Documentation
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Overview ¶
Package sync provides a no-op drop-in replacement for standard "sync"
Let's say: You have a gr8 package. And it's concurrency safe due to import ("sync") and good use of "sync.Mutex" and friends.
Problem: Now, You also want to use (some of) it's type in another thing, which is concurrency safe by itself, or does not need to be.
Solution: Copy Your concurrency safe package (e.g. to some "oneway"/xyz path) and change the import ("sync") to here.
Benefit: Easy and swiftly to achieve.
Added benefit: Future maintenance will also be easy: just diff the "ccsafe" and the "oneway" packages - You should only see Your changed import!
Further benefit: You reduce memory footprint and improve performance - given the compiler is clever, he may even optimise the no-op function calls away.
Note: intentionally changes to the original code are kept to a minimum - to ease future maintenance.
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
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Types ¶
type Cond ¶
type Cond struct {
}
Cond implements a condition variable, a rendezvous point for goroutines waiting for or announcing the occurrence of an event.
Each Cond has an associated Locker L (often a *Mutex or *RWMutex), which must be held when changing the condition and when calling the Wait method.
A Cond can be created as part of other structures. A Cond must not be copied after first use.
func (*Cond) Broadcast ¶
func (c *Cond) Broadcast()
Broadcast wakes all goroutines waiting on c.
It is allowed but not required for the caller to hold c.L during the call.
func (*Cond) Signal ¶
func (c *Cond) Signal()
Signal wakes one goroutine waiting on c, if there is any.
It is allowed but not required for the caller to hold c.L during the call.
func (*Cond) Wait ¶
func (c *Cond) Wait()
Wait atomically unlocks c.L and suspends execution of the calling goroutine. After later resuming execution, Wait locks c.L before returning. Unlike in other systems, Wait cannot return unless awoken by Broadcast or Signal.
Because c.L is not locked when Wait first resumes, the caller typically cannot assume that the condition is true when Wait returns. Instead, the caller should Wait in a loop:
c.L.Lock()
for !condition() {
c.Wait()
}
... make use of condition ...
c.L.Unlock()
type Locker ¶
type Locker interface {
Lock()
Unlock()
}
A Locker represents an object that can be locked and unlocked.
type Mutex ¶
type Mutex struct {
}
A Mutex is a mutual exclusion lock. Mutexes can be created as part of other structures; the zero value for a Mutex is an unlocked mutex.
A Mutex must not be copied after first use.
type Once ¶
type Once struct {
}
Once is an object that will perform exactly one action.
func (*Once) Do ¶
func (o *Once) Do(f func())
Do calls the function f if and only if Do is being called for the first time for this instance of Once. In other words, given
var once Once
if once.Do(f) is called multiple times, only the first call will invoke f, even if f has a different value in each invocation. A new instance of Once is required for each function to execute.
Do is intended for initialization that must be run exactly once. Since f is niladic, it may be necessary to use a function literal to capture the arguments to a function to be invoked by Do:
config.once.Do(func() { config.init(filename) })
Because no call to Do returns until the one call to f returns, if f causes Do to be called, it will deadlock.
If f panics, Do considers it to have returned; future calls of Do return without calling f.
type RWMutex ¶
type RWMutex struct {
}
An RWMutex is a reader/writer mutual exclusion lock. The lock can be held by an arbitrary number of readers or a single writer. RWMutexes can be created as part of other structures; the zero value for a RWMutex is an unlocked mutex.
An RWMutex must not be copied after first use.
If a goroutine holds a RWMutex for reading, it must not expect this or any other goroutine to be able to also take the read lock until the first read lock is released. In particular, this prohibits recursive read locking. This is to ensure that the lock eventually becomes available; a blocked Lock call excludes new readers from acquiring the lock.
func (*RWMutex) Lock ¶
func (rw *RWMutex) Lock()
Lock locks rw for writing. If the lock is already locked for reading or writing, Lock blocks until the lock is available.
func (*RWMutex) RLocker ¶
RLocker returns a Locker interface that implements the Lock and Unlock methods by calling rw.RLock and rw.RUnlock.
func (*RWMutex) RUnlock ¶
func (rw *RWMutex) RUnlock()
RUnlock undoes a single RLock call; it does not affect other simultaneous readers. It is a run-time error if rw is not locked for reading on entry to RUnlock.
func (*RWMutex) Unlock ¶
func (rw *RWMutex) Unlock()
Unlock unlocks rw for writing. It is a run-time error if rw is not locked for writing on entry to Unlock.
As with Mutexes, a locked RWMutex is not associated with a particular goroutine. One goroutine may RLock (Lock) an RWMutex and then arrange for another goroutine to RUnlock (Unlock) it.
type WaitGroup ¶
type WaitGroup struct {
}
A WaitGroup waits for a collection of goroutines to finish. The main goroutine calls Add to set the number of goroutines to wait for. Then each of the goroutines runs and calls Done when finished. At the same time, Wait can be used to block until all goroutines have finished.
A WaitGroup must not be copied after first use.
func (*WaitGroup) Add ¶
Add adds delta, which may be negative, to the WaitGroup counter. If the counter becomes zero, all goroutines blocked on Wait are released. If the counter goes negative, Add panics.
Note that calls with a positive delta that occur when the counter is zero must happen before a Wait. Calls with a negative delta, or calls with a positive delta that start when the counter is greater than zero, may happen at any time. Typically this means the calls to Add should execute before the statement creating the goroutine or other event to be waited for. If a WaitGroup is reused to wait for several independent sets of events, new Add calls must happen after all previous Wait calls have returned. See the WaitGroup example.
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