src/runtime/iface.go - go - Git at Google

 // Copyright 2014 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.

 package runtime

 import (
 	"unsafe"
 )

 const (
 	hashSize = 1009
 )

 var (
 	ifaceLock mutex // lock for accessing hash
 	hash      [hashSize]*itab
 )

 // fInterface is our standard non-empty interface.  We use it instead
 // of interface{f()} in function prototypes because gofmt insists on
 // putting lots of newlines in the otherwise concise interface{f()}.
 type fInterface interface {
 	f()
 }

 func getitab(inter *interfacetype, typ *_type, canfail bool) *itab {
 	if len(inter.mhdr) == 0 {
 		throw("internal error - misuse of itab")
 	}

 	// easy case
 	x := typ.x
 	if x == nil {
 		if canfail {
 			return nil
 		}
 		panic(&TypeAssertionError{"", *typ._string, *inter.typ._string, *inter.mhdr[0].name})
 	}

 	// compiler has provided some good hash codes for us.
 	h := inter.typ.hash
 	h += 17 * typ.hash
 	// TODO(rsc): h += 23 * x.mhash ?
 	h %= hashSize

 	// look twice - once without lock, once with.
 	// common case will be no lock contention.
 	var m *itab
 	var locked int
 	for locked = 0; locked < 2; locked++ {
 		if locked != 0 {
 			lock(&ifaceLock)
 		}
 		for m = (*itab)(atomicloadp(unsafe.Pointer(&hash[h]))); m != nil; m = m.link {
 			if m.inter == inter && m._type == typ {
 				if m.bad != 0 {
 					m = nil
 					if !canfail {
 						// this can only happen if the conversion
 						// was already done once using the , ok form
 						// and we have a cached negative result.
 						// the cached result doesn't record which
 						// interface function was missing, so jump
 						// down to the interface check, which will
 						// do more work but give a better error.
 						goto search
 					}
 				}
 				if locked != 0 {
 					unlock(&ifaceLock)
 				}
 				return m
 			}
 		}
 	}

 	m = (*itab)(persistentalloc(unsafe.Sizeof(itab{})+uintptr(len(inter.mhdr)-1)*ptrSize, 0, &memstats.other_sys))
 	m.inter = inter
 	m._type = typ

 search:
 	// both inter and typ have method sorted by name,
 	// and interface names are unique,
 	// so can iterate over both in lock step;
 	// the loop is O(ni+nt) not O(ni*nt).
 	ni := len(inter.mhdr)
 	nt := len(x.mhdr)
 	j := 0
 	for k := 0; k < ni; k++ {
 		i := &inter.mhdr[k]
 		iname := i.name
 		ipkgpath := i.pkgpath
 		itype := i._type
 		for ; j < nt; j++ {
 			t := &x.mhdr[j]
 			if t.mtyp == itype && (t.name == iname || *t.name == *iname) && t.pkgpath == ipkgpath {
 				if m != nil {
 					*(*unsafe.Pointer)(add(unsafe.Pointer(&m.fun[0]), uintptr(k)*ptrSize)) = t.ifn
 				}
 				goto nextimethod
 			}
 		}
 		// didn't find method
 		if !canfail {
 			if locked != 0 {
 				unlock(&ifaceLock)
 			}
 			panic(&TypeAssertionError{"", *typ._string, *inter.typ._string, *iname})
 		}
 		m.bad = 1
 		break
 	nextimethod:
 	}
 	if locked == 0 {
 		throw("invalid itab locking")
 	}
 	m.link = hash[h]
 	atomicstorep(unsafe.Pointer(&hash[h]), unsafe.Pointer(m))
 	unlock(&ifaceLock)
 	if m.bad != 0 {
 		return nil
 	}
 	return m
 }

 func typ2Itab(t *_type, inter *interfacetype, cache **itab) *itab {
 	tab := getitab(inter, t, false)
 	atomicstorep(unsafe.Pointer(cache), unsafe.Pointer(tab))
 	return tab
 }

 func convT2E(t *_type, elem unsafe.Pointer, x unsafe.Pointer) (e interface{}) {
 	ep := (*eface)(unsafe.Pointer(&e))
 	if isDirectIface(t) {
 		ep._type = t
 		typedmemmove(t, unsafe.Pointer(&ep.data), elem)
 	} else {
 		if x == nil {
 			x = newobject(t)
 		}
 		// TODO: We allocate a zeroed object only to overwrite it with
 		// actual data.  Figure out how to avoid zeroing.  Also below in convT2I.
 		typedmemmove(t, x, elem)
 		ep._type = t
 		ep.data = x
 	}
 	return
 }

 func convT2I(t *_type, inter *interfacetype, cache **itab, elem unsafe.Pointer, x unsafe.Pointer) (i fInterface) {
 	tab := (*itab)(atomicloadp(unsafe.Pointer(cache)))
 	if tab == nil {
 		tab = getitab(inter, t, false)
 		atomicstorep(unsafe.Pointer(cache), unsafe.Pointer(tab))
 	}
 	pi := (*iface)(unsafe.Pointer(&i))
 	if isDirectIface(t) {
 		pi.tab = tab
 		typedmemmove(t, unsafe.Pointer(&pi.data), elem)
 	} else {
 		if x == nil {
 			x = newobject(t)
 		}
 		typedmemmove(t, x, elem)
 		pi.tab = tab
 		pi.data = x
 	}
 	return
 }

 func panicdottype(have, want, iface *_type) {
 	haveString := ""
 	if have != nil {
 		haveString = *have._string
 	}
 	panic(&TypeAssertionError{*iface._string, haveString, *want._string, ""})
 }

 func assertI2T(t *_type, i fInterface, r unsafe.Pointer) {
 	ip := (*iface)(unsafe.Pointer(&i))
 	tab := ip.tab
 	if tab == nil {
 		panic(&TypeAssertionError{"", "", *t._string, ""})
 	}
 	if tab._type != t {
 		panic(&TypeAssertionError{*tab.inter.typ._string, *tab._type._string, *t._string, ""})
 	}
 	if r != nil {
 		if isDirectIface(t) {
 			writebarrierptr((*uintptr)(r), uintptr(ip.data))
 		} else {
 			typedmemmove(t, r, ip.data)
 		}
 	}
 }

 func assertI2T2(t *_type, i fInterface, r unsafe.Pointer) bool {
 	ip := (*iface)(unsafe.Pointer(&i))
 	tab := ip.tab
 	if tab == nil || tab._type != t {
 		if r != nil {
 			memclr(r, uintptr(t.size))
 		}
 		return false
 	}
 	if r != nil {
 		if isDirectIface(t) {
 			writebarrierptr((*uintptr)(r), uintptr(ip.data))
 		} else {
 			typedmemmove(t, r, ip.data)
 		}
 	}
 	return true
 }

 func assertE2T(t *_type, e interface{}, r unsafe.Pointer) {
 	ep := (*eface)(unsafe.Pointer(&e))
 	if ep._type == nil {
 		panic(&TypeAssertionError{"", "", *t._string, ""})
 	}
 	if ep._type != t {
 		panic(&TypeAssertionError{"", *ep._type._string, *t._string, ""})
 	}
 	if r != nil {
 		if isDirectIface(t) {
 			writebarrierptr((*uintptr)(r), uintptr(ep.data))
 		} else {
 			typedmemmove(t, r, ep.data)
 		}
 	}
 }

 // The compiler ensures that r is non-nil.
 func assertE2T2(t *_type, e interface{}, r unsafe.Pointer) bool {
 	ep := (*eface)(unsafe.Pointer(&e))
 	if ep._type != t {
 		memclr(r, uintptr(t.size))
 		return false
 	}
 	if isDirectIface(t) {
 		writebarrierptr((*uintptr)(r), uintptr(ep.data))
 	} else {
 		typedmemmove(t, r, ep.data)
 	}
 	return true
 }

 func convI2E(i fInterface) (r interface{}) {
 	ip := (*iface)(unsafe.Pointer(&i))
 	tab := ip.tab
 	if tab == nil {
 		return
 	}
 	rp := (*eface)(unsafe.Pointer(&r))
 	rp._type = tab._type
 	rp.data = ip.data
 	return
 }

 func assertI2E(inter *interfacetype, i fInterface, r *interface{}) {
 	ip := (*iface)(unsafe.Pointer(&i))
 	tab := ip.tab
 	if tab == nil {
 		// explicit conversions require non-nil interface value.
 		panic(&TypeAssertionError{"", "", *inter.typ._string, ""})
 	}
 	rp := (*eface)(unsafe.Pointer(r))
 	rp._type = tab._type
 	rp.data = ip.data
 	return
 }

 // The compiler ensures that r is non-nil.
 func assertI2E2(inter *interfacetype, i fInterface, r *interface{}) bool {
 	ip := (*iface)(unsafe.Pointer(&i))
 	tab := ip.tab
 	if tab == nil {
 		return false
 	}
 	rp := (*eface)(unsafe.Pointer(r))
 	rp._type = tab._type
 	rp.data = ip.data
 	return true
 }

 func convI2I(inter *interfacetype, i fInterface) (r fInterface) {
 	ip := (*iface)(unsafe.Pointer(&i))
 	tab := ip.tab
 	if tab == nil {
 		return
 	}
 	rp := (*iface)(unsafe.Pointer(&r))
 	if tab.inter == inter {
 		rp.tab = tab
 		rp.data = ip.data
 		return
 	}
 	rp.tab = getitab(inter, tab._type, false)
 	rp.data = ip.data
 	return
 }

 func assertI2I(inter *interfacetype, i fInterface, r *fInterface) {
 	ip := (*iface)(unsafe.Pointer(&i))
 	tab := ip.tab
 	if tab == nil {
 		// explicit conversions require non-nil interface value.
 		panic(&TypeAssertionError{"", "", *inter.typ._string, ""})
 	}
 	rp := (*iface)(unsafe.Pointer(r))
 	if tab.inter == inter {
 		rp.tab = tab
 		rp.data = ip.data
 		return
 	}
 	rp.tab = getitab(inter, tab._type, false)
 	rp.data = ip.data
 }

 func assertI2I2(inter *interfacetype, i fInterface, r *fInterface) bool {
 	ip := (*iface)(unsafe.Pointer(&i))
 	tab := ip.tab
 	if tab == nil {
 		if r != nil {
 			*r = nil
 		}
 		return false
 	}
 	if tab.inter != inter {
 		tab = getitab(inter, tab._type, true)
 		if tab == nil {
 			if r != nil {
 				*r = nil
 			}
 			return false
 		}
 	}
 	if r != nil {
 		rp := (*iface)(unsafe.Pointer(r))
 		rp.tab = tab
 		rp.data = ip.data
 	}
 	return true
 }

 func assertE2I(inter *interfacetype, e interface{}, r *fInterface) {
 	ep := (*eface)(unsafe.Pointer(&e))
 	t := ep._type
 	if t == nil {
 		// explicit conversions require non-nil interface value.
 		panic(&TypeAssertionError{"", "", *inter.typ._string, ""})
 	}
 	rp := (*iface)(unsafe.Pointer(r))
 	rp.tab = getitab(inter, t, false)
 	rp.data = ep.data
 }

 func assertE2I2(inter *interfacetype, e interface{}, r *fInterface) bool {
 	ep := (*eface)(unsafe.Pointer(&e))
 	t := ep._type
 	if t == nil {
 		if r != nil {
 			*r = nil
 		}
 		return false
 	}
 	tab := getitab(inter, t, true)
 	if tab == nil {
 		if r != nil {
 			*r = nil
 		}
 		return false
 	}
 	if r != nil {
 		rp := (*iface)(unsafe.Pointer(r))
 		rp.tab = tab
 		rp.data = ep.data
 	}
 	return true
 }

 //go:linkname reflect_ifaceE2I reflect.ifaceE2I
 func reflect_ifaceE2I(inter *interfacetype, e interface{}, dst *fInterface) {
 	assertE2I(inter, e, dst)
 }

 func assertE2E(inter *interfacetype, e interface{}, r *interface{}) {
 	ep := (*eface)(unsafe.Pointer(&e))
 	if ep._type == nil {
 		// explicit conversions require non-nil interface value.
 		panic(&TypeAssertionError{"", "", *inter.typ._string, ""})
 	}
 	*r = e
 }

 // The compiler ensures that r is non-nil.
 func assertE2E2(inter *interfacetype, e interface{}, r *interface{}) bool {
 	ep := (*eface)(unsafe.Pointer(&e))
 	if ep._type == nil {
 		*r = nil
 		return false
 	}
 	*r = e
 	return true
 }

 func ifacethash(i fInterface) uint32 {
 	ip := (*iface)(unsafe.Pointer(&i))
 	tab := ip.tab
 	if tab == nil {
 		return 0
 	}
 	return tab._type.hash
 }

 func efacethash(e interface{}) uint32 {
 	ep := (*eface)(unsafe.Pointer(&e))
 	t := ep._type
 	if t == nil {
 		return 0
 	}
 	return t.hash
 }

 func iterate_itabs(fn func(*itab)) {
 	for _, h := range &hash {
 		for ; h != nil; h = h.link {
 			fn(h)
 		}
 	}
 }
	// Copyright 2014 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.

	package runtime

	import (
	"unsafe"
	)

	const (
	hashSize = 1009
	)

	var (
	ifaceLock mutex // lock for accessing hash
	hash [hashSize]*itab
	)

	// fInterface is our standard non-empty interface. We use it instead
	// of interface{f()} in function prototypes because gofmt insists on
	// putting lots of newlines in the otherwise concise interface{f()}.
	type fInterface interface {
	f()
	}

	func getitab(inter interfacetype, typ _type, canfail bool) *itab {
	if len(inter.mhdr) == 0 {
	throw("internal error - misuse of itab")
	}

	// easy case
	x := typ.x
	if x == nil {
	if canfail {
	return nil
	}
	panic(&TypeAssertionError{"", typ._string, inter.typ._string, *inter.mhdr[0].name})
	}

	// compiler has provided some good hash codes for us.
	h := inter.typ.hash
	h += 17 * typ.hash
	// TODO(rsc): h += 23 * x.mhash ?
	h %= hashSize

	// look twice - once without lock, once with.
	// common case will be no lock contention.
	var m *itab
	var locked int
	for locked = 0; locked < 2; locked++ {
	if locked != 0 {
	lock(&ifaceLock)
	}
	for m = (*itab)(atomicloadp(unsafe.Pointer(&hash[h]))); m != nil; m = m.link {
	if m.inter == inter && m._type == typ {
	if m.bad != 0 {
	m = nil
	if !canfail {
	// this can only happen if the conversion
	// was already done once using the , ok form
	// and we have a cached negative result.
	// the cached result doesn't record which
	// interface function was missing, so jump
	// down to the interface check, which will
	// do more work but give a better error.
	goto search
	}
	}
	if locked != 0 {
	unlock(&ifaceLock)
	}
	return m
	}
	}
	}

	m = (itab)(persistentalloc(unsafe.Sizeof(itab{})+uintptr(len(inter.mhdr)-1)ptrSize, 0, &memstats.other_sys))
	m.inter = inter
	m._type = typ

	search:
	// both inter and typ have method sorted by name,
	// and interface names are unique,
	// so can iterate over both in lock step;
	// the loop is O(ni+nt) not O(ni*nt).
	ni := len(inter.mhdr)
	nt := len(x.mhdr)
	j := 0
	for k := 0; k < ni; k++ {
	i := &inter.mhdr[k]
	iname := i.name
	ipkgpath := i.pkgpath
	itype := i._type
	for ; j < nt; j++ {
	t := &x.mhdr[j]
	if t.mtyp == itype && (t.name == iname \|\| t.name == iname) && t.pkgpath == ipkgpath {
	if m != nil {
	(unsafe.Pointer)(add(unsafe.Pointer(&m.fun[0]), uintptr(k)*ptrSize)) = t.ifn
	}
	goto nextimethod
	}
	}
	// didn't find method
	if !canfail {
	if locked != 0 {
	unlock(&ifaceLock)
	}
	panic(&TypeAssertionError{"", typ._string, inter.typ._string, *iname})
	}
	m.bad = 1
	break
	nextimethod:
	}
	if locked == 0 {
	throw("invalid itab locking")
	}
	m.link = hash[h]
	atomicstorep(unsafe.Pointer(&hash[h]), unsafe.Pointer(m))
	unlock(&ifaceLock)
	if m.bad != 0 {
	return nil
	}
	return m
	}

	func typ2Itab(t _type, inter interfacetype, cache *itab) itab {
	tab := getitab(inter, t, false)
	atomicstorep(unsafe.Pointer(cache), unsafe.Pointer(tab))
	return tab
	}

	func convT2E(t *_type, elem unsafe.Pointer, x unsafe.Pointer) (e interface{}) {
	ep := (*eface)(unsafe.Pointer(&e))
	if isDirectIface(t) {
	ep._type = t
	typedmemmove(t, unsafe.Pointer(&ep.data), elem)
	} else {
	if x == nil {
	x = newobject(t)
	}
	// TODO: We allocate a zeroed object only to overwrite it with
	// actual data. Figure out how to avoid zeroing. Also below in convT2I.
	typedmemmove(t, x, elem)
	ep._type = t
	ep.data = x
	}
	return
	}

	func convT2I(t _type, inter interfacetype, cache **itab, elem unsafe.Pointer, x unsafe.Pointer) (i fInterface) {
	tab := (*itab)(atomicloadp(unsafe.Pointer(cache)))
	if tab == nil {
	tab = getitab(inter, t, false)
	atomicstorep(unsafe.Pointer(cache), unsafe.Pointer(tab))
	}
	pi := (*iface)(unsafe.Pointer(&i))
	if isDirectIface(t) {
	pi.tab = tab
	typedmemmove(t, unsafe.Pointer(&pi.data), elem)
	} else {
	if x == nil {
	x = newobject(t)
	}
	typedmemmove(t, x, elem)
	pi.tab = tab
	pi.data = x
	}
	return
	}

	func panicdottype(have, want, iface *_type) {
	haveString := ""
	if have != nil {
	haveString = *have._string
	}
	panic(&TypeAssertionError{iface._string, haveString, want._string, ""})
	}

	func assertI2T(t *_type, i fInterface, r unsafe.Pointer) {
	ip := (*iface)(unsafe.Pointer(&i))
	tab := ip.tab
	if tab == nil {
	panic(&TypeAssertionError{"", "", *t._string, ""})
	}
	if tab._type != t {
	panic(&TypeAssertionError{tab.inter.typ._string, tab._type._string, *t._string, ""})
	}
	if r != nil {
	if isDirectIface(t) {
	writebarrierptr((*uintptr)(r), uintptr(ip.data))
	} else {
	typedmemmove(t, r, ip.data)
	}
	}
	}

	func assertI2T2(t *_type, i fInterface, r unsafe.Pointer) bool {
	ip := (*iface)(unsafe.Pointer(&i))
	tab := ip.tab
	if tab == nil \|\| tab._type != t {
	if r != nil {
	memclr(r, uintptr(t.size))
	}
	return false
	}
	if r != nil {
	if isDirectIface(t) {
	writebarrierptr((*uintptr)(r), uintptr(ip.data))
	} else {
	typedmemmove(t, r, ip.data)
	}
	}
	return true
	}

	func assertE2T(t *_type, e interface{}, r unsafe.Pointer) {
	ep := (*eface)(unsafe.Pointer(&e))
	if ep._type == nil {
	panic(&TypeAssertionError{"", "", *t._string, ""})
	}
	if ep._type != t {
	panic(&TypeAssertionError{"", ep._type._string, t._string, ""})
	}
	if r != nil {
	if isDirectIface(t) {
	writebarrierptr((*uintptr)(r), uintptr(ep.data))
	} else {
	typedmemmove(t, r, ep.data)
	}
	}
	}

	// The compiler ensures that r is non-nil.
	func assertE2T2(t *_type, e interface{}, r unsafe.Pointer) bool {
	ep := (*eface)(unsafe.Pointer(&e))
	if ep._type != t {
	memclr(r, uintptr(t.size))
	return false
	}
	if isDirectIface(t) {
	writebarrierptr((*uintptr)(r), uintptr(ep.data))
	} else {
	typedmemmove(t, r, ep.data)
	}
	return true
	}

	func convI2E(i fInterface) (r interface{}) {
	ip := (*iface)(unsafe.Pointer(&i))
	tab := ip.tab
	if tab == nil {
	return
	}
	rp := (*eface)(unsafe.Pointer(&r))
	rp._type = tab._type
	rp.data = ip.data
	return
	}

	func assertI2E(inter interfacetype, i fInterface, r interface{}) {
	ip := (*iface)(unsafe.Pointer(&i))
	tab := ip.tab
	if tab == nil {
	// explicit conversions require non-nil interface value.
	panic(&TypeAssertionError{"", "", *inter.typ._string, ""})
	}
	rp := (*eface)(unsafe.Pointer(r))
	rp._type = tab._type
	rp.data = ip.data
	return
	}

	// The compiler ensures that r is non-nil.
	func assertI2E2(inter interfacetype, i fInterface, r interface{}) bool {
	ip := (*iface)(unsafe.Pointer(&i))
	tab := ip.tab
	if tab == nil {
	return false
	}
	rp := (*eface)(unsafe.Pointer(r))
	rp._type = tab._type
	rp.data = ip.data
	return true
	}

	func convI2I(inter *interfacetype, i fInterface) (r fInterface) {
	ip := (*iface)(unsafe.Pointer(&i))
	tab := ip.tab
	if tab == nil {
	return
	}
	rp := (*iface)(unsafe.Pointer(&r))
	if tab.inter == inter {
	rp.tab = tab
	rp.data = ip.data
	return
	}
	rp.tab = getitab(inter, tab._type, false)
	rp.data = ip.data
	return
	}

	func assertI2I(inter interfacetype, i fInterface, r fInterface) {
	ip := (*iface)(unsafe.Pointer(&i))
	tab := ip.tab
	if tab == nil {
	// explicit conversions require non-nil interface value.
	panic(&TypeAssertionError{"", "", *inter.typ._string, ""})
	}
	rp := (*iface)(unsafe.Pointer(r))
	if tab.inter == inter {
	rp.tab = tab
	rp.data = ip.data
	return
	}
	rp.tab = getitab(inter, tab._type, false)
	rp.data = ip.data
	}

	func assertI2I2(inter interfacetype, i fInterface, r fInterface) bool {
	ip := (*iface)(unsafe.Pointer(&i))
	tab := ip.tab
	if tab == nil {
	if r != nil {
	*r = nil
	}
	return false
	}
	if tab.inter != inter {
	tab = getitab(inter, tab._type, true)
	if tab == nil {
	if r != nil {
	*r = nil
	}
	return false
	}
	}
	if r != nil {
	rp := (*iface)(unsafe.Pointer(r))
	rp.tab = tab
	rp.data = ip.data
	}
	return true
	}

	func assertE2I(inter interfacetype, e interface{}, r fInterface) {
	ep := (*eface)(unsafe.Pointer(&e))
	t := ep._type
	if t == nil {
	// explicit conversions require non-nil interface value.
	panic(&TypeAssertionError{"", "", *inter.typ._string, ""})
	}
	rp := (*iface)(unsafe.Pointer(r))
	rp.tab = getitab(inter, t, false)
	rp.data = ep.data
	}

	func assertE2I2(inter interfacetype, e interface{}, r fInterface) bool {
	ep := (*eface)(unsafe.Pointer(&e))
	t := ep._type
	if t == nil {
	if r != nil {
	*r = nil
	}
	return false
	}
	tab := getitab(inter, t, true)
	if tab == nil {
	if r != nil {
	*r = nil
	}
	return false
	}
	if r != nil {
	rp := (*iface)(unsafe.Pointer(r))
	rp.tab = tab
	rp.data = ep.data
	}
	return true
	}

	//go:linkname reflect_ifaceE2I reflect.ifaceE2I
	func reflect_ifaceE2I(inter interfacetype, e interface{}, dst fInterface) {
	assertE2I(inter, e, dst)
	}

	func assertE2E(inter interfacetype, e interface{}, r interface{}) {
	ep := (*eface)(unsafe.Pointer(&e))
	if ep._type == nil {
	// explicit conversions require non-nil interface value.
	panic(&TypeAssertionError{"", "", *inter.typ._string, ""})
	}
	*r = e
	}

	// The compiler ensures that r is non-nil.
	func assertE2E2(inter interfacetype, e interface{}, r interface{}) bool {
	ep := (*eface)(unsafe.Pointer(&e))
	if ep._type == nil {
	*r = nil
	return false
	}
	*r = e
	return true
	}

	func ifacethash(i fInterface) uint32 {
	ip := (*iface)(unsafe.Pointer(&i))
	tab := ip.tab
	if tab == nil {
	return 0
	}
	return tab._type.hash
	}

	func efacethash(e interface{}) uint32 {
	ep := (*eface)(unsafe.Pointer(&e))
	t := ep._type
	if t == nil {
	return 0
	}
	return t.hash
	}

	func iterate_itabs(fn func(*itab)) {
	for _, h := range &hash {
	for ; h != nil; h = h.link {
	fn(h)
	}
	}
	}