Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 221 insertions, 0 deletions

diff --git a/pkg/state/map.go b/pkg/state/map.go
new file mode 100644
index 000000000..c3d165501
--- /dev/null
+++ b/pkg/state/map.go
@@ -0,0 +1,221 @@
+// Copyright 2018 Google Inc.
+//
+// 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 (
+	"fmt"
+	"reflect"
+	"sort"
+	"sync"
+
+	pb "gvisor.googlesource.com/gvisor/pkg/state/object_go_proto"
+)
+
+// entry is a single map entry.
+type entry struct {
+	name   string
+	object *pb.Object
+}
+
+// internalMap is the internal Map state.
+//
+// These are recycled via a pool to avoid churn.
+type internalMap struct {
+	// es is encodeState.
+	es *encodeState
+
+	// ds is decodeState.
+	ds *decodeState
+
+	// os is current object being decoded.
+	//
+	// This will always be nil during encode.
+	os *objectState
+
+	// data stores the encoded values.
+	data []entry
+}
+
+var internalMapPool = sync.Pool{
+	New: func() interface{} {
+		return new(internalMap)
+	},
+}
+
+// newInternalMap returns a cached map.
+func newInternalMap(es *encodeState, ds *decodeState, os *objectState) *internalMap {
+	m := internalMapPool.Get().(*internalMap)
+	m.es = es
+	m.ds = ds
+	m.os = os
+	if m.data != nil {
+		m.data = m.data[:0]
+	}
+	return m
+}
+
+// Map is a generic state container.
+//
+// This is the object passed to Save and Load in order to store their state.
+//
+// Detailed documentation is available in individual methods.
+type Map struct {
+	*internalMap
+}
+
+// Save adds the given object to the map.
+//
+// You should pass always pointers to the object you are saving. For example:
+//
+// type X struct {
+// 	A int
+// 	B *int
+// }
+//
+// func (x *X) Save(m Map) {
+// 	m.Save("A", &x.A)
+// 	m.Save("B", &x.B)
+// }
+//
+// func (x *X) Load(m Map) {
+// 	m.Load("A", &x.A)
+// 	m.Load("B", &x.B)
+// }
+func (m Map) Save(name string, objPtr interface{}) {
+	m.save(name, reflect.ValueOf(objPtr).Elem(), ".%s")
+}
+
+// SaveValue adds the given object value to the map.
+//
+// This should be used for values where pointers are not available, or casts
+// are required during Save/Load.
+//
+// For example, if we want to cast external package type P.Foo to int64:
+//
+// type X struct {
+//	A P.Foo
+// }
+//
+// func (x *X) Save(m Map) {
+//	m.SaveValue("A", int64(x.A))
+// }
+//
+// func (x *X) Load(m Map) {
+//	m.LoadValue("A", new(int64), func(x interface{}) {
+//		x.A = P.Foo(x.(int64))
+//	})
+// }
+func (m Map) SaveValue(name string, obj interface{}) {
+	m.save(name, reflect.ValueOf(obj), ".(value %s)")
+}
+
+// save is helper for the above. It takes the name of value to save the field
+// to, the field object (obj), and a format string that specifies how the
+// field's saving logic is dispatched from the struct (normal, value, etc.). The
+// format string should expect one string parameter, which is the name of the
+// field.
+func (m Map) save(name string, obj reflect.Value, format string) {
+	if m.es == nil {
+		// Not currently encoding.
+		m.Failf("no encode state for %q", name)
+	}
+
+	// Attempt the encode.
+	//
+	// These are sorted at the end, after all objects are added and will be
+	// sorted and checked for duplicates (see encodeStruct).
+	m.data = append(m.data, entry{
+		name:   name,
+		object: m.es.encodeObject(obj, false, format, name),
+	})
+}
+
+// Load loads the given object from the map.
+//
+// See Save for an example.
+func (m Map) Load(name string, objPtr interface{}) {
+	m.load(name, reflect.ValueOf(objPtr), false, nil, ".%s")
+}
+
+// LoadWait loads the given objects from the map, and marks it as requiring all
+// AfterLoad executions to complete prior to running this object's AfterLoad.
+//
+// See Save for an example.
+func (m Map) LoadWait(name string, objPtr interface{}) {
+	m.load(name, reflect.ValueOf(objPtr), true, nil, ".(wait %s)")
+}
+
+// LoadValue loads the given object value from the map.
+//
+// See SaveValue for an example.
+func (m Map) LoadValue(name string, objPtr interface{}, fn func(interface{})) {
+	o := reflect.ValueOf(objPtr)
+	m.load(name, o, true, func() { fn(o.Elem().Interface()) }, ".(value %s)")
+}
+
+// load is helper for the above. It takes the name of value to load the field
+// from, the target field pointer (objPtr), whether load completion of the
+// struct depends on the field's load completion (wait), the load completion
+// logic (fn), and a format string that specifies how the field's loading logic
+// is dispatched from the struct (normal, wait, value, etc.). The format string
+// should expect one string parameter, which is the name of the field.
+func (m Map) load(name string, objPtr reflect.Value, wait bool, fn func(), format string) {
+	if m.ds == nil {
+		// Not currently decoding.
+		m.Failf("no decode state for %q", name)
+	}
+
+	// Find the object.
+	//
+	// These are sorted up front (and should appear in the state file
+	// sorted as well), so we can do a binary search here to ensure that
+	// large structs don't behave badly.
+	i := sort.Search(len(m.data), func(i int) bool {
+		return m.data[i].name >= name
+	})
+	if i >= len(m.data) || m.data[i].name != name {
+		// There is no data for this name?
+		m.Failf("no data found for %q", name)
+	}
+
+	// Perform the decode.
+	m.ds.decodeObject(m.os, objPtr.Elem(), m.data[i].object, format, name)
+	if wait {
+		// Mark this individual object a blocker.
+		m.ds.waitObject(m.os, m.data[i].object, fn)
+	}
+}
+
+// Failf fails the save or restore with the provided message. Processing will
+// stop after calling Failf, as the state package uses a panic & recover
+// mechanism for state errors. You should defer any cleanup required.
+func (m Map) Failf(format string, args ...interface{}) {
+	panic(fmt.Errorf(format, args...))
+}
+
+// AfterLoad schedules a function execution when all objects have been allocated
+// and their automated loading and customized load logic have been executed. fn
+// will not be executed until all of current object's dependencies' AfterLoad()
+// logic, if exist, have been executed.
+func (m Map) AfterLoad(fn func()) {
+	if m.ds == nil {
+		// Not currently decoding.
+		m.Failf("not decoding")
+	}
+
+	// Queue the local callback; this will execute when all of the above
+	// data dependencies have been cleared.
+	m.os.callbacks = append(m.os.callbacks, fn)
+}