concurrency.md

Concurrency

Package concurrency contain some functions to support concurrent programming. eg, goroutine, channel.

Source:

• https://github.com/duke-git/lancet/blob/main/concurrency/channel.go

Usage:

import (
    "github.com/duke-git/lancet/v2/concurrency"
)

Index

Channel

• NewChannel
• Bridge
• FanIn
• Generate
• Or
• OrDone
• Repeat
• RepeatFn
• Take
• Tee

Documentation

Channel

NewChannel

Create a Channel pointer instance.

Signature:

type Channel[T any] struct
func NewChannel[T any]() *Channel[T]

Example: Run

package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/concurrency"
)

func main() {
    c := concurrency.NewChannel[int]()
}

Bridge

Link multiple channels into one channel until cancel the context.

Signature:

func (c *Channel[T]) Bridge(ctx context.Context, chanStream <-chan <-chan T) <-chan T

Example: Run

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[int]()
    genVals := func() <-chan <-chan int {
        out := make(chan (<-chan int))
        go func() {
            defer close(out)
            for i := 1; i <= 5; i++ {
                stream := make(chan int, 1)
                stream <- i
                close(stream)
                out <- stream
            }
        }()
        return out
    }

    for v := range c.Bridge(ctx, genVals()) {
        fmt.Println(v)
    }

    // Output:
    // 1
    // 2
    // 3
    // 4
    // 5
}

FanIn

Merge multiple channels into one channel until cancel the context.

Signature:

func (c *Channel[T]) FanIn(ctx context.Context, channels ...<-chan T) <-chan T

Example: Run

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[int]()
    channels := make([]<-chan int, 2)

    for i := 0; i < 2; i++ {
        channels[i] = c.Take(ctx, c.Repeat(ctx, i), 2)
    }

    chs := c.FanIn(ctx, channels...)

    for v := range chs {
        fmt.Println(v) //1 1 0 0 or 0 0 1 1
    }
}

Repeat

Create channel, put values into the channel repeatly until cancel the context.

Signature: Run

func (c *Channel[T]) Repeat(ctx context.Context, values ...T) <-chan T

Example:

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[int]()
    intStream := c.Take(ctx, c.Repeat(ctx, 1, 2), 4)

    for v := range intStream {
        fmt.Println(v)
    }

    // Output:
    // 1
    // 2
    // 1
    // 2
}

Generate

Creates a channel, then put values into the channel.

Signature:

func (c *Channel[T]) Generate(ctx context.Context, values ...T) <-chan T

Example: Run

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[int]()
    intStream := c.Generate(ctx, 1, 2, 3)

    fmt.Println(<-intStream)
    fmt.Println(<-intStream)
    fmt.Println(<-intStream)

    // Output:
    // 1
    // 2
    // 3
}

RepeatFn

Create a channel, excutes fn repeatly, and put the result into the channel, until close context.

Signature: Run

func (c *Channel[T]) RepeatFn(ctx context.Context, fn func() T) <-chan T

Example:

package main

import (
    "context"
    "fmt"
    "github.com/duke-git/lancet/v2/concurrency"
)

func main() {
    ctx, cancel := context.WithCancel(context.Background())
    defer cancel()

    fn := func() string {
        return "hello"
    }

    c := concurrency.NewChannel[string]()
    intStream := c.Take(ctx, c.RepeatFn(ctx, fn), 3)

    for v := range intStream {
        fmt.Println(v)
    }

    // Output:
    // hello
    // hello
    // hello
}

Or

Read one or more channels into one channel, will close when any readin channel is closed.

Signature: Run

func (c *Channel[T]) Or(channels ...<-chan T) <-chan T

Example:

package main

import (
    "context"
    "fmt"
    "github.com/duke-git/lancet/v2/concurrency"
)

func main() {
    sig := func(after time.Duration) <-chan any {
        c := make(chan any)
        go func() {
            defer close(c)
            time.Sleep(after)
        }()
        return c
    }

    start := time.Now()

    c := concurrency.NewChannel[any]()
    <-c.Or(
        sig(1*time.Second),
        sig(2*time.Second),
        sig(3*time.Second),
    )

    fmt.Println("done after %v", time.Since(start)) //1.003s
}

OrDone

Read a channel into another channel, will close until cancel context.

Signature: Run

func (c *Channel[T]) OrDone(ctx context.Context, channel <-chan T) <-chan T

Example:

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[int]()
    intStream := c.Take(ctx, c.Repeat(ctx, 1), 3)

    for v := range c.OrDone(ctx, intStream) {
        fmt.Println(v)
    }

    // Output:
    // 1
    // 1
    // 1
}

Take

Create a channel whose values are taken from another channel with limit number.

Signature: Run

func (c *Channel[T]) Take(ctx context.Context, valueStream <-chan T, number int) <-chan T

Example:

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 int, 5)
    numbers <- 1
    numbers <- 2
    numbers <- 3
    numbers <- 4
    numbers <- 5
    defer close(numbers)

    c := concurrency.NewChannel[int]()
    intStream := c.Take(ctx, numbers, 3)

    for v := range intStream {
        fmt.Println(v)
    }

    // Output:
    // 1
    // 2
    // 3
}

Tee

Split one chanel into two channels, until cancel the context.

Signature: Run

func (c *Channel[T]) Tee(ctx context.Context, in <-chan T) (<-chan T, <-chan T)

Example:

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[int]()
    intStream := c.Take(ctx, c.Repeat(ctx, 1), 2)

    ch1, ch2 := c.Tee(ctx, intStream)

    for v := range ch1 {
        fmt.Println(v)
        fmt.Println(<-ch2)
    }
    
    // Output:
    // 1
    // 1
    // 1
    // 1
}