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// Copyright 2020 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 vfs2
import (
"reflect"
"runtime"
"unsafe"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/gohacks"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/usermem"
)
const sizeofEpollEvent = int(unsafe.Sizeof(linux.EpollEvent{}))
func copyOutEvents(t *kernel.Task, addr usermem.Addr, events []linux.EpollEvent) (int, error) {
if len(events) == 0 {
return 0, nil
}
// Cast events to a byte slice for copying.
var eventBytes []byte
eventBytesHdr := (*reflect.SliceHeader)(unsafe.Pointer(&eventBytes))
eventBytesHdr.Data = uintptr(gohacks.Noescape(unsafe.Pointer(&events[0])))
eventBytesHdr.Len = len(events) * sizeofEpollEvent
eventBytesHdr.Cap = len(events) * sizeofEpollEvent
copiedBytes, err := t.CopyOutBytes(addr, eventBytes)
runtime.KeepAlive(events)
copiedEvents := copiedBytes / sizeofEpollEvent // rounded down
return copiedEvents, err
}
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