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// 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 (
"runtime/internal/atomic"
"runtime/internal/sys"
"unsafe"
)
const (
hashSize = 1009
)
var (
ifaceLock mutex // lock for accessing hash
hash [hashSize]*itab
)
func itabhash(inter *interfacetype, typ *_type) uint32 {
// compiler has provided some good hash codes for us.
h := inter.typ.hash
h += 17 * typ.hash
// TODO(rsc): h += 23 * x.mhash ?
return h % hashSize
}
func getitab(inter *interfacetype, typ *_type, canfail bool) *itab {
if len(inter.mhdr) == 0 {
throw("internal error - misuse of itab")
}
// easy case
if typ.tflag&tflagUncommon == 0 {
if canfail {
return nil
}
name := inter.typ.nameOff(inter.mhdr[0].name)
panic(&TypeAssertionError{"", typ.string(), inter.typ.string(), name.name()})
}
h := itabhash(inter, typ)
// 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)(atomic.Loadp(unsafe.Pointer(&hash[h]))); m != nil; m = m.link {
if m.inter == inter && m._type == typ {
if m.bad != 0 {
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 try
// adding the itab again, which will throw an error.
additab(m, locked != 0, false)
}
m = nil
}
if locked != 0 {
unlock(&ifaceLock)
}
return m
}
}
}
m = (*itab)(persistentalloc(unsafe.Sizeof(itab{})+uintptr(len(inter.mhdr)-1)*sys.PtrSize, 0, &memstats.other_sys))
m.inter = inter
m._type = typ
additab(m, true, canfail)
unlock(&ifaceLock)
if m.bad != 0 {
return nil
}
return m
}
func additab(m *itab, locked, canfail bool) {
inter := m.inter
typ := m._type
x := typ.uncommon()
// 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 := int(x.mcount)
xmhdr := (*[1 << 16]method)(add(unsafe.Pointer(x), uintptr(x.moff)))[:nt:nt]
j := 0
for k := 0; k < ni; k++ {
i := &inter.mhdr[k]
itype := inter.typ.typeOff(i.ityp)
name := inter.typ.nameOff(i.name)
iname := name.name()
ipkg := name.pkgPath()
if ipkg == "" {
ipkg = inter.pkgpath.name()
}
for ; j < nt; j++ {
t := &xmhdr[j]
tname := typ.nameOff(t.name)
if typ.typeOff(t.mtyp) == itype && tname.name() == iname {
pkgPath := tname.pkgPath()
if pkgPath == "" {
pkgPath = typ.nameOff(x.pkgpath).name()
}
if tname.isExported() || pkgPath == ipkg {
if m != nil {
ifn := typ.textOff(t.ifn)
*(*unsafe.Pointer)(add(unsafe.Pointer(&m.fun[0]), uintptr(k)*sys.PtrSize)) = ifn
}
goto nextimethod
}
}
}
// didn't find method
if !canfail {
if locked {
unlock(&ifaceLock)
}
panic(&TypeAssertionError{"", typ.string(), inter.typ.string(), iname})
}
m.bad = 1
break
nextimethod:
}
if !locked {
throw("invalid itab locking")
}
h := itabhash(inter, typ)
m.link = hash[h]
atomicstorep(unsafe.Pointer(&hash[h]), unsafe.Pointer(m))
}
func itabsinit() {
lock(&ifaceLock)
for m := &firstmoduledata; m != nil; m = m.next {
for _, i := range m.itablinks {
additab(i, true, false)
}
}
unlock(&ifaceLock)
}
func convT2E(t *_type, elem unsafe.Pointer, x unsafe.Pointer) (e eface) {
if raceenabled {
raceReadObjectPC(t, elem, getcallerpc(unsafe.Pointer(&t)), funcPC(convT2E))
}
if msanenabled {
msanread(elem, t.size)
}
if isDirectIface(t) {
throw("direct convT2E")
}
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)
e._type = t
e.data = x
return
}
func convT2I(tab *itab, elem unsafe.Pointer, x unsafe.Pointer) (i iface) {
t := tab._type
if raceenabled {
raceReadObjectPC(t, elem, getcallerpc(unsafe.Pointer(&tab)), funcPC(convT2I))
}
if msanenabled {
msanread(elem, t.size)
}
if isDirectIface(t) {
throw("direct convT2I")
}
if x == nil {
x = newobject(t)
}
typedmemmove(t, x, elem)
i.tab = tab
i.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 iface, r unsafe.Pointer) {
tab := i.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(i.data))
} else {
typedmemmove(t, r, i.data)
}
}
}
func assertI2T2(t *_type, i iface, r unsafe.Pointer) bool {
tab := i.tab
if tab == nil || tab._type != t {
if r != nil {
memclr(r, t.size)
}
return false
}
if r != nil {
if isDirectIface(t) {
writebarrierptr((*uintptr)(r), uintptr(i.data))
} else {
typedmemmove(t, r, i.data)
}
}
return true
}
func assertE2T(t *_type, e eface, r unsafe.Pointer) {
if e._type == nil {
panic(&TypeAssertionError{"", "", t.string(), ""})
}
if e._type != t {
panic(&TypeAssertionError{"", e._type.string(), t.string(), ""})
}
if r != nil {
if isDirectIface(t) {
writebarrierptr((*uintptr)(r), uintptr(e.data))
} else {
typedmemmove(t, r, e.data)
}
}
}
var testingAssertE2T2GC bool
// The compiler ensures that r is non-nil.
func assertE2T2(t *_type, e eface, r unsafe.Pointer) bool {
if testingAssertE2T2GC {
GC()
}
if e._type != t {
memclr(r, t.size)
return false
}
if isDirectIface(t) {
writebarrierptr((*uintptr)(r), uintptr(e.data))
} else {
typedmemmove(t, r, e.data)
}
return true
}
func convI2E(i iface) (r eface) {
tab := i.tab
if tab == nil {
return
}
r._type = tab._type
r.data = i.data
return
}
func assertI2E(inter *interfacetype, i iface, r *eface) {
tab := i.tab
if tab == nil {
// explicit conversions require non-nil interface value.
panic(&TypeAssertionError{"", "", inter.typ.string(), ""})
}
r._type = tab._type
r.data = i.data
return
}
// The compiler ensures that r is non-nil.
func assertI2E2(inter *interfacetype, i iface, r *eface) bool {
tab := i.tab
if tab == nil {
return false
}
r._type = tab._type
r.data = i.data
return true
}
func convI2I(inter *interfacetype, i iface) (r iface) {
tab := i.tab
if tab == nil {
return
}
if tab.inter == inter {
r.tab = tab
r.data = i.data
return
}
r.tab = getitab(inter, tab._type, false)
r.data = i.data
return
}
func assertI2I(inter *interfacetype, i iface, r *iface) {
tab := i.tab
if tab == nil {
// explicit conversions require non-nil interface value.
panic(&TypeAssertionError{"", "", inter.typ.string(), ""})
}
if tab.inter == inter {
r.tab = tab
r.data = i.data
return
}
r.tab = getitab(inter, tab._type, false)
r.data = i.data
}
func assertI2I2(inter *interfacetype, i iface, r *iface) bool {
tab := i.tab
if tab == nil {
if r != nil {
*r = iface{}
}
return false
}
if tab.inter != inter {
tab = getitab(inter, tab._type, true)
if tab == nil {
if r != nil {
*r = iface{}
}
return false
}
}
if r != nil {
r.tab = tab
r.data = i.data
}
return true
}
func assertE2I(inter *interfacetype, e eface, r *iface) {
t := e._type
if t == nil {
// explicit conversions require non-nil interface value.
panic(&TypeAssertionError{"", "", inter.typ.string(), ""})
}
r.tab = getitab(inter, t, false)
r.data = e.data
}
var testingAssertE2I2GC bool
func assertE2I2(inter *interfacetype, e eface, r *iface) bool {
if testingAssertE2I2GC {
GC()
}
t := e._type
if t == nil {
if r != nil {
*r = iface{}
}
return false
}
tab := getitab(inter, t, true)
if tab == nil {
if r != nil {
*r = iface{}
}
return false
}
if r != nil {
r.tab = tab
r.data = e.data
}
return true
}
//go:linkname reflect_ifaceE2I reflect.ifaceE2I
func reflect_ifaceE2I(inter *interfacetype, e eface, dst *iface) {
assertE2I(inter, e, dst)
}
func assertE2E(inter *interfacetype, e eface, r *eface) {
if e._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 eface, r *eface) bool {
if e._type == nil {
*r = eface{}
return false
}
*r = e
return true
}
func iterate_itabs(fn func(*itab)) {
for _, h := range &hash {
for ; h != nil; h = h.link {
fn(h)
}
}
}