The differences between channel buffer capacity of zero and one in golang

user_7055701 0
Viewed 2270

I have set channel buffer size to zero, like var intChannelZero = make(chan int) , when getting value from the intChannelZero will be blocked until the intChannelZero has value.

Also, I set channel buffer size to one, like var intChannelOne = make(chan int, 1), when getting value from the intChannelOne will be blocked until the intChannelOne has value.

We know the capacity of intChannelZero is zero, the capacity of intChannelOne is one, so I want to know:

  • When putting a value to the intChannelZero like intChannelZero <- 1, where the value be saved?
  • The differences between intChannelZero and intChannelOne when putting a value to them.

Who can explain it at the level of Golang Runtime Enviroment? Thanks a lot.

go
2 Answers

If the channel is unbuffered (capacity is zero), then communication succeeds only when the sender and receiver are both ready.

If the channel is buffered (capacity >= 1), then send succeeds without blocking if the channel is not full and receive succeeds without blocking if the buffer is not empty.

When putting a value to the intChannelZero like intChannelZero <- 1, where the value be saved?

The value is copied from the sender to the receiver. The value is not saved anywhere other than whatever temporary variables the implementation might use.

The differences between intChannelZero and intChannelOne when putting a value to them.

Send on intChannelZero blocks until a receiver is ready.

Send on intChannelOne blocks until space is available in the buffer.

user_57289910

Both unbuffered and buffered channel differences will be in terms of,

  1. Sends to channel is blocked
  2. Receives from channel is blocked

For unbuffered channels

Sends will be blocked if the channel already send a message and hasn't yet been received.

Receives will be blocked if no sends ever happened.

For buffered channels

Sends will be blocked if already n(channel size) sends happened and none of them received. ie entire channel size has been used by messages send but nothing was received.

Receives will be blocked if the buffer is empty ie doesn't have any unconsumed sends

Runtime errors

Receive blocked will throw the bellow error

fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan receive]:

Send blocked will throw the bellow error

fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan send]:
user_13046420
Related