95 lines
2.5 KiB
Go
95 lines
2.5 KiB
Go
// Copyright 2020 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 buffer provides the implementation of a buffer view.
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//
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// A view is an flexible buffer, backed by a pool, supporting the safecopy
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// operations natively as well as the ability to grow via either prepend or
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// append, as well as shrink.
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package buffer
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import (
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"sync"
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)
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const bufferSize = 8144 // See below.
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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 is done
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// intentionally to ensure that the buffer object aligns with runtime
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// internals. We have no hard size or alignment requirements. This two page
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// size will effectively minimize internal fragmentation, but still have a
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// large enough chunk 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 [bufferSize]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 returning the buffer to the pool.
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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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// 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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// ReadSize returns the number of bytes available for reading.
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func (b *buffer) ReadSize() int {
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return b.write - b.read
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}
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// ReadMove advances the read index by the given amount.
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func (b *buffer) ReadMove(n int) {
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b.read += n
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}
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// ReadSlice returns the read slice for this buffer.
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func (b *buffer) ReadSlice() []byte {
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return b.data[b.read:b.write]
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}
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// WriteSize returns the number of bytes available for writing.
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func (b *buffer) WriteSize() int {
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return len(b.data) - b.write
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}
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// WriteMove advances the write index by the given amount.
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func (b *buffer) WriteMove(n int) {
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b.write += n
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}
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// WriteSlice returns the write slice for this buffer.
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func (b *buffer) WriteSlice() []byte {
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return b.data[b.write:]
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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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