blob: 656bb4b8e5c227d74541be12b8e9dcccb55201bc [file] [log] [blame]
// 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)
}
}
}