- In short, the channel maintains an accept and send queue with pointers, which contains mutex locks to ensure concurrency security, data type, number of elements, element size, channel status
- Then read and write operations, first check whether the queue can be retrieved, then look at the buffer, and finally put it in the accept/send queue
- Close means to wake up all goroutines and set their flag to 1, indicating that they are closed. In the future, it is nil
Structure source code
type hchan struct {
qcount uint // The number of elements in the current queue dataqsiz uint // Buffer size, that is, the number of elements that can be cached buf // Point to the buffer of the queue elemsize uint16 // Size of each element closed uint32 // The channel is closed. elemtype *_type // Types of elements in channel sendx uint // The location of the next element sent recvx uint // The location of the next element is received recvq waitq // A goroutine queue waiting to be received sendq waitq // The goroutine queue waiting to be sent lock mutex // Mutex locks used to protect channel}Send data
When a goroutine is to send data to the channel, it executeschansendFunction.
- This function will first perform the channelAdd lock,ThenDetermine whether there is a goroutine waiting to be received
- If there is, then send the data directly to it; otherwise, if the buffer is not full, then put the data into the buffer and add one to the number of elements in the queue;
- If the queue is full, then add the current goroutineA goroutine queue waiting to be sentandblockIt, waiting for other goroutines to receive data.
Accept data
When a goroutine is to receive data from the channel, it executessrc/runtime/InchanrecvFunction.
- This function will also perform channelAdd lock, and then determine whether there is a goroutine waiting to be sent, and if so, receive data directly from it;
- Otherwise, ifBufferThe number of elements is greater than 0, thenBufferTake out an element and reduce the number of elements in the queue by one.
- ifBufferIf empty, the current goroutine is addedA goroutine queue waiting to be receivedand block it, waiting for other goroutines to send data.
Close channel
When a goroutine is about to close the channel, it executessrc/runtime/InclosechanFunction.
- This function will lock the channel and then
closedSetting the flag to 1 means that the channel has been closed. - Then iterate over the goroutine queues waiting to be sent and waiting to be received, wake them all up, and return a special value to indicate that the channel has been closed.
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