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// _ _
// __ _____ __ ___ ___ __ _| |_ ___
// \ \ /\ / / _ \/ _` \ \ / / |/ _` | __/ _ \
// \ V V / __/ (_| |\ V /| | (_| | || __/
// \_/\_/ \___|\__,_| \_/ |_|\__,_|\__\___|
//
// Copyright © 2016 - 2024 Weaviate B.V. All rights reserved.
//
// CONTACT: [email protected]
//
package indexcounter
import (
"encoding/binary"
"fmt"
"os"
"sync"
"github.com/pkg/errors"
)
type Counter struct {
count uint64
sync.Mutex
f *os.File
}
func New(shardPath string) (*Counter, error) {
fileName := fmt.Sprintf("%s/indexcount", shardPath)
f, err := os.OpenFile(fileName, os.O_RDWR|os.O_CREATE, 0o666)
if err != nil {
return nil, err
}
stat, err := f.Stat()
if err != nil {
return nil, err
}
var initialCount uint64 = 0
if stat.Size() > 0 {
// the file has existed before, we need to initialize with its content
err := binary.Read(f, binary.LittleEndian, &initialCount)
if err != nil {
return nil, errors.Wrap(err, "read initial count from file")
}
}
return &Counter{
count: initialCount,
f: f,
}, nil
}
func (c *Counter) Get() uint64 {
c.Lock()
defer c.Unlock()
return c.count
}
func (c *Counter) GetAndInc() (uint64, error) {
c.Lock()
defer c.Unlock()
before := c.count
c.count++
c.f.Seek(0, 0)
err := binary.Write(c.f, binary.LittleEndian, &c.count)
if err != nil {
return 0, errors.Wrap(err, "increase counter on disk")
}
c.f.Seek(0, 0)
return before, nil
}
// PreviewNext can be used to check if there is data present in the index, if
// it returns 0, you can be certain that no data exists
func (c *Counter) PreviewNext() uint64 {
c.Lock()
defer c.Unlock()
return c.count
}
func (c *Counter) Drop() error {
c.Lock()
defer c.Unlock()
if c.f == nil {
return nil
}
filename := c.FileName()
c.f.Close()
err := os.Remove(filename)
if err != nil {
return errors.Wrap(err, "drop counter file")
}
return nil
}
func (c *Counter) FileName() string {
return c.f.Name()
}
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