deprecate Compression::new

src/lib.rs

@@ -77,32 +77,50 @@ pub mod write;
 
 /// When compressing data, the compression level can be specified by a value in
 /// this enum.
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct Compression(u32);
 
 impl Compression {
-    /// Create a new compression spec with a specific numeric level (0-9).
-    pub fn new(level: u32) -> Compression {
-        Compression(level)
+    /// Create a new compression spec with a specific numeric level in the range `1..=9`.
+    ///
+    /// # Panics
+    ///
+    /// A level outside of the `1..=9` range will throw a panic. Use [`Self::try_new`] to
+    /// gracefully handle invalid levels (e.g. from user input).
+    #[track_caller]
+    pub const fn new(level: u32) -> Compression {
+        match Self::try_new(level) {
+            Some(v) => v,
+            None => panic!("expected a compression level in the range 1..=9"),
+        }
+    }
+
+    /// Create a new compression spec with a specific numeric level in the range `1..=9`.
+    pub const fn try_new(level: u32) -> Option<Compression> {
+        match level {
+            1..=9 => Some(Compression(level)),
+            _ => None,
+        }
     }
 
     /// Do not compress.
+    #[deprecated(since = "0.5.1", note = "libbz2 does not support compression level 0")]
     pub fn none() -> Compression {
         Compression(0)
     }
 
     /// Optimize for the best speed of encoding.
-    pub fn fast() -> Compression {
+    pub const fn fast() -> Compression {
         Compression(1)
     }
 
-    /// Optimize for the size of data being encoded.
-    pub fn best() -> Compression {
+    /// Optimize for smallest output size.
+    pub const fn best() -> Compression {
         Compression(9)
     }
 
     /// Return the compression level as an integer.
-    pub fn level(&self) -> u32 {
+    pub const fn level(&self) -> u32 {
         self.0
     }
 }
@@ -113,3 +131,30 @@ impl Default for Compression {
         Compression(6)
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    #[should_panic]
+    fn new_level_0() {
+        Compression::new(0);
+    }
+
+    #[test]
+    #[should_panic]
+    fn new_level_10() {
+        Compression::new(10);
+    }
+
+    #[test]
+    fn try_new() {
+        assert!(Compression::try_new(0).is_none());
+        assert!(Compression::try_new(10).is_none());
+
+        assert_eq!(Compression::try_new(1), Some(Compression::fast()));
+        assert_eq!(Compression::try_new(6), Some(Compression::default()));
+        assert_eq!(Compression::try_new(9), Some(Compression::best()));
+    }
+}