1 files changed, 439 insertions, 0 deletions
diff --git a/src/runtime/iface.go b/src/runtime/iface.go
new file mode 100644
index 000000000..f60b6a79c
--- /dev/null
+++ b/src/runtime/iface.go
@@ -0,0 +1,439 @@
+// 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 {
+		gothrow("internal error - misuse of itab")
+	}
+
+	// easy case
+	x := typ.x
+	if x == nil {
+		if canfail {
+			return nil
+		}
+		i := (*imethod)(add(unsafe.Pointer(inter), unsafe.Sizeof(interfacetype{})))
+		panic(&TypeAssertionError{"", *typ._string, *inter.typ._string, *i.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))*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 := (*imethod)(add(unsafe.Pointer(inter), unsafe.Sizeof(interfacetype{})+uintptr(k)*unsafe.Sizeof(imethod{})))
+		iname := i.name
+		ipkgpath := i.pkgpath
+		itype := i._type
+		for ; j < nt; j++ {
+			t := (*method)(add(unsafe.Pointer(x), unsafe.Sizeof(uncommontype{})+uintptr(j)*unsafe.Sizeof(method{})))
+			if t.mtyp == itype && t.name == iname && t.pkgpath == ipkgpath {
+				if m != nil {
+					*(*unsafe.Pointer)(add(unsafe.Pointer(m), unsafe.Sizeof(itab{})+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 {
+		gothrow("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) (e interface{}) {
+	size := uintptr(t.size)
+	ep := (*eface)(unsafe.Pointer(&e))
+	if isDirectIface(t) {
+		ep._type = t
+		memmove(unsafe.Pointer(&ep.data), elem, size)
+	} else {
+		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.
+		memmove(x, elem, size)
+		ep._type = t
+		ep.data = x
+	}
+	return
+}
+
+func convT2I(t *_type, inter *interfacetype, cache **itab, elem 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))
+	}
+	size := uintptr(t.size)
+	pi := (*iface)(unsafe.Pointer(&i))
+	if isDirectIface(t) {
+		pi.tab = tab
+		memmove(unsafe.Pointer(&pi.data), elem, size)
+	} else {
+		x := newobject(t)
+		memmove(x, elem, size)
+		pi.tab = tab
+		pi.data = x
+	}
+	return
+}
+
+// TODO: give these routines a pointer to the result area instead of writing
+// extra data in the outargs section.  Then we can get rid of go:nosplit.
+//go:nosplit
+func assertI2T(t *_type, i fInterface) (r struct{}) {
+	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, ""})
+	}
+	size := uintptr(t.size)
+	if isDirectIface(t) {
+		memmove(unsafe.Pointer(&r), unsafe.Pointer(&ip.data), size)
+	} else {
+		memmove(unsafe.Pointer(&r), ip.data, size)
+	}
+	return
+}
+
+//go:nosplit
+func assertI2T2(t *_type, i fInterface) (r byte) {
+	ip := (*iface)(unsafe.Pointer(&i))
+	size := uintptr(t.size)
+	ok := (*bool)(add(unsafe.Pointer(&r), size))
+	tab := ip.tab
+	if tab == nil || tab._type != t {
+		*ok = false
+		memclr(unsafe.Pointer(&r), size)
+		return
+	}
+	*ok = true
+	if isDirectIface(t) {
+		memmove(unsafe.Pointer(&r), unsafe.Pointer(&ip.data), size)
+	} else {
+		memmove(unsafe.Pointer(&r), ip.data, size)
+	}
+	return
+}
+
+func assertI2TOK(t *_type, i fInterface) bool {
+	ip := (*iface)(unsafe.Pointer(&i))
+	tab := ip.tab
+	return tab != nil && tab._type == t
+}
+
+//go:nosplit
+func assertE2T(t *_type, e interface{}) (r struct{}) {
+	ep := (*eface)(unsafe.Pointer(&e))
+	if ep._type == nil {
+		panic(&TypeAssertionError{"", "", *t._string, ""})
+	}
+	if ep._type != t {
+		panic(&TypeAssertionError{"", *ep._type._string, *t._string, ""})
+	}
+	size := uintptr(t.size)
+	if isDirectIface(t) {
+		memmove(unsafe.Pointer(&r), unsafe.Pointer(&ep.data), size)
+	} else {
+		memmove(unsafe.Pointer(&r), ep.data, size)
+	}
+	return
+}
+
+//go:nosplit
+func assertE2T2(t *_type, e interface{}) (r byte) {
+	ep := (*eface)(unsafe.Pointer(&e))
+	size := uintptr(t.size)
+	ok := (*bool)(add(unsafe.Pointer(&r), size))
+	if ep._type != t {
+		*ok = false
+		memclr(unsafe.Pointer(&r), size)
+		return
+	}
+	*ok = true
+	if isDirectIface(t) {
+		memmove(unsafe.Pointer(&r), unsafe.Pointer(&ep.data), size)
+	} else {
+		memmove(unsafe.Pointer(&r), ep.data, size)
+	}
+	return
+}
+
+func assertE2TOK(t *_type, e interface{}) bool {
+	ep := (*eface)(unsafe.Pointer(&e))
+	return t == ep._type
+}
+
+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
+}
+
+func assertI2E2(inter *interfacetype, i fInterface) (r interface{}, ok bool) {
+	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
+	ok = true
+	return
+}
+
+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
+	return
+}
+
+func assertI2I2(inter *interfacetype, i fInterface) (r fInterface, ok bool) {
+	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
+		ok = true
+		return
+	}
+	tab = getitab(inter, tab._type, true)
+	if tab == nil {
+		rp.data = nil
+		rp.tab = nil
+		ok = false
+		return
+	}
+	rp.tab = tab
+	rp.data = ip.data
+	ok = true
+	return
+}
+
+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
+	return
+}
+
+func assertE2I2(inter *interfacetype, e interface{}) (r fInterface, ok bool) {
+	ep := (*eface)(unsafe.Pointer(&e))
+	t := ep._type
+	if t == nil {
+		return
+	}
+	tab := getitab(inter, t, true)
+	if tab == nil {
+		return
+	}
+	rp := (*iface)(unsafe.Pointer(&r))
+	rp.tab = tab
+	rp.data = ep.data
+	ok = true
+	return
+}
+
+func reflect_ifaceE2I(inter *interfacetype, e interface{}, dst *fInterface) {
+	*dst = assertE2I(inter, e)
+}
+
+func assertE2E(inter *interfacetype, e interface{}) interface{} {
+	ep := (*eface)(unsafe.Pointer(&e))
+	if ep._type == nil {
+		// explicit conversions require non-nil interface value.
+		panic(&TypeAssertionError{"", "", *inter.typ._string, ""})
+	}
+	return e
+}
+
+func assertE2E2(inter *interfacetype, e interface{}) (interface{}, bool) {
+	ep := (*eface)(unsafe.Pointer(&e))
+	if ep._type == nil {
+		return nil, false
+	}
+	return e, 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)
+		}
+	}
+}
+
+func ifaceE2I2(inter *interfacetype, e interface{}, r *fInterface) (ok bool) {
+	*r, ok = assertE2I2(inter, e)
+	return
+}