package redis import ( "context" "sync" ) // ScanIterator is used to incrementally iterate over a collection of elements. // It's safe for concurrent use by multiple goroutines. type ScanIterator struct { mu sync.Mutex // protects Scanner and pos cmd *ScanCmd pos int } // Err returns the last iterator error, if any. func (it *ScanIterator) Err() error { it.mu.Lock() err := it.cmd.Err() it.mu.Unlock() return err } // Next advances the cursor and returns true if more values can be read. func (it *ScanIterator) Next(ctx context.Context) bool { it.mu.Lock() defer it.mu.Unlock() // Instantly return on errors. if it.cmd.Err() != nil { return false } // Advance cursor, check if we are still within range. if it.pos < len(it.cmd.page) { it.pos++ return true } for { // Return if there is no more data to fetch. if it.cmd.cursor == 0 { return false } // Fetch next page. switch it.cmd.args[0] { case "scan", "qscan": it.cmd.args[1] = it.cmd.cursor default: it.cmd.args[2] = it.cmd.cursor } err := it.cmd.process(ctx, it.cmd) if err != nil { return false } it.pos = 1 // Redis can occasionally return empty page. if len(it.cmd.page) > 0 { return true } } } // Val returns the key/field at the current cursor position. func (it *ScanIterator) Val() string { var v string it.mu.Lock() if it.cmd.Err() == nil && it.pos > 0 && it.pos <= len(it.cmd.page) { v = it.cmd.page[it.pos-1] } it.mu.Unlock() return v }