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Copy pathioutil.go
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159 lines (139 loc) · 3.86 KB
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/*
* Minio Cloud Storage, (C) 2017, 2018 Minio, Inc.
*
* 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
*
* http://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 ioutil implements some I/O utility functions which are not covered
// by the standard library.
package ioutil
import (
"io"
humanize "github.com/dustin/go-humanize"
)
// defaultAppendBufferSize - Default buffer size for the AppendFile
const defaultAppendBufferSize = humanize.MiByte
// WriteOnCloser implements io.WriteCloser and always
// exectues at least one write operation if it is closed.
//
// This can be useful within the context of HTTP. At least
// one write operation must happen to send the HTTP headers
// to the peer.
type WriteOnCloser struct {
io.Writer
hasWritten bool
}
func (w *WriteOnCloser) Write(p []byte) (int, error) {
w.hasWritten = true
return w.Writer.Write(p)
}
// Close closes the WriteOnCloser. It behaves like io.Closer.
func (w *WriteOnCloser) Close() error {
if !w.hasWritten {
_, err := w.Write(nil)
if err != nil {
return err
}
}
if closer, ok := w.Writer.(io.Closer); ok {
return closer.Close()
}
return nil
}
// HasWritten returns true if at least one write operation was performed.
func (w *WriteOnCloser) HasWritten() bool { return w.hasWritten }
// WriteOnClose takes an io.Writer and returns an ioutil.WriteOnCloser.
func WriteOnClose(w io.Writer) *WriteOnCloser {
return &WriteOnCloser{w, false}
}
// LimitWriter implements io.WriteCloser.
//
// This is implemented such that we want to restrict
// an enscapsulated writer upto a certain length
// and skip a certain number of bytes.
type LimitWriter struct {
io.Writer
skipBytes int64
wLimit int64
}
// Implements the io.Writer interface limiting upto
// configured length, also skips the first N bytes.
func (w *LimitWriter) Write(p []byte) (n int, err error) {
n = len(p)
var n1 int
if w.skipBytes > 0 {
if w.skipBytes >= int64(len(p)) {
w.skipBytes = w.skipBytes - int64(len(p))
return n, nil
}
p = p[w.skipBytes:]
w.skipBytes = 0
}
if w.wLimit == 0 {
return n, nil
}
if w.wLimit < int64(len(p)) {
n1, err = w.Writer.Write(p[:w.wLimit])
w.wLimit = w.wLimit - int64(n1)
return n, err
}
n1, err = w.Writer.Write(p)
w.wLimit = w.wLimit - int64(n1)
return n, err
}
// Close closes the LimitWriter. It behaves like io.Closer.
func (w *LimitWriter) Close() error {
if closer, ok := w.Writer.(io.Closer); ok {
return closer.Close()
}
return nil
}
// LimitedWriter takes an io.Writer and returns an ioutil.LimitWriter.
func LimitedWriter(w io.Writer, skipBytes int64, limit int64) *LimitWriter {
return &LimitWriter{w, skipBytes, limit}
}
type nopCloser struct {
io.Writer
}
func (nopCloser) Close() error { return nil }
// NopCloser returns a WriteCloser with a no-op Close method wrapping
// the provided Writer w.
func NopCloser(w io.Writer) io.WriteCloser {
return nopCloser{w}
}
// SkipReader skips a given number of bytes and then returns all
// remaining data.
type SkipReader struct {
io.Reader
skipCount int64
}
func (s *SkipReader) Read(p []byte) (int, error) {
l := int64(len(p))
if l == 0 {
return 0, nil
}
for s.skipCount > 0 {
if l > s.skipCount {
l = s.skipCount
}
n, err := s.Reader.Read(p[:l])
if err != nil {
return 0, err
}
s.skipCount -= int64(n)
}
return s.Reader.Read(p)
}
// NewSkipReader - creates a SkipReader
func NewSkipReader(r io.Reader, n int64) io.Reader {
return &SkipReader{r, n}
}