chan

陳

純C實施GO頻道。

未封閉的頻道

未封閉的通道既提供了通信和同步的機制。當數據發送到頻道時，發件人塊直到接收器準備就緒為止。同樣，接收器將阻止直到發件人準備就緒。

 #include <pthread.h>
#include <stdio.h>
#include "chan.h"

chan_t * chan ;

void * ping ()
{
    // Send blocks until receiver is ready.
    chan_send ( chan , "ping" );
    return NULL ;
}

int main ()
{
    // Initialize unbuffered channel.
    chan = chan_init ( 0 );

    pthread_t th ;
    pthread_create ( & th , NULL , ping , NULL );

    // Receive blocks until sender is ready.
    void * msg ;
    chan_recv ( chan , & msg );
    printf ( "%sn" , msg );

    // Clean up channel.
    chan_dispose ( chan );
}

使用未封閉的通道，發件人和接收器已同步，因此上述程序將打印ping 。

緩衝通道

緩衝通道接受有限數量的值，而這些值沒有相應的接收器。除非通道已滿，否則發送數據將不會阻止。僅當通道為空時，接收數據才會阻止。

 #include <stdio.h>
#include "chan.h"

int main ()
{
    // Initialize buffered channel with a capacity of 2.
    chan_t * chan = chan_init ( 2 );

    // Send up to 2 values without receiver.
    chan_send ( chan , "buffered" );
    chan_send ( chan , "channel" );

    // Later receive the values.
    void * msg ;
    chan_recv ( chan , & msg );
    printf ( "%sn" , msg );

    chan_recv ( chan , & msg );
    printf ( "%sn" , msg );

    // Clean up channel.
    chan_dispose ( chan );
}

上面的程序將打印buffered ，然後channel 。發送不會阻止，因為通道的容量為2。在此之後發送更多的發送將阻止直到收到值。

關閉渠道

關閉通道時，不再可以在其上發送更多值。在封閉的通道上接收將返回通道已關閉的指示代碼。這對於將完成與頻道的接收器傳達可能很有用。如果封閉的通道被緩衝，將在其上接收值，直到空。

 #include <pthread.h>
#include <stdint.h>
#include <stdio.h>
#include "chan.h"

chan_t * jobs ;
chan_t * done ;

void * worker ()
{
    // Process jobs until channel is closed.
    void * job ;
    while ( chan_recv ( jobs , & job ) == 0 )
    {
        printf ( "received job %dn" , ( int ) job );
    }

    // Notify that all jobs were received.
    printf ( "received all jobsn" );
    chan_send ( done , "1" );
    return NULL ;
}

int main ()
{
    // Initialize channels.
    jobs = chan_init ( 5 );
    done = chan_init ( 0 );

    pthread_t th ;
    pthread_create ( & th , NULL , worker , NULL );

    // Send 3 jobs over the jobs channel then close it.
    int i ;
    for ( i = 1 ; i <= 3 ; i ++ )
    {
        chan_send ( jobs , ( void * ) ( uintptr_t ) i );
        printf ( "sent job %dn" , i );
    }
    chan_close ( jobs );
    printf ( "sent all jobsn" );

    // Wait for all jobs to be received.
    chan_recv ( done , NULL );

    // Clean up channels.
    chan_dispose ( jobs );
    chan_dispose ( done );
}

該程序將打印：

 sent job 1
received job 1
sent job 2
received job 2
sent job 3
received job 3
sent all jobs
received all jobs

選擇語句

選擇語句選擇將繼續進行哪一組可能的發送或接收操作。他們還提供了執行非阻滯發送和接收的方法。選擇對於在多個渠道上多路復用溝通特別有用。

 #include <stdio.h>
#include "chan.h"

chan_t * messages ;
chan_t * signals ;

int main ()
{
    // Initialize channels.
    messages = chan_init ( 0 );
    signals = chan_init ( 0 );
    void * msg ;

    // This is a non-blocking receive. If a value is available on messages,
    // select will take the messages (0) case with that value. If not, it will
    // immediately take the default case.
    switch ( chan_select ( & messages , 1 , & msg , NULL , 0 , NULL ))
    {
        case 0 :
            printf ( "received message %sn" , msg );
            break ;
        default :
            printf ( "no message receivedn" );
    }

    // A non-blocking send works similarly.
    msg = "foo" ;
    switch ( chan_select ( NULL , 0 , NULL , & messages , 1 , & msg ))
    {
        case 0 :
            printf ( "sent message %sn" , msg );
            break ;
        default :
            printf ( "no message sentn" );
    }

    // We can use multiple cases above the default clause to implement a
    // multi-way non-blocking select. Here we attempt non-blocking receives on
    // both messages and signals.
    chan_t * chans [ 2 ] = { messages , signals };
    switch ( chan_select ( chans , 2 , & msg , NULL , 0 , NULL ))
    {
        case 0 :
            printf ( "received message %sn" , msg );
            break ;
        case 1 :
            printf ( "received signal %sn" , msg );
            break ;
        default :
            printf ( "no activityn" );
    }

    // Clean up channels.
    chan_dispose ( messages );
    chan_dispose ( signals );
}

該程序將打印：

 no message received
no message sent
no activity