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// Copyright (c) 2011 CZ.NIC z.s.p.o. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// blame: jnml, labs.nic.cz
package storage
import "sync/atomic"
// Probe collects usage statistics of the embeded Accessor.
// Probe itself IS an Accessor.
type Probe struct {
Accessor
Chain *Probe
OpsRd int64
OpsWr int64
BytesRd int64
BytesWr int64
SectorsRd int64 // Assuming 512 byte sector size
SectorsWr int64
}
// NewProbe returns a newly created probe which embedes the src Accessor.
// The retuned *Probe satisfies Accessor. if chain != nil then Reset()
// is cascaded down the chained Probes.
func NewProbe(src Accessor, chain *Probe) *Probe {
return &Probe{Accessor: src, Chain: chain}
}
func reset(n *int64) {
atomic.AddInt64(n, -atomic.AddInt64(n, 0))
}
// Reset zeroes the collected statistics of p.
func (p *Probe) Reset() {
if p.Chain != nil {
p.Chain.Reset()
}
reset(&p.OpsRd)
reset(&p.OpsWr)
reset(&p.BytesRd)
reset(&p.BytesWr)
reset(&p.SectorsRd)
reset(&p.SectorsWr)
}
func (p *Probe) ReadAt(b []byte, off int64) (n int, err error) {
n, err = p.Accessor.ReadAt(b, off)
atomic.AddInt64(&p.OpsRd, 1)
atomic.AddInt64(&p.BytesRd, int64(n))
if n <= 0 {
return
}
sectorFirst := off >> 9
sectorLast := (off + int64(n) - 1) >> 9
atomic.AddInt64(&p.SectorsRd, sectorLast-sectorFirst+1)
return
}
func (p *Probe) WriteAt(b []byte, off int64) (n int, err error) {
n, err = p.Accessor.WriteAt(b, off)
atomic.AddInt64(&p.OpsWr, 1)
atomic.AddInt64(&p.BytesWr, int64(n))
if n <= 0 {
return
}
sectorFirst := off >> 9
sectorLast := (off + int64(n) - 1) >> 9
atomic.AddInt64(&p.SectorsWr, sectorLast-sectorFirst+1)
return
}
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