openpgp: De-duplicate cert components before checking signatures.

  - Before we do anything, we'll order and deduplicate the components.
    If two components are the same, they will be merged, and their
    signatures will also be deduplicated.  This improves the
    performance considerably when we update a certificate, because the
    certificates will be most likely almost identical, and we avoid
    about half of the signature verifications.

  - And indeed, benchmarking shows a 45% performance improvement on a
    typical cert.

  - Fixes #644.

1 files changed, 20 insertions, 0 deletions

diff --git a/openpgp/benches/merge_cert.rs b/openpgp/benches/merge_cert.rs
new file mode 100644
index 00000000..a628e60a
--- /dev/null
+++ b/openpgp/benches/merge_cert.rs
@@ -0,0 +1,20 @@
+use criterion::{
+    criterion_group, Criterion,
+};
+
+use sequoia_openpgp as openpgp;
+use openpgp::cert::Cert;
+use openpgp::parse::Parse;
+
+/// Benchmark merging a typical cert with itself.
+fn bench_merge_certs(c: &mut Criterion) {
+    let mut group = c.benchmark_group("merge cert with itself");
+    let neal = Cert::from_bytes(include_bytes!("../tests/data/keys/neal.pgp"))
+        .unwrap();
+    group.bench_function("neal.pgp", |b| b.iter(|| {
+        neal.clone().merge_public(neal.clone()).unwrap();
+    }));
+    group.finish();
+}
+
+criterion_group!(benches, bench_merge_certs);