CBD-6348: [BP] [C++20] Add SerialisedDocKey::operator== ...

C++ wants an operator for A == B and B == A. Our SerialisedDocKey had
just an operator for DocKeyView which would cause B to be converted to
DocKeyView (as we have an operator for that) and now we can't
necessarily know if one could flip the order.

This is a cherryy-pick from trinity

Change-Id: I2c3cd6594c34f3a67e299d47a6978f8d8eeb17ae
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/234992
Well-Formed: Restriction Checker
Tested-by: Trond Norbye <[email protected]>
Reviewed-by: Faizan Alam <[email protected]>

Author: trondn

engines/ep/src/storeddockey.cc

@@ -126,6 +126,10 @@ bool SerialisedDocKey::operator==(const DocKey& rhs) const {
            std::equal(rhs.begin(), rhs.end(), data() + 1);
 }
 
+bool SerialisedDocKey::operator==(const SerialisedDocKey& rhs) const {
+    return rhs.size() == size() && std::memcmp(data(), rhs.data(), size()) == 0;
+}
+
 SerialisedDocKey::SerialisedDocKey(cb::const_byte_buffer key,
                                    CollectionID cid) {
     cb::mcbp::unsigned_leb128<CollectionIDType> leb128(uint32_t{cid});

engines/ep/src/storeddockey.h

@@ -239,6 +239,7 @@ class SerialisedDocKey : public DocKeyInterface<SerialisedDocKey> {
     }
 
     bool operator==(const DocKey& rhs) const;
+    bool operator==(const SerialisedDocKey& rhs) const;
 
     /**
      * Return how many bytes are (or need to be) allocated to this object