objc: add RegisterClass API (#59)

adds RegisterClass function which takes a Selector interface that it uses to add methods based on the argument sent to RegisterClass. It returns an Objective-C class that matches the pointer to struct or an error if something failed. I also included an example under example/objc/main_darwin.go.

* AddMethod & objc tag support Protocol

This adds Selector interface which allows to convert Go method names to Objc methods. There is a handwritten parser for the objc tag which matches that of an Objc Class definition. This adds support for adding Protocols from the tag.

commit: 13a6f7821dfb5973706cdd8718243385b0a8e0c9
author: TotallyGamerJet · 3y ago · 2022-11-04 13:30 UTC
committer: GitHub · 3y ago · 2022-11-04 13:30 UTC
parent: 4f3e551
signature: GPG Unverified4AEE18F83AFDEB23 The key is unknown

2 files · +384 -2

A example/objc/main_darwin.go +61 -0

@@ -0,0 +1,61 @@
	1	+	// SPDX-License-Identifier: Apache-2.0
	2	+	// SPDX-FileCopyrightText: 2022 The Ebitengine Authors
	3	+
	4	+	package main
	5	+
	6	+	import (
	7	+	"fmt"
	8	+	"unsafe"
	9	+
	10	+	"github.com/ebitengine/purego/objc"
	11	+	)
	12	+
	13	+	var (
	14	+	sel_new = objc.RegisterName("new")
	15	+	sel_init = objc.RegisterName("init")
	16	+	sel_setBar = objc.RegisterName("setBar:")
	17	+	sel_bar = objc.RegisterName("bar")
	18	+	)
	19	+
	20	+	type barObject struct {
	21	+	isa objc.Class `objc:"BarObject : NSObject <NSDelegateWindow>"`
	22	+	bar int
	23	+	}
	24	+
	25	+	func (b *barObject) Init(_cmd objc.SEL) objc.ID {
	26	+	return objc.ID(unsafe.Pointer(b)).SendSuper(_cmd)
	27	+	}
	28	+
	29	+	func (b *barObject) Bar(_cmd objc.SEL) int {
	30	+	return b.bar
	31	+	}
	32	+
	33	+	func (b *barObject) SetBar(_cmd objc.SEL, bar int) {
	34	+	b.bar = bar
	35	+	}
	36	+
	37	+	func (_ *barObject) Selector(metName string) objc.SEL {
	38	+	switch metName {
	39	+	case "Init":
	40	+	return sel_init
	41	+	case "SetBar":
	42	+	return sel_setBar
	43	+	case "Bar":
	44	+	return sel_bar
	45	+	default:
	46	+	return 0
	47	+	}
	48	+	}
	49	+
	50	+	func main() {
	51	+	class, err := objc.RegisterClass(&barObject{})
	52	+	if err != nil {
	53	+	panic(err)
	54	+	}
	55	+
	56	+	var object = objc.ID(class).Send(sel_new)
	57	+	object.Send(sel_setBar, 123)
	58	+	var bar = int(object.Send(sel_bar))
	59	+	fmt.Println(bar)
	60	+	// Output: 123
	61	+	}

@@ -0,0 +1,61 @@
	1	+	// SPDX-License-Identifier: Apache-2.0
	2	+	// SPDX-FileCopyrightText: 2022 The Ebitengine Authors
	3	+
	4	+	package main
	5	+
	6	+	import (
	7	+	"fmt"
	8	+	"unsafe"
	9	+
	10	+	"github.com/ebitengine/purego/objc"
	11	+	)
	12	+
	13	+	var (
	14	+	sel_new = objc.RegisterName("new")
	15	+	sel_init = objc.RegisterName("init")
	16	+	sel_setBar = objc.RegisterName("setBar:")
	17	+	sel_bar = objc.RegisterName("bar")
	18	+	)
	19	+
	20	+	type barObject struct {
	21	+	isa objc.Class `objc:"BarObject : NSObject <NSDelegateWindow>"`
	22	+	bar int
	23	+	}
	24	+
	25	+	func (b *barObject) Init(_cmd objc.SEL) objc.ID {
	26	+	return objc.ID(unsafe.Pointer(b)).SendSuper(_cmd)
	27	+	}
	28	+
	29	+	func (b *barObject) Bar(_cmd objc.SEL) int {
	30	+	return b.bar
	31	+	}
	32	+
	33	+	func (b *barObject) SetBar(_cmd objc.SEL, bar int) {
	34	+	b.bar = bar
	35	+	}
	36	+
	37	+	func (_ *barObject) Selector(metName string) objc.SEL {
	38	+	switch metName {
	39	+	case "Init":
	40	+	return sel_init
	41	+	case "SetBar":
	42	+	return sel_setBar
	43	+	case "Bar":
	44	+	return sel_bar
	45	+	default:
	46	+	return 0
	47	+	}
	48	+	}
	49	+
	50	+	func main() {
	51	+	class, err := objc.RegisterClass(&barObject{})
	52	+	if err != nil {
	53	+	panic(err)
	54	+	}
	55	+
	56	+	var object = objc.ID(class).Send(sel_new)
	57	+	object.Send(sel_setBar, 123)
	58	+	var bar = int(object.Send(sel_bar))
	59	+	fmt.Println(bar)
	60	+	// Output: 123
	61	+	}

M objc/objc_runtime_darwin.go +323 -2


@@ -6,9 +6,12 @@
6	6		package objc
7	7
8	8		import (
9		-	"github.com/ebitengine/purego"
	9	+	"errors"
	10	+	"fmt"
10	11		"math"
11	12		"reflect"
	13	+
	14	+	"github.com/ebitengine/purego"
12	15		)
13	16
14	17		//TODO: support try/catch?

@@ -24,6 +27,7 @@ var (
24	27		sel_registerName func(name string) SEL
25	28		class_getSuperclass func(class Class) Class
26	29		class_getInstanceVariable func(class Class, name string) Ivar
	30	+	class_getInstanceSize func(class Class) uintptr
27	31		class_addMethod func(class Class, name SEL, imp IMP, types string) bool
28	32		class_addIvar func(class Class, name string, size uintptr, alignment uint8, types string) bool
29	33		class_addProtocol func(class Class, protocol *Protocol) bool

@@ -47,6 +51,7 @@ func init() {
47	51		purego.RegisterLibFunc(&class_addMethod, objc, "class_addMethod")
48	52		purego.RegisterLibFunc(&class_addIvar, objc, "class_addIvar")
49	53		purego.RegisterLibFunc(&class_addProtocol, objc, "class_addProtocol")
	54	+	purego.RegisterLibFunc(&class_getInstanceSize, objc, "class_getInstanceSize")
50	55		purego.RegisterLibFunc(&ivar_getOffset, objc, "ivar_getOffset")
51	56		}
52	57

@@ -98,10 +103,317 @@ func GetClass(name string) Class {
98	103		}
99	104
100	105		// AllocateClassPair creates a new class and metaclass. Then returns the new class, or Nil if the class could not be created
	106	+	//
	107	+	// Deprecated: use RegisterClass instead
101	108		func AllocateClassPair(super Class, name string, extraBytes uintptr) Class {
102	109		return objc_allocateClassPair(super, name, extraBytes)
103	110		}
104	111
	112	+	// Selector is an interface that takes a Go method name
	113	+	// and returns the selector equivalent name.
	114	+	// If it returns a nil SEL then that method
	115	+	// is not added to the class object.
	116	+	type Selector interface {
	117	+	Selector(string) SEL
	118	+	}
	119	+
	120	+	// TagFormatError occurs when the parser fails to parse the objc tag in a Selector object
	121	+	var TagFormatError = errors.New(`objc tag doesn't match "ClassName : SuperClassName <Protocol, ...>""`)
	122	+
	123	+	// MismatchError occurs when the Go struct definition doesn't match that of Objective-C
	124	+	var MismatchError = errors.New("go struct doesn't match objective-c struct")
	125	+
	126	+	// RegisterClass takes a pointer to a struct that implements the Selector interface.
	127	+	// It will register the structs fields and pointer receiver methods in the Objective-C
	128	+	// runtime using the SEL returned from Selector. Any errors that occur trying to add
	129	+	// a Method or Ivar is returned as an error. Such errors may occur in parsing or because
	130	+	// the size of the struct does not match the size in Objective-C. If no errors occur
	131	+	// then the returned Class has been registered successfully.
	132	+	//
	133	+	// The struct's first field must be of type Class and have a tag that matches the format
	134	+	// `objc:"ClassName : SuperClassName <Protocol, ...>`. This tag is equal to how the class
	135	+	// would be defined in Objective-C.
	136	+	func RegisterClass(object Selector) (Class, error) {
	137	+	ptr := reflect.TypeOf(object)
	138	+	strct := ptr.Elem()
	139	+	if strct.NumField() == 0 \|\| strct.Field(0).Type != reflect.TypeOf(Class(0)) {
	140	+	return 0, fmt.Errorf("objc: need objc.Class as first field: %w", MismatchError)
	141	+	}
	142	+	isa := strct.Field(0)
	143	+	tag := isa.Tag.Get("objc")
	144	+	if tag == "" {
	145	+	return 0, fmt.Errorf("objc: missing objc tag: %w", TagFormatError)
	146	+	}
	147	+	// split contains the class name and super class name followed by all the Protocols
	148	+	// start with two for ClassName : SuperClassName
	149	+	var split = make([]string, 2)
	150	+	{
	151	+	// This is a simple parser for the objc tag that looks for the format
	152	+	// "ClassName : SuperClassName <Protocol, ...>"
	153	+	// It appends to the split variable with the [ClassName, SuperClassName, Protocol, ...]
	154	+
	155	+	var i int // from tag[0:i] is whatever identifier is next
	156	+	var r rune // r is the current rune
	157	+	skipSpace := func() {
	158	+	for _, c := range tag {
	159	+	if c == ' ' {
	160	+	tag = tag[1:]
	161	+	continue
	162	+	}
	163	+	break
	164	+	}
	165	+	}
	166	+	skipSpace()
	167	+	// get ClassName
	168	+	for i, r = range tag {
	169	+	if r == ' ' \|\| r == ':' {
	170	+	break
	171	+	}
	172	+	}
	173	+	split[0] = tag[0:i] // store ClassName
	174	+	tag = tag[i:]
	175	+
	176	+	skipSpace()
	177	+
	178	+	// check for ':'
	179	+	if len(tag) > 0 && tag[0] != ':' {
	180	+	return 0, fmt.Errorf("objc: missing ':': %w", TagFormatError)
	181	+	}
	182	+	tag = tag[1:] // skip ':'
	183	+	skipSpace()
	184	+
	185	+	// get SuperClassName
	186	+	for i, r = range tag {
	187	+	if r == ' ' {
	188	+	break
	189	+	} else if i+1 == len(tag) {
	190	+	// if this is the last character in the string
	191	+	// make sure to increment i so that tag[:i]
	192	+	// includes the last character
	193	+	i++
	194	+	break
	195	+	}
	196	+	}
	197	+	if len(tag) < i {
	198	+	return 0, fmt.Errorf("objc: missing SuperClassName: %w", TagFormatError)
	199	+	}
	200	+	split[1] = tag[:i] // store SuperClassName
	201	+	tag = tag[i:] // drop SuperClassName
	202	+	skipSpace()
	203	+	if len(tag) > 0 {
	204	+	if tag[0] != '<' {
	205	+	return 0, fmt.Errorf("objc: expected '<': %w", TagFormatError)
	206	+	}
	207	+	tag = tag[1:] // drop '<'
	208	+	// get Protocols
	209	+	outer:
	210	+	for {
	211	+	skipSpace()
	212	+	for i, r = range tag {
	213	+	switch r {
	214	+	case ' ':
	215	+	split = append(split, tag[:i])
	216	+	tag = tag[i:]
	217	+	continue outer
	218	+	case ',':
	219	+	// If there is actually an identifier - add it.
	220	+	if i > 0 {
	221	+	split = append(split, tag[:i])
	222	+	tag = tag[i:]
	223	+	} else {
	224	+	// Otherwise, drop ','
	225	+	tag = tag[1:]
	226	+	}
	227	+	continue outer
	228	+	case '>':
	229	+	// If there is actually an identifier - add it.
	230	+	if i > 0 {
	231	+	split = append(split, tag[:i])
	232	+	tag = tag[i:]
	233	+	}
	234	+	break outer
	235	+	}
	236	+	}
	237	+	return 0, fmt.Errorf("objc: expected '>': %w", TagFormatError)
	238	+	}
	239	+	}
	240	+	}
	241	+	class := objc_allocateClassPair(GetClass(split[1]), split[0], 0)
	242	+	if class == 0 {
	243	+	return 0, fmt.Errorf("objc: failed to create class with name '%s'", split[0])
	244	+	}
	245	+	if len(split) > 2 {
	246	+	// Add Protocols
	247	+	for _, n := range split[2:] {
	248	+	succeed := class.AddProtocol(GetProtocol(n))
	249	+	if !succeed {
	250	+	return 0, fmt.Errorf("objc: couldn't add Protocol %s", n)
	251	+	}
	252	+	}
	253	+	}
	254	+	// Add exported methods based on the selectors returned from Selector(string) SEL
	255	+	for i := 0; i < ptr.NumMethod(); i++ {
	256	+	met := ptr.Method(i)
	257	+	// we know this method is the interface one since RegisterClass
	258	+	// requires that the struct implement Selector.
	259	+	if met.Name == "Selector" {
	260	+	continue
	261	+	}
	262	+	sel := object.Selector(met.Name)
	263	+	if sel == 0 {
	264	+	continue
	265	+	}
	266	+	fn := met.Func.Interface()
	267	+	imp, err := func() (imp IMP, err error) {
	268	+	defer func() {
	269	+	if r := recover(); r != nil {
	270	+	err = fmt.Errorf("objc: failed to create IMP: %s", r)
	271	+	}
	272	+	}()
	273	+	return NewIMP(fn), nil
	274	+	}()
	275	+	if err != nil {
	276	+	return 0, fmt.Errorf("objc: couldn't add Method %s: %w", met.Name, err)
	277	+	}
	278	+	succeed := class.AddMethod(sel, imp, encodeFunc(fn))
	279	+	if !succeed {
	280	+	return 0, fmt.Errorf("objc: couldn't add Method %s", met.Name)
	281	+	}
	282	+	}
	283	+	// Add Ivars
	284	+	// Start at 1 because we skip the class object which is first
	285	+	for i := 1; i < strct.NumField(); i++ {
	286	+	f := strct.Field(i)
	287	+	size := f.Type.Size()
	288	+	alignment := uint8(math.Log2(float64(f.Type.Align())))
	289	+	succeed := class_addIvar(class, f.Name, size, alignment, encodeType(f.Type))
	290	+	if !succeed {
	291	+	return 0, fmt.Errorf("objc: couldn't add Ivar %s", f.Name)
	292	+	}
	293	+	if offset := class.InstanceVariable(f.Name).Offset(); offset != f.Offset {
	294	+	return 0, fmt.Errorf("objc: couldn't add Ivar %s", f.Name)
	295	+	}
	296	+	}
	297	+	objc_registerClassPair(class)
	298	+	if size1, size2 := class.InstanceSize(), strct.Size(); size1 != size2 {
	299	+	return 0, fmt.Errorf("objc: sizes don't match %d != %d: %w", size1, size2, MismatchError)
	300	+	}
	301	+	return class, nil
	302	+	}
	303	+
	304	+	const (
	305	+	encId = "@"
	306	+	encClass = "#"
	307	+	encSelector = ":"
	308	+	encChar = "c"
	309	+	encUChar = "C"
	310	+	encShort = "s"
	311	+	encUShort = "S"
	312	+	encInt = "i"
	313	+	encUInt = "I"
	314	+	encLong = "l"
	315	+	encULong = "L"
	316	+	encFloat = "f"
	317	+	encDouble = "d"
	318	+	encBool = "B"
	319	+	encVoid = "v"
	320	+	encPtr = "^"
	321	+	encCharPtr = "*"
	322	+	encStructBegin = "{"
	323	+	encStructEnd = "}"
	324	+	)
	325	+
	326	+	// encodeType returns a string representing a type as if it was given to @encode(typ)
	327	+	// Source: https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtTypeEncodings.html#//apple_ref/doc/uid/TP40008048-CH100
	328	+	func encodeType(typ reflect.Type) string {
	329	+	switch typ {
	330	+	case reflect.TypeOf(Class(0)):
	331	+	return encClass
	332	+	case reflect.TypeOf(ID(0)):
	333	+	return encId
	334	+	case reflect.TypeOf(SEL(0)):
	335	+	return encSelector
	336	+	}
	337	+
	338	+	kind := typ.Kind()
	339	+	switch kind {
	340	+	case reflect.Bool:
	341	+	return encBool
	342	+	case reflect.Int:
	343	+	return encLong
	344	+	case reflect.Int8:
	345	+	return encChar
	346	+	case reflect.Int16:
	347	+	return encShort
	348	+	case reflect.Int32:
	349	+	return encInt
	350	+	case reflect.Int64:
	351	+	return encULong
	352	+	case reflect.Uint:
	353	+	return encULong
	354	+	case reflect.Uint8:
	355	+	return encUChar
	356	+	case reflect.Uint16:
	357	+	return encUShort
	358	+	case reflect.Uint32:
	359	+	return encUInt
	360	+	case reflect.Uint64:
	361	+	return encULong
	362	+	case reflect.Uintptr:
	363	+	return encPtr
	364	+	case reflect.Float32:
	365	+	return encFloat
	366	+	case reflect.Float64:
	367	+	return encDouble
	368	+	case reflect.Ptr:
	369	+	return encPtr + encodeType(typ.Elem())
	370	+	case reflect.Struct:
	371	+	var encoding = encStructBegin
	372	+	encoding += typ.Name()
	373	+	encoding += "="
	374	+	for i := 0; i < typ.NumField(); i++ {
	375	+	f := typ.Field(i)
	376	+	encoding += encodeType(f.Type)
	377	+	}
	378	+	encoding = encStructEnd
	379	+	return encoding
	380	+	case reflect.String:
	381	+	return encCharPtr
	382	+	}
	383	+
	384	+	panic(fmt.Sprintf("objc: unhandled/invalid kind %v typed %v", kind, typ))
	385	+	}
	386	+
	387	+	// encodeFunc returns a functions type as if it was given to @encode(fn)
	388	+	func encodeFunc(fn interface{}) string {
	389	+	typ := reflect.TypeOf(fn)
	390	+	if typ.Kind() != reflect.Func {
	391	+	panic("objc: not a func")
	392	+	}
	393	+
	394	+	encoding := ""
	395	+	switch typ.NumOut() {
	396	+	case 0:
	397	+	encoding += encVoid
	398	+	case 1:
	399	+	encoding += encodeType(typ.Out(0))
	400	+	default:
	401	+	panic("objc: too many output parameters")
	402	+	}
	403	+
	404	+	if typ.NumIn() == 0 {
	405	+	panic("objc: func doesn't take ID and SEL as its first two parameters")
	406	+	}
	407	+
	408	+	encoding += encodeType(typ.In(0))
	409	+	encoding += encSelector
	410	+
	411	+	for i := 1; i < typ.NumIn(); i++ {
	412	+	encoding += encodeType(typ.In(i))
	413	+	}
	414	+	return encoding
	415	+	}
	416	+
105	417		// SuperClass returns the superclass of a class.
106	418		// You should usually use NSObject‘s superclass method instead of this function.
107	419		func (c Class) SuperClass() Class {

@@ -121,6 +433,8 @@ func (c Class) AddMethod(name SEL, imp IMP, types string) bool {
121	433		// Adding an instance variable to an existing class is not supported.
122	434		// The class must not be a metaclass. Adding an instance variable to a metaclass is not supported.
123	435		// It takes the instance of the type of the Ivar and a string representing the type.
	436	+	//
	437	+	// Deprecated: use RegisterClass instead
124	438		func (c Class) AddIvar(name string, ty interface{}, types string) bool {
125	439		typeOf := reflect.TypeOf(ty)
126	440		size := typeOf.Size()

@@ -135,6 +449,11 @@ func (c Class) AddProtocol(protocol *Protocol) bool {
135	449		return class_addProtocol(c, protocol)
136	450		}
137	451
	452	+	// InstanceSize returns the size in bytes of instances of the class or 0 if cls is nil
	453	+	func (c Class) InstanceSize() uintptr {
	454	+	return class_getInstanceSize(c)
	455	+	}
	456	+
138	457		// InstanceVariable returns an Ivar data structure containing information about the instance variable specified by name.
139	458		func (c Class) InstanceVariable(name string) Ivar {
140	459		return class_getInstanceVariable(c, name)

@@ -142,6 +461,8 @@ func (c Class) InstanceVariable(name string) Ivar {
142	461
143	462		// Register registers a class that was allocated using AllocateClassPair.
144	463		// It can now be used to make objects by sending it either alloc and init or new.
	464	+	//
	465	+	// Deprecated: use RegisterClass instead
145	466		func (c Class) Register() {
146	467		objc_registerClassPair(c)
147	468		}

@@ -189,7 +510,7 @@ func NewIMP(fn interface{}) IMP {
189	510		ty.In(0).Elem().Field(0).Type != reflect.TypeOf(Class(0))):
190	511		fallthrough
191	512		case ty.In(1).Kind() != reflect.Uintptr:
192		-	panic("objc: NewIMP must take a (id, SEL) as its first two arguments")
	513	+	panic("objc: NewIMP must take a (id, SEL) as its first two arguments; got " + ty.String())
193	514		}
194	515		return IMP(purego.NewCallback(fn))
195	516		}


@@ -6,9 +6,12 @@
6		package objc	6		package objc
7			7
8		import (	8		import (
9	-	"github.com/ebitengine/purego"	9	+	"errors"
			10	+	"fmt"
10		"math"	11		"math"
11		"reflect"	12		"reflect"
			13	+
			14	+	"github.com/ebitengine/purego"
12		)	15		)
13			16
14		//TODO: support try/catch?	17		//TODO: support try/catch?

@@ -24,6 +27,7 @@ var (
24		sel_registerName func(name string) SEL	27		sel_registerName func(name string) SEL
25		class_getSuperclass func(class Class) Class	28		class_getSuperclass func(class Class) Class
26		class_getInstanceVariable func(class Class, name string) Ivar	29		class_getInstanceVariable func(class Class, name string) Ivar
			30	+	class_getInstanceSize func(class Class) uintptr
27		class_addMethod func(class Class, name SEL, imp IMP, types string) bool	31		class_addMethod func(class Class, name SEL, imp IMP, types string) bool
28		class_addIvar func(class Class, name string, size uintptr, alignment uint8, types string) bool	32		class_addIvar func(class Class, name string, size uintptr, alignment uint8, types string) bool
29		class_addProtocol func(class Class, protocol *Protocol) bool	33		class_addProtocol func(class Class, protocol *Protocol) bool

@@ -47,6 +51,7 @@ func init() {
47		purego.RegisterLibFunc(&class_addMethod, objc, "class_addMethod")	51		purego.RegisterLibFunc(&class_addMethod, objc, "class_addMethod")
48		purego.RegisterLibFunc(&class_addIvar, objc, "class_addIvar")	52		purego.RegisterLibFunc(&class_addIvar, objc, "class_addIvar")
49		purego.RegisterLibFunc(&class_addProtocol, objc, "class_addProtocol")	53		purego.RegisterLibFunc(&class_addProtocol, objc, "class_addProtocol")
			54	+	purego.RegisterLibFunc(&class_getInstanceSize, objc, "class_getInstanceSize")
50		purego.RegisterLibFunc(&ivar_getOffset, objc, "ivar_getOffset")	55		purego.RegisterLibFunc(&ivar_getOffset, objc, "ivar_getOffset")
51		}	56		}
52			57

@@ -98,10 +103,317 @@ func GetClass(name string) Class {
98		}	103		}
99			104
100		// AllocateClassPair creates a new class and metaclass. Then returns the new class, or Nil if the class could not be created	105		// AllocateClassPair creates a new class and metaclass. Then returns the new class, or Nil if the class could not be created
			106	+	//
			107	+	// Deprecated: use RegisterClass instead
101		func AllocateClassPair(super Class, name string, extraBytes uintptr) Class {	108		func AllocateClassPair(super Class, name string, extraBytes uintptr) Class {
102		return objc_allocateClassPair(super, name, extraBytes)	109		return objc_allocateClassPair(super, name, extraBytes)
103		}	110		}
104			111
			112	+	// Selector is an interface that takes a Go method name
			113	+	// and returns the selector equivalent name.
			114	+	// If it returns a nil SEL then that method
			115	+	// is not added to the class object.
			116	+	type Selector interface {
			117	+	Selector(string) SEL
			118	+	}
			119	+
			120	+	// TagFormatError occurs when the parser fails to parse the objc tag in a Selector object
			121	+	var TagFormatError = errors.New(`objc tag doesn't match "ClassName : SuperClassName <Protocol, ...>""`)
			122	+
			123	+	// MismatchError occurs when the Go struct definition doesn't match that of Objective-C
			124	+	var MismatchError = errors.New("go struct doesn't match objective-c struct")
			125	+
			126	+	// RegisterClass takes a pointer to a struct that implements the Selector interface.
			127	+	// It will register the structs fields and pointer receiver methods in the Objective-C
			128	+	// runtime using the SEL returned from Selector. Any errors that occur trying to add
			129	+	// a Method or Ivar is returned as an error. Such errors may occur in parsing or because
			130	+	// the size of the struct does not match the size in Objective-C. If no errors occur
			131	+	// then the returned Class has been registered successfully.
			132	+	//
			133	+	// The struct's first field must be of type Class and have a tag that matches the format
			134	+	// `objc:"ClassName : SuperClassName <Protocol, ...>`. This tag is equal to how the class
			135	+	// would be defined in Objective-C.
			136	+	func RegisterClass(object Selector) (Class, error) {
			137	+	ptr := reflect.TypeOf(object)
			138	+	strct := ptr.Elem()
			139	+	if strct.NumField() == 0 \|\| strct.Field(0).Type != reflect.TypeOf(Class(0)) {
			140	+	return 0, fmt.Errorf("objc: need objc.Class as first field: %w", MismatchError)
			141	+	}
			142	+	isa := strct.Field(0)
			143	+	tag := isa.Tag.Get("objc")
			144	+	if tag == "" {
			145	+	return 0, fmt.Errorf("objc: missing objc tag: %w", TagFormatError)
			146	+	}
			147	+	// split contains the class name and super class name followed by all the Protocols
			148	+	// start with two for ClassName : SuperClassName
			149	+	var split = make([]string, 2)
			150	+	{
			151	+	// This is a simple parser for the objc tag that looks for the format
			152	+	// "ClassName : SuperClassName <Protocol, ...>"
			153	+	// It appends to the split variable with the [ClassName, SuperClassName, Protocol, ...]
			154	+
			155	+	var i int // from tag[0:i] is whatever identifier is next
			156	+	var r rune // r is the current rune
			157	+	skipSpace := func() {
			158	+	for _, c := range tag {
			159	+	if c == ' ' {
			160	+	tag = tag[1:]
			161	+	continue
			162	+	}
			163	+	break
			164	+	}
			165	+	}
			166	+	skipSpace()
			167	+	// get ClassName
			168	+	for i, r = range tag {
			169	+	if r == ' ' \|\| r == ':' {
			170	+	break
			171	+	}
			172	+	}
			173	+	split[0] = tag[0:i] // store ClassName
			174	+	tag = tag[i:]
			175	+
			176	+	skipSpace()
			177	+
			178	+	// check for ':'
			179	+	if len(tag) > 0 && tag[0] != ':' {
			180	+	return 0, fmt.Errorf("objc: missing ':': %w", TagFormatError)
			181	+	}
			182	+	tag = tag[1:] // skip ':'
			183	+	skipSpace()
			184	+
			185	+	// get SuperClassName
			186	+	for i, r = range tag {
			187	+	if r == ' ' {
			188	+	break
			189	+	} else if i+1 == len(tag) {
			190	+	// if this is the last character in the string
			191	+	// make sure to increment i so that tag[:i]
			192	+	// includes the last character
			193	+	i++
			194	+	break
			195	+	}
			196	+	}
			197	+	if len(tag) < i {
			198	+	return 0, fmt.Errorf("objc: missing SuperClassName: %w", TagFormatError)
			199	+	}
			200	+	split[1] = tag[:i] // store SuperClassName
			201	+	tag = tag[i:] // drop SuperClassName
			202	+	skipSpace()
			203	+	if len(tag) > 0 {
			204	+	if tag[0] != '<' {
			205	+	return 0, fmt.Errorf("objc: expected '<': %w", TagFormatError)
			206	+	}
			207	+	tag = tag[1:] // drop '<'
			208	+	// get Protocols
			209	+	outer:
			210	+	for {
			211	+	skipSpace()
			212	+	for i, r = range tag {
			213	+	switch r {
			214	+	case ' ':
			215	+	split = append(split, tag[:i])
			216	+	tag = tag[i:]
			217	+	continue outer
			218	+	case ',':
			219	+	// If there is actually an identifier - add it.
			220	+	if i > 0 {
			221	+	split = append(split, tag[:i])
			222	+	tag = tag[i:]
			223	+	} else {
			224	+	// Otherwise, drop ','
			225	+	tag = tag[1:]
			226	+	}
			227	+	continue outer
			228	+	case '>':
			229	+	// If there is actually an identifier - add it.
			230	+	if i > 0 {
			231	+	split = append(split, tag[:i])
			232	+	tag = tag[i:]
			233	+	}
			234	+	break outer
			235	+	}
			236	+	}
			237	+	return 0, fmt.Errorf("objc: expected '>': %w", TagFormatError)
			238	+	}
			239	+	}
			240	+	}
			241	+	class := objc_allocateClassPair(GetClass(split[1]), split[0], 0)
			242	+	if class == 0 {
			243	+	return 0, fmt.Errorf("objc: failed to create class with name '%s'", split[0])
			244	+	}
			245	+	if len(split) > 2 {
			246	+	// Add Protocols
			247	+	for _, n := range split[2:] {
			248	+	succeed := class.AddProtocol(GetProtocol(n))
			249	+	if !succeed {
			250	+	return 0, fmt.Errorf("objc: couldn't add Protocol %s", n)
			251	+	}
			252	+	}
			253	+	}
			254	+	// Add exported methods based on the selectors returned from Selector(string) SEL
			255	+	for i := 0; i < ptr.NumMethod(); i++ {
			256	+	met := ptr.Method(i)
			257	+	// we know this method is the interface one since RegisterClass
			258	+	// requires that the struct implement Selector.
			259	+	if met.Name == "Selector" {
			260	+	continue
			261	+	}
			262	+	sel := object.Selector(met.Name)
			263	+	if sel == 0 {
			264	+	continue
			265	+	}
			266	+	fn := met.Func.Interface()
			267	+	imp, err := func() (imp IMP, err error) {
			268	+	defer func() {
			269	+	if r := recover(); r != nil {
			270	+	err = fmt.Errorf("objc: failed to create IMP: %s", r)
			271	+	}
			272	+	}()
			273	+	return NewIMP(fn), nil
			274	+	}()
			275	+	if err != nil {
			276	+	return 0, fmt.Errorf("objc: couldn't add Method %s: %w", met.Name, err)
			277	+	}
			278	+	succeed := class.AddMethod(sel, imp, encodeFunc(fn))
			279	+	if !succeed {
			280	+	return 0, fmt.Errorf("objc: couldn't add Method %s", met.Name)
			281	+	}
			282	+	}
			283	+	// Add Ivars
			284	+	// Start at 1 because we skip the class object which is first
			285	+	for i := 1; i < strct.NumField(); i++ {
			286	+	f := strct.Field(i)
			287	+	size := f.Type.Size()
			288	+	alignment := uint8(math.Log2(float64(f.Type.Align())))
			289	+	succeed := class_addIvar(class, f.Name, size, alignment, encodeType(f.Type))
			290	+	if !succeed {
			291	+	return 0, fmt.Errorf("objc: couldn't add Ivar %s", f.Name)
			292	+	}
			293	+	if offset := class.InstanceVariable(f.Name).Offset(); offset != f.Offset {
			294	+	return 0, fmt.Errorf("objc: couldn't add Ivar %s", f.Name)
			295	+	}
			296	+	}
			297	+	objc_registerClassPair(class)
			298	+	if size1, size2 := class.InstanceSize(), strct.Size(); size1 != size2 {
			299	+	return 0, fmt.Errorf("objc: sizes don't match %d != %d: %w", size1, size2, MismatchError)
			300	+	}
			301	+	return class, nil
			302	+	}
			303	+
			304	+	const (
			305	+	encId = "@"
			306	+	encClass = "#"
			307	+	encSelector = ":"
			308	+	encChar = "c"
			309	+	encUChar = "C"
			310	+	encShort = "s"
			311	+	encUShort = "S"
			312	+	encInt = "i"
			313	+	encUInt = "I"
			314	+	encLong = "l"
			315	+	encULong = "L"
			316	+	encFloat = "f"
			317	+	encDouble = "d"
			318	+	encBool = "B"
			319	+	encVoid = "v"
			320	+	encPtr = "^"
			321	+	encCharPtr = "*"
			322	+	encStructBegin = "{"
			323	+	encStructEnd = "}"
			324	+	)
			325	+
			326	+	// encodeType returns a string representing a type as if it was given to @encode(typ)
			327	+	// Source: https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtTypeEncodings.html#//apple_ref/doc/uid/TP40008048-CH100
			328	+	func encodeType(typ reflect.Type) string {
			329	+	switch typ {
			330	+	case reflect.TypeOf(Class(0)):
			331	+	return encClass
			332	+	case reflect.TypeOf(ID(0)):
			333	+	return encId
			334	+	case reflect.TypeOf(SEL(0)):
			335	+	return encSelector
			336	+	}
			337	+
			338	+	kind := typ.Kind()
			339	+	switch kind {
			340	+	case reflect.Bool:
			341	+	return encBool
			342	+	case reflect.Int:
			343	+	return encLong
			344	+	case reflect.Int8:
			345	+	return encChar
			346	+	case reflect.Int16:
			347	+	return encShort
			348	+	case reflect.Int32:
			349	+	return encInt
			350	+	case reflect.Int64:
			351	+	return encULong
			352	+	case reflect.Uint:
			353	+	return encULong
			354	+	case reflect.Uint8:
			355	+	return encUChar
			356	+	case reflect.Uint16:
			357	+	return encUShort
			358	+	case reflect.Uint32:
			359	+	return encUInt
			360	+	case reflect.Uint64:
			361	+	return encULong
			362	+	case reflect.Uintptr:
			363	+	return encPtr
			364	+	case reflect.Float32:
			365	+	return encFloat
			366	+	case reflect.Float64:
			367	+	return encDouble
			368	+	case reflect.Ptr:
			369	+	return encPtr + encodeType(typ.Elem())
			370	+	case reflect.Struct:
			371	+	var encoding = encStructBegin
			372	+	encoding += typ.Name()
			373	+	encoding += "="
			374	+	for i := 0; i < typ.NumField(); i++ {
			375	+	f := typ.Field(i)
			376	+	encoding += encodeType(f.Type)
			377	+	}
			378	+	encoding = encStructEnd
			379	+	return encoding
			380	+	case reflect.String:
			381	+	return encCharPtr
			382	+	}
			383	+
			384	+	panic(fmt.Sprintf("objc: unhandled/invalid kind %v typed %v", kind, typ))
			385	+	}
			386	+
			387	+	// encodeFunc returns a functions type as if it was given to @encode(fn)
			388	+	func encodeFunc(fn interface{}) string {
			389	+	typ := reflect.TypeOf(fn)
			390	+	if typ.Kind() != reflect.Func {
			391	+	panic("objc: not a func")
			392	+	}
			393	+
			394	+	encoding := ""
			395	+	switch typ.NumOut() {
			396	+	case 0:
			397	+	encoding += encVoid
			398	+	case 1:
			399	+	encoding += encodeType(typ.Out(0))
			400	+	default:
			401	+	panic("objc: too many output parameters")
			402	+	}
			403	+
			404	+	if typ.NumIn() == 0 {
			405	+	panic("objc: func doesn't take ID and SEL as its first two parameters")
			406	+	}
			407	+
			408	+	encoding += encodeType(typ.In(0))
			409	+	encoding += encSelector
			410	+
			411	+	for i := 1; i < typ.NumIn(); i++ {
			412	+	encoding += encodeType(typ.In(i))
			413	+	}
			414	+	return encoding
			415	+	}
			416	+
105		// SuperClass returns the superclass of a class.	417		// SuperClass returns the superclass of a class.
106		// You should usually use NSObject‘s superclass method instead of this function.	418		// You should usually use NSObject‘s superclass method instead of this function.
107		func (c Class) SuperClass() Class {	419		func (c Class) SuperClass() Class {

@@ -121,6 +433,8 @@ func (c Class) AddMethod(name SEL, imp IMP, types string) bool {
121		// Adding an instance variable to an existing class is not supported.	433		// Adding an instance variable to an existing class is not supported.
122		// The class must not be a metaclass. Adding an instance variable to a metaclass is not supported.	434		// The class must not be a metaclass. Adding an instance variable to a metaclass is not supported.
123		// It takes the instance of the type of the Ivar and a string representing the type.	435		// It takes the instance of the type of the Ivar and a string representing the type.
			436	+	//
			437	+	// Deprecated: use RegisterClass instead
124		func (c Class) AddIvar(name string, ty interface{}, types string) bool {	438		func (c Class) AddIvar(name string, ty interface{}, types string) bool {
125		typeOf := reflect.TypeOf(ty)	439		typeOf := reflect.TypeOf(ty)
126		size := typeOf.Size()	440		size := typeOf.Size()

@@ -135,6 +449,11 @@ func (c Class) AddProtocol(protocol *Protocol) bool {
135		return class_addProtocol(c, protocol)	449		return class_addProtocol(c, protocol)
136		}	450		}
137			451
			452	+	// InstanceSize returns the size in bytes of instances of the class or 0 if cls is nil
			453	+	func (c Class) InstanceSize() uintptr {
			454	+	return class_getInstanceSize(c)
			455	+	}
			456	+
138		// InstanceVariable returns an Ivar data structure containing information about the instance variable specified by name.	457		// InstanceVariable returns an Ivar data structure containing information about the instance variable specified by name.
139		func (c Class) InstanceVariable(name string) Ivar {	458		func (c Class) InstanceVariable(name string) Ivar {
140		return class_getInstanceVariable(c, name)	459		return class_getInstanceVariable(c, name)

@@ -142,6 +461,8 @@ func (c Class) InstanceVariable(name string) Ivar {
142			461
143		// Register registers a class that was allocated using AllocateClassPair.	462		// Register registers a class that was allocated using AllocateClassPair.
144		// It can now be used to make objects by sending it either alloc and init or new.	463		// It can now be used to make objects by sending it either alloc and init or new.
			464	+	//
			465	+	// Deprecated: use RegisterClass instead
145		func (c Class) Register() {	466		func (c Class) Register() {
146		objc_registerClassPair(c)	467		objc_registerClassPair(c)
147		}	468		}

@@ -189,7 +510,7 @@ func NewIMP(fn interface{}) IMP {
189		ty.In(0).Elem().Field(0).Type != reflect.TypeOf(Class(0))):	510		ty.In(0).Elem().Field(0).Type != reflect.TypeOf(Class(0))):
190		fallthrough	511		fallthrough
191		case ty.In(1).Kind() != reflect.Uintptr:	512		case ty.In(1).Kind() != reflect.Uintptr:
192	-	panic("objc: NewIMP must take a (id, SEL) as its first two arguments")	513	+	panic("objc: NewIMP must take a (id, SEL) as its first two arguments; got " + ty.String())
193		}	514		}
194		return IMP(purego.NewCallback(fn))	515		return IMP(purego.NewCallback(fn))
195		}	516		}