85 lines
2.5 KiB
Go
85 lines
2.5 KiB
Go
|
// 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 hostfd provides efficient I/O with host file descriptors.
|
||
|
package hostfd
|
||
|
|
||
|
import (
|
||
|
"gvisor.dev/gvisor/pkg/safemem"
|
||
|
"gvisor.dev/gvisor/pkg/sync"
|
||
|
)
|
||
|
|
||
|
// ReadWriterAt implements safemem.Reader and safemem.Writer by reading from
|
||
|
// and writing to a host file descriptor respectively. ReadWriterAts should be
|
||
|
// obtained by calling GetReadWriterAt.
|
||
|
//
|
||
|
// Clients should usually prefer to use Preadv2 and Pwritev2 directly.
|
||
|
type ReadWriterAt struct {
|
||
|
fd int32
|
||
|
offset int64
|
||
|
flags uint32
|
||
|
}
|
||
|
|
||
|
var rwpool = sync.Pool{
|
||
|
New: func() interface{} {
|
||
|
return &ReadWriterAt{}
|
||
|
},
|
||
|
}
|
||
|
|
||
|
// GetReadWriterAt returns a ReadWriterAt that reads from / writes to the given
|
||
|
// host file descriptor, starting at the given offset and using the given
|
||
|
// preadv2(2)/pwritev2(2) flags. If offset is -1, the host file descriptor's
|
||
|
// offset is used instead. Users are responsible for ensuring that fd remains
|
||
|
// valid for the lifetime of the returned ReadWriterAt, and must call
|
||
|
// PutReadWriterAt when it is no longer needed.
|
||
|
func GetReadWriterAt(fd int32, offset int64, flags uint32) *ReadWriterAt {
|
||
|
rw := rwpool.Get().(*ReadWriterAt)
|
||
|
*rw = ReadWriterAt{
|
||
|
fd: fd,
|
||
|
offset: offset,
|
||
|
flags: flags,
|
||
|
}
|
||
|
return rw
|
||
|
}
|
||
|
|
||
|
// PutReadWriterAt releases a ReadWriterAt returned by a previous call to
|
||
|
// GetReadWriterAt that is no longer in use.
|
||
|
func PutReadWriterAt(rw *ReadWriterAt) {
|
||
|
rwpool.Put(rw)
|
||
|
}
|
||
|
|
||
|
// ReadToBlocks implements safemem.Reader.ReadToBlocks.
|
||
|
func (rw *ReadWriterAt) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
|
||
|
if dsts.IsEmpty() {
|
||
|
return 0, nil
|
||
|
}
|
||
|
n, err := Preadv2(rw.fd, dsts, rw.offset, rw.flags)
|
||
|
if rw.offset >= 0 {
|
||
|
rw.offset += int64(n)
|
||
|
}
|
||
|
return n, err
|
||
|
}
|
||
|
|
||
|
// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
|
||
|
func (rw *ReadWriterAt) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
|
||
|
if srcs.IsEmpty() {
|
||
|
return 0, nil
|
||
|
}
|
||
|
n, err := Pwritev2(rw.fd, srcs, rw.offset, rw.flags)
|
||
|
if rw.offset >= 0 {
|
||
|
rw.offset += int64(n)
|
||
|
}
|
||
|
return n, err
|
||
|
}
|