Add support for pre-update hooks

callback.go

@@ -77,6 +77,21 @@ func updateHookTrampoline(handle uintptr, op int, db *C.char, table *C.char, row
 	callback(op, C.GoString(db), C.GoString(table), rowid)
 }
 
+//export preUpdateHookTrampoline
+func preUpdateHookTrampoline(handle uintptr, dbHandle uintptr, op int, db *C.char, table *C.char, oldrowid int64, newrowid int64) {
+	hval := lookupHandleVal(handle)
+	data := SQLitePreUpdateData{
+		Conn:         hval.db,
+		Op:           op,
+		DatabaseName: C.GoString(db),
+		TableName:    C.GoString(table),
+		OldRowID:     oldrowid,
+		NewRowID:     newrowid,
+	}
+	callback := hval.val.(func(SQLitePreUpdateData))
+	callback(data)
+}
+
 // Use handles to avoid passing Go pointers to C.
 
 type handleVal struct {
@@ -97,7 +112,7 @@ func newHandle(db *SQLiteConn, v interface{}) uintptr {
 	return i
 }
 
-func lookupHandle(handle uintptr) interface{} {
+func lookupHandleVal(handle uintptr) handleVal {
 	handleLock.Lock()
 	defer handleLock.Unlock()
 	r, ok := handleVals[handle]
@@ -108,7 +123,11 @@ func lookupHandle(handle uintptr) interface{} {
 			panic("invalid handle")
 		}
 	}
-	return r.val
+	return r
+}
+
+func lookupHandle(handle uintptr) interface{} {
+	return lookupHandleVal(handle).val
 }
 
 func deleteHandles(db *SQLiteConn) {

convert.go

@@ -0,0 +1,301 @@
+// Extracted from Go database/sql source code
+
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Type conversions for Scan.
+
+package sqlite3
+
+import (
+	"database/sql"
+	"database/sql/driver"
+	"errors"
+	"fmt"
+	"reflect"
+	"strconv"
+	"time"
+)
+
+var errNilPtr = errors.New("destination pointer is nil") // embedded in descriptive error
+
+// convertAssign copies to dest the value in src, converting it if possible.
+// An error is returned if the copy would result in loss of information.
+// dest should be a pointer type.
+func convertAssign(dest, src interface{}) error {
+	// Common cases, without reflect.
+	switch s := src.(type) {
+	case string:
+		switch d := dest.(type) {
+		case *string:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = s
+			return nil
+		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = []byte(s)
+			return nil
+		case *sql.RawBytes:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = append((*d)[:0], s...)
+			return nil
+		}
+	case []byte:
+		switch d := dest.(type) {
+		case *string:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = string(s)
+			return nil
+		case *interface{}:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = cloneBytes(s)
+			return nil
+		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = cloneBytes(s)
+			return nil
+		case *sql.RawBytes:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = s
+			return nil
+		}
+	case time.Time:
+		switch d := dest.(type) {
+		case *time.Time:
+			*d = s
+			return nil
+		case *string:
+			*d = s.Format(time.RFC3339Nano)
+			return nil
+		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = []byte(s.Format(time.RFC3339Nano))
+			return nil
+		case *sql.RawBytes:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = s.AppendFormat((*d)[:0], time.RFC3339Nano)
+			return nil
+		}
+	case nil:
+		switch d := dest.(type) {
+		case *interface{}:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = nil
+			return nil
+		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = nil
+			return nil
+		case *sql.RawBytes:
+			if d == nil {
+				return errNilPtr
+			}
+			*d = nil
+			return nil
+		}
+	}
+
+	var sv reflect.Value
+
+	switch d := dest.(type) {
+	case *string:
+		sv = reflect.ValueOf(src)
+		switch sv.Kind() {
+		case reflect.Bool,
+			reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+			reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
+			reflect.Float32, reflect.Float64:
+			*d = asString(src)
+			return nil
+		}
+	case *[]byte:
+		sv = reflect.ValueOf(src)
+		if b, ok := asBytes(nil, sv); ok {
+			*d = b
+			return nil
+		}
+	case *sql.RawBytes:
+		sv = reflect.ValueOf(src)
+		if b, ok := asBytes([]byte(*d)[:0], sv); ok {
+			*d = sql.RawBytes(b)
+			return nil
+		}
+	case *bool:
+		bv, err := driver.Bool.ConvertValue(src)
+		if err == nil {
+			*d = bv.(bool)
+		}
+		return err
+	case *interface{}:
+		*d = src
+		return nil
+	}
+
+	if scanner, ok := dest.(sql.Scanner); ok {
+		return scanner.Scan(src)
+	}
+
+	dpv := reflect.ValueOf(dest)
+	if dpv.Kind() != reflect.Ptr {
+		return errors.New("destination not a pointer")
+	}
+	if dpv.IsNil() {
+		return errNilPtr
+	}
+
+	if !sv.IsValid() {
+		sv = reflect.ValueOf(src)
+	}
+
+	dv := reflect.Indirect(dpv)
+	if sv.IsValid() && sv.Type().AssignableTo(dv.Type()) {
+		switch b := src.(type) {
+		case []byte:
+			dv.Set(reflect.ValueOf(cloneBytes(b)))
+		default:
+			dv.Set(sv)
+		}
+		return nil
+	}
+
+	if dv.Kind() == sv.Kind() && sv.Type().ConvertibleTo(dv.Type()) {
+		dv.Set(sv.Convert(dv.Type()))
+		return nil
+	}
+
+	// The following conversions use a string value as an intermediate representation
+	// to convert between various numeric types.
+	//
+	// This also allows scanning into user defined types such as "type Int int64".
+	// For symmetry, also check for string destination types.
+	switch dv.Kind() {
+	case reflect.Ptr:
+		if src == nil {
+			dv.Set(reflect.Zero(dv.Type()))
+			return nil
+		} else {
+			dv.Set(reflect.New(dv.Type().Elem()))
+			return convertAssign(dv.Interface(), src)
+		}
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		s := asString(src)
+		i64, err := strconv.ParseInt(s, 10, dv.Type().Bits())
+		if err != nil {
+			err = strconvErr(err)
+			return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
+		}
+		dv.SetInt(i64)
+		return nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		s := asString(src)
+		u64, err := strconv.ParseUint(s, 10, dv.Type().Bits())
+		if err != nil {
+			err = strconvErr(err)
+			return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
+		}
+		dv.SetUint(u64)
+		return nil
+	case reflect.Float32, reflect.Float64:
+		s := asString(src)
+		f64, err := strconv.ParseFloat(s, dv.Type().Bits())
+		if err != nil {
+			err = strconvErr(err)
+			return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
+		}
+		dv.SetFloat(f64)
+		return nil
+	case reflect.String:
+		switch v := src.(type) {
+		case string:
+			dv.SetString(v)
+			return nil
+		case []byte:
+			dv.SetString(string(v))
+			return nil
+		}
+	}
+
+	return fmt.Errorf("unsupported Scan, storing driver.Value type %T into type %T", src, dest)
+}
+
+func strconvErr(err error) error {
+	if ne, ok := err.(*strconv.NumError); ok {
+		return ne.Err
+	}
+	return err
+}
+
+func cloneBytes(b []byte) []byte {
+	if b == nil {
+		return nil
+	} else {
+		c := make([]byte, len(b))
+		copy(c, b)
+		return c
+	}
+}
+
+func asString(src interface{}) string {
+	switch v := src.(type) {
+	case string:
+		return v
+	case []byte:
+		return string(v)
+	}
+	rv := reflect.ValueOf(src)
+	switch rv.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return strconv.FormatInt(rv.Int(), 10)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		return strconv.FormatUint(rv.Uint(), 10)
+	case reflect.Float64:
+		return strconv.FormatFloat(rv.Float(), 'g', -1, 64)
+	case reflect.Float32:
+		return strconv.FormatFloat(rv.Float(), 'g', -1, 32)
+	case reflect.Bool:
+		return strconv.FormatBool(rv.Bool())
+	}
+	return fmt.Sprintf("%v", src)
+}
+
+func asBytes(buf []byte, rv reflect.Value) (b []byte, ok bool) {
+	switch rv.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return strconv.AppendInt(buf, rv.Int(), 10), true
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		return strconv.AppendUint(buf, rv.Uint(), 10), true
+	case reflect.Float32:
+		return strconv.AppendFloat(buf, rv.Float(), 'g', -1, 32), true
+	case reflect.Float64:
+		return strconv.AppendFloat(buf, rv.Float(), 'g', -1, 64), true
+	case reflect.Bool:
+		return strconv.AppendBool(buf, rv.Bool()), true
+	case reflect.String:
+		s := rv.String()
+		return append(buf, s...), true
+	}
+	return
+}

sqlite3.go

@@ -14,6 +14,7 @@ package sqlite3
 #cgo CFLAGS: -DSQLITE_ENABLE_FTS3 -DSQLITE_ENABLE_FTS3_PARENTHESIS -DSQLITE_ENABLE_FTS4_UNICODE61
 #cgo CFLAGS: -DSQLITE_TRACE_SIZE_LIMIT=15
 #cgo CFLAGS: -DSQLITE_DISABLE_INTRINSIC
+#cgo CFLAGS: -DSQLITE_ENABLE_PREUPDATE_HOOK
 #cgo CFLAGS: -Wno-deprecated-declarations
 #ifndef USE_LIBSQLITE3
 #include <sqlite3-binding.h>
@@ -110,6 +111,7 @@ int compareTrampoline(void*, int, char*, int, char*);
 int commitHookTrampoline(void*);
 void rollbackHookTrampoline(void*);
 void updateHookTrampoline(void*, int, char*, char*, sqlite3_int64);
+void preUpdateHookTrampoline(void*, sqlite3 *, int, char *, char *, sqlite3_int64, sqlite3_int64);
 
 #ifdef SQLITE_LIMIT_WORKER_THREADS
 # define _SQLITE_HAS_LIMIT
@@ -239,6 +241,17 @@ type SQLiteRows struct {
 	done     chan struct{}
 }
 
+// SQLitePreUpdateData represents all of the data available during a
+// pre-update hook call.
+type SQLitePreUpdateData struct {
+	Conn         *SQLiteConn
+	Op           int
+	DatabaseName string
+	TableName    string
+	OldRowID     int64
+	NewRowID     int64
+}
+
 type functionInfo struct {
 	f                 reflect.Value
 	argConverters     []callbackArgConverter
@@ -426,6 +439,22 @@ func (c *SQLiteConn) RegisterUpdateHook(callback func(int, string, string, int64
 	}
 }
 
+// RegisterPreUpdateHook sets the pre-update hook for a connection.
+//
+// The callback is passed a SQLitePreUpdateData struct with the data for
+// the update, as well as methods for fetching copies of impacted data.
+//
+// If there is an existing update hook for this connection, it will be
+// removed. If callback is nil the existing hook (if any) will be removed
+// without creating a new one.
+func (c *SQLiteConn) RegisterPreUpdateHook(callback func(SQLitePreUpdateData)) {
+	if callback == nil {
+		C.sqlite3_preupdate_hook(c.db, nil, nil)
+	} else {
+		C.sqlite3_preupdate_hook(c.db, (*[0]byte)(unsafe.Pointer(C.preUpdateHookTrampoline)), unsafe.Pointer(newHandle(c, callback)))
+	}
+}
+
 // RegisterFunc makes a Go function available as a SQLite function.
 //
 // The Go function can have arguments of the following types: any
@@ -1351,3 +1380,70 @@ func (rc *SQLiteRows) Next(dest []driver.Value) error {
 	}
 	return nil
 }
+
+// Depth returns the source path of the write, see sqlite3_preupdate_depth()
+func (d *SQLitePreUpdateData) Depth() int {
+	return int(C.sqlite3_preupdate_depth(d.Conn.db))
+}
+
+// Count returns the number of columns in the row
+func (d *SQLitePreUpdateData) Count() int {
+	return int(C.sqlite3_preupdate_count(d.Conn.db))
+}
+
+func (d *SQLitePreUpdateData) row(dest []interface{}, new bool) error {
+	for i := 0; i < d.Count() && i < len(dest); i++ {
+		var val *C.sqlite3_value
+		var src interface{}
+
+		// Initially I tried making this just a function pointer argument, but
+		// it's absurdly complicated to pass C function pointers.
+		if new {
+			C.sqlite3_preupdate_new(d.Conn.db, C.int(i), &val)
+		} else {
+			C.sqlite3_preupdate_old(d.Conn.db, C.int(i), &val)
+		}
+
+		switch C.sqlite3_value_type(val) {
+		case C.SQLITE_INTEGER:
+			src = int64(C.sqlite3_value_int64(val))
+		case C.SQLITE_FLOAT:
+			src = float64(C.sqlite3_value_double(val))
+		case C.SQLITE_BLOB:
+			len := C.sqlite3_value_bytes(val)
+			blobptr := C.sqlite3_value_blob(val)
+			src = C.GoBytes(blobptr, len)
+		case C.SQLITE_TEXT:
+			len := C.sqlite3_value_bytes(val)
+			cstrptr := unsafe.Pointer(C.sqlite3_value_text(val))
+			src = C.GoBytes(cstrptr, len)
+		case C.SQLITE_NULL:
+			src = nil
+		}
+
+		err := convertAssign(&dest[i], src)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// Old populates dest with the row data to be replaced. This works similar to
+// database/sql's Rows.Scan()
+func (d *SQLitePreUpdateData) Old(dest ...interface{}) error {
+	if d.Op == SQLITE_INSERT {
+		return errors.New("There is no old row for INSERT operations")
+	}
+	return d.row(dest, false)
+}
+
+// New populates dest with the replacement row data. This works similar to
+// database/sql's Rows.Scan()
+func (d *SQLitePreUpdateData) New(dest ...interface{}) error {
+	if d.Op == SQLITE_DELETE {
+		return errors.New("There is no new row for DELETE operations")
+	}
+	return d.row(dest, true)
+}

sqlite3_test.go

@@ -1464,6 +1464,120 @@ func TestPinger(t *testing.T) {
 	}
 }
 
+type preUpdateHookDataForTest struct {
+	databaseName string
+	tableName    string
+	count        int
+	op           int
+	oldRow       []interface{}
+	newRow       []interface{}
+}
+
+func TestPreUpdateHook(t *testing.T) {
+	var events []preUpdateHookDataForTest
+
+	sql.Register("sqlite3_PreUpdateHook", &SQLiteDriver{
+		ConnectHook: func(conn *SQLiteConn) error {
+			conn.RegisterPreUpdateHook(func(data SQLitePreUpdateData) {
+				eval := -1
+				oldRow := []interface{}{eval}
+				if data.Op != SQLITE_INSERT {
+					err := data.Old(oldRow...)
+					if err != nil {
+						t.Fatalf("Unexpected error calling SQLitePreUpdateData.Old: %v", err)
+					}
+				}
+
+				eval2 := -1
+				newRow := []interface{}{eval2}
+				if data.Op != SQLITE_DELETE {
+					err := data.New(newRow...)
+					if err != nil {
+						t.Fatalf("Unexpected error calling SQLitePreUpdateData.New: %v", err)
+					}
+				}
+
+				// tests dest bound checks in loop
+				var tooSmallRow []interface{}
+				if data.Op != SQLITE_INSERT {
+					err := data.Old(tooSmallRow...)
+					if err != nil {
+						t.Fatalf("Unexpected error calling SQLitePreUpdateData.Old: %v", err)
+					}
+					if len(tooSmallRow) != 0 {
+						t.Errorf("Expected tooSmallRow to be empty, got: %v", tooSmallRow)
+					}
+				}
+
+				events = append(events, preUpdateHookDataForTest{
+					databaseName: data.DatabaseName,
+					tableName:    data.TableName,
+					count:        data.Count(),
+					op:           data.Op,
+					oldRow:       oldRow,
+					newRow:       newRow,
+				})
+			})
+			return nil
+		},
+	})
+
+	db, err := sql.Open("sqlite3_PreUpdateHook", ":memory:")
+	if err != nil {
+		t.Fatal("Failed to open database:", err)
+	}
+	defer db.Close()
+
+	statements := []string{
+		"create table foo (id integer primary key)",
+		"insert into foo values (9)",
+		"update foo set id = 99 where id = 9",
+		"delete from foo where id = 99",
+	}
+	for _, statement := range statements {
+		_, err = db.Exec(statement)
+		if err != nil {
+			t.Fatalf("Unable to prepare test data [%v]: %v", statement, err)
+		}
+	}
+
+	if len(events) != 3 {
+		t.Errorf("Events should be 3 entries, got: %d", len(events))
+	}
+
+	if events[0].op != SQLITE_INSERT {
+		t.Errorf("Op isn't as expected: %v", events[0].op)
+	}
+
+	if events[1].op != SQLITE_UPDATE {
+		t.Errorf("Op isn't as expected: %v", events[1].op)
+	}
+
+	if events[1].count != 1 {
+		t.Errorf("Expected event row 1 to have 1 column, had: %v", events[1].count)
+	}
+
+	newRow_0_0 := events[0].newRow[0].(int64)
+	if newRow_0_0 != 9 {
+		t.Errorf("Expected event row 0 new column 0 to be == 9, got: %v", newRow_0_0)
+	}
+
+	oldRow_1_0 := events[1].oldRow[0].(int64)
+	if oldRow_1_0 != 9 {
+		t.Errorf("Expected event row 1 old column 0 to be == 9, got: %v", oldRow_1_0)
+	}
+
+	newRow_1_0 := events[1].newRow[0].(int64)
+	if newRow_1_0 != 99 {
+		t.Errorf("Expected event row 1 new column 0 to be == 99, got: %v", newRow_1_0)
+	}
+
+	oldRow_2_0 := events[2].oldRow[0].(int64)
+	if oldRow_2_0 != 99 {
+		t.Errorf("Expected event row 1 new column 0 to be == 99, got: %v", oldRow_2_0)
+	}
+}
+
 func TestUpdateAndTransactionHooks(t *testing.T) {
 	var events []string
 	var commitHookReturn = 0