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@akshayjshah @abhinav @suyash
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// Copyright (c) 2016 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package zapcore
import (
"io"
"sync"
"go.uber.org/multierr"
)
// A WriteSyncer is an io.Writer that can also flush any buffered data. Note
// that *os.File (and thus, os.Stderr and os.Stdout) implement WriteSyncer.
type WriteSyncer interface {
io.Writer
Sync() error
}
// AddSync converts an io.Writer to a WriteSyncer. It attempts to be
// intelligent: if the concrete type of the io.Writer implements WriteSyncer,
// we'll use the existing Sync method. If it doesn't, we'll add a no-op Sync.
func AddSync(w io.Writer) WriteSyncer {
switch w := w.(type) {
case WriteSyncer:
return w
default:
return writerWrapper{w}
}
}
type lockedWriteSyncer struct {
sync.Mutex
ws WriteSyncer
}
// Lock wraps a WriteSyncer in a mutex to make it safe for concurrent use. In
// particular, *os.Files must be locked before use.
func Lock(ws WriteSyncer) WriteSyncer {
if _, ok := ws.(*lockedWriteSyncer); ok {
// no need to layer on another lock
return ws
}
return &lockedWriteSyncer{ws: ws}
}
func (s *lockedWriteSyncer) Write(bs []byte) (int, error) {
s.Lock()
n, err := s.ws.Write(bs)
s.Unlock()
return n, err
}
func (s *lockedWriteSyncer) Sync() error {
s.Lock()
err := s.ws.Sync()
s.Unlock()
return err
}
type writerWrapper struct {
io.Writer
}
func (w writerWrapper) Sync() error {
return nil
}
type multiWriteSyncer []WriteSyncer
// NewMultiWriteSyncer creates a WriteSyncer that duplicates its writes
// and sync calls, much like io.MultiWriter.
func NewMultiWriteSyncer(ws ...WriteSyncer) WriteSyncer {
if len(ws) == 1 {
return ws[0]
}
// Copy to protect against https://github.com/golang/go/issues/7809
return multiWriteSyncer(append([]WriteSyncer(nil), ws...))
}
// See https://golang.org/src/io/multi.go
// When not all underlying syncers write the same number of bytes,
// the smallest number is returned even though Write() is called on
// all of them.
func (ws multiWriteSyncer) Write(p []byte) (int, error) {
var writeErr error
nWritten := 0
for _, w := range ws {
n, err := w.Write(p)
writeErr = multierr.Append(writeErr, err)
if nWritten == 0 && n != 0 {
nWritten = n
} else if n < nWritten {
nWritten = n
}
}
return nWritten, writeErr
}
func (ws multiWriteSyncer) Sync() error {
var err error
for _, w := range ws {
err = multierr.Append(err, w.Sync())
}
return err
}
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