Add scan iterator.

iterator.go

@@ -0,0 +1,75 @@
+package redis
+
+import "sync"
+
+type Scanner struct {
+	client *commandable
+	*ScanCmd
+}
+
+// Iterator creates a new ScanIterator.
+func (s Scanner) Iterator() *ScanIterator {
+	return &ScanIterator{
+		Scanner: s,
+	}
+}
+
+// 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
+	Scanner
+	pos int
+}
+
+// Err returns the last iterator error, if any.
+func (it *ScanIterator) Err() error {
+	it.mu.Lock()
+	err := it.ScanCmd.Err()
+	it.mu.Unlock()
+	return err
+}
+
+// Next advances the cursor and returns true if more values can be read.
+func (it *ScanIterator) Next() bool {
+	it.mu.Lock()
+	defer it.mu.Unlock()
+
+	// Instantly return on errors.
+	if it.ScanCmd.Err() != nil {
+		return false
+	}
+
+	// Advance cursor, check if we are still within range.
+	if it.pos < len(it.ScanCmd.page) {
+		it.pos++
+		return true
+	}
+
+	// Return if there is more data to fetch.
+	if it.ScanCmd.cursor == 0 {
+		return false
+	}
+
+	// Fetch next page.
+	it.ScanCmd._args[1] = it.ScanCmd.cursor
+	it.ScanCmd.reset()
+	it.client.Process(it.ScanCmd)
+	if it.ScanCmd.Err() != nil {
+		return false
+	}
+
+	it.pos = 1
+	return len(it.ScanCmd.page) > 0
+}
+
+// Val returns the key/field at the current cursor position.
+func (it *ScanIterator) Val() string {
+	var v string
+	it.mu.Lock()
+	if it.ScanCmd.Err() == nil && it.pos > 0 && it.pos <= len(it.ScanCmd.page) {
+		v = it.ScanCmd.page[it.pos-1]
+	}
+	it.mu.Unlock()
+	return v
+}