TagExt: Add TagExt::len

CHANGELOG.md

@@ -25,6 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **OGG**: `OggPictureStorage`
   - This was added to cover the overlap in functionality between `VorbisComments` and `FlacFile` in that they both
     store `(Picture, PictureInformation)`.
+- **TagExt**: `TagExt::len`
 
 ### Changed
 - **MP4**: `AtomIdent` stores freeform identifiers as `Cow<str>` opposed to `String` ([PR](https://github.com/Serial-ATA/lofty-rs/pull/95))

src/ape/tag/mod.rs

@@ -214,6 +214,10 @@ impl TagExt for ApeTag {
 	type Err = LoftyError;
 	type RefKey<'a> = &'a str;
 
+	fn len(&self) -> usize {
+		self.items.len()
+	}
+
 	fn contains<'a>(&'a self, key: Self::RefKey<'a>) -> bool {
 		self.items.iter().any(|i| i.key().eq_ignore_ascii_case(key))
 	}

src/id3/v1/tag.rs

@@ -175,6 +175,16 @@ impl TagExt for ID3v1Tag {
 	type Err = LoftyError;
 	type RefKey<'a> = &'a ItemKey;
 
+	fn len(&self) -> usize {
+		usize::from(self.title.is_some())
+			+ usize::from(self.artist.is_some())
+			+ usize::from(self.album.is_some())
+			+ usize::from(self.year.is_some())
+			+ usize::from(self.comment.is_some())
+			+ usize::from(self.track_number.is_some())
+			+ usize::from(self.genre.is_some())
+	}
+
 	fn contains<'a>(&'a self, key: Self::RefKey<'a>) -> bool {
 		match key {
 			ItemKey::TrackTitle => self.title.is_some(),

src/id3/v2/tag.rs

@@ -440,6 +440,10 @@ impl TagExt for ID3v2Tag {
 	type Err = LoftyError;
 	type RefKey<'a> = &'a FrameID<'a>;
 
+	fn len(&self) -> usize {
+		self.frames.len()
+	}
+
 	fn contains<'a>(&'a self, key: Self::RefKey<'a>) -> bool {
 		self.frames.iter().any(|frame| &frame.id == key)
 	}

src/iff/aiff/tag.rs

@@ -140,6 +140,14 @@ impl TagExt for AIFFTextChunks {
 	type Err = LoftyError;
 	type RefKey<'a> = &'a ItemKey;
 
+	fn len(&self) -> usize {
+		usize::from(self.name.is_some())
+			+ usize::from(self.author.is_some())
+			+ usize::from(self.copyright.is_some())
+			+ self.annotations.as_ref().map_or(0, Vec::len)
+			+ self.comments.as_ref().map_or(0, Vec::len)
+	}
+
 	fn contains<'a>(&'a self, key: Self::RefKey<'a>) -> bool {
 		match key {
 			ItemKey::TrackTitle => self.name.is_some(),

src/iff/wav/tag/mod.rs

@@ -134,6 +134,10 @@ impl TagExt for RIFFInfoList {
 	type Err = LoftyError;
 	type RefKey<'a> = &'a str;
 
+	fn len(&self) -> usize {
+		self.items.len()
+	}
+
 	fn contains<'a>(&'a self, key: Self::RefKey<'a>) -> bool {
 		self.items
 			.iter()

src/mp4/ilst/mod.rs

@@ -341,6 +341,10 @@ impl TagExt for Ilst {
 	type Err = LoftyError;
 	type RefKey<'a> = &'a AtomIdent<'a>;
 
+	fn len(&self) -> usize {
+		self.atoms.len()
+	}
+
 	fn contains<'a>(&'a self, key: Self::RefKey<'a>) -> bool {
 		self.atoms.iter().any(|atom| &atom.ident == key)
 	}

src/ogg/tag.rs

@@ -245,6 +245,10 @@ impl TagExt for VorbisComments {
 	type Err = LoftyError;
 	type RefKey<'a> = &'a str;
 
+	fn len(&self) -> usize {
+		self.items.len() + self.pictures.len()
+	}
+
 	fn contains<'a>(&'a self, key: Self::RefKey<'a>) -> bool {
 		self.items
 			.iter()

src/tag/mod.rs

@@ -520,6 +520,10 @@ impl TagExt for Tag {
 	type Err = LoftyError;
 	type RefKey<'a> = &'a ItemKey;
 
+	fn len(&self) -> usize {
+		self.items.len() + self.pictures.len()
+	}
+
 	fn contains<'a>(&'a self, key: Self::RefKey<'a>) -> bool {
 		self.items.iter().any(|item| item.key() == key)
 	}

src/traits.rs

@@ -138,6 +138,24 @@ pub trait TagExt: Accessor + Into<Tag> + Sized {
 	where
 		Self: 'a;
 
+	/// Returns the number of items in the tag
+	///
+	/// This will also include any extras, such as pictures.
+	///
+	/// # Example
+	///
+	/// ```rust
+	/// use lofty::{Accessor, ItemKey, Tag, TagExt};
+	/// # let tag_type = lofty::TagType::ID3v2;
+	///
+	/// let mut tag = Tag::new(tag_type);
+	/// assert_eq!(tag.len(), 0);
+	///
+	/// tag.set_artist(String::from("Foo artist"));
+	/// assert_eq!(tag.len(), 1);
+	/// ```
+	fn len(&self) -> usize;
+
 	/// Whether the tag contains an item with the key
 	///
 	/// # Example