Add Serialize and Deserialize support (mattn#1089)

Add support for Serialize and Deserialize, which wrap sqlite3_serialize and sqlite3_deserialize.

Author: otoolep

README.md

@@ -165,6 +165,7 @@ go build --tags "icu json1 fts5 secure_delete"
 | Allow URI Authority | sqlite_allow_uri_authority | URI filenames normally throws an error if the authority section is not either empty or "localhost".<br><br>However, if SQLite is compiled with the SQLITE_ALLOW_URI_AUTHORITY compile-time option, then the URI is converted into a Uniform Naming Convention (UNC) filename and passed down to the underlying operating system that way |
 | App Armor | sqlite_app_armor | When defined, this C-preprocessor macro activates extra code that attempts to detect misuse of the SQLite API, such as passing in NULL pointers to required parameters or using objects after they have been destroyed. <br><br>App Armor is not available under `Windows`. |
 | Disable Load Extensions | sqlite_omit_load_extension | Loading of external extensions is enabled by default.<br><br>To disable extension loading add the build tag `sqlite_omit_load_extension`. |
+| Enable Serialization with `libsqlite3` | sqlite_serialize | Serialization and deserialization of a SQLite database is available by default, unless the build tag `libsqlite3` is set.<br><br>To enable this functionality even if `libsqlite3` is set, add the build tag `sqlite_serialize`. |
 | Foreign Keys | sqlite_foreign_keys | This macro determines whether enforcement of foreign key constraints is enabled or disabled by default for new database connections.<br><br>Each database connection can always turn enforcement of foreign key constraints on and off and run-time using the foreign_keys pragma.<br><br>Enforcement of foreign key constraints is normally off by default, but if this compile-time parameter is set to 1, enforcement of foreign key constraints will be on by default | 
 | Full Auto Vacuum | sqlite_vacuum_full | Set the default auto vacuum to full |
 | Incremental Auto Vacuum | sqlite_vacuum_incr | Set the default auto vacuum to incremental |

sqlite3_opt_serialize.go

@@ -0,0 +1,82 @@
+// +build !libsqlite3 sqlite_serialize
+
+package sqlite3
+
+/*
+#ifndef USE_LIBSQLITE3
+#include <sqlite3-binding.h>
+#else
+#include <sqlite3.h>
+#endif
+#include <stdlib.h>
+#include <stdint.h>
+*/
+import "C"
+
+import (
+	"fmt"
+	"math"
+	"reflect"
+	"unsafe"
+)
+
+// Serialize returns a byte slice that is a serialization of the database.
+//
+// See https://www.sqlite.org/c3ref/serialize.html
+func (c *SQLiteConn) Serialize(schema string) ([]byte, error) {
+	if schema == "" {
+		schema = "main"
+	}
+	var zSchema *C.char
+	zSchema = C.CString(schema)
+	defer C.free(unsafe.Pointer(zSchema))
+
+	var sz C.sqlite3_int64
+	ptr := C.sqlite3_serialize(c.db, zSchema, &sz, 0)
+	if ptr == nil {
+		return nil, fmt.Errorf("serialize failed")
+	}
+	defer C.sqlite3_free(unsafe.Pointer(ptr))
+
+	if sz > C.sqlite3_int64(math.MaxInt) {
+		return nil, fmt.Errorf("serialized database is too large (%d bytes)", sz)
+	}
+
+	cBuf := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(ptr)),
+		Len:  int(sz),
+		Cap:  int(sz),
+	}))
+
+	res := make([]byte, int(sz))
+	copy(res, cBuf)
+	return res, nil
+}
+
+// Deserialize causes the connection to disconnect from the current database and
+// then re-open as an in-memory database based on the contents of the byte slice.
+//
+// See https://www.sqlite.org/c3ref/deserialize.html
+func (c *SQLiteConn) Deserialize(b []byte, schema string) error {
+	if schema == "" {
+		schema = "main"
+	}
+	var zSchema *C.char
+	zSchema = C.CString(schema)
+	defer C.free(unsafe.Pointer(zSchema))
+
+	tmpBuf := (*C.uchar)(C.sqlite3_malloc64(C.sqlite3_uint64(len(b))))
+	cBuf := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(tmpBuf)),
+		Len:  len(b),
+		Cap:  len(b),
+	}))
+	copy(cBuf, b)
+
+	rc := C.sqlite3_deserialize(c.db, zSchema, tmpBuf, C.sqlite3_int64(len(b)),
+		C.sqlite3_int64(len(b)), C.SQLITE_DESERIALIZE_FREEONCLOSE)
+	if rc != C.SQLITE_OK {
+		return fmt.Errorf("deserialize failed with return %v", rc)
+	}
+	return nil
+}

sqlite3_opt_serialize_omit.go

@@ -0,0 +1,20 @@
+// +build libsqlite3,!sqlite_serialize
+
+package sqlite3
+
+import (
+	"errors"
+)
+
+/*
+#cgo CFLAGS: -DSQLITE_OMIT_DESERIALIZE
+*/
+import "C"
+
+func (c *SQLiteConn) Serialize(schema string) ([]byte, error) {
+	return nil, errors.New("sqlite3: Serialize requires the sqlite_serialize build tag when using the libsqlite3 build tag")
+}
+
+func (c *SQLiteConn) Deserialize(b []byte, schema string) error {
+	return errors.New("sqlite3: Deserialize requires the sqlite_serialize build tag when using the libsqlite3 build tag")
+}

sqlite3_opt_serialize_test.go

@@ -0,0 +1,99 @@
+// +build !libsqlite3 sqlite_serialize
+
+package sqlite3
+
+import (
+	"context"
+	"database/sql"
+	"os"
+	"testing"
+)
+
+func TestSerializeDeserialize(t *testing.T) {
+	// Connect to the source database.
+	srcTempFilename := TempFilename(t)
+	defer os.Remove(srcTempFilename)
+	srcDb, err := sql.Open(driverName, srcTempFilename)
+	if err != nil {
+		t.Fatal("Failed to open the source database:", err)
+	}
+	defer srcDb.Close()
+	err = srcDb.Ping()
+	if err != nil {
+		t.Fatal("Failed to connect to the source database:", err)
+	}
+
+	// Connect to the destination database.
+	destTempFilename := TempFilename(t)
+	defer os.Remove(destTempFilename)
+	destDb, err := sql.Open(driverName, destTempFilename)
+	if err != nil {
+		t.Fatal("Failed to open the destination database:", err)
+	}
+	defer destDb.Close()
+	err = destDb.Ping()
+	if err != nil {
+		t.Fatal("Failed to connect to the destination database:", err)
+	}
+
+	// Write data to source database.
+	_, err = srcDb.Exec(`CREATE TABLE foo (name string)`)
+	if err != nil {
+		t.Fatal("Failed to create table in source database:", err)
+	}
+	_, err = srcDb.Exec(`INSERT INTO foo(name) VALUES("alice")`)
+	if err != nil {
+		t.Fatal("Failed to insert data into source database", err)
+	}
+
+	// Serialize the source database
+	srcConn, err := srcDb.Conn(context.Background())
+	if err != nil {
+		t.Fatal("Failed to get connection to source database:", err)
+	}
+	defer srcConn.Close()
+
+	var serialized []byte
+	if err := srcConn.Raw(func(raw interface{}) error {
+		var err error
+		serialized, err = raw.(*SQLiteConn).Serialize("")
+		return err
+	}); err != nil {
+		t.Fatal("Failed to serialize source database:", err)
+	}
+	srcConn.Close()
+
+	// Confirm that the destination database is initially empty.
+	var destTableCount int
+	err = destDb.QueryRow("SELECT COUNT(*) FROM sqlite_master WHERE type = 'table'").Scan(&destTableCount)
+	if err != nil {
+		t.Fatal("Failed to check the destination table count:", err)
+	}
+	if destTableCount != 0 {
+		t.Fatalf("The destination database is not empty; %v table(s) found.", destTableCount)
+	}
+
+	// Deserialize to destination database
+	destConn, err := destDb.Conn(context.Background())
+	if err != nil {
+		t.Fatal("Failed to get connection to destination database:", err)
+	}
+	defer destConn.Close()
+
+	if err := destConn.Raw(func(raw interface{}) error {
+		return raw.(*SQLiteConn).Deserialize(serialized, "")
+	}); err != nil {
+		t.Fatal("Failed to deserialize source database:", err)
+	}
+	destConn.Close()
+
+	// Confirm that destination database has been loaded correctly.
+	var destRowCount int
+	err = destDb.QueryRow(`SELECT COUNT(*) FROM foo`).Scan(&destRowCount)
+	if err != nil {
+		t.Fatal("Failed to count rows in destination database table", err)
+	}
+	if destRowCount != 1 {
+		t.Fatalf("Destination table does not have the expected records")
+	}
+}