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filter.go
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/
filter.go
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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
}