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// Copyright 2018 Google LLC
//
// 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 ashmem
import "gvisor.googlesource.com/gvisor/pkg/abi/linux"
const maxUint64 = ^uint64(0)
// setFunctions implements segment.Functions generated from segment.Functions for
// uint64 Key and noValue Value. For more information, see the build file and
// segment set implementation at pkg/segment/set.go.
type setFunctions struct{}
// noValue is a type of range attached value, which is irrelevant here.
type noValue struct{}
// MinKey implements segment.Functions.MinKey.
func (setFunctions) MinKey() uint64 {
return 0
}
// MaxKey implements segment.Functions.MaxKey.
func (setFunctions) MaxKey() uint64 {
return maxUint64
}
// ClearValue implements segment.Functions.ClearValue.
func (setFunctions) ClearValue(*noValue) {
return
}
// Merge implements segment.Functions.Merge.
func (setFunctions) Merge(Range, noValue, Range, noValue) (noValue, bool) {
return noValue{}, true
}
// Split implements segment.Functions.Split.
func (setFunctions) Split(Range, noValue, uint64) (noValue, noValue) {
return noValue{}, noValue{}
}
// PinBoard represents a set of pinned ranges in ashmem.
//
// segment.Set is used for implementation where segments represent
// ranges of pinned bytes, while gaps represent ranges of unpinned
// bytes. All ranges are page-aligned.
//
// +stateify savable
type PinBoard struct {
Set
}
// NewPinBoard creates a new pin board with all pages pinned.
func NewPinBoard() *PinBoard {
var pb PinBoard
pb.PinRange(Range{0, maxUint64})
return &pb
}
// PinRange pins all pages in the specified range and returns true
// if there are any newly pinned pages.
func (pb *PinBoard) PinRange(r Range) bool {
pinnedPages := false
for gap := pb.LowerBoundGap(r.Start); gap.Ok() && gap.Start() < r.End; {
common := gap.Range().Intersect(r)
if common.Length() == 0 {
gap = gap.NextGap()
continue
}
pinnedPages = true
gap = pb.Insert(gap, common, noValue{}).NextGap()
}
return pinnedPages
}
// UnpinRange unpins all pages in the specified range.
func (pb *PinBoard) UnpinRange(r Range) {
for seg := pb.LowerBoundSegment(r.Start); seg.Ok() && seg.Start() < r.End; {
common := seg.Range().Intersect(r)
if common.Length() == 0 {
seg = seg.NextSegment()
continue
}
seg = pb.RemoveRange(common).NextSegment()
}
}
// RangePinnedStatus returns false if there's at least one unpinned page in the
// specified range.
func (pb *PinBoard) RangePinnedStatus(r Range) bool {
for gap := pb.LowerBoundGap(r.Start); gap.Ok() && gap.Start() < r.End; {
common := gap.Range().Intersect(r)
if common.Length() == 0 {
gap = gap.NextGap()
continue
}
return false
}
return true
}
// RangeFromAshmemPin converts ashmem's original pin structure
// to Range.
func RangeFromAshmemPin(ap linux.AshmemPin) Range {
if ap.Len == 0 {
return Range{
uint64(ap.Offset),
maxUint64,
}
}
return Range{
uint64(ap.Offset),
uint64(ap.Offset) + uint64(ap.Len),
}
}
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