feat(tls): Add utility api to Certificate

tonic/src/transport/tls.rs

@@ -22,9 +22,9 @@ impl Certificate {
         Self { kind }
     }
 
-    /// Parse a PEM encoded X509 Certificate.
+    /// Parse a DER encoded X509 Certificate.
     ///
-    /// The provided PEM should include at least one PEM encoded certificate.
+    /// The provided DER should include at least one PEM encoded certificate.
     pub fn from_der(der: impl AsRef<[u8]>) -> Self {
         let der = der.as_ref().into();
         Self::new(CertKind::Der(der))
@@ -37,6 +37,50 @@ impl Certificate {
         let pem = pem.as_ref().into();
         Self::new(CertKind::Pem(pem))
     }
+
+    /// Returns whether this is a DER encoded certificate.
+    pub fn is_der(&self) -> bool {
+        matches!(self.kind, CertKind::Der(_))
+    }
+
+    /// Returns whether this is a PEM encoded certificate.
+    pub fn is_pem(&self) -> bool {
+        matches!(self.kind, CertKind::Pem(_))
+    }
+
+    /// Returns the reference to DER encoded certificate.
+    /// Returns `None` When this is not encoded as DER.
+    pub fn der(&self) -> Option<&[u8]> {
+        match &self.kind {
+            CertKind::Der(der) => Some(der),
+            _ => None,
+        }
+    }
+
+    /// Returns the reference to PEM encoded certificate.
+    /// Returns `None` When this is not encoded as PEM.
+    pub fn pem(&self) -> Option<&[u8]> {
+        match &self.kind {
+            CertKind::Pem(pem) => Some(pem),
+            _ => None,
+        }
+    }
+
+    /// Turns this value into the DER encoded bytes.
+    pub fn into_der(self) -> Result<Vec<u8>, Self> {
+        match self.kind {
+            CertKind::Der(der) => Ok(der),
+            _ => Err(self),
+        }
+    }
+
+    /// Turns this value into the PEM encoded bytes.
+    pub fn into_pem(self) -> Result<Vec<u8>, Self> {
+        match self.kind {
+            CertKind::Pem(pem) => Ok(pem),
+            _ => Err(self),
+        }
+    }
 }
 
 impl Identity {