firewaldb: single implementation of BBolt DBExecutor

The `kvStores` and `privacyMapDB` types have very similar looking
`Update` and `View` methods. Instead of the duplication, here we let
things be more generic by defining a generic `kvdbExecutor` which has
Update and View methods defined.

Author: ellemouton

firewalldb/kvdb_store.go

@@ -0,0 +1,50 @@
+package firewalldb
+
+import (
+	"context"
+
+	"go.etcd.io/bbolt"
+)
+
+// kvdbExecutor is a concrete implementation of the DBExecutor interface that
+// uses a bbolt database as its backing store.
+type kvdbExecutor[T any] struct {
+	db      *bbolt.DB
+	wrapper txWrapper[T]
+}
+
+// txWrapper is an interface that wraps a bbolt transaction.
+type txWrapper[T any] interface {
+	// wrap wraps a bbolt transaction with extra functionality.
+	wrap(tx *bbolt.Tx) T
+}
+
+// Update opens a database read/write transaction and executes the function f
+// with the transaction passed as a parameter. After f exits, if f did not
+// error, the transaction is committed. Otherwise, if f did error, the
+// transaction is rolled back. If the rollback fails, the original error
+// returned by f is still returned. If the commit fails, the commit error is
+// returned.
+//
+// NOTE: this is part of the DBExecutor interface.
+func (e *kvdbExecutor[T]) Update(ctx context.Context,
+	fn func(ctx context.Context, tx T) error) error {
+
+	return e.db.Update(func(tx *bbolt.Tx) error {
+		return fn(ctx, e.wrapper.wrap(tx))
+	})
+}
+
+// View opens a database read transaction and executes the function f with the
+// transaction passed as a parameter. After f exits, the transaction is rolled
+// back. If f errors, its error is returned, not a rollback error (if any
+// occur).
+//
+// NOTE: this is part of the DBExecutor interface.
+func (e *kvdbExecutor[T]) View(ctx context.Context,
+	fn func(ctx context.Context, tx T) error) error {
+
+	return e.db.View(func(tx *bbolt.Tx) error {
+		return fn(ctx, e.wrapper.wrap(tx))
+	})
+}

firewalldb/kvstores.go

@@ -107,11 +107,14 @@ type RulesDB interface {
 func (db *DB) GetKVStores(rule string, groupID session.ID,
 	feature string) KVStores {
 
-	return &kvStores{
-		db:          db.DB,
-		ruleName:    rule,
-		groupID:     groupID,
-		featureName: feature,
+	return &kvdbExecutor[KVStoreTx]{
+		db: db.DB,
+		wrapper: &kvStores{
+			db:          db.DB,
+			ruleName:    rule,
+			groupID:     groupID,
+			featureName: feature,
+		},
 	}
 }
 
@@ -123,44 +126,15 @@ type kvStores struct {
 	featureName string
 }
 
-// Update opens a database read/write transaction and executes the function f
-// with the transaction passed as a parameter. After f exits, if f did not
-// error, the transaction is committed. Otherwise, if f did error, the
-// transaction is rolled back. If the rollback fails, the original error
-// returned by f is still returned. If the commit fails, the commit error is
-// returned.
+// wrap wraps a bbolt transaction with  the fields in kvStores and returns a
+// KVStoreTx.
 //
-// NOTE: this is part of the KVStores interface.
-func (s *kvStores) Update(ctx context.Context, fn func(ctx context.Context,
-	tx KVStoreTx) error) error {
-
-	return s.db.Update(func(tx *bbolt.Tx) error {
-		boltTx := &kvStoreTx{
-			boltTx:   tx,
-			kvStores: s,
-		}
-
-		return fn(ctx, boltTx)
-	})
-}
-
-// View opens a database read transaction and executes the function f with the
-// transaction passed as a parameter. After f exits, the transaction is rolled
-// back. If f errors, its error is returned, not a rollback error (if any
-// occur).
-//
-// NOTE: this is part of the KVStores interface.
-func (s *kvStores) View(ctx context.Context, fn func(ctx context.Context,
-	tx KVStoreTx) error) error {
-
-	return s.db.View(func(tx *bbolt.Tx) error {
-		boltTx := &kvStoreTx{
-			boltTx:   tx,
-			kvStores: s,
-		}
-
-		return fn(ctx, boltTx)
-	})
+// NOTE: this is part of the txWrapper interface.
+func (s *kvStores) wrap(tx *bbolt.Tx) KVStoreTx {
+	return &kvStoreTx{
+		boltTx:   tx,
+		kvStores: s,
+	}
 }
 
 // getBucketFunc defines the signature of the bucket creation/fetching function

firewalldb/privacy_mapper.go

@@ -42,9 +42,12 @@ type NewPrivacyMapDB func(groupID session.ID) PrivacyMapDB
 // PrivacyDB constructs a PrivacyMapDB that will be indexed under the given
 // group ID key.
 func (db *DB) PrivacyDB(groupID session.ID) PrivacyMapDB {
-	return &privacyMapDB{
-		db:      db,
-		groupID: groupID,
+	return &kvdbExecutor[PrivacyMapTx]{
+		db: db.DB,
+		wrapper: &privacyMapDB{
+			db:      db,
+			groupID: groupID,
+		},
 	}
 }
 
@@ -78,44 +81,14 @@ type privacyMapDB struct {
 	groupID session.ID
 }
 
-// Update opens a database read/write transaction and executes the function f
-// with the transaction passed as a parameter. After f exits, if f did not
-// error, the transaction is committed. Otherwise, if f did error, the
-// transaction is rolled back. If the rollback fails, the original error
-// returned by f is still returned. If the commit fails, the commit error is
-// returned.
+// wrap returns a new PrivacyMapTx that wraps the given bolt transaction.
 //
-// NOTE: this is part of the PrivacyMapDB interface.
-func (p *privacyMapDB) Update(ctx context.Context, fn func(ctx context.Context,
-	tx PrivacyMapTx) error) error {
-
-	return p.db.Update(func(tx *bbolt.Tx) error {
-		boltTx := &privacyMapTx{
-			privacyMapDB: p,
-			boltTx:       tx,
-		}
-
-		return fn(ctx, boltTx)
-	})
-}
-
-// View opens a database read transaction and executes the function f with the
-// transaction passed as a parameter. After f exits, the transaction is rolled
-// back. If f errors, its error is returned, not a rollback error (if any
-// occur).
-//
-// NOTE: this is part of the PrivacyMapDB interface.
-func (p *privacyMapDB) View(ctx context.Context, fn func(ctx context.Context,
-	tx PrivacyMapTx) error) error {
-
-	return p.db.View(func(tx *bbolt.Tx) error {
-		boltTx := &privacyMapTx{
-			privacyMapDB: p,
-			boltTx:       tx,
-		}
-
-		return fn(ctx, boltTx)
-	})
+// NOTE: this is part of the txWrapper interface.
+func (p *privacyMapDB) wrap(tx *bbolt.Tx) PrivacyMapTx {
+	return &privacyMapTx{
+		boltTx:       tx,
+		privacyMapDB: p,
+	}
 }
 
 // privacyMapTx is an implementation of PrivacyMapTx.