distribution/registry/storage/driver/azure/blockid.go

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package azure
import (
"encoding/base64"
"fmt"
"math/rand"
"sync"
"time"
azure "github.com/MSOpenTech/azure-sdk-for-go/storage"
)
type blockIDGenerator struct {
pool map[string]bool
r *rand.Rand
m sync.Mutex
}
// Generate returns an unused random block id and adds the generated ID
// to list of used IDs so that the same block name is not used again.
func (b *blockIDGenerator) Generate() string {
b.m.Lock()
defer b.m.Unlock()
var id string
for {
id = toBlockID(int(b.r.Int()))
if !b.exists(id) {
break
}
}
b.pool[id] = true
return id
}
func (b *blockIDGenerator) exists(id string) bool {
_, used := b.pool[id]
return used
}
func (b *blockIDGenerator) Feed(blocks azure.BlockListResponse) {
b.m.Lock()
defer b.m.Unlock()
for _, bl := range append(blocks.CommittedBlocks, blocks.UncommittedBlocks...) {
b.pool[bl.Name] = true
}
}
func newBlockIDGenerator() *blockIDGenerator {
return &blockIDGenerator{
pool: make(map[string]bool),
r: rand.New(rand.NewSource(time.Now().UnixNano()))}
}
// toBlockId converts given integer to base64-encoded block ID of a fixed length.
func toBlockID(i int) string {
s := fmt.Sprintf("%029d", i) // add zero padding for same length-blobs
return base64.StdEncoding.EncodeToString([]byte(s))
}