chore: import upstream snapshot with attribution

core/extensions/serialization.go

@@ -0,0 +1,68 @@
+// Copyright 2025 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package extensions
+
+import (
+	"context"
+
+	"github.com/cockroachdb/errors"
+
+	"github.com/dolthub/doltgresql/core/id"
+	"github.com/dolthub/doltgresql/utils"
+)
+
+// Serialize returns the Extension as a byte slice. If the Extension is invalid (invalid ExtName), then this returns a
+// nil slice.
+func (ext Extension) Serialize(ctx context.Context) ([]byte, error) {
+	if !ext.ExtName.IsValid() {
+		return nil, nil
+	}
+
+	// Initialize the writer
+	writer := utils.NewWriter(256)
+	writer.VariableUint(0) // Version
+	// Write the extension data
+	writer.Id(ext.ExtName.AsId())
+	writer.Id(ext.Namespace.AsId())
+	writer.Bool(ext.Relocatable)
+	writer.String(string(ext.LibIdentifier))
+	// Returns the data
+	return writer.Data(), nil
+}
+
+// DeserializeExtension returns the Extension that was serialized in the byte slice. Returns an empty Extension (has an
+// invalid ID) if data is nil or empty.
+func DeserializeExtension(ctx context.Context, data []byte) (Extension, error) {
+	if len(data) == 0 {
+		return Extension{}, nil
+	}
+	reader := utils.NewReader(data)
+	version := reader.VariableUint()
+	if version != 0 {
+		return Extension{}, errors.Errorf("version %d of extensions are not supported, please upgrade the server", version)
+	}
+
+	// Read from the reader
+	ext := Extension{}
+	ext.ExtName = id.Extension(reader.Id())
+	ext.Namespace = id.Namespace(reader.Id())
+	ext.Relocatable = reader.Bool()
+	ext.LibIdentifier = LibraryIdentifier(reader.String())
+	if !reader.IsEmpty() {
+		return Extension{}, errors.Errorf("extra data found while deserializing an extension")
+	}
+	// Return the deserialized object
+	return ext, nil
+}