1 files changed, 94 insertions, 0 deletions
diff --git a/src/class.rs b/src/class.rs
new file mode 100644
index 0000000..9a4f9de
--- /dev/null
+++ b/src/class.rs
@@ -0,0 +1,94 @@
+use core::convert::TryFrom;
+use core::fmt;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub struct BerClassFromIntError(pub(crate) ());
+
+/// BER Object class of tag
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+#[repr(u8)]
+pub enum Class {
+    /// `Universal` class of tags (`0b00`)
+    Universal = 0b00,
+    /// `Application` class of tags (`0b01`)
+    Application = 0b01,
+    /// `Context-Specific` class of tags (`0b10`)
+    ContextSpecific = 0b10,
+    /// `Private` class of tags (`0b11`)
+    Private = 0b11,
+}
+
+impl Class {
+    /// `Universal` class of tags (`0b00`)
+    pub const UNIVERSAL: u8 = 0b00;
+    /// `Application` class of tags (`0b01`)
+    pub const APPLICATION: u8 = 0b01;
+    /// `Context-Specific` class of tags (`0b10`)
+    pub const CONTEXT_SPECIFIC: u8 = 0b10;
+    /// `Private` class of tags (`0b11`)
+    pub const PRIVATE: u8 = 0b11;
+
+    pub const fn assert_eq(&self, class: Class) -> Result<(), crate::error::Error> {
+        if *self as u8 == class as u8 {
+            Ok(())
+        } else {
+            Err(crate::error::Error::UnexpectedClass {
+                expected: Some(class),
+                actual: *self,
+            })
+        }
+    }
+}
+
+impl fmt::Display for Class {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let s = match self {
+            Class::Universal => "UNIVERSAL",
+            Class::Application => "APPLICATION",
+            Class::ContextSpecific => "CONTEXT-SPECIFIC",
+            Class::Private => "PRIVATE",
+        };
+        write!(f, "{}", s)
+    }
+}
+
+impl TryFrom<u8> for Class {
+    type Error = BerClassFromIntError;
+
+    #[inline]
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        match value {
+            0b00 => Ok(Class::Universal),
+            0b01 => Ok(Class::Application),
+            0b10 => Ok(Class::ContextSpecific),
+            0b11 => Ok(Class::Private),
+            _ => Err(BerClassFromIntError(())),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn methods_class() {
+        let c = Class::Universal;
+        assert!(c.assert_eq(Class::Universal).is_ok());
+        assert!(c.assert_eq(Class::Private).is_err());
+
+        assert_eq!(Class::Universal.to_string().as_str(), "UNIVERSAL");
+        assert_eq!(Class::Application.to_string().as_str(), "APPLICATION");
+        assert_eq!(
+            Class::ContextSpecific.to_string().as_str(),
+            "CONTEXT-SPECIFIC"
+        );
+        assert_eq!(Class::Private.to_string().as_str(), "PRIVATE");
+
+        assert!(Class::try_from(0b00).is_ok());
+        assert!(Class::try_from(0b01).is_ok());
+        assert!(Class::try_from(0b10).is_ok());
+        assert!(Class::try_from(0b11).is_ok());
+        assert!(Class::try_from(4).is_err());
+    }
+}