1. 1
2. 2
3. 3
4. 4
5. 5
6. 6
7. 7
8. 8
9. 9
10. 10
11. 11
12. 12
13. 13
14. 14
15. 15
16. 16
17. 17
18. 18
19. 19
20. 20
21. 21
22. 22
23. 23
24. 24
25. 25
26. 26
27. 27
28. 28
29. 29
30. 30
31. 31
32. 32
33. 33
34. 34
35. 35
36. 36
37. 37
38. 38
39. 39
40. 40
41. 41
42. 42
43. 43
44. 44
45. 45
46. 46
47. 47
48. 48
49. 49
50. 50
51. 51
52. 52
53. 53
54. 54
55. 55
56. 56
57. 57
58. 58
59. 59
60. 60
61. 61
62. 62
63. 63
64. 64
65. 65
66. 66
67. 67
68. 68
69. 69
70. 70
71. 71
72. 72
73. 73
74. 74
75. 75
76. 76
77. 77

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
}