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/*
* Copyright 2003-2021 The Music Player Daemon Project
* http://www.musicpd.org
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef MPD_TAG_HANDLER_HXX
#define MPD_TAG_HANDLER_HXX
#include "Type.h"
#include "Chrono.hxx"
#include "util/Compiler.h"
template<typename T> struct ConstBuffer;
struct StringView;
struct AudioFormat;
class TagBuilder;
/**
* An interface for receiving metadata of a song.
*/
class TagHandler {
const unsigned want_mask;
public:
static constexpr unsigned WANT_DURATION = 0x1;
static constexpr unsigned WANT_TAG = 0x2;
static constexpr unsigned WANT_PAIR = 0x4;
static constexpr unsigned WANT_AUDIO_FORMAT = 0x8;
static constexpr unsigned WANT_PICTURE = 0x10;
explicit TagHandler(unsigned _want_mask) noexcept
:want_mask(_want_mask) {}
TagHandler(const TagHandler &) = delete;
TagHandler &operator=(const TagHandler &) = delete;
bool WantDuration() const noexcept {
return want_mask & WANT_DURATION;
}
bool WantTag() const noexcept {
return want_mask & WANT_TAG;
}
bool WantPair() const noexcept {
return want_mask & WANT_PAIR;
}
bool WantAudioFormat() const noexcept {
return want_mask & WANT_AUDIO_FORMAT;
}
bool WantPicture() const noexcept {
return want_mask & WANT_PICTURE;
}
/**
* Declare the duration of a song. Do not call
* this when the duration could not be determined, because
* there is no magic value for "unknown duration".
*/
virtual void OnDuration(SongTime duration) noexcept = 0;
/**
* A tag has been read.
*
* @param the value of the tag; the pointer will become
* invalid after returning
*/
virtual void OnTag(TagType type, StringView value) noexcept = 0;
/**
* A name-value pair has been read. It is the codec specific
* representation of tags.
*/
virtual void OnPair(StringView key, StringView value) noexcept = 0;
/**
* Declare the audio format of a song.
*
* Because the #AudioFormat type is limited to formats
* supported by MPD, the value passed to this method may be an
* approximation (should be the one passed to
* DecoderClient::Ready()). For example, some codecs such as
* MP3 are bit depth agnostic, so the decoder plugin chooses a
* bit depth depending on what the codec library emits.
*
* This method is only called by those decoder plugins which
* implement it. Some may not have any code for calling it,
* and others may decide that determining the audio format is
* too expensive.
*/
virtual void OnAudioFormat(AudioFormat af) noexcept = 0;
/**
* A picture has been read.
*
* This method will only be called if #WANT_PICTURE was enabled.
*
* @param mime_type an optional MIME type string
* @param buffer the picture file contents; the buffer will be
* invalidated after this method returns
*/
virtual void OnPicture(const char *mime_type,
ConstBuffer<void> buffer) noexcept = 0;
};
class NullTagHandler : public TagHandler {
public:
explicit NullTagHandler(unsigned _want_mask) noexcept
:TagHandler(_want_mask) {}
void OnDuration([[maybe_unused]] SongTime duration) noexcept override {}
void OnTag(TagType type, StringView value) noexcept override;
void OnPair(StringView key, StringView value) noexcept override;
void OnAudioFormat(AudioFormat af) noexcept override;
void OnPicture(const char *mime_type,
ConstBuffer<void> buffer) noexcept override;
};
/**
* This #TagHandler implementation adds tag values to a #TagBuilder
* object.
*/
class AddTagHandler : public NullTagHandler {
protected:
TagBuilder &tag;
AddTagHandler(unsigned _want_mask, TagBuilder &_builder) noexcept
:NullTagHandler(WANT_DURATION|WANT_TAG|_want_mask),
tag(_builder) {}
public:
explicit AddTagHandler(TagBuilder &_builder) noexcept
:AddTagHandler(0, _builder) {}
void OnDuration(SongTime duration) noexcept override;
void OnTag(TagType type, StringView value) noexcept override;
};
/**
* This #TagHandler implementation adds tag values to a #TagBuilder object
* (casted from the context pointer), and supports the has_playlist
* attribute.
*/
class FullTagHandler : public AddTagHandler {
AudioFormat *const audio_format;
protected:
FullTagHandler(unsigned _want_mask, TagBuilder &_builder,
AudioFormat *_audio_format) noexcept
:AddTagHandler(WANT_PAIR|_want_mask
|(_audio_format ? WANT_AUDIO_FORMAT : 0),
_builder),
audio_format(_audio_format) {}
public:
explicit FullTagHandler(TagBuilder &_builder,
AudioFormat *_audio_format=nullptr) noexcept
:FullTagHandler(0, _builder, _audio_format) {}
void OnPair(StringView key, StringView value) noexcept override;
void OnAudioFormat(AudioFormat af) noexcept override;
};
#endif
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