openpgp: Move accessors from SubpacketArea to SubpacketAreas

  - `SubpacketAreas`'s high-level subpacket accessors implement
    routing.  For instance, `SubpacketAreas::embedded_signature` first
    looks for the `Embedded Signature` subpacket in the hashed
    subpacket area, and, if it is not found there, it falls back to
    the unhashed subpacket area.  In contrast,
    `SubpacketAreas::signature_creation_time` only looks for the
    `Signature Creation Time` subpacket in the hashed subpacket area.

  - This is potentially confusing.  `SubpacketArea` also implements
    the `embedded_signature` accessor and the
    `signature_creation_time` accessor.  They only look in the
    associated subpacket area.  That is,
    `SubpacketArea::embedded_signature` only looks in the selected
    subpacket area, not both.  And,
    `SubpacketArea::signature_creation_time` may look in the "wrong"
    subpacket area: if the `Signature Creation Time` subpacket occurs
    in the the unhashed subpacket area, it should normally be ignored.

  - Instead, only provide high-level accessors for `SubpacketAreas`.

  - If necessary, it is still possible to work with an individual
    SubpacketArea using `SubpacketArea::lookup`, etc.

1 files changed, 4 insertions, 72 deletions

diff --git a/openpgp/src/packet/signature/subpacket.rs b/openpgp/src/packet/signature/subpacket.rs
index 6945b8a3..214a33cd 100644
--- a/openpgp/src/packet/signature/subpacket.rs
+++ b/openpgp/src/packet/signature/subpacket.rs
@@ -1143,7 +1143,9 @@ impl SubpacketArea {
                   -> impl Iterator<Item = &Subpacket> {
         self.iter().filter(move |sp| sp.tag() == target)
     }
+}
 
+impl SubpacketAreas {
     /// Returns the value of the Creation Time subpacket, which
     /// contains the time when the signature was created as a unix
     /// timestamp.
@@ -1852,7 +1854,7 @@ impl SubpacketAreas {
 
     /// Returns the *last* instance of the specified subpacket.
     fn subpacket<'a>(&'a self, tag: SubpacketTag) -> Option<&Subpacket> {
-        if let Some(sb) = self.hashed_area().lookup(tag) {
+        if let Some(sb) = self.hashed_area().subpacket(tag) {
             return Some(sb);
         }
 
@@ -1865,7 +1867,7 @@ impl SubpacketAreas {
             return None;
         }
 
-        self.unhashed_area().lookup(tag)
+        self.unhashed_area().subpacket(tag)
     }
 
 
@@ -2014,76 +2016,6 @@ impl SubpacketAreas {
             _ => Ok(()),
         }
     }
-
-    /// Returns the value of the Issuer subpacket, which contains the
-    /// KeyID of the key that allegedly created this signature.
-    ///
-    /// If the subpacket is not present, this returns `None`.
-    ///
-    /// Note: if the signature contains multiple instances of this
-    /// subpacket, only the last one is considered.
-    pub fn issuer(&self) -> Option<&KeyID> {
-        // 8-octet Key ID
-        if let Some(sb)
-                = self.subpacket(SubpacketTag::Issuer) {
-            if let SubpacketValue::Issuer(v) = &sb.value {
-                Some(v)
-            } else {
-                None
-            }
-        } else {
-            None
-        }
-    }
-
-    /// Returns the value of the Embedded Signature subpacket, which
-    /// contains a signature.
-    ///
-    /// This is used, for instance, to store a subkey's primary key
-    /// binding signature (0x19).
-    ///
-    /// If the subpacket is not present, this returns `None`.
-    ///
-    /// Note: if the signature contains multiple instances of this
-    /// subpacket, only the last one is considered.
-    pub fn embedded_signature(&self) -> Option<&Signature> {
-        // 1 signature packet body
-        if let Some(sb)
-                = self.subpacket(SubpacketTag::EmbeddedSignature) {
-            if let SubpacketValue::EmbeddedSignature(v) = &sb.value {
-                Some(v)
-            } else {
-                None
-            }
-        } else {
-            None
-        }
-    }
-
-    /// Returns the value of the Issuer Fingerprint subpacket, which
-    /// contains the fingerprint of the key that allegedly created
-    /// this signature.
-    ///
-    /// This subpacket should be preferred to the Issuer subpacket,
-    /// because Fingerprints are not subject to collisions.
-    ///
-    /// If the subpacket is not present, this returns `None`.
-    ///
-    /// Note: if the signature contains multiple instances of this
-    /// subpacket, only the last one is considered.
-    pub fn issuer_fingerprint(&self) -> Option<&Fingerprint> {
-        // 1 octet key version number, N octets of fingerprint
-        if let Some(sb)
-                = self.subpacket(SubpacketTag::IssuerFingerprint) {
-            if let SubpacketValue::IssuerFingerprint(v) = &sb.value {
-                Some(v)
-            } else {
-                None
-            }
-        } else {
-            None
-        }
-    }
 }
 
 impl TryFrom<Signature> for Signature4 {