英文:
Is there any way to check if values are buffered in a Go chan?
问题
我该如何实现类似以下的功能？：
func foo(input <-chan char, output chan<- string) {
var c char
var ok bool
for {
if input中有缓冲值 {
c, ok = <-input
} else {
output <- "更新消息"
c, ok = <-input
}
对c和ok进行操作
}
}
基本上，我想要检查通道中是否有缓冲值，以便在线程被阻塞之前，如果没有缓冲值，我可以发送一条更新消息。
英文:
How can I do something like the following?:
func foo(input <-chan char, output chan<- string) {
var c char
var ok bool
for {
if ThereAreValuesBufferedIn(input) {
c, ok = <-input
} else {
output <- "update message"
c, ok = <-input
}
DoSomethingWith(c, ok)
}
}
Basically, I want to check if there are buffered values in the chan so that if there aren't, I could send an update message before the thread is blocked.
答案1
得分: 3
是的，这就是select调用允许你做的事情。它可以让你检查一个或多个通道是否准备好读取值。
英文:
Yes, this is what the select call allows you to do. It will enable you to check one or more channels for values ready to be read.
答案2
得分: 3
package main
func foo(input <-chan char, output chan<- string) {
for {
select {
case c, ok := <-input:
if ok { // ThereAreValuesBufferedIn(input)
... process c
} else { // input is closed
... handle closed input
}
default:
output <- "update message"
c, ok := <-input // will block
DoSomethingWith(c, ok)
}
}
}
英文:
package main
func foo(input <-chan char, output chan<- string) {
for {
select {
case c, ok := <-input:
if ok { // ThereAreValuesBufferedIn(input)
... process c
} else { // input is closed
... handle closed input
}
default:
output <- "update message"
c, ok := <-input // will block
DoSomethingWith(c, ok)
}
}
}
EDIT: Fixed scoping bug.
答案3
得分: 1
其他人已经回答了你关于代码的问题（使用select），但为了完整起见，并回答你问题标题中特定的问题（“有没有办法检查Go通道中的值是否已缓冲？”），len和cap内置函数在缓冲通道上的工作方式与预期相同（len返回缓冲元素的数量，cap返回通道的最大容量）。
http://tip.golang.org/ref/spec#Length_and_capacity
英文:
Others have answered your question for what you wanted to do with your code (use a select), but for completeness' sake, and to answer the specific question asked by your question's title ("Is there any way to check if values are buffered in a Go chan?"), the len and cap built-in functions work as expected on buffered channels (len returns the number of buffered elements, cap returns the maximum capacity of the channel).
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