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delay.go
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delay.go
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package syslogger
import (
"sync"
"github.com/proidiot/gone/errors"
"github.com/proidiot/gone/log/pri"
)
type sysloggerHandle struct {
s Syslogger
}
// Delay is a syslogger.Syslogger that delays the initialization of another
// syslogger.Syslogger until the first time that Syslog is called.
type Delay struct {
h *sysloggerHandle
cb func() (Syslogger, error)
x sync.Mutex
}
// Syslog logs messages. In the case of Delay, these messages are passed
// unaltered to another syslogger.Syslogger, and that syslogger.Syslogger would
// be created at this point if it had not already existed.
func (d *Delay) Syslog(p pri.Priority, msg interface{}) error {
d.x.Lock()
// Not deferring the unlock here because the actual Syslog call at the
// end may take some time.
if d.h == nil {
s, e := d.cb()
if e != nil {
d.x.Unlock()
return e
}
d.h = &sysloggerHandle{s}
}
h := d.h
d.x.Unlock()
return h.s.Syslog(p, msg)
}
// NewDelay gives a Delay syslogger.Syslogger given the callback function which
// will ultimately be used to create the real syslogger.Syslogger to be used.
func NewDelay(cb func() (Syslogger, error)) (*Delay, error) {
if cb == nil {
return nil, errors.New(
"A syslogger.Delay must have a valid callback for" +
" generating a Syslogger, but a nil callback" +
" was given to syslogger.NewDelay(...).",
)
}
return &Delay{cb: cb}, nil
}