forked from TrueCloudLab/restic
89 lines
1.8 KiB
Go
89 lines
1.8 KiB
Go
package archiver
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import (
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"context"
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"sync"
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)
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// Buffer is a reusable buffer. After the buffer has been used, Release should
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// be called so the underlying slice is put back into the pool.
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type Buffer struct {
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Data []byte
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Put func(*Buffer)
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}
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// Release puts the buffer back into the pool it came from.
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func (b *Buffer) Release() {
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if b.Put != nil {
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b.Put(b)
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}
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}
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// BufferPool implements a limited set of reusable buffers.
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type BufferPool struct {
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ch chan *Buffer
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chM sync.Mutex
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defaultSize int
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clearOnce sync.Once
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}
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// NewBufferPool initializes a new buffer pool. When the context is cancelled,
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// all buffers are released. The pool stores at most max items. New buffers are
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// created with defaultSize, buffers that are larger are released and not put
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// back.
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func NewBufferPool(ctx context.Context, max int, defaultSize int) *BufferPool {
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b := &BufferPool{
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ch: make(chan *Buffer, max),
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defaultSize: defaultSize,
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}
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go func() {
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<-ctx.Done()
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b.clear()
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}()
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return b
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}
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// Get returns a new buffer, either from the pool or newly allocated.
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func (pool *BufferPool) Get() *Buffer {
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pool.chM.Lock()
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defer pool.chM.Unlock()
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select {
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case buf := <-pool.ch:
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return buf
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default:
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}
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b := &Buffer{
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Put: pool.Put,
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Data: make([]byte, pool.defaultSize),
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}
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return b
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}
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// Put returns a buffer to the pool for reuse.
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func (pool *BufferPool) Put(b *Buffer) {
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if cap(b.Data) > pool.defaultSize {
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return
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}
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pool.chM.Lock()
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defer pool.chM.Unlock()
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select {
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case pool.ch <- b:
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default:
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}
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}
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// clear empties the buffer so that all items can be garbage collected.
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func (pool *BufferPool) clear() {
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pool.clearOnce.Do(func() {
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ch := pool.ch
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pool.chM.Lock()
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pool.ch = nil
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pool.chM.Unlock()
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close(ch)
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for range ch {
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}
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})
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}
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