it is NOT a member of the banned songs group.
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- Album:
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class library :: Album : public DatabaseEntry {
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string name;
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short year;
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};
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File << year << name
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- Artist:
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class library :: Artist : public DatabaseEntry {
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string name;
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};
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File << name
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- Genre:
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class library :: Genre : public DatabaseEntry {
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string name;
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};
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File << name
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- Path:
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class library :: Path : public DatabaseEntry {
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string root_path;
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bool enabled;
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};
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File << enabled << root_path
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- Track:
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class library :: Track : public DatabaseEntry {
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unsigned int artist_id;
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unsigned int album_id;
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unsigned int genre_id;
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unsigned int library_id;
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short track;
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short last_year;
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short last_month;
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short last_day;
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unsigned int play_count;
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unsigned int length;
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string title;
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string length_str;
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string filepath;
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};
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File << artist_id << album_id << genre_id << library_id << track << last_year
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File << last_year << last_month << last_day << play_count << length << endl
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File << title << endl;
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File << filepath << endl;
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- Track: /* This struct lies outside the library namespace */
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struct Track {
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library :: Album *album;
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library :: Artist *artist;
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library :: Genre *genre;
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library :: Library *library;
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library :: Track *track;
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};
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- Databases:
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Database<library :: Album> album_db(album.db);
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Database<library :: Artist> artist_db(artist.db);
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Database<library :: Album> genre_db(genre.db);
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Database<library :: Library> library_db(library.db);
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Database<library :: Track> track_db(track.db);
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- Updating algorithm:
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set<pair<lib_id, track_path>> known_tracks;
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1) For each track currently in the library, check if the track exists
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in the filesystem.
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1a) If the track does exist, add to the known_tracks map.
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1b) Else, mark track invalid.
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2) For each file in the scan directory, check if (lib_id, track_path)
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exists in the known_tracks map.
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2a) If the file is in the map, do nothing.
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2b) Else, add track to the library, to the groups "All Music" and
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"Library", and then to the filter index.
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3) Save all databases
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The taglib library should be used for finding artist, album, etc. tags
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for each track.
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Use idle tasks for step 2 to break up tagging new files into chunks.
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This way the user will still be able to use Ocarina and scanning can
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happen while idle.
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- API
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library :: init();
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Initialize all databases
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library :: add_path(string dir);
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Add new row to paths table, update
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library :: del_path(unsigned int lib_id);
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Invalidate a path row
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library :: update_path(lib_id);
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Update the given library path, if valid.
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const Database<LibraryEntry> &library :: get_db();
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Returns the database containing library information.
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struct Track library :: resolve(track_id)
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Fill out a Track structure for the provided track_id
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Playlist: (lib/playlist.cpp)
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Playlists are a list of songs that the user has configured to play. I
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will create a pool of playlists that will be filled by user actions.
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Playlists will be put on a "deck" that is used to give an order to the
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next songs played. When deck :: next() is called, find the first
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playlist with PL_ENABLED set and call that playlists next() function.
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When a playlist is empty, remove it from the deck.
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- Flags:
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enum playlist_flags {
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PL_ENABLED (1 << 0),
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PL_RANDOM (1 << 1),
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PL_DRAIN (1 << 2),
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};
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- Playlist:
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class Playlist : public Database {
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private:
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database<track_id> tracks; /* Keyed on track id */
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unsigned int cur;
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unsigned int flags;
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public:
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Playlist();
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void add(vector<track_id> &);
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void del(vector<track_id> &);
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void set_flag(playlist_flags);
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const unsigned int get_flags();
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unsigned int size()
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File &operator<<(File &);
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File &operator>>(File &);
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void sort();
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void next();
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}
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File << flags << cur << tracks[0] << tracks[1] << ... << tracks[N];
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- Deck:
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list<Playlist> deck;
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File << deck[0] << endl;
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File << deck[1] << endl;
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File << deck[N] << endl;
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- API
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deck :: init();
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Read in the playlist file
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deck :: new();
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Adds a new playlist to the deck
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deck :: rm(N)
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Removes playlist N from the deck
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Playlist *deck :: get(N)
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Return playlist N from the deck
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- TODO <<<<<
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What if each playlist has its own playlist_id for tracks? This would
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allow for simpler removals, since I won't need to search for a track id.
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I can easily create a function for mapping a list of playlist_ids to
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track_ids...
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Preferences: (lib/prefs.cpp)
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Preferences make use of a special index where the set<int> is always
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size 1. Preferences will be in the prefs namespace.
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- Index:
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Index prefs(prefs.idx);
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- API:
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prefs :: set(string, val);
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prefs.replace(string, val);
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prefs :: get(string)
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return prefs[string].begin()
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Future work:
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I want to set reasonable expectations for Ocarina 6 so that I don't
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have to spend a large amount of time coding before releasing something
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to the wild. This section will be a list of features that I want, but
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should be deferred to a future release so basic support can be coded.
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Hint: If feature B depends on A, implement A in 6.x and B in 6.x+1
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- New default groups: (6.1)
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Unplayed tracks
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- Categories: (6.1)
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Use these to make "groups of groups" for better organization.
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Different categories can include Album, Artist and Genere
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dynamic groups in addition to user created groups (see below)
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The Artist, Album and Genre "tables" can be used to populate
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these categories.
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- User created song groups: (6.2)
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Basic add and remove features can be implemented using the
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Library and Banned Songs groups. This will give me a chance
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to test saving groups on a small scale before letting users
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create anything they want.
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- Save a user's playlist as a group: (6.2)
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- Library defragment: (6.1)
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Ocarina 6.0 will leave holes in the library when tracks are
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deleted, potentially leading to fragmentation and larger-than-
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needed file sizes. A "defragment" utility can be created to
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clean up unused slots.
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To help with fixing groups, a mapping of (old values) ->
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(new values) should be kept.
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- Fix track durations: (6.1)
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Some tracks in my library are tagged with the wrong duration,
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so fix them as they are played.
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- Track tag editor: (6.2)
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Make a pop-up window for editing the tags of a track. Be sure
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to update the library information and the on-disk file.
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- Album art: (6.1)
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- Playlist custom sorting: (6.1)
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Click column headers to choos sort order
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Keep a list of fields that the user has selected and place new
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fields in the front of this list. Use a recursive stable sort
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to do the sorting.
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