mirror of https://github.com/golang/go.git
414 lines
8.7 KiB
Go
414 lines
8.7 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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import (
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"runtime/internal/atomic"
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"runtime/internal/sys"
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"unsafe"
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)
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const (
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hashSize = 1009
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)
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var (
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ifaceLock mutex // lock for accessing hash
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hash [hashSize]*itab
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)
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func itabhash(inter *interfacetype, typ *_type) uint32 {
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// compiler has provided some good hash codes for us.
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h := inter.typ.hash
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h += 17 * typ.hash
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// TODO(rsc): h += 23 * x.mhash ?
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return h % hashSize
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}
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func getitab(inter *interfacetype, typ *_type, canfail bool) *itab {
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if len(inter.mhdr) == 0 {
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throw("internal error - misuse of itab")
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}
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// easy case
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if typ.tflag&tflagUncommon == 0 {
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if canfail {
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return nil
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}
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name := inter.typ.nameOff(inter.mhdr[0].name)
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panic(&TypeAssertionError{"", typ.string(), inter.typ.string(), name.name()})
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}
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h := itabhash(inter, typ)
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// look twice - once without lock, once with.
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// common case will be no lock contention.
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var m *itab
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var locked int
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for locked = 0; locked < 2; locked++ {
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if locked != 0 {
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lock(&ifaceLock)
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}
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for m = (*itab)(atomic.Loadp(unsafe.Pointer(&hash[h]))); m != nil; m = m.link {
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if m.inter == inter && m._type == typ {
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if m.bad != 0 {
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if !canfail {
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// this can only happen if the conversion
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// was already done once using the , ok form
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// and we have a cached negative result.
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// the cached result doesn't record which
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// interface function was missing, so try
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// adding the itab again, which will throw an error.
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additab(m, locked != 0, false)
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}
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m = nil
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}
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if locked != 0 {
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unlock(&ifaceLock)
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}
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return m
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}
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}
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}
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m = (*itab)(persistentalloc(unsafe.Sizeof(itab{})+uintptr(len(inter.mhdr)-1)*sys.PtrSize, 0, &memstats.other_sys))
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m.inter = inter
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m._type = typ
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additab(m, true, canfail)
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unlock(&ifaceLock)
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if m.bad != 0 {
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return nil
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}
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return m
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}
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func additab(m *itab, locked, canfail bool) {
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inter := m.inter
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typ := m._type
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x := typ.uncommon()
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// both inter and typ have method sorted by name,
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// and interface names are unique,
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// so can iterate over both in lock step;
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// the loop is O(ni+nt) not O(ni*nt).
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ni := len(inter.mhdr)
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nt := int(x.mcount)
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xmhdr := (*[1 << 16]method)(add(unsafe.Pointer(x), uintptr(x.moff)))[:nt:nt]
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j := 0
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for k := 0; k < ni; k++ {
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i := &inter.mhdr[k]
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itype := inter.typ.typeOff(i.ityp)
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name := inter.typ.nameOff(i.name)
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iname := name.name()
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ipkg := name.pkgPath()
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if ipkg == "" {
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ipkg = inter.pkgpath.name()
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}
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for ; j < nt; j++ {
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t := &xmhdr[j]
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tname := typ.nameOff(t.name)
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if typ.typeOff(t.mtyp) == itype && tname.name() == iname {
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pkgPath := tname.pkgPath()
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if pkgPath == "" {
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pkgPath = typ.nameOff(x.pkgpath).name()
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}
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if tname.isExported() || pkgPath == ipkg {
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if m != nil {
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ifn := typ.textOff(t.ifn)
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*(*unsafe.Pointer)(add(unsafe.Pointer(&m.fun[0]), uintptr(k)*sys.PtrSize)) = ifn
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}
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goto nextimethod
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}
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}
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}
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// didn't find method
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if !canfail {
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if locked {
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unlock(&ifaceLock)
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}
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panic(&TypeAssertionError{"", typ.string(), inter.typ.string(), iname})
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}
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m.bad = 1
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break
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nextimethod:
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}
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if !locked {
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throw("invalid itab locking")
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}
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h := itabhash(inter, typ)
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if m == hash[h] {
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println("duplicate itab for", typ.string(), "and", inter.typ.string())
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throw("duplicate itabs")
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}
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m.link = hash[h]
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atomicstorep(unsafe.Pointer(&hash[h]), unsafe.Pointer(m))
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}
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func itabsinit() {
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lock(&ifaceLock)
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for _, md := range activeModules() {
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for _, i := range md.itablinks {
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additab(i, true, false)
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}
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}
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unlock(&ifaceLock)
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}
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func convT2E(t *_type, elem unsafe.Pointer) (e eface) {
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if raceenabled {
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raceReadObjectPC(t, elem, getcallerpc(unsafe.Pointer(&t)), funcPC(convT2E))
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}
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if msanenabled {
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msanread(elem, t.size)
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}
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if isDirectIface(t) {
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throw("direct convT2E")
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}
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x := newobject(t)
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// TODO: We allocate a zeroed object only to overwrite it with
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// actual data. Figure out how to avoid zeroing. Also below in convT2I.
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typedmemmove(t, x, elem)
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e._type = t
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e.data = x
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return
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}
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func convT2I(tab *itab, elem unsafe.Pointer) (i iface) {
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t := tab._type
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if raceenabled {
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raceReadObjectPC(t, elem, getcallerpc(unsafe.Pointer(&tab)), funcPC(convT2I))
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}
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if msanenabled {
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msanread(elem, t.size)
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}
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if isDirectIface(t) {
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throw("direct convT2I")
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}
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x := newobject(t)
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typedmemmove(t, x, elem)
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i.tab = tab
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i.data = x
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return
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}
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func panicdottype(have, want, iface *_type) {
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haveString := ""
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if have != nil {
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haveString = have.string()
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}
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panic(&TypeAssertionError{iface.string(), haveString, want.string(), ""})
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}
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func assertI2T(t *_type, i iface, r unsafe.Pointer) {
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tab := i.tab
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if tab == nil {
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panic(&TypeAssertionError{"", "", t.string(), ""})
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}
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if tab._type != t {
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panic(&TypeAssertionError{tab.inter.typ.string(), tab._type.string(), t.string(), ""})
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}
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if r != nil {
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if isDirectIface(t) {
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writebarrierptr((*uintptr)(r), uintptr(i.data))
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} else {
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typedmemmove(t, r, i.data)
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}
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}
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}
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// The compiler ensures that r is non-nil.
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func assertI2T2(t *_type, i iface, r unsafe.Pointer) bool {
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tab := i.tab
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if tab == nil || tab._type != t {
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typedmemclr(t, r)
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return false
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}
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if isDirectIface(t) {
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writebarrierptr((*uintptr)(r), uintptr(i.data))
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} else {
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typedmemmove(t, r, i.data)
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}
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return true
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}
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func assertE2T(t *_type, e eface, r unsafe.Pointer) {
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if e._type == nil {
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panic(&TypeAssertionError{"", "", t.string(), ""})
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}
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if e._type != t {
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panic(&TypeAssertionError{"", e._type.string(), t.string(), ""})
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}
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if r != nil {
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if isDirectIface(t) {
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writebarrierptr((*uintptr)(r), uintptr(e.data))
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} else {
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typedmemmove(t, r, e.data)
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}
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}
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}
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var testingAssertE2T2GC bool
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// The compiler ensures that r is non-nil.
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func assertE2T2(t *_type, e eface, r unsafe.Pointer) bool {
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if testingAssertE2T2GC {
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GC()
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}
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if e._type != t {
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typedmemclr(t, r)
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return false
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}
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if isDirectIface(t) {
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writebarrierptr((*uintptr)(r), uintptr(e.data))
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} else {
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typedmemmove(t, r, e.data)
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}
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return true
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}
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func assertI2E(inter *interfacetype, i iface, r *eface) {
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tab := i.tab
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if tab == nil {
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// explicit conversions require non-nil interface value.
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panic(&TypeAssertionError{"", "", inter.typ.string(), ""})
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}
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r._type = tab._type
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r.data = i.data
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return
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}
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// The compiler ensures that r is non-nil.
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func assertI2E2(inter *interfacetype, i iface, r *eface) bool {
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tab := i.tab
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if tab == nil {
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return false
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}
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r._type = tab._type
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r.data = i.data
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return true
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}
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func convI2I(inter *interfacetype, i iface) (r iface) {
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tab := i.tab
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if tab == nil {
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return
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}
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if tab.inter == inter {
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r.tab = tab
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r.data = i.data
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return
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}
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r.tab = getitab(inter, tab._type, false)
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r.data = i.data
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return
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}
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func assertI2I(inter *interfacetype, i iface, r *iface) {
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tab := i.tab
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if tab == nil {
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// explicit conversions require non-nil interface value.
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panic(&TypeAssertionError{"", "", inter.typ.string(), ""})
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}
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if tab.inter == inter {
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r.tab = tab
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r.data = i.data
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return
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}
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r.tab = getitab(inter, tab._type, false)
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r.data = i.data
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}
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func assertI2I2(inter *interfacetype, i iface, r *iface) bool {
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tab := i.tab
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if tab == nil {
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if r != nil {
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*r = iface{}
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}
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return false
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}
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if tab.inter != inter {
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tab = getitab(inter, tab._type, true)
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if tab == nil {
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if r != nil {
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*r = iface{}
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}
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return false
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}
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}
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if r != nil {
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r.tab = tab
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r.data = i.data
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}
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return true
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}
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func assertE2I(inter *interfacetype, e eface, r *iface) {
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t := e._type
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if t == nil {
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// explicit conversions require non-nil interface value.
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panic(&TypeAssertionError{"", "", inter.typ.string(), ""})
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}
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r.tab = getitab(inter, t, false)
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r.data = e.data
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}
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var testingAssertE2I2GC bool
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func assertE2I2(inter *interfacetype, e eface, r *iface) bool {
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if testingAssertE2I2GC {
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GC()
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}
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t := e._type
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if t == nil {
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if r != nil {
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*r = iface{}
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}
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return false
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}
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tab := getitab(inter, t, true)
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if tab == nil {
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if r != nil {
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*r = iface{}
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}
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return false
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}
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if r != nil {
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r.tab = tab
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r.data = e.data
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}
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return true
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}
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//go:linkname reflect_ifaceE2I reflect.ifaceE2I
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func reflect_ifaceE2I(inter *interfacetype, e eface, dst *iface) {
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assertE2I(inter, e, dst)
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}
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func assertE2E(inter *interfacetype, e eface, r *eface) {
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if e._type == nil {
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// explicit conversions require non-nil interface value.
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panic(&TypeAssertionError{"", "", inter.typ.string(), ""})
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}
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*r = e
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}
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// The compiler ensures that r is non-nil.
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func assertE2E2(inter *interfacetype, e eface, r *eface) bool {
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if e._type == nil {
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*r = eface{}
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return false
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}
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*r = e
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return true
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}
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func iterate_itabs(fn func(*itab)) {
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for _, h := range &hash {
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for ; h != nil; h = h.link {
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fn(h)
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}
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}
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}
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