// 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中的数据结构是hchan{}
chan如何初始化：
func makechan(t *chantype, size int) *hchan
内存分配方式：
不带缓冲区
c = (*hchan)(mallocgc(hchanSize, nil, true))
带缓冲区
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"))
}
——————
因为chansend中有加锁的步骤，故多个goroutine读写是安全的。
PipedInputStream类 与 PipedOutputStream类 用于在应用程序中创建管道通信。
一个PipedInputStream实例对象必须和一个PipedOutputStream实例对象进行连接而产生一个通信管道。
(必须使用connect,in.connect(out) 或out.connect(in),效果是等价的)
PipedOutputStream可以向管道中写入数据，PipedIntputStream可以读取PipedOutputStream向管道中写入的数据，这两个类主要用来完成线程之间的通信。
数据从[out,in)范围内读取，并写入到[in,out)范围内
{ - - - X X X X X X X - - - - - }
^ ^
| |
out in
{ X X X X - - - - - - - - X X X }
^ ^
| |
in out
在PipedIntputStream中，缓冲区默认大小是：
private static final int DEFAULT_PIPE_SIZE = 1024;
写入数据时：
synchronized void receive(byte b[], int off, int len) throws IOException
会对byte[]，及偏移量进行计算