sqlite: add serialize() and deserialize()

Add database.serialize() and database.deserialize() methods to
DatabaseSync, wrapping the sqlite3_serialize and sqlite3_deserialize
C APIs. These allow extracting an in-memory database as a Uint8Array
and loading one back, enabling snapshots, cloning, and transfer of
databases without filesystem I/O.

Author: thisalihassan

doc/api/sqlite.md

@@ -531,6 +531,64 @@ Opens the database specified in the `path` argument of the `DatabaseSync`
 constructor. This method should only be used when the database is not opened via
 the constructor. An exception is thrown if the database is already open.
 
+### `database.serialize([dbName])`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `dbName` {string} Name of the database to serialize. This can be `'main'`
+  (the default primary database) or any other database that has been added with
+  [`ATTACH DATABASE`][]. **Default:** `'main'`.
+* Returns: {Uint8Array} A binary representation of the database.
+
+Serializes the database into a binary representation, returned as a
+`Uint8Array`. This is useful for saving, cloning, or transferring an in-memory
+database. This method is a wrapper around [`sqlite3_serialize()`][].
+
+```cjs
+const { DatabaseSync } = require('node:sqlite');
+
+const db = new DatabaseSync(':memory:');
+db.exec('CREATE TABLE t(key INTEGER PRIMARY KEY, value TEXT)');
+db.exec("INSERT INTO t VALUES (1, 'hello')");
+const buffer = db.serialize();
+console.log(buffer.length); // Prints the byte length of the database
+```
+
+### `database.deserialize(buffer[, options])`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `buffer` {Uint8Array} A binary representation of a database, such as the
+  output of [`database.serialize()`][].
+* `options` {Object} Optional configuration for the deserialization.
+  * `dbName` {string} Name of the database to deserialize into.
+    **Default:** `'main'`.
+
+Loads a serialized database into this connection, replacing the current
+database. The deserialized database is writable. Existing prepared statements
+are finalized before deserialization is attempted, even if the operation
+subsequently fails. This method is a wrapper around
+[`sqlite3_deserialize()`][].
+
+```cjs
+const { DatabaseSync } = require('node:sqlite');
+
+const original = new DatabaseSync(':memory:');
+original.exec('CREATE TABLE t(key INTEGER PRIMARY KEY, value TEXT)');
+original.exec("INSERT INTO t VALUES (1, 'hello')");
+const buffer = original.serialize();
+original.close();
+
+const clone = new DatabaseSync(':memory:');
+clone.deserialize(buffer);
+console.log(clone.prepare('SELECT value FROM t').get());
+// Prints: { value: 'hello' }
+```
+
 ### `database.prepare(sql[, options])`
 
 <!-- YAML
@@ -1545,6 +1603,7 @@ callback function to indicate what type of operation is being authorized.
 [`SQLTagStore`]: #class-sqltagstore
 [`database.applyChangeset()`]: #databaseapplychangesetchangeset-options
 [`database.createTagStore()`]: #databasecreatetagstoremaxsize
+[`database.serialize()`]: #databaseserializedbname
 [`database.setAuthorizer()`]: #databasesetauthorizercallback
 [`sqlite3_backup_finish()`]: https://www.sqlite.org/c3ref/backup_finish.html#sqlite3backupfinish
 [`sqlite3_backup_init()`]: https://www.sqlite.org/c3ref/backup_finish.html#sqlite3backupinit
@@ -1559,12 +1618,14 @@ callback function to indicate what type of operation is being authorized.
 [`sqlite3_create_function_v2()`]: https://www.sqlite.org/c3ref/create_function.html
 [`sqlite3_create_window_function()`]: https://www.sqlite.org/c3ref/create_function.html
 [`sqlite3_db_filename()`]: https://sqlite.org/c3ref/db_filename.html
+[`sqlite3_deserialize()`]: https://sqlite.org/c3ref/deserialize.html
 [`sqlite3_exec()`]: https://www.sqlite.org/c3ref/exec.html
 [`sqlite3_expanded_sql()`]: https://www.sqlite.org/c3ref/expanded_sql.html
 [`sqlite3_get_autocommit()`]: https://sqlite.org/c3ref/get_autocommit.html
 [`sqlite3_last_insert_rowid()`]: https://www.sqlite.org/c3ref/last_insert_rowid.html
 [`sqlite3_load_extension()`]: https://www.sqlite.org/c3ref/load_extension.html
 [`sqlite3_prepare_v2()`]: https://www.sqlite.org/c3ref/prepare.html
+[`sqlite3_serialize()`]: https://sqlite.org/c3ref/serialize.html
 [`sqlite3_set_authorizer()`]: https://sqlite.org/c3ref/set_authorizer.html
 [`sqlite3_sql()`]: https://www.sqlite.org/c3ref/expanded_sql.html
 [`sqlite3changeset_apply()`]: https://www.sqlite.org/session/sqlite3changeset_apply.html

src/node_sqlite.cc

@@ -23,6 +23,7 @@ namespace sqlite {
 using v8::Array;
 using v8::ArrayBuffer;
 using v8::BackingStoreInitializationMode;
+using v8::BackingStoreOnFailureMode;
 using v8::BigInt;
 using v8::Boolean;
 using v8::ConstructorBehavior;
@@ -1719,6 +1720,133 @@ void DatabaseSync::Location(const FunctionCallbackInfo<Value>& args) {
   }
 }
 
+void DatabaseSync::Serialize(const FunctionCallbackInfo<Value>& args) {
+  DatabaseSync* db;
+  ASSIGN_OR_RETURN_UNWRAP(&db, args.This());
+  Environment* env = Environment::GetCurrent(args);
+  THROW_AND_RETURN_ON_BAD_STATE(env, !db->IsOpen(), "database is not open");
+
+  std::string db_name = "main";
+  if (!args[0]->IsUndefined()) {
+    if (!args[0]->IsString()) {
+      THROW_ERR_INVALID_ARG_TYPE(env->isolate(),
+                                 "The \"dbName\" argument must be a string.");
+      return;
+    }
+    db_name = Utf8Value(env->isolate(), args[0].As<String>()).ToString();
+  }
+
+  sqlite3_int64 size = 0;
+  unsigned char* data =
+      sqlite3_serialize(db->connection_, db_name.c_str(), &size, 0);
+
+  if (data == nullptr) {
+    if (size == 0) {
+      Local<ArrayBuffer> ab = ArrayBuffer::New(env->isolate(), 0);
+      args.GetReturnValue().Set(Uint8Array::New(ab, 0, 0));
+      return;
+    }
+    THROW_ERR_SQLITE_ERROR(env->isolate(), db);
+    return;
+  }
+
+  // V8 sandbox forbids external backing stores so allocate inside the
+  // sandbox and copy. Without sandbox wrap the output directly using
+  // sqlite3_free as the destructor to avoid the copy.
+#ifdef V8_ENABLE_SANDBOX
+  auto free_data = OnScopeLeave([&] { sqlite3_free(data); });
+  auto store = ArrayBuffer::NewBackingStore(
+      env->isolate(),
+      size,
+      BackingStoreInitializationMode::kUninitialized,
+      BackingStoreOnFailureMode::kReturnNull);
+  if (!store) {
+    THROW_ERR_MEMORY_ALLOCATION_FAILED(env);
+    return;
+  }
+  memcpy(store->Data(), data, size);
+  Local<ArrayBuffer> ab = ArrayBuffer::New(env->isolate(), std::move(store));
+#else
+  auto store = ArrayBuffer::NewBackingStore(
+      data, size, [](void* ptr, size_t, void*) { sqlite3_free(ptr); }, nullptr);
+  Local<ArrayBuffer> ab = ArrayBuffer::New(env->isolate(), std::move(store));
+#endif
+
+  args.GetReturnValue().Set(Uint8Array::New(ab, 0, size));
+}
+
+void DatabaseSync::Deserialize(const FunctionCallbackInfo<Value>& args) {
+  DatabaseSync* db;
+  ASSIGN_OR_RETURN_UNWRAP(&db, args.This());
+  Environment* env = Environment::GetCurrent(args);
+  THROW_AND_RETURN_ON_BAD_STATE(env, !db->IsOpen(), "database is not open");
+
+  if (!args[0]->IsUint8Array()) {
+    THROW_ERR_INVALID_ARG_TYPE(env->isolate(),
+                               "The \"buffer\" argument must be a Uint8Array.");
+    return;
+  }
+
+  Local<Uint8Array> input = args[0].As<Uint8Array>();
+  size_t byte_length = input->ByteLength();
+
+  if (byte_length == 0) {
+    THROW_ERR_INVALID_ARG_VALUE(env,
+                                "The \"buffer\" argument must not be empty.");
+    return;
+  }
+
+  std::string db_name = "main";
+  if (args.Length() > 1 && !args[1]->IsUndefined()) {
+    if (!args[1]->IsObject()) {
+      THROW_ERR_INVALID_ARG_TYPE(env->isolate(),
+                                 "The \"options\" argument must be an object.");
+      return;
+    }
+
+    Local<Object> options = args[1].As<Object>();
+    Local<String> db_name_key = FIXED_ONE_BYTE_STRING(env->isolate(), "dbName");
+    Local<Value> db_name_value;
+    if (!options->Get(env->context(), db_name_key).ToLocal(&db_name_value)) {
+      return;
+    }
+
+    if (!db_name_value->IsUndefined()) {
+      if (!db_name_value->IsString()) {
+        THROW_ERR_INVALID_ARG_TYPE(
+            env->isolate(),
+            "The \"options.dbName\" argument must be a string.");
+        return;
+      }
+      db_name =
+          Utf8Value(env->isolate(), db_name_value.As<String>()).ToString();
+    }
+  }
+
+  unsigned char* buf =
+      static_cast<unsigned char*>(sqlite3_malloc64(byte_length));
+  if (buf == nullptr) {
+    THROW_ERR_MEMORY_ALLOCATION_FAILED(env);
+    return;
+  }
+
+  input->CopyContents(buf, byte_length);
+
+  db->FinalizeStatements();
+
+  int r = sqlite3_deserialize(
+      db->connection_,
+      db_name.c_str(),
+      buf,
+      byte_length,
+      byte_length,
+      SQLITE_DESERIALIZE_FREEONCLOSE | SQLITE_DESERIALIZE_RESIZEABLE);
+  if (r != SQLITE_OK) {
+    THROW_ERR_SQLITE_ERROR(env->isolate(), db);
+    return;
+  }
+}
+
 void DatabaseSync::AggregateFunction(const FunctionCallbackInfo<Value>& args) {
   DatabaseSync* db;
   ASSIGN_OR_RETURN_UNWRAP(&db, args.This());
@@ -3766,6 +3894,8 @@ static void Initialize(Local<Object> target,
       isolate, db_tmpl, "enableDefensive", DatabaseSync::EnableDefensive);
   SetProtoMethod(
       isolate, db_tmpl, "loadExtension", DatabaseSync::LoadExtension);
+  SetProtoMethod(isolate, db_tmpl, "serialize", DatabaseSync::Serialize);
+  SetProtoMethod(isolate, db_tmpl, "deserialize", DatabaseSync::Deserialize);
   SetProtoMethod(
       isolate, db_tmpl, "setAuthorizer", DatabaseSync::SetAuthorizer);
   SetSideEffectFreeGetter(isolate,

src/node_sqlite.h

@@ -195,6 +195,8 @@ class DatabaseSync : public BaseObject {
   static void EnableDefensive(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void LimitsGetter(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void LoadExtension(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void Serialize(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void Deserialize(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void SetAuthorizer(const v8::FunctionCallbackInfo<v8::Value>& args);
   static int AuthorizerCallback(void* user_data,
                                 int action_code,