How Can Buffered Channels Implement Buffered Locking in Go?

Implementing Buffered Lock Patterns in Go

In Go, the concept of a buffered channel exists, allowing channels that prevent blocking until their buffers are full. Additionally, there are use cases for a generalized pattern of "buffered locking," where a resource is locked for a specific number of clients.

Semaphore as a Buffered Lock

A suitable primitive for implementing buffered locking is a semaphore. Semaphores control access to a resource by signaling when the resource is available for use.

Implementation Using Buffered Channel

In Go, a semaphore can be conveniently realized using a buffered channel. For instance:

var semaphore = make(chan struct{}, 4) // allow four concurrent users

func f() {
    // Grab the lock. Blocks if four other instances of f are already running.
    semaphore <- struct{}{}

    // Release the lock upon exiting.
    defer func() { <-semaphore }()

    // Perform necessary task here...
}

In this example, the buffered channel semaphore with a capacity of four ensures that only four clients can simultaneously access the protected resource. To acquire the lock, clients write to the channel, blocking if the buffer is full, and release the lock by reading from the channel.

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