为什么Go通道会限制缓冲区大小

Question

I am new to Go and I might be missing the point but why are Go channels limited in the maximum buffer size buffered channels can have? For example if I make a channel like so

channel := make(chan int, 100)

I cannot add more than 100 elements to the channel without blocking, is there a reason for this? Further they cannot dynamically be resized, because the channel API does not support that.

This seems sort of limiting in the language's support for universal synchronization with a single mechanism since it lacks convenience compared to an unbounded semaphore. For example a generalized semaphore's value can be increased without bounds.

Answer 1

The buffer size is the number of elements that can be sent to the channel without the send blocking. By default, a channel has a buffer size of 0 (you get this with make(chan int)). This means that every single send will block until another goroutine receives from the channel. A channel of buffer size 1 can hold 1 element until sending blocks, so you'd get

c := make(chan int, 1)
c <- 1 // doesn't block
c <- 2 // blocks until another goroutine receives from the channel

I suggest you to look this for more clarification: https://rogpeppe.wordpress.com/2010/02/10/unlimited-buffering-with-low-overhead/ http://openmymind.net/Introduction-To-Go-Buffered-Channels/