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copy.go
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copy.go
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//
// Copyright (C) 2019-2022 vdaas.org vald team <vald@vdaas.org>
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Package io provides io functions
package io
import (
"bytes"
"errors"
"io"
"math"
"sync"
"sync/atomic"
)
var cio = NewCopier(0)
func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
return cio.Copy(dst, src)
}
type Copier interface {
Copy(dst io.Writer, src io.Reader) (written int64, err error)
}
type copier struct {
bufSize int64
pool sync.Pool
}
const (
defaultBufferSize int = 64 * 1024
)
func NewCopier(size int) Copier {
c := new(copier)
if size > 0 {
atomic.StoreInt64(&c.bufSize, int64(size))
} else {
atomic.StoreInt64(&c.bufSize, int64(defaultBufferSize))
}
c.pool = sync.Pool{
New: func() interface{} {
return bytes.NewBuffer(make([]byte, int(atomic.LoadInt64(&c.bufSize))))
},
}
return c
}
func (c *copier) Copy(dst io.Writer, src io.Reader) (written int64, err error) {
if dst == nil || src == nil {
return 0, errors.New("empty source or destination")
}
var (
wt io.WriterTo
rf io.ReaderFrom
ok bool
)
if wt, ok = src.(io.WriterTo); ok {
return wt.WriteTo(dst)
}
if rf, ok = dst.(io.ReaderFrom); ok {
return rf.ReadFrom(src)
}
var (
limit int64 = math.MaxInt64
size int64 = atomic.LoadInt64(&c.bufSize)
l *io.LimitedReader
buf *bytes.Buffer
)
if l, ok = src.(*io.LimitedReader); ok && l.N >= 1 && size > l.N {
limit = l.N
size = limit
}
buf, ok = c.pool.Get().(*bytes.Buffer)
if !ok || buf == nil {
buf = bytes.NewBuffer(make([]byte, size))
}
defer func() {
if atomic.LoadInt64(&c.bufSize) < size {
atomic.StoreInt64(&c.bufSize, size)
buf.Grow(int(size))
}
buf.Reset()
c.pool.Put(buf)
}()
if size > int64(buf.Cap()) {
size = int64(buf.Cap())
}
var nr, nw int
for err != io.EOF {
nr, err = src.Read(buf.Bytes()[:size])
if nr > 0 {
if int64(nr) > size {
if int64(nr) >= limit {
size = limit
} else {
size = int64(nr)
}
}
nw, err = dst.Write(buf.Bytes()[0:nr])
if nw < 0 || nr < int(nw) {
if err == nil {
return written, errors.New("invalid write result")
}
nw = 0
}
written += int64(nw)
if err != nil {
return written, err
}
if nr != int(nw) {
return written, io.ErrShortWrite
}
}
if err != nil && err != io.EOF {
return written, err
}
}
return written, nil
}