diff options
Diffstat (limited to 'sqlite3.go')
| -rw-r--r-- | sqlite3.go | 127 |
1 files changed, 127 insertions, 0 deletions
@@ -100,6 +100,8 @@ int _sqlite3_create_function( } void callbackTrampoline(sqlite3_context*, int, sqlite3_value**); +void stepTrampoline(sqlite3_context*, int, sqlite3_value**); +void doneTrampoline(sqlite3_context*); int compareTrampoline(void*, int, char*, int, char*); int commitHookTrampoline(void*); @@ -503,6 +505,131 @@ func sqlite3CreateFunction(db *C.sqlite3, zFunctionName *C.char, nArg C.int, eTe return C._sqlite3_create_function(db, zFunctionName, nArg, eTextRep, C.uintptr_t(pApp), (*[0]byte)(unsafe.Pointer(xFunc)), (*[0]byte)(unsafe.Pointer(xStep)), (*[0]byte)(unsafe.Pointer(xFinal))) } +// RegisterAggregator makes a Go type available as a SQLite aggregation function. +// +// Because aggregation is incremental, it's implemented in Go with a +// type that has 2 methods: func Step(values) accumulates one row of +// data into the accumulator, and func Done() ret finalizes and +// returns the aggregate value. "values" and "ret" may be any type +// supported by RegisterFunc. +// +// RegisterAggregator takes as implementation a constructor function +// that constructs an instance of the aggregator type each time an +// aggregation begins. The constructor must return a pointer to a +// type, or an interface that implements Step() and Done(). +// +// The constructor function and the Step/Done methods may optionally +// return an error in addition to their other return values. +// +// See _example/go_custom_funcs for a detailed example. +func (c *SQLiteConn) RegisterAggregator(name string, impl interface{}, pure bool) error { + var ai aggInfo + ai.constructor = reflect.ValueOf(impl) + t := ai.constructor.Type() + if t.Kind() != reflect.Func { + return errors.New("non-function passed to RegisterAggregator") + } + if t.NumOut() != 1 && t.NumOut() != 2 { + return errors.New("SQLite aggregator constructors must return 1 or 2 values") + } + if t.NumOut() == 2 && !t.Out(1).Implements(reflect.TypeOf((*error)(nil)).Elem()) { + return errors.New("Second return value of SQLite function must be error") + } + if t.NumIn() != 0 { + return errors.New("SQLite aggregator constructors must not have arguments") + } + + agg := t.Out(0) + switch agg.Kind() { + case reflect.Ptr, reflect.Interface: + default: + return errors.New("SQlite aggregator constructor must return a pointer object") + } + stepFn, found := agg.MethodByName("Step") + if !found { + return errors.New("SQlite aggregator doesn't have a Step() function") + } + step := stepFn.Type + if step.NumOut() != 0 && step.NumOut() != 1 { + return errors.New("SQlite aggregator Step() function must return 0 or 1 values") + } + if step.NumOut() == 1 && !step.Out(0).Implements(reflect.TypeOf((*error)(nil)).Elem()) { + return errors.New("type of SQlite aggregator Step() return value must be error") + } + + stepNArgs := step.NumIn() + start := 0 + if agg.Kind() == reflect.Ptr { + // Skip over the method receiver + stepNArgs-- + start++ + } + if step.IsVariadic() { + stepNArgs-- + } + for i := start; i < start+stepNArgs; i++ { + conv, err := callbackArg(step.In(i)) + if err != nil { + return err + } + ai.stepArgConverters = append(ai.stepArgConverters, conv) + } + if step.IsVariadic() { + conv, err := callbackArg(t.In(start + stepNArgs).Elem()) + if err != nil { + return err + } + ai.stepVariadicConverter = conv + // Pass -1 to sqlite so that it allows any number of + // arguments. The call helper verifies that the minimum number + // of arguments is present for variadic functions. + stepNArgs = -1 + } + + doneFn, found := agg.MethodByName("Done") + if !found { + return errors.New("SQlite aggregator doesn't have a Done() function") + } + done := doneFn.Type + doneNArgs := done.NumIn() + if agg.Kind() == reflect.Ptr { + // Skip over the method receiver + doneNArgs-- + } + if doneNArgs != 0 { + return errors.New("SQlite aggregator Done() function must have no arguments") + } + if done.NumOut() != 1 && done.NumOut() != 2 { + return errors.New("SQLite aggregator Done() function must return 1 or 2 values") + } + if done.NumOut() == 2 && !done.Out(1).Implements(reflect.TypeOf((*error)(nil)).Elem()) { + return errors.New("second return value of SQLite aggregator Done() function must be error") + } + + conv, err := callbackRet(done.Out(0)) + if err != nil { + return err + } + ai.doneRetConverter = conv + ai.active = make(map[int64]reflect.Value) + ai.next = 1 + + // ai must outlast the database connection, or we'll have dangling pointers. + c.aggregators = append(c.aggregators, &ai) + + cname := C.CString(name) + defer C.free(unsafe.Pointer(cname)) + opts := C.SQLITE_UTF8 + if pure { + opts |= C.SQLITE_DETERMINISTIC + } + rv := sqlite3CreateFunction(c.db, cname, C.int(stepNArgs), C.int(opts), newHandle(c, &ai), nil, C.stepTrampoline, C.doneTrampoline) + if rv != C.SQLITE_OK { + return c.lastError() + } + return nil +} + // AutoCommit return which currently auto commit or not. func (c *SQLiteConn) AutoCommit() bool { return int(C.sqlite3_get_autocommit(c.db)) != 0 |