EBML: Make SimpleTag creation easier

Author: Serial-ATA

lofty/src/ebml/read/segment_tags.rs

@@ -28,7 +28,7 @@ where
 	Ok(())
 }
 
-fn read_tag<R>(children_reader: &mut ElementChildIterator<'_, R>) -> Result<Tag>
+fn read_tag<R>(children_reader: &mut ElementChildIterator<'_, R>) -> Result<Tag<'static>>
 where
 	R: Read + Seek,
 {
@@ -132,7 +132,9 @@ where
 	Ok(target)
 }
 
-fn read_simple_tag<R>(children_reader: &mut ElementChildIterator<'_, R>) -> Result<SimpleTag>
+fn read_simple_tag<R>(
+	children_reader: &mut ElementChildIterator<'_, R>,
+) -> Result<SimpleTag<'static>>
 where
 	R: Read + Seek,
 {
@@ -185,7 +187,7 @@ where
 					continue;
 				}
 
-				value = Some(TagValue::String(children_reader.read_string(size.value())?));
+				value = Some(TagValue::from(children_reader.read_string(size.value())?));
 			},
 			ElementIdent::TagBinary => {
 				if value.is_some() {
@@ -194,7 +196,7 @@ where
 					continue;
 				}
 
-				value = Some(TagValue::Binary(children_reader.read_binary(size.value())?));
+				value = Some(TagValue::from(children_reader.read_binary(size.value())?));
 			},
 			_ => {
 				unreachable!(
@@ -212,7 +214,7 @@ where
 	};
 
 	Ok(SimpleTag {
-		name,
+		name: name.into(),
 		language,
 		default,
 		value,

lofty/src/ebml/tag/mod.rs

@@ -24,7 +24,7 @@ use lofty_attr::tag;
 #[derive(Default, Debug, PartialEq, Eq, Clone)]
 #[tag(description = "An `EBML` tag", supported_formats(Ebml))]
 pub struct EbmlTag {
-	pub(crate) tags: Vec<Tag>,
+	pub(crate) tags: Vec<Tag<'static>>,
 	pub(crate) attached_files: Vec<AttachedFile>,
 }
 
@@ -40,11 +40,7 @@ impl TagExt for EbmlTag {
 	}
 
 	fn len(&self) -> usize {
-		self.tags
-			.iter()
-			.map(|tag| tag.simple_tags.len())
-			.sum::<usize>()
-			+ self.attached_files.len()
+		self.tags.iter().map(Tag::len).sum::<usize>() + self.attached_files.len()
 	}
 
 	fn contains<'a>(&'a self, _key: Self::RefKey<'a>) -> bool {

lofty/src/ebml/tag/simple_tag.rs

@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 use crate::tag::ItemValue;
 
 /// The language of a [`SimpleTag`] or chapter
@@ -35,27 +37,72 @@ pub enum Language {
 /// - [`ItemValue::Text`] | [`ItemValue::Locator`] -> [`TagValue::String`]
 /// - [`ItemValue::Binary`] -> [`TagValue::Binary`]
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub enum TagValue {
+pub enum TagValue<'a> {
 	/// A UTF-8 string tag value
-	String(String),
+	String(Cow<'a, str>),
 	/// A binary tag value
-	Binary(Vec<u8>),
+	Binary(Cow<'a, [u8]>),
 }
 
-impl From<TagValue> for ItemValue {
-	fn from(value: TagValue) -> Self {
+impl From<TagValue<'_>> for ItemValue {
+	fn from(value: TagValue<'_>) -> Self {
 		match value {
-			TagValue::String(s) => ItemValue::Text(s),
-			TagValue::Binary(b) => ItemValue::Binary(b),
+			TagValue::String(s) => ItemValue::Text(s.into_owned()),
+			TagValue::Binary(b) => ItemValue::Binary(b.into_owned()),
 		}
 	}
 }
 
-impl From<ItemValue> for TagValue {
+impl From<ItemValue> for TagValue<'_> {
 	fn from(value: ItemValue) -> Self {
 		match value {
-			ItemValue::Text(s) | ItemValue::Locator(s) => TagValue::String(s),
-			ItemValue::Binary(b) => TagValue::Binary(b),
+			ItemValue::Text(s) | ItemValue::Locator(s) => TagValue::String(Cow::Owned(s)),
+			ItemValue::Binary(b) => TagValue::Binary(Cow::Owned(b)),
+		}
+	}
+}
+
+impl From<String> for TagValue<'_> {
+	fn from(value: String) -> Self {
+		TagValue::String(value.into())
+	}
+}
+
+impl<'a> From<Cow<'a, str>> for TagValue<'a> {
+	fn from(value: Cow<'a, str>) -> Self {
+		TagValue::String(value)
+	}
+}
+
+impl<'a> From<&'a str> for TagValue<'a> {
+	fn from(value: &'a str) -> Self {
+		TagValue::String(Cow::Borrowed(value))
+	}
+}
+
+impl From<Vec<u8>> for TagValue<'_> {
+	fn from(value: Vec<u8>) -> Self {
+		TagValue::Binary(value.into())
+	}
+}
+
+impl<'a> From<Cow<'a, [u8]>> for TagValue<'a> {
+	fn from(value: Cow<'a, [u8]>) -> Self {
+		TagValue::Binary(value)
+	}
+}
+
+impl<'a> From<&'a [u8]> for TagValue<'a> {
+	fn from(value: &'a [u8]) -> Self {
+		TagValue::Binary(Cow::Borrowed(value))
+	}
+}
+
+impl TagValue<'_> {
+	fn into_owned(self) -> TagValue<'static> {
+		match self {
+			TagValue::String(s) => TagValue::String(Cow::Owned(s.into_owned())),
+			TagValue::Binary(b) => TagValue::Binary(Cow::Owned(b.into_owned())),
 		}
 	}
 }
@@ -69,7 +116,7 @@ impl From<ItemValue> for TagValue {
 ///   - This also means that multiple tags can describe the same target.
 /// - They **do not** need to have a value.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct SimpleTag {
+pub struct SimpleTag<'a> {
 	/// The name of the tag as it is stored
 	///
 	/// This field can essentially contain anything, but the following conditions are recommended:
@@ -78,12 +125,12 @@ pub struct SimpleTag {
 	/// - It **SHOULD NOT** contain any space.
 	///
 	/// When in doubt, the [`TagName`] enum can be used, which covers all specified tags.
-	pub name: String,
+	pub name: Cow<'a, str>,
 	/// The language of the tag
 	///
 	/// See [`Language`] for more information.
 	pub language: Option<Language>,
-	/// Whether [`language`] is the default/original langauge to use
+	/// Whether [`language`] is the default/original language to use
 	///
 	/// This is used when multiple languages are present in a file. This field will be ignored
 	/// if [`language`] is `None`.
@@ -93,5 +140,38 @@ pub struct SimpleTag {
 	/// The actual tag value
 	///
 	/// For more information, see [`TagValue`]
-	pub value: Option<TagValue>,
+	pub value: Option<TagValue<'a>>,
+}
+
+impl<'a> SimpleTag<'a> {
+	/// Create a new `SimpleTag` with the given name and value
+	///
+	/// # Example
+	///
+	/// ```
+	/// use lofty::ebml::{SimpleTag, TagValue};
+	///
+	/// let tag = SimpleTag::new("TITLE", "My Title");
+	/// ```
+	pub fn new<N, V>(name: N, value: V) -> Self
+	where
+		N: Into<Cow<'a, str>>,
+		V: Into<TagValue<'a>>,
+	{
+		Self {
+			name: name.into(),
+			language: None,
+			default: false,
+			value: Some(value.into()),
+		}
+	}
+
+	pub(crate) fn into_owned(self) -> SimpleTag<'static> {
+		SimpleTag {
+			name: Cow::Owned(self.name.into_owned()),
+			language: self.language,
+			default: self.default,
+			value: self.value.map(TagValue::into_owned),
+		}
+	}
 }

lofty/src/ebml/tag/tag.rs

@@ -8,9 +8,50 @@ use super::{SimpleTag, Target};
 /// This structure is very different from other formats. See [`Target`] and [`SimpleTag`] for more
 /// information on how these work.
 #[derive(Default, Debug, PartialEq, Eq, Clone)]
-pub struct Tag {
+pub struct Tag<'a> {
 	/// The target for which the tags are applied.
 	pub target: Target,
 	/// General information about the target
-	pub simple_tags: Vec<SimpleTag>,
+	pub simple_tags: Vec<SimpleTag<'a>>,
+}
+
+impl Tag<'_> {
+	/// Get the number of simple tags in this tag.
+	///
+	/// # Example
+	///
+	/// ```
+	/// use lofty::ebml::{SimpleTag, Tag, Target};
+	///
+	/// let tag = Tag {
+	/// 	target: Target::default(),
+	/// 	simple_tags: vec![
+	/// 		SimpleTag::new("TITLE", "My Title"),
+	/// 		SimpleTag::new("ARTIST", "My Artist"),
+	/// 	],
+	/// };
+	///
+	/// assert_eq!(tag.len(), 2);
+	/// ```
+	pub fn len(&self) -> usize {
+		self.simple_tags.len()
+	}
+
+	/// Check if there are no simple tags in this tag.
+	///
+	/// # Example
+	///
+	/// ```
+	/// use lofty::ebml::{SimpleTag, Tag, Target};
+	///
+	/// let tag = Tag {
+	/// 	target: Target::default(),
+	/// 	simple_tags: vec![],
+	/// };
+	///
+	/// assert!(tag.is_empty());
+	/// ```
+	pub fn is_empty(&self) -> bool {
+		self.simple_tags.is_empty()
+	}
 }