remove dependency on num

src/compression_code.rs

@@ -0,0 +1,41 @@
+use CompressionCode::*;
+
+/// Specifies the kind of compression to use. Availability depends on features.
+#[repr(u16)]
+#[derive(Debug, Clone, Copy)]
+pub enum CompressionCode {
+    Uncompressed = 0x0,
+    #[cfg(feature = "compression-gz")]
+    Gz = 0x677a,
+    #[cfg(feature = "compression-bz")]
+    Bz = 0x627a,
+    #[cfg(feature = "compression-lz")]
+    Lz = 0x6c7a,
+    #[cfg(feature = "compression-zs")]
+    Zs = 0x7a73,
+}
+
+impl Into<u16> for CompressionCode {
+    fn into(self) -> u16 {
+        self as u16
+    }
+}
+
+impl TryFrom<u16> for CompressionCode {
+    type Error = ();
+
+    fn try_from(value: u16) -> Result<Self, Self::Error> {
+        match value {
+            value if value == Uncompressed as u16 => Ok(Uncompressed),
+            #[cfg(feature = "compression-gz")]
+            value if value == Gz as u16 => Ok(Gz),
+            #[cfg(feature = "compression-bz")]
+            value if value == Bz as u16 => Ok(Bz),
+            #[cfg(feature = "compression-lz")]
+            value if value == Lz as u16 => Ok(Lz),
+            #[cfg(feature = "compression-zs")]
+            value if value == Zs as u16 => Ok(Zs),
+            _ => Err(())
+        }
+    }
+}