GO语言中Chan实现原理的示例详解_Golang_

type hchan struct { qcount uint // total data in the queue dataqsiz uint // size of the circular queue buf unsafe.Pointer // points to an array of dataqsiz elements elemsize uint16 closed uint32 elemtype *_type // element type sendx uint // send index recvx uint // receive index recvq waitq // list of recv waiters sendq waitq // list of send waiters // lock protects all fields in hchan, as well as several // fields in sudogs blocked on this channel. // // Do not change another G's status while holding this lock // (in particular, do not ready a G), as this can deadlock // with stack shrinking. lock mutex }

type waitq struct { first *sudog last *sudog }

// sudog represents a g in a wait list, such as for sending/receiving // on a channel. type sudog struct { // The following fields are protected by the hchan.lock of the // channel this sudog is blocking on. shrinkstack depends on // this for sudogs involved in channel ops. g *g next *sudog prev *sudog elem unsafe.Pointer // data element (may point to stack) // The following fields are never accessed concurrently. // For channels, waitlink is only accessed by g. // For semaphores, all fields (including the ones above) // are only accessed when holding a semaRoot lock. acquiretime int64 releasetime int64 ticket uint32 // isSelect indicates g is participating in a select, so // g.selectDone must be CAS'd to win the wake-up race. isSelect bool // success indicates whether communication over channel c // succeeded. It is true if the goroutine was awoken because a // value was delivered over channel c, and false if awoken // because c was closed. success bool parent *sudog // semaRoot binary tree waitlink *sudog // g.waiting list or semaRoot waittail *sudog // semaRoot c *hchan // channel }

func makechan(t *chantype, size int) *hchan { elem := t.elem // compiler checks this but be safe. if elem.size >= 1<<16 { throw("makechan: invalid channel element type") } if hchanSize%maxAlign != 0 || elem.align > maxAlign { throw("makechan: bad alignment") } mem, overflow := math.MulUintptr(elem.size, uintptr(size)) if overflow || mem > maxAlloc-hchanSize || size < 0 { panic(plainError("makechan: size out of range")) } // Hchan does not contain pointers interesting for GC when elements stored in buf do not contain pointers. // buf points into the same allocation, elemtype is persistent. // SudoG's are referenced from their owning thread so they can't be collected. // TODO(dvyukov,rlh): Rethink when collector can move allocated objects. var c *hchan switch { case mem == 0: // Queue or element size is zero. c = (*hchan)(mallocgc(hchanSize, nil, true)) // Race detector uses this location for synchronization. c.buf = c.raceaddr() case elem.ptrdata == 0: // Elements do not contain pointers. // Allocate hchan and buf in one call. c = (*hc
                
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