rewrite KeyFormatVersions

src/types/key_format_versions.rs

@@ -1,8 +1,11 @@
+use std::cmp::Ordering;
 use std::fmt;
+use std::hash::{Hash, Hasher};
+use std::iter::{Extend, FromIterator};
+use std::ops::{Index, IndexMut};
+use std::slice::SliceIndex;
 use std::str::FromStr;
 
-use derive_more::{Deref, DerefMut};
-
 use crate::types::ProtocolVersion;
 use crate::utils::{quote, unquote};
 use crate::Error;
@@ -12,18 +15,49 @@ use crate::RequiredVersion;
 /// this instance complies with, if more than one version of a particular
 /// [`KeyFormat`] is defined.
 ///
+/// ## Note on maximum size
+///
+/// To reduce the memory usage and to make this struct implement [`Copy`], a
+/// fixed size array is used internally (`[u8; 9]`), which can store a maximum
+/// number of 9 `u8` numbers.
+///
+/// If you encounter any m3u8 file, which fails to parse, because the buffer is
+/// too small, feel free to [make an issue](https://github.com/sile/hls_m3u8/issues).
+///
+/// ## Example
+///
+/// ```
+/// use hls_m3u8::types::KeyFormatVersions;
+///
+/// assert_eq!(
+///     KeyFormatVersions::from([0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]).to_string(),
+///     "\"255/255/255/255/255/255/255/255/255\"".to_string()
+/// );
+/// ```
+///
 /// [`KeyFormat`]: crate::types::KeyFormat
-#[derive(Deref, DerefMut, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
+#[derive(Debug, Clone, Copy)]
-pub struct KeyFormatVersions(Vec<usize>);
+pub struct KeyFormatVersions {
+    // NOTE(Luro02): if the current array is not big enough one can easily increase
+    //               the number of elements or change the type to something bigger,
+    //               but it would be kinda wasteful to use a `Vec` here, which requires
+    //               allocations and has a size of at least 24 bytes
+    //               (::std::mem::size_of::<Vec<u8>>() = 24).
+    buffer: [u8; 9],
+    // Indicates the number of used items in the array.
+    len: u8,
+}
 
 impl KeyFormatVersions {
-    /// Makes a new [`KeyFormatVersions`].
+    /// Constructs an empty [`KeyFormatVersions`].
     ///
     /// # Example
     ///
     /// ```
     /// # use hls_m3u8::types::KeyFormatVersions;
-    /// let key_format_versions = KeyFormatVersions::new();
+    /// let versions = KeyFormatVersions::new();
+    ///
+    /// assert_eq!(versions, KeyFormatVersions::default());
     /// ```
     #[inline]
     #[must_use]
@@ -31,40 +65,299 @@ impl KeyFormatVersions {
 
     /// Add a value to the end of [`KeyFormatVersions`].
     ///
+    /// # Panics
+    ///
+    /// This function panics, if you try to push more elements, than
+    /// [`KeyFormatVersions::remaining`] returns.
+    ///
     /// # Example
     ///
     /// ```
     /// # use hls_m3u8::types::KeyFormatVersions;
-    /// let mut key_format_versions = KeyFormatVersions::new();
+    /// let mut versions = KeyFormatVersions::new();
     ///
-    /// key_format_versions.push(1);
+    /// versions.push(1);
+    /// assert_eq!(versions, KeyFormatVersions::from([1]));
     /// ```
-    pub fn push(&mut self, value: usize) {
+    ///
-        if self.is_default() {
+    /// This will panic, because it exceeded the maximum number of elements:
-            self.0 = vec![value];
+    ///
+    /// ```{.should_panic}
+    /// # use hls_m3u8::types::KeyFormatVersions;
+    /// let mut versions = KeyFormatVersions::new();
+    ///
+    /// for _ in 0..=versions.capacity() {
+    ///     versions.push(1); // <- panics
+    /// }
+    /// ```
+    pub fn push(&mut self, value: u8) {
+        if self.len as usize == self.buffer.len() {
+            panic!("reached maximum number of elements in KeyFormatVersions");
+        }
+
+        self.buffer[self.len()] = value;
+        self.len += 1;
+    }
+
+    /// `KeyFormatVersions` has a limited capacity and this function returns how
+    /// many elements can be pushed, until it panics.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use hls_m3u8::types::KeyFormatVersions;
+    /// let mut versions = KeyFormatVersions::new();
+    ///
+    /// assert_eq!(versions.remaining(), versions.capacity());
+    ///
+    /// versions.push(1);
+    /// versions.push(2);
+    /// versions.push(3);
+    /// assert_eq!(versions.remaining(), 6);
+    /// ```
+    #[inline]
+    #[must_use]
+    pub fn remaining(&self) -> usize { self.capacity().saturating_sub(self.len()) }
+
+    /// Returns the number of elements.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use hls_m3u8::types::KeyFormatVersions;
+    /// let mut versions = KeyFormatVersions::new();
+    ///
+    /// assert_eq!(versions.len(), 0);
+    ///
+    /// versions.push(2);
+    /// assert_eq!(versions.len(), 1);
+    /// ```
+    #[inline]
+    #[must_use]
+    pub const fn len(&self) -> usize { self.len as usize }
+
+    /// Returns the total number of elements that can be stored.
+    ///
+    /// # Note
+    ///
+    /// It should not be relied on that this function will always return 9. In
+    /// the future this number might increase.
+    #[inline]
+    #[must_use]
+    pub fn capacity(&self) -> usize { self.buffer.len() }
+
+    /// Shortens the internal array to the provided length.
+    ///
+    /// # Note
+    ///
+    /// If `len` is greater than the current length, this has no effect.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use hls_m3u8::types::KeyFormatVersions;
+    /// let mut versions = KeyFormatVersions::from([1, 2, 3, 4, 5, 6]);
+    /// versions.truncate(3);
+    ///
+    /// assert_eq!(versions, KeyFormatVersions::from([1, 2, 3]));
+    /// ```
+    pub fn truncate(&mut self, len: usize) {
+        if len > self.len() {
+            return;
+        }
+
+        self.len = len as u8;
+    }
+
+    /// Returns `true` if there are no elements.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use hls_m3u8::types::KeyFormatVersions;
+    /// let mut versions = KeyFormatVersions::new();
+    ///
+    /// assert_eq!(versions.is_empty(), true);
+    ///
+    /// versions.push(2);
+    /// assert_eq!(versions.is_empty(), false);
+    /// ```
+    #[inline]
+    #[must_use]
+    pub fn is_empty(&self) -> bool { self.len() == 0 }
+
+    /// Removes the last element and returns it, or `None` if it is empty.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use hls_m3u8::types::KeyFormatVersions;
+    /// let mut versions = KeyFormatVersions::new();
+    ///
+    /// assert_eq!(versions.pop(), None);
+    ///
+    /// versions.push(2);
+    /// assert_eq!(versions.pop(), Some(2));
+    /// assert_eq!(versions.is_empty(), true);
+    /// ```
+    pub fn pop(&mut self) -> Option<u8> {
+        if self.is_empty() {
+            None
         } else {
-            self.0.push(value);
+            self.len -= 1;
+            Some(self.buffer[self.len()])
         }
     }
 
-    /// Returns `true`, if [`KeyFormatVersions`] has the default value of
+    /// Returns `true`, if it is either empty or has a length of 1 and the first
-    /// `vec![1]`.
+    /// element is 1.
     ///
     /// # Example
     ///
     /// ```
     /// # use hls_m3u8::types::KeyFormatVersions;
-    /// assert!(KeyFormatVersions::from(vec![1]).is_default());
+    /// let mut versions = KeyFormatVersions::new();
+    ///
+    /// assert_eq!(versions.is_default(), true);
+    ///
+    /// versions.push(1);
+    /// assert_eq!(versions.is_default(), true);
+    ///
+    /// assert_eq!(KeyFormatVersions::default().is_default(), true);
     /// ```
     #[must_use]
     pub fn is_default(&self) -> bool {
-        //
+        self.is_empty() || (self.buffer[self.len().saturating_sub(1)] == 1 && self.len() == 1)
-        self.0 == vec![1] && self.0.len() == 1 || self.0.is_empty()
+    }
+}
+
+impl PartialEq for KeyFormatVersions {
+    fn eq(&self, other: &Self) -> bool {
+        if self.len() == other.len() {
+            // only compare the parts in the buffer, that are used:
+            self.as_ref() == self.as_ref()
+        } else {
+            false
+        }
+    }
+}
+
+impl Eq for KeyFormatVersions {}
+
+impl PartialOrd for KeyFormatVersions {
+    #[inline]
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(<Self as Ord>::cmp(self, other))
+    }
+}
+
+impl Ord for KeyFormatVersions {
+    #[inline]
+    fn cmp(&self, other: &Self) -> Ordering { self.as_ref().cmp(other.as_ref()) }
+}
+
+impl Hash for KeyFormatVersions {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        state.write_usize(self.len());
+        self.as_ref().hash(state);
+    }
+}
+
+impl AsRef<[u8]> for KeyFormatVersions {
+    #[inline]
+    #[must_use]
+    fn as_ref(&self) -> &[u8] { &self.buffer[..self.len()] }
+}
+
+impl AsMut<[u8]> for KeyFormatVersions {
+    #[inline]
+    #[must_use]
+    fn as_mut(&mut self) -> &mut [u8] {
+        // this temporary variable is required, because the compiler does not resolve
+        // the borrow to it's value immediately, so there is a shared borrow and
+        // therefore no exclusive borrow can be made.
+        let len = self.len();
+        &mut self.buffer[..len]
+    }
+}
+
+impl Extend<u8> for KeyFormatVersions {
+    fn extend<I: IntoIterator<Item = u8>>(&mut self, iter: I) {
+        for element in iter {
+            if self.remaining() == 0 {
+                break;
+            }
+
+            self.push(element);
+        }
+    }
+}
+
+impl<'a> Extend<&'a u8> for KeyFormatVersions {
+    fn extend<I: IntoIterator<Item = &'a u8>>(&mut self, iter: I) {
+        <Self as Extend<u8>>::extend(self, iter.into_iter().copied())
+    }
+}
+
+impl<I: SliceIndex<[u8]>> Index<I> for KeyFormatVersions {
+    type Output = I::Output;
+
+    #[inline]
+    fn index(&self, index: I) -> &Self::Output { self.as_ref().index(index) }
+}
+
+impl<I: SliceIndex<[u8]>> IndexMut<I> for KeyFormatVersions {
+    #[inline]
+    fn index_mut(&mut self, index: I) -> &mut Self::Output { self.as_mut().index_mut(index) }
+}
+
+impl IntoIterator for KeyFormatVersions {
+    type IntoIter = IntoIter<u8>;
+    type Item = u8;
+
+    fn into_iter(self) -> Self::IntoIter { self.into() }
+}
+
+impl FromIterator<u8> for KeyFormatVersions {
+    fn from_iter<I: IntoIterator<Item = u8>>(iter: I) -> Self {
+        let mut result = Self::default();
+        // an array like [0; 9] as empty
+        let mut is_empty = true;
+
+        for item in iter {
+            if item != 0 {
+                is_empty = false;
+            }
+
+            if result.remaining() == 0 {
+                break;
+            }
+
+            result.push(item);
+        }
+
+        if is_empty {
+            return Self::default();
+        }
+
+        result
+    }
+}
+
+impl<'a> FromIterator<&'a u8> for KeyFormatVersions {
+    fn from_iter<I: IntoIterator<Item = &'a u8>>(iter: I) -> Self {
+        <Self as FromIterator<u8>>::from_iter(iter.into_iter().copied())
     }
 }
 
 impl Default for KeyFormatVersions {
-    fn default() -> Self { Self(vec![1]) }
+    #[inline]
+    fn default() -> Self {
+        Self {
+            buffer: [0; 9],
+            len: 0,
+        }
+    }
 }
 
 /// This tag requires [`ProtocolVersion::V5`].
@@ -76,41 +369,98 @@ impl FromStr for KeyFormatVersions {
     type Err = Error;
 
     fn from_str(input: &str) -> Result<Self, Self::Err> {
-        let mut result = unquote(input)
+        let mut result = Self::default();
+
+        for item in unquote(input)
             .split('/')
             .map(|v| v.parse().map_err(|e| Error::parse_int(v, e)))
-            .collect::<Result<Vec<_>, Error>>()?;
+        {
+            let item = item?;
+
+            if result.remaining() == 0 {
+                return Err(Error::custom(
+                    "reached maximum number of elements in KeyFormatVersions",
+                ));
+            }
+
+            result.push(item);
+        }
 
         if result.is_empty() {
             result.push(1);
         }
 
-        Ok(Self(result))
+        Ok(result)
     }
 }
 
 impl fmt::Display for KeyFormatVersions {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        if self.is_default() {
+        if self.is_default() || self.is_empty() {
             return write!(f, "{}", quote("1"));
         }
 
-        if let Some(value) = self.0.iter().next() {
+        write!(f, "\"{}", self.buffer[0])?;
-            write!(f, "\"{}", value)?;
 
-            for value in self.0.iter().skip(1) {
+        for item in &self.buffer[1..self.len()] {
-                write!(f, "/{}", value)?;
+            write!(f, "/{}", item)?;
         }
 
         write!(f, "\"")?;
-        }
 
         Ok(())
     }
 }
 
-impl<I: IntoIterator<Item = usize>> From<I> for KeyFormatVersions {
+impl<T: AsRef<[usize]>> From<T> for KeyFormatVersions {
-    fn from(value: I) -> Self { Self(value.into_iter().collect()) }
+    fn from(value: T) -> Self { Self::from_iter(value.as_ref().iter().map(|i| *i as u8)) }
+}
+
+/// `Iterator` for [`KeyFormatVersions`].
+#[derive(Debug, Clone, PartialEq)]
+pub struct IntoIter<T> {
+    buffer: [T; 9],
+    position: usize,
+    len: usize,
+}
+
+impl From<KeyFormatVersions> for IntoIter<u8> {
+    fn from(value: KeyFormatVersions) -> Self {
+        Self {
+            buffer: value.buffer,
+            position: 0,
+            len: value.len(),
+        }
+    }
+}
+
+impl<'a> From<&'a KeyFormatVersions> for IntoIter<u8> {
+    fn from(value: &'a KeyFormatVersions) -> Self {
+        Self {
+            buffer: value.buffer,
+            position: 0,
+            len: value.len(),
+        }
+    }
+}
+
+impl<T: Copy> ExactSizeIterator for IntoIter<T> {
+    fn len(&self) -> usize { self.len.saturating_sub(self.position) }
+}
+
+impl<T: Copy> ::core::iter::FusedIterator for IntoIter<T> {}
+
+impl<T: Copy> Iterator for IntoIter<T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.position == self.len {
+            return None;
+        }
+
+        self.position += 1;
+        Some(self.buffer[self.position - 1])
+    }
 }
 
 #[cfg(test)]
@@ -118,27 +468,200 @@ mod tests {
     use super::*;
     use pretty_assertions::assert_eq;
 
+    #[test]
+    fn test_hash() {
+        let mut hasher_left = std::collections::hash_map::DefaultHasher::new();
+        let mut hasher_right = std::collections::hash_map::DefaultHasher::new();
+
+        assert_eq!(
+            KeyFormatVersions::from([1, 2, 3]).hash(&mut hasher_left),
+            KeyFormatVersions::from([1, 2, 3]).hash(&mut hasher_right)
+        );
+
+        assert_eq!(hasher_left.finish(), hasher_right.finish());
+    }
+
+    #[test]
+    fn test_ord() {
+        assert_eq!(
+            KeyFormatVersions::from([1, 2]).cmp(&KeyFormatVersions::from([1, 2])),
+            Ordering::Equal
+        );
+
+        assert_eq!(
+            KeyFormatVersions::from([2]).cmp(&KeyFormatVersions::from([1, 2])),
+            Ordering::Greater
+        );
+
+        assert_eq!(
+            KeyFormatVersions::from([2, 3]).cmp(&KeyFormatVersions::from([1, 2])),
+            Ordering::Greater
+        );
+
+        assert_eq!(
+            KeyFormatVersions::from([]).cmp(&KeyFormatVersions::from([1, 2])),
+            Ordering::Less
+        );
+    }
+
+    #[test]
+    fn test_partial_eq() {
+        let mut versions = KeyFormatVersions::from([1, 2, 3, 4, 5, 6]);
+        versions.truncate(3);
+
+        assert_eq!(versions, KeyFormatVersions::from([1, 2, 3]));
+    }
+
+    #[test]
+    fn test_as_ref() {
+        assert_eq!(KeyFormatVersions::new().as_ref(), &[]);
+        assert_eq!(KeyFormatVersions::from([1, 2, 3]).as_ref(), &[1, 2, 3]);
+        assert_eq!(KeyFormatVersions::from([]).as_ref(), &[]);
+    }
+
+    #[test]
+    fn test_as_mut() {
+        assert_eq!(KeyFormatVersions::new().as_mut(), &mut []);
+        assert_eq!(KeyFormatVersions::from([1, 2, 3]).as_mut(), &mut [1, 2, 3]);
+        assert_eq!(KeyFormatVersions::from([]).as_mut(), &mut []);
+    }
+
+    #[test]
+    fn test_index() {
+        // test index
+        assert_eq!(&KeyFormatVersions::new()[..], &[]);
+        assert_eq!(&KeyFormatVersions::from([1, 2, 3])[..2], &[1, 2]);
+        assert_eq!(&KeyFormatVersions::from([1, 2, 3])[1..2], &[2]);
+        assert_eq!(&KeyFormatVersions::from([1, 2, 3])[..], &[1, 2, 3]);
+
+        // test index_mut
+        assert_eq!(&mut KeyFormatVersions::new()[..], &mut []);
+        assert_eq!(&mut KeyFormatVersions::from([1, 2, 3])[..2], &mut [1, 2]);
+        assert_eq!(&mut KeyFormatVersions::from([1, 2, 3])[1..2], &mut [2]);
+        assert_eq!(&mut KeyFormatVersions::from([1, 2, 3])[..], &mut [1, 2, 3]);
+    }
+
+    #[test]
+    fn test_extend() {
+        let mut versions = KeyFormatVersions::new();
+        versions.extend(&[1, 2, 3]);
+
+        assert_eq!(versions, KeyFormatVersions::from([1, 2, 3]));
+
+        versions.extend(&[1, 2, 3]);
+        assert_eq!(versions, KeyFormatVersions::from([1, 2, 3, 1, 2, 3]));
+
+        versions.extend(&[1, 2, 3, 4]);
+        assert_eq!(
+            versions,
+            KeyFormatVersions::from([1, 2, 3, 1, 2, 3, 1, 2, 3])
+        );
+    }
+
+    #[test]
+    fn test_default() {
+        assert_eq!(KeyFormatVersions::default(), KeyFormatVersions::new());
+    }
+
+    #[test]
+    fn test_into_iter() {
+        assert_eq!(KeyFormatVersions::new().into_iter().next(), None);
+        assert_eq!(KeyFormatVersions::new().into_iter().len(), 0);
+
+        let mut iterator = KeyFormatVersions::from([1, 2, 3, 4, 5]).into_iter();
+
+        assert_eq!(iterator.len(), 5);
+        assert_eq!(iterator.next(), Some(1));
+
+        assert_eq!(iterator.len(), 4);
+        assert_eq!(iterator.next(), Some(2));
+
+        assert_eq!(iterator.len(), 3);
+        assert_eq!(iterator.next(), Some(3));
+
+        assert_eq!(iterator.len(), 2);
+        assert_eq!(iterator.next(), Some(4));
+
+        assert_eq!(iterator.len(), 1);
+        assert_eq!(iterator.next(), Some(5));
+
+        assert_eq!(iterator.len(), 0);
+        assert_eq!(iterator.next(), None);
+    }
+
+    #[test]
+    fn test_from_iter() {
+        assert_eq!(
+            {
+                let mut result = KeyFormatVersions::new();
+                result.push(1);
+                result.push(2);
+                result.push(3);
+                result.push(4);
+                result
+            },
+            KeyFormatVersions::from_iter(&[1, 2, 3, 4])
+        );
+
+        assert_eq!(
+            {
+                let mut result = KeyFormatVersions::new();
+                result.push(0);
+                result.push(1);
+                result.push(2);
+                result.push(3);
+                result.push(4);
+                result
+            },
+            KeyFormatVersions::from_iter(&[0, 1, 2, 3, 4])
+        );
+
+        assert_eq!(KeyFormatVersions::new(), KeyFormatVersions::from_iter(&[]));
+
+        assert_eq!(KeyFormatVersions::new(), KeyFormatVersions::from_iter(&[0]));
+        assert_eq!(
+            KeyFormatVersions::new(),
+            KeyFormatVersions::from_iter(&[0, 0])
+        );
+        assert_eq!(
+            {
+                let mut result = KeyFormatVersions::new();
+                result.push(0);
+                result.push(1);
+                result.push(2);
+                result.push(3);
+                result.push(4);
+                result.push(5);
+                result.push(6);
+                result.push(7);
+                result.push(8);
+                result
+            },
+            KeyFormatVersions::from_iter(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12])
+        );
+    }
+
     #[test]
     fn test_display() {
         assert_eq!(
-            KeyFormatVersions::from(vec![1, 2, 3, 4, 5]).to_string(),
+            KeyFormatVersions::from([1, 2, 3, 4, 5]).to_string(),
             quote("1/2/3/4/5")
         );
 
-        assert_eq!(KeyFormatVersions::from(vec![]).to_string(), quote("1"));
+        assert_eq!(KeyFormatVersions::from([]).to_string(), quote("1"));
         assert_eq!(KeyFormatVersions::new().to_string(), quote("1"));
     }
 
     #[test]
     fn test_parser() {
         assert_eq!(
-            KeyFormatVersions::from(vec![1, 2, 3, 4, 5]),
+            KeyFormatVersions::from([1, 2, 3, 4, 5]),
             quote("1/2/3/4/5").parse().unwrap()
         );
 
-        assert_eq!(KeyFormatVersions::from(vec![1]), "1".parse().unwrap());
+        assert_eq!(KeyFormatVersions::from([1]), "1".parse().unwrap());
+        assert_eq!(KeyFormatVersions::from([1, 2]), "1/2".parse().unwrap());
 
-        assert_eq!(KeyFormatVersions::from(vec![1, 2]), "1/2".parse().unwrap());
         assert!("1/b".parse::<KeyFormatVersions>().is_err());
     }
 
@@ -152,28 +675,20 @@ mod tests {
 
     #[test]
     fn test_is_default() {
-        assert!(KeyFormatVersions::new().is_default());
+        assert_eq!(KeyFormatVersions::new().is_default(), true);
-        assert!(KeyFormatVersions::from(vec![]).is_default());
+        assert_eq!(KeyFormatVersions::default().is_default(), true);
-        assert!(!KeyFormatVersions::from(vec![1, 2, 3]).is_default());
+
+        assert_eq!(KeyFormatVersions::from([]).is_default(), true);
+        assert_eq!(KeyFormatVersions::from([1]).is_default(), true);
+
+        assert_eq!(KeyFormatVersions::from([1, 2, 3]).is_default(), false);
     }
 
     #[test]
     fn test_push() {
-        let mut key_format_versions = KeyFormatVersions::from(vec![]);
+        let mut key_format_versions = KeyFormatVersions::new();
-
         key_format_versions.push(2);
-        assert_eq!(KeyFormatVersions::from(vec![2]), key_format_versions);
-    }
 
-    #[test]
+        assert_eq!(KeyFormatVersions::from([2]), key_format_versions);
-    fn test_deref() {
-        assert!(!KeyFormatVersions::new().is_empty());
-    }
-
-    #[test]
-    fn test_deref_mut() {
-        let mut key_format_versions = KeyFormatVersions::from(vec![1, 2, 3]);
-        key_format_versions.pop();
-        assert_eq!(key_format_versions, KeyFormatVersions::from(vec![1, 2]));
     }
 }