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-rw-r--r--src/runtime/iface.go533
1 files changed, 533 insertions, 0 deletions
diff --git a/src/runtime/iface.go b/src/runtime/iface.go
new file mode 100644
index 0000000..a4d56dd
--- /dev/null
+++ b/src/runtime/iface.go
@@ -0,0 +1,533 @@
+// 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 (
+ "internal/abi"
+ "internal/goarch"
+ "runtime/internal/atomic"
+ "unsafe"
+)
+
+const itabInitSize = 512
+
+var (
+ itabLock mutex // lock for accessing itab table
+ itabTable = &itabTableInit // pointer to current table
+ itabTableInit = itabTableType{size: itabInitSize} // starter table
+)
+
+// Note: change the formula in the mallocgc call in itabAdd if you change these fields.
+type itabTableType struct {
+ size uintptr // length of entries array. Always a power of 2.
+ count uintptr // current number of filled entries.
+ entries [itabInitSize]*itab // really [size] large
+}
+
+func itabHashFunc(inter *interfacetype, typ *_type) uintptr {
+ // compiler has provided some good hash codes for us.
+ return uintptr(inter.typ.hash ^ typ.hash)
+}
+
+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{nil, typ, &inter.typ, name.name()})
+ }
+
+ var m *itab
+
+ // First, look in the existing table to see if we can find the itab we need.
+ // This is by far the most common case, so do it without locks.
+ // Use atomic to ensure we see any previous writes done by the thread
+ // that updates the itabTable field (with atomic.Storep in itabAdd).
+ t := (*itabTableType)(atomic.Loadp(unsafe.Pointer(&itabTable)))
+ if m = t.find(inter, typ); m != nil {
+ goto finish
+ }
+
+ // Not found. Grab the lock and try again.
+ lock(&itabLock)
+ if m = itabTable.find(inter, typ); m != nil {
+ unlock(&itabLock)
+ goto finish
+ }
+
+ // Entry doesn't exist yet. Make a new entry & add it.
+ m = (*itab)(persistentalloc(unsafe.Sizeof(itab{})+uintptr(len(inter.mhdr)-1)*goarch.PtrSize, 0, &memstats.other_sys))
+ m.inter = inter
+ m._type = typ
+ // The hash is used in type switches. However, compiler statically generates itab's
+ // for all interface/type pairs used in switches (which are added to itabTable
+ // in itabsinit). The dynamically-generated itab's never participate in type switches,
+ // and thus the hash is irrelevant.
+ // Note: m.hash is _not_ the hash used for the runtime itabTable hash table.
+ m.hash = 0
+ m.init()
+ itabAdd(m)
+ unlock(&itabLock)
+finish:
+ if m.fun[0] != 0 {
+ return m
+ }
+ if canfail {
+ return nil
+ }
+ // 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 initialize
+ // the itab again to get the missing function name.
+ panic(&TypeAssertionError{concrete: typ, asserted: &inter.typ, missingMethod: m.init()})
+}
+
+// find finds the given interface/type pair in t.
+// Returns nil if the given interface/type pair isn't present.
+func (t *itabTableType) find(inter *interfacetype, typ *_type) *itab {
+ // Implemented using quadratic probing.
+ // Probe sequence is h(i) = h0 + i*(i+1)/2 mod 2^k.
+ // We're guaranteed to hit all table entries using this probe sequence.
+ mask := t.size - 1
+ h := itabHashFunc(inter, typ) & mask
+ for i := uintptr(1); ; i++ {
+ p := (**itab)(add(unsafe.Pointer(&t.entries), h*goarch.PtrSize))
+ // Use atomic read here so if we see m != nil, we also see
+ // the initializations of the fields of m.
+ // m := *p
+ m := (*itab)(atomic.Loadp(unsafe.Pointer(p)))
+ if m == nil {
+ return nil
+ }
+ if m.inter == inter && m._type == typ {
+ return m
+ }
+ h += i
+ h &= mask
+ }
+}
+
+// itabAdd adds the given itab to the itab hash table.
+// itabLock must be held.
+func itabAdd(m *itab) {
+ // Bugs can lead to calling this while mallocing is set,
+ // typically because this is called while panicing.
+ // Crash reliably, rather than only when we need to grow
+ // the hash table.
+ if getg().m.mallocing != 0 {
+ throw("malloc deadlock")
+ }
+
+ t := itabTable
+ if t.count >= 3*(t.size/4) { // 75% load factor
+ // Grow hash table.
+ // t2 = new(itabTableType) + some additional entries
+ // We lie and tell malloc we want pointer-free memory because
+ // all the pointed-to values are not in the heap.
+ t2 := (*itabTableType)(mallocgc((2+2*t.size)*goarch.PtrSize, nil, true))
+ t2.size = t.size * 2
+
+ // Copy over entries.
+ // Note: while copying, other threads may look for an itab and
+ // fail to find it. That's ok, they will then try to get the itab lock
+ // and as a consequence wait until this copying is complete.
+ iterate_itabs(t2.add)
+ if t2.count != t.count {
+ throw("mismatched count during itab table copy")
+ }
+ // Publish new hash table. Use an atomic write: see comment in getitab.
+ atomicstorep(unsafe.Pointer(&itabTable), unsafe.Pointer(t2))
+ // Adopt the new table as our own.
+ t = itabTable
+ // Note: the old table can be GC'ed here.
+ }
+ t.add(m)
+}
+
+// add adds the given itab to itab table t.
+// itabLock must be held.
+func (t *itabTableType) add(m *itab) {
+ // See comment in find about the probe sequence.
+ // Insert new itab in the first empty spot in the probe sequence.
+ mask := t.size - 1
+ h := itabHashFunc(m.inter, m._type) & mask
+ for i := uintptr(1); ; i++ {
+ p := (**itab)(add(unsafe.Pointer(&t.entries), h*goarch.PtrSize))
+ m2 := *p
+ if m2 == m {
+ // A given itab may be used in more than one module
+ // and thanks to the way global symbol resolution works, the
+ // pointed-to itab may already have been inserted into the
+ // global 'hash'.
+ return
+ }
+ if m2 == nil {
+ // Use atomic write here so if a reader sees m, it also
+ // sees the correctly initialized fields of m.
+ // NoWB is ok because m is not in heap memory.
+ // *p = m
+ atomic.StorepNoWB(unsafe.Pointer(p), unsafe.Pointer(m))
+ t.count++
+ return
+ }
+ h += i
+ h &= mask
+ }
+}
+
+// init fills in the m.fun array with all the code pointers for
+// the m.inter/m._type pair. If the type does not implement the interface,
+// it sets m.fun[0] to 0 and returns the name of an interface function that is missing.
+// It is ok to call this multiple times on the same m, even concurrently.
+func (m *itab) init() string {
+ 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
+ methods := (*[1 << 16]unsafe.Pointer)(unsafe.Pointer(&m.fun[0]))[:ni:ni]
+ var fun0 unsafe.Pointer
+imethods:
+ 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)
+ if k == 0 {
+ fun0 = ifn // we'll set m.fun[0] at the end
+ } else {
+ methods[k] = ifn
+ }
+ }
+ continue imethods
+ }
+ }
+ }
+ // didn't find method
+ m.fun[0] = 0
+ return iname
+ }
+ m.fun[0] = uintptr(fun0)
+ return ""
+}
+
+func itabsinit() {
+ lockInit(&itabLock, lockRankItab)
+ lock(&itabLock)
+ for _, md := range activeModules() {
+ for _, i := range md.itablinks {
+ itabAdd(i)
+ }
+ }
+ unlock(&itabLock)
+}
+
+// panicdottypeE is called when doing an e.(T) conversion and the conversion fails.
+// have = the dynamic type we have.
+// want = the static type we're trying to convert to.
+// iface = the static type we're converting from.
+func panicdottypeE(have, want, iface *_type) {
+ panic(&TypeAssertionError{iface, have, want, ""})
+}
+
+// panicdottypeI is called when doing an i.(T) conversion and the conversion fails.
+// Same args as panicdottypeE, but "have" is the dynamic itab we have.
+func panicdottypeI(have *itab, want, iface *_type) {
+ var t *_type
+ if have != nil {
+ t = have._type
+ }
+ panicdottypeE(t, want, iface)
+}
+
+// panicnildottype is called when doing a i.(T) conversion and the interface i is nil.
+// want = the static type we're trying to convert to.
+func panicnildottype(want *_type) {
+ panic(&TypeAssertionError{nil, nil, want, ""})
+ // TODO: Add the static type we're converting from as well.
+ // It might generate a better error message.
+ // Just to match other nil conversion errors, we don't for now.
+}
+
+// The specialized convTx routines need a type descriptor to use when calling mallocgc.
+// We don't need the type to be exact, just to have the correct size, alignment, and pointer-ness.
+// However, when debugging, it'd be nice to have some indication in mallocgc where the types came from,
+// so we use named types here.
+// We then construct interface values of these types,
+// and then extract the type word to use as needed.
+type (
+ uint16InterfacePtr uint16
+ uint32InterfacePtr uint32
+ uint64InterfacePtr uint64
+ stringInterfacePtr string
+ sliceInterfacePtr []byte
+)
+
+var (
+ uint16Eface any = uint16InterfacePtr(0)
+ uint32Eface any = uint32InterfacePtr(0)
+ uint64Eface any = uint64InterfacePtr(0)
+ stringEface any = stringInterfacePtr("")
+ sliceEface any = sliceInterfacePtr(nil)
+
+ uint16Type *_type = efaceOf(&uint16Eface)._type
+ uint32Type *_type = efaceOf(&uint32Eface)._type
+ uint64Type *_type = efaceOf(&uint64Eface)._type
+ stringType *_type = efaceOf(&stringEface)._type
+ sliceType *_type = efaceOf(&sliceEface)._type
+)
+
+// The conv and assert functions below do very similar things.
+// The convXXX functions are guaranteed by the compiler to succeed.
+// The assertXXX functions may fail (either panicking or returning false,
+// depending on whether they are 1-result or 2-result).
+// The convXXX functions succeed on a nil input, whereas the assertXXX
+// functions fail on a nil input.
+
+// convT converts a value of type t, which is pointed to by v, to a pointer that can
+// be used as the second word of an interface value.
+func convT(t *_type, v unsafe.Pointer) unsafe.Pointer {
+ if raceenabled {
+ raceReadObjectPC(t, v, getcallerpc(), abi.FuncPCABIInternal(convT))
+ }
+ if msanenabled {
+ msanread(v, t.size)
+ }
+ if asanenabled {
+ asanread(v, t.size)
+ }
+ x := mallocgc(t.size, t, true)
+ typedmemmove(t, x, v)
+ return x
+}
+func convTnoptr(t *_type, v unsafe.Pointer) unsafe.Pointer {
+ // TODO: maybe take size instead of type?
+ if raceenabled {
+ raceReadObjectPC(t, v, getcallerpc(), abi.FuncPCABIInternal(convTnoptr))
+ }
+ if msanenabled {
+ msanread(v, t.size)
+ }
+ if asanenabled {
+ asanread(v, t.size)
+ }
+
+ x := mallocgc(t.size, t, false)
+ memmove(x, v, t.size)
+ return x
+}
+
+func convT16(val uint16) (x unsafe.Pointer) {
+ if val < uint16(len(staticuint64s)) {
+ x = unsafe.Pointer(&staticuint64s[val])
+ if goarch.BigEndian {
+ x = add(x, 6)
+ }
+ } else {
+ x = mallocgc(2, uint16Type, false)
+ *(*uint16)(x) = val
+ }
+ return
+}
+
+func convT32(val uint32) (x unsafe.Pointer) {
+ if val < uint32(len(staticuint64s)) {
+ x = unsafe.Pointer(&staticuint64s[val])
+ if goarch.BigEndian {
+ x = add(x, 4)
+ }
+ } else {
+ x = mallocgc(4, uint32Type, false)
+ *(*uint32)(x) = val
+ }
+ return
+}
+
+func convT64(val uint64) (x unsafe.Pointer) {
+ if val < uint64(len(staticuint64s)) {
+ x = unsafe.Pointer(&staticuint64s[val])
+ } else {
+ x = mallocgc(8, uint64Type, false)
+ *(*uint64)(x) = val
+ }
+ return
+}
+
+func convTstring(val string) (x unsafe.Pointer) {
+ if val == "" {
+ x = unsafe.Pointer(&zeroVal[0])
+ } else {
+ x = mallocgc(unsafe.Sizeof(val), stringType, true)
+ *(*string)(x) = val
+ }
+ return
+}
+
+func convTslice(val []byte) (x unsafe.Pointer) {
+ // Note: this must work for any element type, not just byte.
+ if (*slice)(unsafe.Pointer(&val)).array == nil {
+ x = unsafe.Pointer(&zeroVal[0])
+ } else {
+ x = mallocgc(unsafe.Sizeof(val), sliceType, true)
+ *(*[]byte)(x) = val
+ }
+ return
+}
+
+// convI2I returns the new itab to be used for the destination value
+// when converting a value with itab src to the dst interface.
+func convI2I(dst *interfacetype, src *itab) *itab {
+ if src == nil {
+ return nil
+ }
+ if src.inter == dst {
+ return src
+ }
+ return getitab(dst, src._type, false)
+}
+
+func assertI2I(inter *interfacetype, tab *itab) *itab {
+ if tab == nil {
+ // explicit conversions require non-nil interface value.
+ panic(&TypeAssertionError{nil, nil, &inter.typ, ""})
+ }
+ if tab.inter == inter {
+ return tab
+ }
+ return getitab(inter, tab._type, false)
+}
+
+func assertI2I2(inter *interfacetype, i iface) (r iface) {
+ tab := i.tab
+ if tab == nil {
+ return
+ }
+ if tab.inter != inter {
+ tab = getitab(inter, tab._type, true)
+ if tab == nil {
+ return
+ }
+ }
+ r.tab = tab
+ r.data = i.data
+ return
+}
+
+func assertE2I(inter *interfacetype, t *_type) *itab {
+ if t == nil {
+ // explicit conversions require non-nil interface value.
+ panic(&TypeAssertionError{nil, nil, &inter.typ, ""})
+ }
+ return getitab(inter, t, false)
+}
+
+func assertE2I2(inter *interfacetype, e eface) (r iface) {
+ t := e._type
+ if t == nil {
+ return
+ }
+ tab := getitab(inter, t, true)
+ if tab == nil {
+ return
+ }
+ r.tab = tab
+ r.data = e.data
+ return
+}
+
+//go:linkname reflect_ifaceE2I reflect.ifaceE2I
+func reflect_ifaceE2I(inter *interfacetype, e eface, dst *iface) {
+ *dst = iface{assertE2I(inter, e._type), e.data}
+}
+
+//go:linkname reflectlite_ifaceE2I internal/reflectlite.ifaceE2I
+func reflectlite_ifaceE2I(inter *interfacetype, e eface, dst *iface) {
+ *dst = iface{assertE2I(inter, e._type), e.data}
+}
+
+func iterate_itabs(fn func(*itab)) {
+ // Note: only runs during stop the world or with itabLock held,
+ // so no other locks/atomics needed.
+ t := itabTable
+ for i := uintptr(0); i < t.size; i++ {
+ m := *(**itab)(add(unsafe.Pointer(&t.entries), i*goarch.PtrSize))
+ if m != nil {
+ fn(m)
+ }
+ }
+}
+
+// staticuint64s is used to avoid allocating in convTx for small integer values.
+var staticuint64s = [...]uint64{
+ 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+ 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+ 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+ 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+ 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
+ 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
+ 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
+ 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
+ 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
+ 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f,
+ 0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
+ 0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
+ 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
+ 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
+ 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
+ 0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
+ 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
+ 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
+ 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
+ 0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
+ 0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
+ 0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
+ 0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
+ 0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
+ 0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
+ 0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
+ 0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
+ 0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
+ 0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
+ 0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
+ 0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
+ 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
+}
+
+// The linker redirects a reference of a method that it determined
+// unreachable to a reference to this function, so it will throw if
+// ever called.
+func unreachableMethod() {
+ throw("unreachable method called. linker bug?")
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-19 15:26:00 +0000