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)) }