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Diffstat (limited to 'pkg/state/encode.go')
| -rw-r--r-- | pkg/state/encode.go | 841 |
1 files changed, 841 insertions, 0 deletions
diff --git a/pkg/state/encode.go b/pkg/state/encode.go new file mode 100644 index 000000000..92fcad4e9 --- /dev/null +++ b/pkg/state/encode.go @@ -0,0 +1,841 @@ +// Copyright 2018 The gVisor Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +package state + +import ( + "context" + "reflect" + + "gvisor.dev/gvisor/pkg/state/wire" +) + +// objectEncodeState the type and identity of an object occupying a memory +// address range. This is the value type for addrSet, and the intrusive entry +// for the pending and deferred lists. +type objectEncodeState struct { + // id is the assigned ID for this object. + id objectID + + // obj is the object value. Note that this may be replaced if we + // encounter an object that contains this object. When this happens (in + // resolve), we will update existing references approprately, below, + // and defer a re-encoding of the object. + obj reflect.Value + + // encoded is the encoded value of this object. Note that this may not + // be up to date if this object is still in the deferred list. + encoded wire.Object + + // how indicates whether this object should be encoded as a value. This + // is used only for deferred encoding. + how encodeStrategy + + // refs are the list of reference objects used by other objects + // referring to this object. When the object is updated, these + // references may be updated directly and automatically. + refs []*wire.Ref + + pendingEntry + deferredEntry +} + +// encodeState is state used for encoding. +// +// The encoding process constructs a representation of the in-memory graph of +// objects before a single object is serialized. This is done to ensure that +// all references can be fully disambiguated. See resolve for more details. +type encodeState struct { + // ctx is the encode context. + ctx context.Context + + // w is the output stream. + w wire.Writer + + // types is the type database. + types typeEncodeDatabase + + // lastID is the last allocated object ID. + lastID objectID + + // values tracks the address ranges occupied by objects, along with the + // types of these objects. This is used to locate pointer targets, + // including pointers to fields within another type. + // + // Multiple objects may overlap in memory iff the larger object fully + // contains the smaller one, and the type of the smaller object matches + // a field or array element's type at the appropriate offset. An + // arbitrary number of objects may be nested in this manner. + // + // Note that this does not track zero-sized objects, those are tracked + // by zeroValues below. + values addrSet + + // zeroValues tracks zero-sized objects. + zeroValues map[reflect.Type]*objectEncodeState + + // deferred is the list of objects to be encoded. + deferred deferredList + + // pendingTypes is the list of types to be serialized. Serialization + // will occur when all objects have been encoded, but before pending is + // serialized. + pendingTypes []wire.Type + + // pending is the list of objects to be serialized. Serialization does + // not actually occur until the full object graph is computed. + pending pendingList + + // stats tracks time data. + stats Stats +} + +// isSameSizeParent returns true if child is a field value or element within +// parent. Only a struct or array can have a child value. +// +// isSameSizeParent deals with objects like this: +// +// struct child { +// // fields.. +// } +// +// struct parent { +// c child +// } +// +// var p parent +// record(&p.c) +// +// Here, &p and &p.c occupy the exact same address range. +// +// Or like this: +// +// struct child { +// // fields +// } +// +// var arr [1]parent +// record(&arr[0]) +// +// Similarly, &arr[0] and &arr[0].c have the exact same address range. +// +// Precondition: parent and child must occupy the same memory. +func isSameSizeParent(parent reflect.Value, childType reflect.Type) bool { + switch parent.Kind() { + case reflect.Struct: + for i := 0; i < parent.NumField(); i++ { + field := parent.Field(i) + if field.Type() == childType { + return true + } + // Recurse through any intermediate types. + if isSameSizeParent(field, childType) { + return true + } + // Does it make sense to keep going if the first field + // doesn't match? Yes, because there might be an + // arbitrary number of zero-sized fields before we get + // a match, and childType itself can be zero-sized. + } + return false + case reflect.Array: + // The only case where an array with more than one elements can + // return true is if childType is zero-sized. In such cases, + // it's ambiguous which element contains the match since a + // zero-sized child object fully fits in any of the zero-sized + // elements in an array... However since all elements are of + // the same type, we only need to check one element. + // + // For non-zero-sized childTypes, parent.Len() must be 1, but a + // combination of the precondition and an implicit comparison + // between the array element size and childType ensures this. + return parent.Len() > 0 && isSameSizeParent(parent.Index(0), childType) + default: + return false + } +} + +// nextID returns the next valid ID. +func (es *encodeState) nextID() objectID { + es.lastID++ + return objectID(es.lastID) +} + +// dummyAddr points to the dummy zero-sized address. +var dummyAddr = reflect.ValueOf(new(struct{})).Pointer() + +// resolve records the address range occupied by an object. +func (es *encodeState) resolve(obj reflect.Value, ref *wire.Ref) { + addr := obj.Pointer() + + // Is this a map pointer? Just record the single address. It is not + // possible to take any pointers into the map internals. + if obj.Kind() == reflect.Map { + if addr == 0 { + // Just leave the nil reference alone. This is fine, we + // may need to encode as a reference in this way. We + // return nil for our objectEncodeState so that anyone + // depending on this value knows there's nothing there. + return + } + if seg, _ := es.values.Find(addr); seg.Ok() { + // Ensure the map types match. + existing := seg.Value() + if existing.obj.Type() != obj.Type() { + Failf("overlapping map objects at 0x%x: [new object] %#v [existing object type] %s", addr, obj, existing.obj) + } + + // No sense recording refs, maps may not be replaced by + // covering objects, they are maximal. + ref.Root = wire.Uint(existing.id) + return + } + + // Record the map. + oes := &objectEncodeState{ + id: es.nextID(), + obj: obj, + how: encodeMapAsValue, + } + es.values.Add(addrRange{addr, addr + 1}, oes) + es.pending.PushBack(oes) + es.deferred.PushBack(oes) + + // See above: no ref recording. + ref.Root = wire.Uint(oes.id) + return + } + + // If not a map, then the object must be a pointer. + if obj.Kind() != reflect.Ptr { + Failf("attempt to record non-map and non-pointer object %#v", obj) + } + + obj = obj.Elem() // Value from here. + + // Is this a zero-sized type? + typ := obj.Type() + size := typ.Size() + if size == 0 { + if addr == dummyAddr { + // Zero-sized objects point to a dummy byte within the + // runtime. There's no sense recording this in the + // address map. We add this to the dedicated + // zeroValues. + // + // Note that zero-sized objects must be *true* + // zero-sized objects. They cannot be part of some + // larger object. In that case, they are assigned a + // 1-byte address at the end of the object. + oes, ok := es.zeroValues[typ] + if !ok { + oes = &objectEncodeState{ + id: es.nextID(), + obj: obj, + } + es.zeroValues[typ] = oes + es.pending.PushBack(oes) + es.deferred.PushBack(oes) + } + + // There's also no sense tracking back references. We + // know that this is a true zero-sized object, and not + // part of a larger container, so it will not change. + ref.Root = wire.Uint(oes.id) + return + } + size = 1 // See above. + } + + // Calculate the container. + end := addr + size + r := addrRange{addr, end} + if seg, _ := es.values.Find(addr); seg.Ok() { + existing := seg.Value() + switch { + case seg.Start() == addr && seg.End() == end && obj.Type() == existing.obj.Type(): + // The object is a perfect match. Happy path. Avoid the + // traversal and just return directly. We don't need to + // encode the type information or any dots here. + ref.Root = wire.Uint(existing.id) + existing.refs = append(existing.refs, ref) + return + + case (seg.Start() < addr && seg.End() >= end) || (seg.Start() <= addr && seg.End() > end): + // The previously registered object is larger than + // this, no need to update. But we expect some + // traversal below. + + case seg.Start() == addr && seg.End() == end: + if !isSameSizeParent(obj, existing.obj.Type()) { + break // Needs traversal. + } + fallthrough // Needs update. + + case (seg.Start() > addr && seg.End() <= end) || (seg.Start() >= addr && seg.End() < end): + // Update the object and redo the encoding. + old := existing.obj + existing.obj = obj + es.deferred.Remove(existing) + es.deferred.PushBack(existing) + + // The previously registered object is superseded by + // this new object. We are guaranteed to not have any + // mergeable neighbours in this segment set. + if !raceEnabled { + seg.SetRangeUnchecked(r) + } else { + // Add extra paranoid. This will be statically + // removed at compile time unless a race build. + es.values.Remove(seg) + es.values.Add(r, existing) + seg = es.values.LowerBoundSegment(addr) + } + + // Compute the traversal required & update references. + dots := traverse(obj.Type(), old.Type(), addr, seg.Start()) + wt := es.findType(obj.Type()) + for _, ref := range existing.refs { + ref.Dots = append(ref.Dots, dots...) + ref.Type = wt + } + default: + // There is a non-sensical overlap. + Failf("overlapping objects: [new object] %#v [existing object] %#v", obj, existing.obj) + } + + // Compute the new reference, record and return it. + ref.Root = wire.Uint(existing.id) + ref.Dots = traverse(existing.obj.Type(), obj.Type(), seg.Start(), addr) + ref.Type = es.findType(obj.Type()) + existing.refs = append(existing.refs, ref) + return + } + + // The only remaining case is a pointer value that doesn't overlap with + // any registered addresses. Create a new entry for it, and start + // tracking the first reference we just created. + oes := &objectEncodeState{ + id: es.nextID(), + obj: obj, + } + if !raceEnabled { + es.values.AddWithoutMerging(r, oes) + } else { + // Merges should never happen. This is just enabled extra + // sanity checks because the Merge function below will panic. + es.values.Add(r, oes) + } + es.pending.PushBack(oes) + es.deferred.PushBack(oes) + ref.Root = wire.Uint(oes.id) + oes.refs = append(oes.refs, ref) +} + +// traverse searches for a target object within a root object, where the target +// object is a struct field or array element within root, with potentially +// multiple intervening types. traverse returns the set of field or element +// traversals required to reach the target. +// +// Note that for efficiency, traverse returns the dots in the reverse order. +// That is, the first traversal required will be the last element of the list. +// +// Precondition: The target object must lie completely within the range defined +// by [rootAddr, rootAddr + sizeof(rootType)]. +func traverse(rootType, targetType reflect.Type, rootAddr, targetAddr uintptr) []wire.Dot { + // Recursion base case: the types actually match. + if targetType == rootType && targetAddr == rootAddr { + return nil + } + + switch rootType.Kind() { + case reflect.Struct: + offset := targetAddr - rootAddr + for i := rootType.NumField(); i > 0; i-- { + field := rootType.Field(i - 1) + // The first field from the end with an offset that is + // smaller than or equal to our address offset is where + // the target is located. Traverse from there. + if field.Offset <= offset { + dots := traverse(field.Type, targetType, rootAddr+field.Offset, targetAddr) + fieldName := wire.FieldName(field.Name) + return append(dots, &fieldName) + } + } + // Should never happen; the target should be reachable. + Failf("no field in root type %v contains target type %v", rootType, targetType) + + case reflect.Array: + // Since arrays have homogenous types, all elements have the + // same size and we can compute where the target lives. This + // does not matter for the purpose of typing, but matters for + // the purpose of computing the address of the given index. + elemSize := int(rootType.Elem().Size()) + n := int(targetAddr-rootAddr) / elemSize // Relies on integer division rounding down. + if rootType.Len() < n { + Failf("traversal target of type %v @%x is beyond the end of the array type %v @%x with %v elements", + targetType, targetAddr, rootType, rootAddr, rootType.Len()) + } + dots := traverse(rootType.Elem(), targetType, rootAddr+uintptr(n*elemSize), targetAddr) + return append(dots, wire.Index(n)) + + default: + // For any other type, there's no possibility of aliasing so if + // the types didn't match earlier then we have an addresss + // collision which shouldn't be possible at this point. + Failf("traverse failed for root type %v and target type %v", rootType, targetType) + } + panic("unreachable") +} + +// encodeMap encodes a map. +func (es *encodeState) encodeMap(obj reflect.Value, dest *wire.Object) { + if obj.IsNil() { + // Because there is a difference between a nil map and an empty + // map, we need to not decode in the case of a truly nil map. + *dest = wire.Nil{} + return + } + l := obj.Len() + m := &wire.Map{ + Keys: make([]wire.Object, l), + Values: make([]wire.Object, l), + } + *dest = m + for i, k := range obj.MapKeys() { + v := obj.MapIndex(k) + // Map keys must be encoded using the full value because the + // type will be omitted after the first key. + es.encodeObject(k, encodeAsValue, &m.Keys[i]) + es.encodeObject(v, encodeAsValue, &m.Values[i]) + } +} + +// objectEncoder is for encoding structs. +type objectEncoder struct { + // es is encodeState. + es *encodeState + + // encoded is the encoded struct. + encoded *wire.Struct +} + +// save is called by the public methods on Sink. +func (oe *objectEncoder) save(slot int, obj reflect.Value) { + fieldValue := oe.encoded.Field(slot) + oe.es.encodeObject(obj, encodeDefault, fieldValue) +} + +// encodeStruct encodes a composite object. +func (es *encodeState) encodeStruct(obj reflect.Value, dest *wire.Object) { + // Ensure that the obj is addressable. There are two cases when it is + // not. First, is when this is dispatched via SaveValue. Second, when + // this is a map key as a struct. Either way, we need to make a copy to + // obtain an addressable value. + if !obj.CanAddr() { + localObj := reflect.New(obj.Type()) + localObj.Elem().Set(obj) + obj = localObj.Elem() + } + + // Prepare the value. + s := &wire.Struct{} + *dest = s + + // Look the type up in the database. + te, ok := es.types.Lookup(obj.Type()) + if te == nil { + if obj.NumField() == 0 { + // Allow unregistered anonymous, empty structs. This + // will just return success without ever invoking the + // passed function. This uses the immutable EmptyStruct + // variable to prevent an allocation in this case. + // + // Note that this mechanism does *not* work for + // interfaces in general. So you can't dispatch + // non-registered empty structs via interfaces because + // then they can't be restored. + s.Alloc(0) + return + } + // We need a SaverLoader for struct types. + Failf("struct %T does not implement SaverLoader", obj.Interface()) + } + if !ok { + // Queue the type to be serialized. + es.pendingTypes = append(es.pendingTypes, te.Type) + } + + // Invoke the provided saver. + s.TypeID = wire.TypeID(te.ID) + s.Alloc(len(te.Fields)) + oe := objectEncoder{ + es: es, + encoded: s, + } + es.stats.start(te.ID) + defer es.stats.done() + if sl, ok := obj.Addr().Interface().(SaverLoader); ok { + // Note: may be a registered empty struct which does not + // implement the saver/loader interfaces. + sl.StateSave(Sink{internal: oe}) + } +} + +// encodeArray encodes an array. +func (es *encodeState) encodeArray(obj reflect.Value, dest *wire.Object) { + l := obj.Len() + a := &wire.Array{ + Contents: make([]wire.Object, l), + } + *dest = a + for i := 0; i < l; i++ { + // We need to encode the full value because arrays are encoded + // using the type information from only the first element. + es.encodeObject(obj.Index(i), encodeAsValue, &a.Contents[i]) + } +} + +// findType recursively finds type information. +func (es *encodeState) findType(typ reflect.Type) wire.TypeSpec { + // First: check if this is a proper type. It's possible for pointers, + // slices, arrays, maps, etc to all have some different type. + te, ok := es.types.Lookup(typ) + if te != nil { + if !ok { + // See encodeStruct. + es.pendingTypes = append(es.pendingTypes, te.Type) + } + return wire.TypeID(te.ID) + } + + switch typ.Kind() { + case reflect.Ptr: + return &wire.TypeSpecPointer{ + Type: es.findType(typ.Elem()), + } + case reflect.Slice: + return &wire.TypeSpecSlice{ + Type: es.findType(typ.Elem()), + } + case reflect.Array: + return &wire.TypeSpecArray{ + Count: wire.Uint(typ.Len()), + Type: es.findType(typ.Elem()), + } + case reflect.Map: + return &wire.TypeSpecMap{ + Key: es.findType(typ.Key()), + Value: es.findType(typ.Elem()), + } + default: + // After potentially chasing many pointers, the + // ultimate type of the object is not known. + Failf("type %q is not known", typ) + } + panic("unreachable") +} + +// encodeInterface encodes an interface. +func (es *encodeState) encodeInterface(obj reflect.Value, dest *wire.Object) { + // Dereference the object. + obj = obj.Elem() + if !obj.IsValid() { + // Special case: the nil object. + *dest = &wire.Interface{ + Type: wire.TypeSpecNil{}, + Value: wire.Nil{}, + } + return + } + + // Encode underlying object. + i := &wire.Interface{ + Type: es.findType(obj.Type()), + } + *dest = i + es.encodeObject(obj, encodeAsValue, &i.Value) +} + +// isPrimitive returns true if this is a primitive object, or a composite +// object composed entirely of primitives. +func isPrimitiveZero(typ reflect.Type) bool { + switch typ.Kind() { + case reflect.Ptr: + // Pointers are always treated as primitive types because we + // won't encode directly from here. Returning true here won't + // prevent the object from being encoded correctly. + return true + case reflect.Bool: + return true + case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64: + return true + case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr: + return true + case reflect.Float32, reflect.Float64: + return true + case reflect.Complex64, reflect.Complex128: + return true + case reflect.String: + return true + case reflect.Slice: + // The slice itself a primitive, but not necessarily the array + // that points to. This is similar to a pointer. + return true + case reflect.Array: + // We cannot treat an array as a primitive, because it may be + // composed of structures or other things with side-effects. + return isPrimitiveZero(typ.Elem()) + case reflect.Interface: + // Since we now that this type is the zero type, the interface + // value must be zero. Therefore this is primitive. + return true + case reflect.Struct: + return false + case reflect.Map: + // The isPrimitiveZero function is called only on zero-types to + // see if it's safe to serialize. Since a zero map has no + // elements, it is safe to treat as a primitive. + return true + default: + Failf("unknown type %q", typ.Name()) + } + panic("unreachable") +} + +// encodeStrategy is the strategy used for encodeObject. +type encodeStrategy int + +const ( + // encodeDefault means types are encoded normally as references. + encodeDefault encodeStrategy = iota + + // encodeAsValue means that types will never take short-circuited and + // will always be encoded as a normal value. + encodeAsValue + + // encodeMapAsValue means that even maps will be fully encoded. + encodeMapAsValue +) + +// encodeObject encodes an object. +func (es *encodeState) encodeObject(obj reflect.Value, how encodeStrategy, dest *wire.Object) { + if how == encodeDefault && isPrimitiveZero(obj.Type()) && obj.IsZero() { + *dest = wire.Nil{} + return + } + switch obj.Kind() { + case reflect.Ptr: // Fast path: first. + r := new(wire.Ref) + *dest = r + if obj.IsNil() { + // May be in an array or elsewhere such that a value is + // required. So we encode as a reference to the zero + // object, which does not exist. Note that this has to + // be handled correctly in the decode path as well. + return + } + es.resolve(obj, r) + case reflect.Bool: + *dest = wire.Bool(obj.Bool()) + case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64: + *dest = wire.Int(obj.Int()) + case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr: + *dest = wire.Uint(obj.Uint()) + case reflect.Float32: + *dest = wire.Float32(obj.Float()) + case reflect.Float64: + *dest = wire.Float64(obj.Float()) + case reflect.Complex64: + c := wire.Complex64(obj.Complex()) + *dest = &c // Needs alloc. + case reflect.Complex128: + c := wire.Complex128(obj.Complex()) + *dest = &c // Needs alloc. + case reflect.String: + s := wire.String(obj.String()) + *dest = &s // Needs alloc. + case reflect.Array: + es.encodeArray(obj, dest) + case reflect.Slice: + s := &wire.Slice{ + Capacity: wire.Uint(obj.Cap()), + Length: wire.Uint(obj.Len()), + } + *dest = s + // Note that we do need to provide a wire.Slice type here as + // how is not encodeDefault. If this were the case, then it + // would have been caught by the IsZero check above and we + // would have just used wire.Nil{}. + if obj.IsNil() { + return + } + // Slices need pointer resolution. + es.resolve(arrayFromSlice(obj), &s.Ref) + case reflect.Interface: + es.encodeInterface(obj, dest) + case reflect.Struct: + es.encodeStruct(obj, dest) + case reflect.Map: + if how == encodeMapAsValue { + es.encodeMap(obj, dest) + return + } + r := new(wire.Ref) + *dest = r + es.resolve(obj, r) + default: + Failf("unknown object %#v", obj.Interface()) + panic("unreachable") + } +} + +// Save serializes the object graph rooted at obj. +func (es *encodeState) Save(obj reflect.Value) { + es.stats.init() + defer es.stats.fini(func(id typeID) string { + return es.pendingTypes[id-1].Name + }) + + // Resolve the first object, which should queue a pile of additional + // objects on the pending list. All queued objects should be fully + // resolved, and we should be able to serialize after this call. + var root wire.Ref + es.resolve(obj.Addr(), &root) + + // Encode the graph. + var oes *objectEncodeState + if err := safely(func() { + for oes = es.deferred.Front(); oes != nil; oes = es.deferred.Front() { + // Remove and encode the object. Note that as a result + // of this encoding, the object may be enqueued on the + // deferred list yet again. That's expected, and why it + // is removed first. + es.deferred.Remove(oes) + es.encodeObject(oes.obj, oes.how, &oes.encoded) + } + }); err != nil { + // Include the object in the error message. + Failf("encoding error at object %#v: %w", oes.obj.Interface(), err) + } + + // Check that items are pending. + if es.pending.Front() == nil { + Failf("pending is empty?") + } + + // Write the header with the number of objects. Note that there is no + // way that es.lastID could conflict with objectID, which would + // indicate that an impossibly large encoding. + if err := WriteHeader(es.w, uint64(es.lastID), true); err != nil { + Failf("error writing header: %w", err) + } + + // Serialize all pending types and pending objects. Note that we don't + // bother removing from this list as we walk it because that just + // wastes time. It will not change after this point. + var id objectID + if err := safely(func() { + for _, wt := range es.pendingTypes { + // Encode the type. + wire.Save(es.w, &wt) + } + for oes = es.pending.Front(); oes != nil; oes = oes.pendingEntry.Next() { + id++ // First object is 1. + if oes.id != id { + Failf("expected id %d, got %d", id, oes.id) + } + + // Marshall the object. + wire.Save(es.w, oes.encoded) + } + }); err != nil { + // Include the object and the error. + Failf("error serializing object %#v: %w", oes.encoded, err) + } + + // Check what we wrote. + if id != es.lastID { + Failf("expected %d objects, wrote %d", es.lastID, id) + } +} + +// objectFlag indicates that the length is a # of objects, rather than a raw +// byte length. When this is set on a length header in the stream, it may be +// decoded appropriately. +const objectFlag uint64 = 1 << 63 + +// WriteHeader writes a header. +// +// Each object written to the statefile should be prefixed with a header. In +// order to generate statefiles that play nicely with debugging tools, raw +// writes should be prefixed with a header with object set to false and the +// appropriate length. This will allow tools to skip these regions. +func WriteHeader(w wire.Writer, length uint64, object bool) error { + // Sanity check the length. + if length&objectFlag != 0 { + Failf("impossibly huge length: %d", length) + } + if object { + length |= objectFlag + } + + // Write a header. + return safely(func() { + wire.SaveUint(w, length) + }) +} + +// pendingMapper is for the pending list. +type pendingMapper struct{} + +func (pendingMapper) linkerFor(oes *objectEncodeState) *pendingEntry { return &oes.pendingEntry } + +// deferredMapper is for the deferred list. +type deferredMapper struct{} + +func (deferredMapper) linkerFor(oes *objectEncodeState) *deferredEntry { return &oes.deferredEntry } + +// addrSetFunctions is used by addrSet. +type addrSetFunctions struct{} + +func (addrSetFunctions) MinKey() uintptr { + return 0 +} + +func (addrSetFunctions) MaxKey() uintptr { + return ^uintptr(0) +} + +func (addrSetFunctions) ClearValue(val **objectEncodeState) { + *val = nil +} + +func (addrSetFunctions) Merge(r1 addrRange, val1 *objectEncodeState, r2 addrRange, val2 *objectEncodeState) (*objectEncodeState, bool) { + if val1.obj == val2.obj { + // This, should never happen. It would indicate that the same + // object exists in two non-contiguous address ranges. Note + // that this assertion can only be triggered if the race + // detector is enabled. + Failf("unexpected merge in addrSet @ %v and %v: %#v and %#v", r1, r2, val1.obj, val2.obj) + } + // Reject the merge. + return val1, false +} + +func (addrSetFunctions) Split(r addrRange, val *objectEncodeState, _ uintptr) (*objectEncodeState, *objectEncodeState) { + // A split should never happen: we don't remove ranges. + Failf("unexpected split in addrSet @ %v: %#v", r, val.obj) + panic("unreachable") +} |