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42 lines
919 B
Go
42 lines
919 B
Go
package filer
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import (
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"sync/atomic"
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)
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type ReaderPattern struct {
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isSequentialCounter int64
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lastReadStopOffset int64
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}
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const ModeChangeLimit = 3
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// For streaming read: only cache the first chunk
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// For random read: only fetch the requested range, instead of the whole chunk
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func NewReaderPattern() *ReaderPattern {
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return &ReaderPattern{
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isSequentialCounter: 0,
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lastReadStopOffset: 0,
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}
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}
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func (rp *ReaderPattern) MonitorReadAt(offset int64, size int) {
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lastOffset := atomic.SwapInt64(&rp.lastReadStopOffset, offset+int64(size))
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counter := atomic.LoadInt64(&rp.isSequentialCounter)
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if lastOffset == offset {
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if counter < ModeChangeLimit {
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atomic.AddInt64(&rp.isSequentialCounter, 1)
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}
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} else {
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if counter > -ModeChangeLimit {
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atomic.AddInt64(&rp.isSequentialCounter, -1)
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}
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}
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}
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func (rp *ReaderPattern) IsRandomMode() bool {
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return atomic.LoadInt64(&rp.isSequentialCounter) < 0
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}
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