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package metrics
import "sync/atomic"
// Counters hold an int64 value that can be incremented and decremented.
type Counter interface {
Clear()
Count() int64
Dec(int64)
Inc(int64)
Snapshot() Counter
}
// GetOrRegisterCounter returns an existing Counter or constructs and registers
// a new StandardCounter.
func GetOrRegisterCounter(name string, r Registry) Counter {
if nil == r {
r = DefaultRegistry
}
return r.GetOrRegister(name, NewCounter).(Counter)
}
// NewCounter constructs a new StandardCounter.
func NewCounter() Counter {
if UseNilMetrics {
return NilCounter{}
}
return &StandardCounter{0}
}
// NewRegisteredCounter constructs and registers a new StandardCounter.
func NewRegisteredCounter(name string, r Registry) Counter {
c := NewCounter()
if nil == r {
r = DefaultRegistry
}
r.Register(name, c)
return c
}
// CounterSnapshot is a read-only copy of another Counter.
type CounterSnapshot int64
// Clear panics.
func (CounterSnapshot) Clear() {
panic("Clear called on a CounterSnapshot")
}
// Count returns the count at the time the snapshot was taken.
func (c CounterSnapshot) Count() int64 { return int64(c) }
// Dec panics.
func (CounterSnapshot) Dec(int64) {
panic("Dec called on a CounterSnapshot")
}
// Inc panics.
func (CounterSnapshot) Inc(int64) {
panic("Inc called on a CounterSnapshot")
}
// Snapshot returns the snapshot.
func (c CounterSnapshot) Snapshot() Counter { return c }
// NilCounter is a no-op Counter.
type NilCounter struct{}
// Clear is a no-op.
func (NilCounter) Clear() {}
// Count is a no-op.
func (NilCounter) Count() int64 { return 0 }
// Dec is a no-op.
func (NilCounter) Dec(i int64) {}
// Inc is a no-op.
func (NilCounter) Inc(i int64) {}
// Snapshot is a no-op.
func (NilCounter) Snapshot() Counter { return NilCounter{} }
// StandardCounter is the standard implementation of a Counter and uses the
// sync/atomic package to manage a single int64 value.
type StandardCounter struct {
count int64
}
// Clear sets the counter to zero.
func (c *StandardCounter) Clear() {
atomic.StoreInt64(&c.count, 0)
}
// Count returns the current count.
func (c *StandardCounter) Count() int64 {
return atomic.LoadInt64(&c.count)
}
// Dec decrements the counter by the given amount.
func (c *StandardCounter) Dec(i int64) {
atomic.AddInt64(&c.count, -i)
}
// Inc increments the counter by the given amount.
func (c *StandardCounter) Inc(i int64) {
atomic.AddInt64(&c.count, i)
}
// Snapshot returns a read-only copy of the counter.
func (c *StandardCounter) Snapshot() Counter {
return CounterSnapshot(c.Count())
}
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