openpgp: Use a Vec instead of a HashMap.

  - A SignatureGroup currently contains a hash mapping hash algorithms
    to hash contexts.  Typically this will only contain one or two
    mappings.  At most it will contain one mapping for each algorithm
    that we support (currently, we support 7 hash algorithms).

  - Given the small expected and small maximum size, a vector is the
    better data structure:

    - The small number of elements means that look up time will be
      comparable whether we do a linear scan or look in a hash (in
      fact, the linear scan is probably cache friendlier).

    - Iterating over a vector is faster than iterating over a hash
      map.  The is the fast path.

    - A vector takes up less space.

  - Change SignatureGroup::hashes to use a Vec instead of a HashMap.

1 files changed, 1 insertions, 1 deletions

diff --git a/openpgp/src/crypto/mod.rs b/openpgp/src/crypto/mod.rs
index 77895837..150014cc 100644
--- a/openpgp/src/crypto/mod.rs
+++ b/openpgp/src/crypto/mod.rs
@@ -193,7 +193,7 @@ pub fn hash_file<R: Read>(reader: R, algos: &[HashAlgorithm])
     let mut hashes =
         mem::replace(&mut reader.cookie_mut().sig_group_mut().hashes,
                      Default::default());
-    let hashes = hashes.drain().collect();
+    let hashes = hashes.drain(..).collect();
     Ok(hashes)
 }