Need further clarification on the difference between unbuffered channels (i.e. capacity 0) and buffered channels of capacity 1 in Golang

php Editor Banana needs to further clarify the difference between unbuffered channels (capacity 0) and buffered channels with capacity 1 in Golang. In Golang, channels are an important mechanism for communication between coroutines, and unbuffered channels and buffered channels are two types of channels. Unbuffered channels require the sender and receiver to be ready at the same time to achieve synchronous communication, while buffered channels allow the sender to send data into the channel even if the receiver is not ready to receive it. Further understanding of the differences between these two channel types will help to better understand and use the channel mechanism in Golang.

Question content

In the link below, one of the answers given regarding the difference between an unbuffered channel and a buffered channel of 1 capacity is that if "The channel is unbuffered Buffered (capacity is zero), communication will succeed only if both the sender and receiver are ready".

When the author says that both the sender and the receiver are ready, what exactly does this mean? Chronologically, am I right in saying that one must precede the other? If so, am I right in saying that the receiver must be ready before the sender?

The difference between channel buffer capacity 0 and 1 in golang

I've been trying to find an explanation on official and unofficial channels. However, I haven't found a satisfactory answer yet. The closest I've come is the explanation below.

Does this mean that any code written below ch <- "C" (if capacity = 3) will still run? Going back to my original question about the difference between capacity 0 and 1, does this mean that any code below the sender won't run (for capacity = 0)? On the other hand, if capacity = 1, even if the full capacity is 1, the code below on the sender side will still run for so long?

https://www.golinuxcloud.com/golang-buffered-channel/

Thanks!

Solution

When the author says that both the sender and the receiver are ready, what does it really mean?

This means that one goroutine is executing receive and another goroutine is executing send. It doesn't matter which goroutine starts operating first.

In other words, sending a goroutine will block until another goroutine receives data on the channel.

Contrast this to a buffered channel with available capacity. A goroutine can complete sending to a channel without waiting for another goroutine to receive on the channel.

The following example illustrates the difference between unbuffered and buffered channels.

sleepRecv := func(c chan int) {
    time.Sleep(time.Second)
    <-c
}

b0 := make(chan int, 0)
go sleepRecv(b0)
start := time.Now()
b0 <- 0                        // must wait for recv in goroutine
fmt.Println(time.Since(start)) // prints 1s

b1 := make(chan int, 1)
go sleepRecv(b1)
start = time.Now()
b1 <- 0                        // does not wait for recv in goroutine
fmt.Println(time.Since(start)) // prints 0s

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