// This file contains the implementation of Go channels.

// Invariants:

// At least one of c.sendq and c.recvq is empty,

// except for the case of an unbuffered channel with a single goroutine

// blocked on it for both sending and receiving using a select statement,

// in which case the length of c.sendq and c.recvq is limited only by the

// size of the select statement.

//

// For buffered channels, also:

// c.qcount > 0 implies that c.recvq is empty.

// c.qcount < c.dataqsiz implies that c.sendq is empty.

import (

"runtime/internal/atomic"

"unsafe"

)

• channel中的數據結構是hchan{}

chan如何初始化：

func makechan(t *chantype, size int) *hchan

內存分配方式：

不帶緩沖區

c = (*hchan)(mallocgc(hchanSize, nil, true))

帶緩沖區

c = (*hchan)(mallocgc(hchanSize+uintptr(size)*elem.size, nil, true))

—————-

lock(&c.lock)

if c.closed != 0 {

unlock(&c.lock)

panic(plainError("send on closed channel"))

}

——————

因為chansend中有加鎖的步驟，故多個goroutine讀寫是安全的。

PipedInputStream類 與 PipedOutputStream類 用於在應用程序中創建管道通信。

一個PipedInputStream實例對象必須和一個PipedOutputStream實例對象進行連接而產生一個通信管道。

(必須使用connect,in.connect(out) 或out.connect(in),效果是等價的)

PipedOutputStream可以向管道中寫入數據，PipedIntputStream可以讀取PipedOutputStream向管道中寫入的數據，這兩個類主要用來完成線程之間的通信。

數據從[out,in)範圍內讀取，並寫入到[in,out)範圍內

{ - - - X X X X X X X - - - - - }

^ ^

| |

out in

{ X X X X - - - - - - - - X X X }

^ ^

| |

in out

在PipedIntputStream中，緩沖區默認大小是：

private static final int DEFAULT_PIPE_SIZE = 1024;

寫入數據時：

synchronized void receive(byte b[], int off, int len) throws IOException

會對byte[]，及偏移量進行計算

Goroutine通信與thread in java間的通信