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Concurrency in Go

Channels Internals

Learn about the hchan struct and some deep concepts in Golang.

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The hchan struct

Internally, the channels implement an hchan struct, which holds the information related to the channels. It includes the buffer size buf, the sender sendx, the receiver recvx, the channel blocked due to sending sendq, the channel blocked due to receiving recvq, the mutex lock, and many more fields.

Go (1.6.2)
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.
	lock mutex
}

Terminology

Let’s explore the terminology of the hchan struct.

  • buf: This represents the circular queue that stores the data.
  • closed:
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