openpgp: Convert `Sexp::from_ciphertext` to `TryFrom<&mpis::Ciphertext>`

2 files changed, 56 insertions, 50 deletions

diff --git a/ipc/src/gnupg.rs b/ipc/src/gnupg.rs
index 408df3cf..7220b7f0 100644
--- a/ipc/src/gnupg.rs
+++ b/ipc/src/gnupg.rs
@@ -3,6 +3,7 @@
 #![warn(missing_docs)]
 
 use std::collections::BTreeMap;
+use std::convert::TryFrom;
 use std::ops::{Deref, DerefMut};
 use std::path::{Path, PathBuf};
 use std::process::Command;
@@ -630,7 +631,7 @@ impl<'a, 'b, 'c, R> Future for DecryptionRequest<'a, 'b, 'c, R>
                     },
                     Async::Ready(None) => {
                         let mut buf = Vec::new();
-                        Sexp::from_ciphertext(&self.ciphertext)?
+                        Sexp::try_from(self.ciphertext)?
                             .serialize(&mut buf)?;
                         self.c.data(&buf)?;
                         self.state = Inquire(Vec::new(), true);
diff --git a/openpgp/src/crypto/sexp.rs b/openpgp/src/crypto/sexp.rs
index a7da7f0c..c4325e57 100644
--- a/openpgp/src/crypto/sexp.rs
+++ b/openpgp/src/crypto/sexp.rs
@@ -6,6 +6,7 @@
 //!
 //! [S-Expressions]: https://people.csail.mit.edu/rivest/Sexp.txt
 
+use std::convert::TryFrom;
 use std::fmt;
 use std::ops::Deref;
 use quickcheck::{Arbitrary, Gen};
@@ -37,55 +38,6 @@ impl fmt::Debug for Sexp {
 }
 
 impl Sexp {
-    /// Constructs an S-Expression representing `ciphertext`.
-    ///
-    /// The resulting expression is suitable for gpg-agent's `INQUIRE
-    /// CIPHERTEXT` inquiry.
-    pub fn from_ciphertext(ciphertext: &mpis::Ciphertext) -> Result<Self> {
-        use crate::crypto::mpis::Ciphertext::*;
-        match ciphertext {
-            RSA { ref c } =>
-                Ok(Sexp::List(vec![
-                    Sexp::String("enc-val".into()),
-                    Sexp::List(vec![
-                        Sexp::String("rsa".into()),
-                        Sexp::List(vec![
-                            Sexp::String("a".into()),
-                            Sexp::String(c.value().into())])])])),
-
-            &ElGamal { ref e, ref c } =>
-                Ok(Sexp::List(vec![
-                    Sexp::String("enc-val".into()),
-                    Sexp::List(vec![
-                        Sexp::String("elg".into()),
-                        Sexp::List(vec![
-                            Sexp::String("a".into()),
-                            Sexp::String(e.value().into())]),
-                        Sexp::List(vec![
-                            Sexp::String("b".into()),
-                            Sexp::String(c.value().into())])])])),
-
-            &ECDH { ref e, ref key } =>
-                Ok(Sexp::List(vec![
-                    Sexp::String("enc-val".into()),
-                    Sexp::List(vec![
-                        Sexp::String("ecdh".into()),
-                        Sexp::List(vec![
-                            Sexp::String("s".into()),
-                            Sexp::String(key.as_ref().into())]),
-                        Sexp::List(vec![
-                            Sexp::String("e".into()),
-                            Sexp::String(e.value().into())])])])),
-
-            &Unknown { .. } =>
-                Err(Error::InvalidArgument(
-                    format!("Don't know how to convert {:?}", ciphertext))
-                    .into()),
-
-            __Nonexhaustive => unreachable!(),
-        }
-    }
-
     /// Completes the decryption of this S-Expression representing a
     /// wrapped session key.
     ///
@@ -288,6 +240,59 @@ impl Sexp {
     }
 }
 
+impl TryFrom<&mpis::Ciphertext> for Sexp {
+    type Error = anyhow::Error;
+
+    /// Constructs an S-Expression representing `ciphertext`.
+    ///
+    /// The resulting expression is suitable for gpg-agent's `INQUIRE
+    /// CIPHERTEXT` inquiry.
+    fn try_from(ciphertext: &mpis::Ciphertext) -> Result<Self> {
+        use crate::crypto::mpis::Ciphertext::*;
+        match ciphertext {
+            RSA { ref c } =>
+                Ok(Sexp::List(vec![
+                    Sexp::String("enc-val".into()),
+                    Sexp::List(vec![
+                        Sexp::String("rsa".into()),
+                        Sexp::List(vec![
+                            Sexp::String("a".into()),
+                            Sexp::String(c.value().into())])])])),
+
+            &ElGamal { ref e, ref c } =>
+                Ok(Sexp::List(vec![
+                    Sexp::String("enc-val".into()),
+                    Sexp::List(vec![
+                        Sexp::String("elg".into()),
+                        Sexp::List(vec![
+                            Sexp::String("a".into()),
+                            Sexp::String(e.value().into())]),
+                        Sexp::List(vec![
+                            Sexp::String("b".into()),
+                            Sexp::String(c.value().into())])])])),
+
+            &ECDH { ref e, ref key } =>
+                Ok(Sexp::List(vec![
+                    Sexp::String("enc-val".into()),
+                    Sexp::List(vec![
+                        Sexp::String("ecdh".into()),
+                        Sexp::List(vec![
+                            Sexp::String("s".into()),
+                            Sexp::String(key.as_ref().into())]),
+                        Sexp::List(vec![
+                            Sexp::String("e".into()),
+                            Sexp::String(e.value().into())])])])),
+
+            &Unknown { .. } =>
+                Err(Error::InvalidArgument(
+                    format!("Don't know how to convert {:?}", ciphertext))
+                    .into()),
+
+            __Nonexhaustive => unreachable!(),
+        }
+    }
+}
+
 impl Arbitrary for Sexp {
     fn arbitrary<G: Gen>(g: &mut G) -> Self {
         if f32::arbitrary(g) < 0.7 {