Use static polymorphism in FieldMapBasedTag

fieldbasedtag.h

@@ -24,18 +24,17 @@ class FieldMapBasedTagTraits
  *        the tag fields using std::multimap.
  *
  * The FieldMapBasedTag class only provides the interface and common functionality.
- * It is meant to be subclassed.
+ * It is meant to be subclassed using CRTP pattern.
  *
- * \tparam FieldType Specifies the class used to store the fields. Should be a subclass
+ * \remarks This template class is intended to be subclassed using
- *                   of TagField.
+ *          with the "Curiously recurring template pattern".
- *
- * \tparam Compare Specifies the key comparsion function. Default is std::less.
  */
 template <class ImplementationType>
 class FieldMapBasedTag : public Tag
 {
-public:
     friend class FieldMapBasedTagTraits<ImplementationType>;
+
+public:
     typedef typename FieldMapBasedTagTraits<ImplementationType>::implementationType implementationType;
     typedef typename FieldMapBasedTagTraits<ImplementationType>::fieldType fieldType;
     typedef typename FieldMapBasedTagTraits<ImplementationType>::fieldType::identifierType identifierType;
@@ -46,29 +45,37 @@ public:
     TagType type() const;
     const char *typeName() const;
     TagTextEncoding proposedTextEncoding() const;
-    virtual const TagValue &value(const identifierType &id) const; // FIXME: use static polymorphism
+    const TagValue &value(const identifierType &id) const;
     const TagValue &value(KnownField field) const;
     std::vector<const TagValue *> values(const identifierType &id) const;
     std::vector<const TagValue *> values(KnownField field) const;
-    virtual bool setValue(const identifierType &id, const TagValue &value); // FIXME: use static polymorphism
+    bool setValue(const identifierType &id, const TagValue &value);
     bool setValue(KnownField field, const TagValue &value);
     bool setValues(const identifierType &id, const std::vector<TagValue> &values);
     bool setValues(KnownField field, const std::vector<TagValue> &values);
     bool hasField(KnownField field) const;
-    virtual bool hasField(const identifierType &id) const; // FIXME: use static polymorphism
+    bool hasField(const identifierType &id) const;
     void removeAllFields();
     const std::multimap<identifierType, fieldType, compare> &fields() const;
     std::multimap<identifierType, fieldType, compare> &fields();
     unsigned int fieldCount() const;
-    virtual identifierType fieldId(KnownField value) const = 0; // FIXME: use static polymorphism
+    identifierType fieldId(KnownField value) const;
-    virtual KnownField knownField(const identifierType &id) const = 0; // FIXME: use static polymorphism
+    KnownField knownField(const identifierType &id) const;
     bool supportsField(KnownField field) const;
     using Tag::proposedDataType;
-    virtual TagDataType proposedDataType(const identifierType &id) const; // FIXME: use static polymorphism
+    TagDataType proposedDataType(const identifierType &id) const;
     int insertFields(const FieldMapBasedTag<ImplementationType> &from, bool overwrite);
     unsigned int insertValues(const Tag &from, bool overwrite);
     void ensureTextValuesAreProperlyEncoded();
 
+protected:
+    const TagValue &internallyGetValue(const identifierType &id) const;
+    bool internallySetValue(const identifierType &id, const TagValue &value);
+    bool internallyHasField(const identifierType &id) const;
+    // no default implementation: identifierType internallyGetFieldId(KnownField field) const;
+    // no default implementation: KnownField internallyGetKnownField(const identifierType &id) const;
+    TagDataType internallyGetProposedDataType(const identifierType &id) const;
+
 private:
     std::multimap<identifierType, fieldType, compare> m_fields;
 };
@@ -112,6 +119,17 @@ TagTextEncoding FieldMapBasedTag<ImplementationType>::proposedTextEncoding() con
     return ImplementationType::defaultTextEncoding;
 }
 
+/*!
+ * \brief Default implementation for value().
+ * \remarks Shadow in subclass to provide custom implementation.
+ */
+template<class ImplementationType>
+const TagValue &FieldMapBasedTag<ImplementationType>::internallyGetValue(const identifierType &id) const
+{
+    auto i = m_fields.find(id);
+    return i != m_fields.end() ? i->second.value() : TagValue::empty();
+}
+
 /*!
  * \brief Returns the value of the field with the specified \a id.
  * \sa Tag::value()
@@ -119,8 +137,7 @@ TagTextEncoding FieldMapBasedTag<ImplementationType>::proposedTextEncoding() con
 template <class ImplementationType>
 inline const TagValue &FieldMapBasedTag<ImplementationType>::value(const identifierType &id) const
 {
-    auto i = m_fields.find(id);
+    return static_cast<const ImplementationType *>(this)->internallyGetValue(id);
-    return i != m_fields.end() ? i->second.value() : TagValue::empty();
 }
 
 template <class ImplementationType>
@@ -159,11 +176,11 @@ inline bool FieldMapBasedTag<ImplementationType>::setValue(KnownField field, con
 }
 
 /*!
- * \brief Assigns the given \a value to the field with the specified \a id.
+ * \brief Default implementation for setValue().
- * \sa Tag::setValue()
+ * \remarks Shadow in subclass to provide custom implementation.
  */
-template <class ImplementationType>
+template<class ImplementationType>
-bool FieldMapBasedTag<ImplementationType>::setValue(const identifierType &id, const Media::TagValue &value)
+bool FieldMapBasedTag<ImplementationType>::internallySetValue(const identifierType &id, const TagValue &value)
 {
     auto i = m_fields.find(id);
     if(i != m_fields.end()) { // field already exists -> set its value
@@ -176,6 +193,16 @@ bool FieldMapBasedTag<ImplementationType>::setValue(const identifierType &id, co
     return true;
 }
 
+/*!
+ * \brief Assigns the given \a value to the field with the specified \a id.
+ * \sa Tag::setValue()
+ */
+template <class ImplementationType>
+bool FieldMapBasedTag<ImplementationType>::setValue(const identifierType &id, const Media::TagValue &value)
+{
+    return static_cast<ImplementationType *>(this)->internallySetValue(id, value);
+}
+
 /*!
  * \brief Assigns the given \a values to the field with the specified \a id.
  * \remarks There might me more than one value assigned to an \a id. Whereas setValue() only alters the first value, this
@@ -225,10 +252,11 @@ inline bool FieldMapBasedTag<ImplementationType>::hasField(KnownField field) con
 }
 
 /*!
- * \brief Returns an indication whether the field with the specified \a id is present.
+ * \brief Default implementation for hasField().
+ * \remarks Shadow in subclass to provide custom implementation.
  */
-template <class ImplementationType>
+template<class ImplementationType>
-inline bool FieldMapBasedTag<ImplementationType>::hasField(const identifierType &id) const
+bool FieldMapBasedTag<ImplementationType>::internallyHasField(const identifierType &id) const
 {
     for (auto range = m_fields.equal_range(id); range.first != range.second; ++range.first) {
         if(!range.first->second.value().isEmpty()) {
@@ -238,6 +266,15 @@ inline bool FieldMapBasedTag<ImplementationType>::hasField(const identifierType
     return false;
 }
 
+/*!
+ * \brief Returns an indication whether the field with the specified \a id is present.
+ */
+template <class ImplementationType>
+inline bool FieldMapBasedTag<ImplementationType>::hasField(const identifierType &id) const
+{
+    return static_cast<const ImplementationType *>(this)->internallyHasField(id);
+}
+
 template <class ImplementationType>
 inline void FieldMapBasedTag<ImplementationType>::removeAllFields()
 {
@@ -274,6 +311,26 @@ unsigned int FieldMapBasedTag<ImplementationType>::fieldCount() const
     return count;
 }
 
+/*!
+ * \brief Returns the field ID for the specified \a value.
+ * \remarks Must be implemented in internallyGetFieldId() when creating subclass.
+ */
+template<class ImplementationType>
+inline typename FieldMapBasedTag<ImplementationType>::identifierType FieldMapBasedTag<ImplementationType>::fieldId(KnownField value) const
+{
+    return static_cast<const ImplementationType *>(this)->internallyGetFieldId(value);
+}
+
+/*!
+ * \brief Returns the KnownField for the specified \a id.
+ * \remarks Must be implemented in internallyGetKnownField() when creating subclass.
+ */
+template<class ImplementationType>
+inline KnownField FieldMapBasedTag<ImplementationType>::knownField(const identifierType &id) const
+{
+    return static_cast<FieldMapBasedTag<ImplementationType> *>(this)->internallyGetKnownField(id);
+}
+
 template <class ImplementationType>
 inline bool FieldMapBasedTag<ImplementationType>::supportsField(KnownField field) const
 {
@@ -281,13 +338,23 @@ inline bool FieldMapBasedTag<ImplementationType>::supportsField(KnownField field
     return fieldId(field) != def;
 }
 
+/*!
+ * \brief Default implementation for proposedDataType().
+ * \remarks Shadow in subclass to provide custom implementation.
+ */
+template<class ImplementationType>
+inline TagDataType FieldMapBasedTag<ImplementationType>::internallyGetProposedDataType(const identifierType &id) const
+{
+    return Tag::proposedDataType(knownField(id));
+}
+
 /*!
  * \brief Returns the proposed data type for the field with the specified \a id.
  */
 template <class ImplementationType>
 inline TagDataType FieldMapBasedTag<ImplementationType>::proposedDataType(const identifierType &id) const
 {
-    return Tag::proposedDataType(knownField(id));
+    return static_cast<ImplementationType *>(this)->determineProposedDataType(id);
 }
 
 /*!

genericfileelement.h

@@ -108,8 +108,9 @@ class FileElementTraits
  * \class Media::GenericFileElement
  * \brief The GenericFileElement class helps to parse binary files which consist
  *        of an arboreal element strucutre.
- *
  * \tparam ImplementationType Specifies the type of the actual implementation.
+ * \remarks This template class is intended to be subclassed using
+ *          with the "Curiously recurring template pattern".
  */
 template <class ImplementationType>
 class TAG_PARSER_EXPORT GenericFileElement : public StatusProvider

generictagfield.h

@@ -25,7 +25,8 @@ class TagFieldTraits
  * might be assigned as well. The usage of the type info depends on the
  * particular tag implementation.
  *
- * \remarks This template class is intended to be used
+ * \tparam ImplementationType Specifies the type of the actual implementation.
+ * \remarks This template class is intended to be subclassed using
  *          with the "Curiously recurring template pattern".
  */
 template <class ImplementationType>

id3/id3v2tag.cpp

@@ -17,7 +17,7 @@ namespace Media {
  * \brief Implementation of Media::Tag for ID3v2 tags.
  */
 
-uint32 Id3v2Tag::fieldId(KnownField field) const
+Id3v2Tag::identifierType Id3v2Tag::internallyGetFieldId(KnownField field) const
 {
     using namespace Id3v2FrameIds;
     if(m_majorVersion >= 3) {
@@ -78,7 +78,7 @@ uint32 Id3v2Tag::fieldId(KnownField field) const
     return 0;
 }
 
-KnownField Id3v2Tag::knownField(const uint32 &id) const
+KnownField Id3v2Tag::internallyGetKnownField(const identifierType &id) const
 {
     using namespace Id3v2FrameIds;
     switch(id) {
@@ -125,7 +125,7 @@ KnownField Id3v2Tag::knownField(const uint32 &id) const
     }
 }
 
-TagDataType Id3v2Tag::proposedDataType(const uint32 &id) const
+TagDataType Id3v2Tag::internallyGetProposedDataType(const uint32 &id) const
 {
     using namespace Id3v2FrameIds;
     switch(id) {

id3/id3v2tag.h

@@ -66,6 +66,8 @@ public:
 
 class TAG_PARSER_EXPORT Id3v2Tag : public FieldMapBasedTag<Id3v2Tag>
 {
+    friend class FieldMapBasedTag<Id3v2Tag>;
+
 public:
     Id3v2Tag();
 
@@ -74,11 +76,6 @@ public:
     static constexpr TagTextEncoding defaultTextEncoding = TagTextEncoding::Utf16LittleEndian;
     TagTextEncoding proposedTextEncoding() const;
     bool canEncodingBeUsed(TagTextEncoding encoding) const;
-    uint32 fieldId(KnownField value) const;
-    KnownField knownField(const uint32 &id) const;
-    TagDataType proposedDataType(const uint32 &id) const;
-    using FieldMapBasedTag<Id3v2Tag>::value;
-    using FieldMapBasedTag<Id3v2Tag>::setValue;
     bool supportsDescription(KnownField field) const;
     bool supportsMimeType(KnownField field) const;
 
@@ -98,6 +95,11 @@ public:
     uint32 extendedHeaderSize() const;
     uint32 paddingSize() const;
 
+protected:
+    identifierType internallyGetFieldId(KnownField field) const;
+    KnownField internallyGetKnownField(const identifierType &id) const;
+    TagDataType internallyGetProposedDataType(const uint32 &id) const;
+
 private:
     byte m_majorVersion;
     byte m_revisionVersion;

matroska/matroskatag.cpp

@@ -15,7 +15,7 @@ namespace Media {
  * \brief Implementation of Media::Tag for the Matroska container.
  */
 
-std::string MatroskaTag::fieldId(KnownField field) const
+MatroskaTag::identifierType MatroskaTag::internallyGetFieldId(KnownField field) const
 {
     using namespace MatroskaTagIds;
     switch(field) {
@@ -45,7 +45,7 @@ std::string MatroskaTag::fieldId(KnownField field) const
     }
 }
 
-KnownField MatroskaTag::knownField(const std::string &id) const
+KnownField MatroskaTag::internallyGetKnownField(const identifierType &id) const
 {
     using namespace MatroskaTagIds;
     static const map<string, KnownField> map({

matroska/matroskatag.h

@@ -61,6 +61,8 @@ public:
 
 class TAG_PARSER_EXPORT MatroskaTag : public FieldMapBasedTag<MatroskaTag>
 {
+    friend class FieldMapBasedTag<MatroskaTag>;
+
 public:
     MatroskaTag();
 
@@ -71,13 +73,14 @@ public:
     bool supportsTarget() const;
     TagTargetLevel targetLevel() const;
 
-    std::string fieldId(KnownField field) const;
-    KnownField knownField(const std::string &id) const;
-
     void parse(EbmlElement &tagElement);
     MatroskaTagMaker prepareMaking();
     void make(std::ostream &stream);
 
+protected:
+    identifierType internallyGetFieldId(KnownField field) const;
+    KnownField internallyGetKnownField(const identifierType &id) const;
+
 private:
     void parseTargets(EbmlElement &targetsElement);
 };

mp4/mp4tag.cpp

@@ -119,7 +119,7 @@ const TagValue &Mp4Tag::value(const string mean, const string name) const
     return (this->*static_cast<const TagValue &(Mp4Tag::*)(const string &, const string &) const>(&Mp4Tag::value))(mean, name);
 }
 
-uint32 Mp4Tag::fieldId(KnownField field) const
+Mp4Tag::identifierType Mp4Tag::internallyGetFieldId(KnownField field) const
 {
     using namespace Mp4TagAtomIds;
     switch(field) {
@@ -146,7 +146,7 @@ uint32 Mp4Tag::fieldId(KnownField field) const
     }
 }
 
-KnownField Mp4Tag::knownField(const uint32 &id) const
+KnownField Mp4Tag::internallyGetKnownField(const identifierType &id) const
 {
     using namespace Mp4TagAtomIds;
     switch(id) {

mp4/mp4tag.h

@@ -101,6 +101,8 @@ public:
 
 class TAG_PARSER_EXPORT Mp4Tag : public FieldMapBasedTag<Mp4Tag>
 {
+    friend class FieldMapBasedTag<Mp4Tag>;
+
 public:
     Mp4Tag();
 
@@ -109,8 +111,6 @@ public:
     static constexpr TagTextEncoding defaultTextEncoding = TagTextEncoding::Utf8;
     bool canEncodingBeUsed(TagTextEncoding encoding) const;
 
-    uint32 fieldId(KnownField field) const;
-    KnownField knownField(const uint32 &id) const;
     bool supportsField(KnownField field) const;
     using FieldMapBasedTag<Mp4Tag>::value;
     const TagValue &value(KnownField value) const;
@@ -136,6 +136,11 @@ public:
     void parse(Mp4Atom &metaAtom);
     Mp4TagMaker prepareMaking();
     void make(std::ostream &stream);
+
+protected:
+    identifierType internallyGetFieldId(KnownField field) const;
+    KnownField internallyGetKnownField(const identifierType &id) const;
+
 };
 
 /*!

vorbis/vorbiscomment.cpp

@@ -44,7 +44,7 @@ bool VorbisComment::setValue(KnownField field, const TagValue &value)
     }
 }
 
-string VorbisComment::fieldId(KnownField field) const
+VorbisComment::identifierType VorbisComment::internallyGetFieldId(KnownField field) const
 {
     using namespace VorbisCommentIds;
     switch(field) {
@@ -70,7 +70,7 @@ string VorbisComment::fieldId(KnownField field) const
     }
 }
 
-KnownField VorbisComment::knownField(const string &id) const
+KnownField VorbisComment::internallyGetKnownField(const identifierType &id) const
 {
     using namespace VorbisCommentIds;
     static const map<string, KnownField> fieldMap({

vorbis/vorbiscomment.h

@@ -26,6 +26,8 @@ public:
 
 class TAG_PARSER_EXPORT VorbisComment : public FieldMapBasedTag<VorbisComment>
 {
+    friend class FieldMapBasedTag<VorbisComment>;
+
 public:
     VorbisComment();
 
@@ -34,10 +36,10 @@ public:
     static constexpr TagTextEncoding defaultTextEncoding = TagTextEncoding::Utf8;
     bool canEncodingBeUsed(TagTextEncoding encoding) const;
 
+    using FieldMapBasedTag<VorbisComment>::value;
     const TagValue &value(KnownField field) const;
+    using FieldMapBasedTag<VorbisComment>::setValue;
     bool setValue(KnownField field, const TagValue &value);
-    std::string fieldId(KnownField field) const;
-    KnownField knownField(const std::string &id) const;
 
     void parse(OggIterator &iterator, VorbisCommentFlags flags = VorbisCommentFlags::None);
     void parse(std::istream &stream, uint64 maxSize, VorbisCommentFlags flags = VorbisCommentFlags::None);
@@ -46,6 +48,10 @@ public:
     const TagValue &vendor() const;
     void setVendor(const TagValue &vendor);
 
+protected:
+    identifierType internallyGetFieldId(KnownField field) const;
+    KnownField internallyGetKnownField(const identifierType &id) const;
+
 private:
     template<class StreamType>
     void internalParse(StreamType &stream, uint64 maxSize, VorbisCommentFlags flags);