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lancet/docs/concurrency.md
2022-07-20 15:13:44 +08:00

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# Concurrency
Package concurrency contain some functions to support concurrent programming. eg, goroutine, channel, async.
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## Source:
- [https://github.com/duke-git/lancet/blob/main/concurrency/channel.go](https://github.com/duke-git/lancet/blob/main/concurrency/channel.go)
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## Usage:
```go
import (
"github.com/duke-git/lancet/v2/concurrency"
)
```
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## Index
### Channel
- [NewChannel](#NewChannel)
- [Bridge](#Bridge)
- [FanIn](#FanIn)
- [Generate](#Generate)
- [Or](#Or)
- [OrDone](#OrDone)
- [Repeat](#Repeat)
- [RepeatFn](#RepeatFn)
- [Take](#Take)
- [Tee](#Tee)
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## Documentation
## Channel
### <span id="NewChannel">NewChannel</span>
<p>return a Channel pointer instance.</p>
<b>Signature:</b>
```go
type Channel struct {}
func NewChannel() *Channel
```
<b>Example:</b>
```go
package main
import (
"fmt"
"github.com/duke-git/lancet/v2/concurrency"
)
func main() {
c := concurrency.NewChannel()
}
```
### <span id="Bridge">Bridge</span>
<p>Link multiple channels into one channel until cancel the context.</p>
<b>Signature:</b>
```go
func (c *Channel) Bridge(ctx context.Context, chanStream <-chan <-chan any) <-chan any
```
<b>Example:</b>
```go
package main
import (
"context"
"fmt"
"github.com/duke-git/lancet/v2/concurrency"
)
func main() {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
c := concurrency.NewChannel()
genVals := func() <-chan <-chan any {
chanStream := make(chan (<-chan any))
go func() {
defer close(chanStream)
for i := 0; i < 10; i++ {
stream := make(chan any, 1)
stream <- i
close(stream)
chanStream <- stream
}
}()
return chanStream
}
index := 0
for val := range c.Bridge(ctx, genVals()) {
fmt.Printf("%v ", val) //0 1 2 3 4 5 6 7 8 9
}
}
```
### <span id="FanIn">FanIn</span>
<p>merge multiple channels into one channel until cancel the context.</p>
<b>Signature:</b>
```go
func (c *Channel) FanIn(ctx context.Context, channels ...<-chan any) <-chan any
```
<b>Example:</b>
```go
package main
import (
"context"
"fmt"
"github.com/duke-git/lancet/v2/concurrency"
)
func main() {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
c := concurrency.NewChannel()
channels := make([]<-chan any, 3)
for i := 0; i < 3; i++ {
channels[i] = c.Take(ctx, c.Repeat(ctx, i), 3)
}
mergedChannel := c.FanIn(ctx, channels...)
for val := range mergedChannel {
fmt.Println("\t%d\n", val) //1,2,1,0,0,1,0,2,2 (order not for sure)
}
}
```
### <span id="Repeat">Repeat</span>
<p>Return a chan, put param `values` into the chan repeatly until cancel the context.</p>
<b>Signature:</b>
```go
func (c *Channel) Repeat(ctx context.Context, values ...any) <-chan any
```
<b>Example:</b>
```go
package main
import (
"context"
"fmt"
"github.com/duke-git/lancet/v2/concurrency"
)
func main() {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
c := concurrency.NewChannel()
intStream := c.Take(ctx, c.Repeat(ctx, 1, 2), 5)
for v := range intStream {
fmt.Println(v) //1, 2, 1, 2, 1
}
}
```
### <span id="RepeatFn">RepeatFn</span>
<p>Return a chan, excutes fn repeatly, and put the result into retruned chan until cancel context.</p>
<b>Signature:</b>
```go
func (c *Channel) RepeatFn(ctx context.Context, fn func() any) <-chan any
```
<b>Example:</b>
```go
package main
import (
"context"
"fmt"
"github.com/duke-git/lancet/v2/concurrency"
)
func main() {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
fn := func() any {
s := "a"
return s
}
c := concurrency.NewChannel()
dataStream := c.Take(ctx, c.RepeatFn(ctx, fn), 3)
for v := range dataStream {
fmt.Println(v) //a, a, a
}
}
```
### <span id="Or">Or</span>
<p>Read one or more channels into one channel, will close when any readin channel is closed.</p>
<b>Signature:</b>
```go
func (c *Channel) Or(channels ...<-chan any) <-chan any
```
<b>Example:</b>
```go
package main
import (
"context"
"fmt"
"github.com/duke-git/lancet/v2/concurrency"
)
func main() {
sig := func(after time.Duration) <-chan any {
c := make(chan interface{})
go func() {
defer close(c)
time.Sleep(after)
}()
return c
}
start := time.Now()
c := concurrency.NewChannel()
<-c.Or(
sig(1*time.Second),
sig(2*time.Second),
sig(3*time.Second),
sig(4*time.Second),
sig(5*time.Second),
)
fmt.Println("done after %v", time.Since(start)) //1.003s
}
```
### <span id="OrDone">OrDone</span>
<p>Read a channel into another channel, will close until cancel context.</p>
<b>Signature:</b>
```go
func (c *Channel) OrDone(ctx context.Context, channel <-chan any) <-chan any
```
<b>Example:</b>
```go
package main
import (
"context"
"fmt"
"github.com/duke-git/lancet/v2/concurrency"
)
func main() {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
c := concurrency.NewChannel()
intStream := c.Take(ctx, c.Repeat(ctx, 1), 3)
for val := range c.OrDone(ctx, intStream) {
fmt.Println(val) //1
}
}
```
### <span id="Take">Take</span>
<p>Return a chan whose values are tahken from another chan until cancel context.</p>
<b>Signature:</b>
```go
func (c *Channel) Take(ctx context.Context, valueStream <-chan any, number int) <-chan any
```
<b>Example:</b>
```go
package main
import (
"context"
"fmt"
"github.com/duke-git/lancet/v2/concurrency"
)
func main() {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
numbers := make(chan any, 5)
numbers <- 1
numbers <- 2
numbers <- 3
numbers <- 4
numbers <- 5
defer close(numbers)
c := concurrency.NewChannel()
intStream := c.Take(ctx, numbers, 3)
for val := range intStream {
fmt.Println(val) //1, 2, 3
}
}
```
### <span id="Tee">Tee</span>
<p>Split one chanel into two channels until cancel context.</p>
<b>Signature:</b>
```go
func (c *Channel) Tee(ctx context.Context, in <-chan any) (<-chan any, <-chan any)
```
<b>Example:</b>
```go
package main
import (
"context"
"fmt"
"github.com/duke-git/lancet/v2/concurrency"
)
func main() {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
c := concurrency.NewChannel()
inStream := c.Take(ctx, c.Repeat(ctx, 1, 2), 4)
out1, out2 := c.Tee(ctx, inStream)
for val := range out1 {
fmt.Println(val) //1
fmt.Println(<-out2) //1
}
}
```