openpgp: Improve debug formatting of the bitfield types.

  - Do not erroneously report padding for KeyFlags.

  - Print unknown flags and padding for KeyServerPreferences.

  - Provide nicer output for Features.

3 files changed, 55 insertions, 2 deletions

diff --git a/openpgp/src/types/features.rs b/openpgp/src/types/features.rs
index ca4ac999..c17c9676 100644
--- a/openpgp/src/types/features.rs
+++ b/openpgp/src/types/features.rs
@@ -1,7 +1,8 @@
+use std::fmt;
 use std::hash::{Hash, Hasher};
 
 /// Describes features supported by an OpenPGP implementation.
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct Features{
     mdc: bool,
     aead: bool,
@@ -21,6 +22,34 @@ impl Default for Features {
     }
 }
 
+impl fmt::Debug for Features {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let mut dirty = false;
+        if self.supports_mdc() {
+            f.write_str("MDC")?;
+            dirty = true;
+        }
+        if self.supports_aead() {
+            if dirty { f.write_str(", ")?; }
+            f.write_str("AEAD")?;
+            dirty = true;
+        }
+        if ! self.unknown.is_empty() {
+            if dirty { f.write_str(", ")?; }
+            f.write_str("+0x")?;
+            f.write_str(
+                &crate::fmt::hex::encode_pretty(&self.unknown))?;
+            dirty = true;
+        }
+        if self.pad_to > FEATURE_FLAGS_N_KNOWN_BYTES + self.unknown.len() {
+            if dirty { f.write_str(", ")?; }
+            write!(f, "+padding({} bytes)", self.pad_to - self.unknown.len())?;
+        }
+
+        Ok(())
+    }
+}
+
 impl PartialEq for Features {
     fn eq(&self, other: &Self) -> bool {
         self.mdc == other.mdc
@@ -131,6 +160,9 @@ const FEATURE_FLAG_MDC: u8 = 0x01;
 /// Encrypted Session Key Packets (packet 3).
 const FEATURE_FLAG_AEAD: u8 = 0x02;
 
+/// Number of bytes with known flags.
+const FEATURE_FLAGS_N_KNOWN_BYTES: usize = 1;
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/openpgp/src/types/key_flags.rs b/openpgp/src/types/key_flags.rs
index 51e8a9f6..9109abe9 100644
--- a/openpgp/src/types/key_flags.rs
+++ b/openpgp/src/types/key_flags.rs
@@ -53,7 +53,7 @@ impl fmt::Debug for KeyFlags {
             f.write_str(
                 &crate::fmt::hex::encode_pretty(&self.unknown))?;
         }
-        if self.pad_to > self.unknown.len() {
+        if self.pad_to > KEY_FLAGS_N_KNOWN_BYTES + self.unknown.len() {
             write!(f, "+padding({} bytes)", self.pad_to - self.unknown.len())?;
         }
 
@@ -327,6 +327,9 @@ const KEY_FLAG_AUTHENTICATE: u8 = 0x20;
 /// than one person.
 const KEY_FLAG_GROUP_KEY: u8 = 0x80;
 
+/// Number of bytes with known flags.
+const KEY_FLAGS_N_KNOWN_BYTES: usize = 1;
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/openpgp/src/types/server_preferences.rs b/openpgp/src/types/server_preferences.rs
index 549ae07e..42c0a74d 100644
--- a/openpgp/src/types/server_preferences.rs
+++ b/openpgp/src/types/server_preferences.rs
@@ -18,8 +18,23 @@ impl Default for KeyServerPreferences {
 
 impl fmt::Debug for KeyServerPreferences {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let mut dirty = false;
         if self.no_modify() {
             f.write_str("no modify")?;
+            dirty = true;
+        }
+        if ! self.unknown.is_empty() {
+            if dirty { f.write_str(", ")?; }
+            f.write_str("+0x")?;
+            f.write_str(
+                &crate::fmt::hex::encode_pretty(&self.unknown))?;
+            dirty = true;
+        }
+        if self.pad_to >
+            KEYSERVER_PREFERENCES_N_KNOWN_BYTES + self.unknown.len()
+        {
+            if dirty { f.write_str(", ")?; }
+            write!(f, "+padding({} bytes)", self.pad_to - self.unknown.len())?;
         }
 
         Ok(())
@@ -105,6 +120,9 @@ impl KeyServerPreferences {
 /// than one person.
 const KEYSERVER_PREFERENCE_NO_MODIFY: u8 = 0x80;
 
+/// Number of bytes with known flags.
+const KEYSERVER_PREFERENCES_N_KNOWN_BYTES: usize = 1;
+
 #[cfg(test)]
 mod tests {
     use super::*;