wallet: Cache SigningProviders

achow101 · achow101 · commit fcc2160d1c4e · 2022-04-10T15:38:45.000-04:00
In order to avoid constantly re-deriving the same keys in
DescriptorScriptPubKeyMan, cache the SigningProviders generated inside
of GetSigningProvider.

This makes GetSigningProvider non-const, which cauess a bunch of
functions to also not be const and that results in a much larger diff
than expected.
diff --git a/src/script/signingprovider.cpp b/src/script/signingprovider.cpp
@@ -82,6 +82,17 @@ FlatSigningProvider Merge(const FlatSigningProvider& a, const FlatSigningProvide
     return ret;
 }
 
+void MergeInto(FlatSigningProvider& a, const FlatSigningProvider& b)
+{
+    a.scripts.insert(b.scripts.begin(), b.scripts.end());
+    a.pubkeys.insert(b.pubkeys.begin(), b.pubkeys.end());
+    a.keys.insert(b.keys.begin(), b.keys.end());
+    a.origins.insert(b.origins.begin(), b.origins.end());
+    for (const auto& [output_key, spenddata] : b.tr_spenddata) {
+        a.tr_spenddata[output_key].Merge(spenddata);
+    }
+}
+
 void FillableSigningProvider::ImplicitlyLearnRelatedKeyScripts(const CPubKey& pubkey)
 {
     AssertLockHeld(cs_KeyStore);
diff --git a/src/script/signingprovider.h b/src/script/signingprovider.h
@@ -85,6 +85,7 @@ struct FlatSigningProvider final : public SigningProvider
 };
 
 FlatSigningProvider Merge(const FlatSigningProvider& a, const FlatSigningProvider& b);
+void MergeInto(FlatSigningProvider& a, const FlatSigningProvider& b);
 
 /** Fillable signing provider that keeps keys in an address->secret map */
 class FillableSigningProvider : public SigningProvider
diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
@@ -2076,10 +2076,22 @@ std::unique_ptr<FlatSigningProvider> DescriptorScriptPubKeyMan::GetSigningProvid
 std::unique_ptr<FlatSigningProvider> DescriptorScriptPubKeyMan::GetSigningProvider(int32_t index, bool include_private) const
 {
     AssertLockHeld(cs_desc_man);
-    // Get the scripts, keys, and key origins for this script
+
     std::unique_ptr<FlatSigningProvider> out_keys = std::make_unique<FlatSigningProvider>();
-    std::vector<CScript> scripts_temp;
-    if (!m_wallet_descriptor.descriptor->ExpandFromCache(index, m_wallet_descriptor.cache, scripts_temp, *out_keys)) return nullptr;
+
+    // Fetch SigningProvider from cache to avoid re-deriving
+    auto it = m_map_signing_providers.find(index);
+    if (it != m_map_signing_providers.end()) {
+        MergeInto(*out_keys, it->second);
+    } else {
+        // Get the scripts, keys, and key origins for this script
+        std::vector<CScript> scripts_temp;
+        if (!m_wallet_descriptor.descriptor->ExpandFromCache(index, m_wallet_descriptor.cache, scripts_temp, *out_keys)) return nullptr;
+
+        // Cache SigningProvider so we don't need to re-derive if we need this SigningProvider again
+        m_map_signing_providers.insert({index, {}});
+        MergeInto(m_map_signing_providers[index], *out_keys);
+    }
 
     if (HavePrivateKeys() && include_private) {
         FlatSigningProvider master_provider;
diff --git a/src/wallet/scriptpubkeyman.h b/src/wallet/scriptpubkeyman.h
@@ -546,6 +546,8 @@ class DescriptorScriptPubKeyMan : public ScriptPubKeyMan
 
     KeyMap GetKeys() const EXCLUSIVE_LOCKS_REQUIRED(cs_desc_man);
 
+    // Cached FlatSigningProviders to avoid regenerating them each time they are needed.
+    mutable std::map<int32_t, FlatSigningProvider> m_map_signing_providers;
     // Fetch the SigningProvider for the given script and optionally include private keys
     std::unique_ptr<FlatSigningProvider> GetSigningProvider(const CScript& script, bool include_private = false) const;
     // Fetch the SigningProvider for the given pubkey and always include private keys. This should only be called by signing code.
