pipe/filter.go at main · msacore/pipe · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
package pipe

import (
	"sync"
)

// Filter takes message and forwards it if filter function return positive.
// If input channel is closed then output channel is closed.
// Creates a new channel with the same capacity as input.
//
// # Strategies
//
//   - Processing: Parallel
//   - Closing: Single
//   - Capacity: Same
//
// # Usages
//
//	// input := make(chan int, 4) with random values [1, 2, 3, 4]
//
//	output := Filter(func(value int) bool {
//		fmt.Print(value)
//	    return value % 2 == 0
//	}, input)
//
//	// stdout: 4 1 2 3
//	// output: [4 2]
func Filter[T any](filter func(T) bool, in <-chan T) <-chan T {
	out := make(chan T, cap(in))
	wg := sync.WaitGroup{}

	go func() {
		for {
			if in, ok := <-in; ok {
				wg.Add(1)
				go func() {
					if filter(in) {
						out <- in
					}
					wg.Done()
				}()
			} else {
				wg.Wait()
				close(out)
				break
			}
		}
	}()

	return out
}

// FilterSync takes message and forwards it if filter function return positive.
// If input channel is closed then output channel is closed.
// Creates a new channel with the same capacity as input.
//
// # Strategies
//
//   - Processing: Sync
//   - Closing: Single
//   - Capacity: Same
//
// # Usages
//
//	// input := make(chan int, 4) with random values [1, 2, 3, 4]
//
//	output := FilterSync(func(value int) bool {
//		fmt.Print(value)
//	    return value % 2 == 0
//	}, input)
//
//	// stdout: 4 1 2 3
//	// output: [2 4]
func FilterSync[T any](filter func(T) bool, in <-chan T) <-chan T {
	out := make(chan T, cap(in))
	queue := make(chan func() <-chan T, cap(in))
	wg := sync.WaitGroup{}

	go func() {
		for {
			if in, ok := <-in; ok {
				wg.Add(1)
				queue <- func() <-chan T {
					out := make(chan T)
					go func() {
						if filter(in) {
							out <- in
						}
						close(out)
						wg.Done()
					}()
					return out
				}
			} else {
				wg.Wait()
				close(queue)
				break
			}
		}
	}()

	go func() {
		for {
			if handler, ok := <-queue; ok {
				if data, ok := <-handler(); ok {
					out <- data
				}
			} else {
				close(out)
				break
			}
		}
	}()

	return out
}

// FilterSequential takes message and forwards it if filter function return positive.
// If input channel is closed then output channel is closed.
// Creates a new channel with the same capacity as input.
//
// # Strategies
//
//   - Processing: Sequential
//   - Closing: Single
//   - Capacity: Same
//
// # Usages
//
//	// input := make(chan int, 4) with random values [1, 2, 3, 4]
//
//	output := FilterSequential(func(value int) bool {
//		fmt.Print(value)
//	    return value % 2 == 0
//	}, input)
//
//	// stdout: 1 2 3 4
//	// output: [2 4]
func FilterSequential[T any](filter func(T) bool, in <-chan T) <-chan T {
	out := make(chan T, cap(in))

	go func() {
		for {
			if in, ok := <-in; ok {
				if filter(in) {
					out <- in
				}
			} else {
				close(out)
				break
			}
		}
	}()

	return out
}