116 lines
3.0 KiB
Go
116 lines
3.0 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package pipe
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import (
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"io"
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"sync"
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"gvisor.dev/gvisor/pkg/sentry/safemem"
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)
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// buffer encapsulates a queueable byte buffer.
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//
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// Note that the total size is slightly less than two pages. This
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// is done intentionally to ensure that the buffer object aligns
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// with runtime internals. We have no hard size or alignment
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// requirements. This two page size will effectively minimize
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// internal fragmentation, but still have a large enough chunk
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// to limit excessive segmentation.
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//
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// +stateify savable
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type buffer struct {
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data [8144]byte
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read int
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write int
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bufferEntry
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}
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// Reset resets internal data.
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//
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// This must be called before use.
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func (b *buffer) Reset() {
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b.read = 0
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b.write = 0
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}
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// Empty indicates the buffer is empty.
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//
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// This indicates there is no data left to read.
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func (b *buffer) Empty() bool {
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return b.read == b.write
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}
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// Full indicates the buffer is full.
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//
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// This indicates there is no capacity left to write.
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func (b *buffer) Full() bool {
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return b.write == len(b.data)
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}
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// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
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func (b *buffer) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
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dst := safemem.BlockSeqOf(safemem.BlockFromSafeSlice(b.data[b.write:]))
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n, err := safemem.CopySeq(dst, srcs)
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b.write += int(n)
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return n, err
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}
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// WriteFromReader writes to the buffer from an io.Reader.
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func (b *buffer) WriteFromReader(r io.Reader, count int64) (int64, error) {
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dst := b.data[b.write:]
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if count < int64(len(dst)) {
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dst = b.data[b.write:][:count]
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}
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n, err := r.Read(dst)
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b.write += n
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return int64(n), err
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}
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// ReadToBlocks implements safemem.Reader.ReadToBlocks.
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func (b *buffer) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
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src := safemem.BlockSeqOf(safemem.BlockFromSafeSlice(b.data[b.read:b.write]))
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n, err := safemem.CopySeq(dsts, src)
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b.read += int(n)
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return n, err
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}
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// ReadToWriter reads from the buffer into an io.Writer.
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func (b *buffer) ReadToWriter(w io.Writer, count int64, dup bool) (int64, error) {
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src := b.data[b.read:b.write]
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if count < int64(len(src)) {
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src = b.data[b.read:][:count]
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}
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n, err := w.Write(src)
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if !dup {
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b.read += n
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}
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return int64(n), err
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}
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// bufferPool is a pool for buffers.
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var bufferPool = sync.Pool{
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New: func() interface{} {
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return new(buffer)
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},
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}
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// newBuffer grabs a new buffer from the pool.
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func newBuffer() *buffer {
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b := bufferPool.Get().(*buffer)
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b.Reset()
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return b
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}
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