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128 lines
3.3 KiB
128 lines
3.3 KiB
/*
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* Minio Cloud Storage, (C) 2017, 2018 Minio, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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// Package ioutil implements some I/O utility functions which are not covered
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// by the standard library.
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package ioutil
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import (
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"io"
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humanize "github.com/dustin/go-humanize"
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)
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// defaultAppendBufferSize - Default buffer size for the AppendFile
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const defaultAppendBufferSize = humanize.MiByte
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// WriteOnCloser implements io.WriteCloser and always
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// exectues at least one write operation if it is closed.
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//
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// This can be useful within the context of HTTP. At least
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// one write operation must happen to send the HTTP headers
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// to the peer.
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type WriteOnCloser struct {
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io.Writer
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hasWritten bool
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}
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func (w *WriteOnCloser) Write(p []byte) (int, error) {
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w.hasWritten = true
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return w.Writer.Write(p)
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}
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// Close closes the WriteOnCloser. It behaves like io.Closer.
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func (w *WriteOnCloser) Close() error {
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if !w.hasWritten {
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_, err := w.Write(nil)
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if err != nil {
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return err
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}
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}
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if closer, ok := w.Writer.(io.Closer); ok {
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return closer.Close()
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}
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return nil
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}
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// HasWritten returns true if at least one write operation was performed.
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func (w *WriteOnCloser) HasWritten() bool { return w.hasWritten }
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// WriteOnClose takes an io.Writer and returns an ioutil.WriteOnCloser.
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func WriteOnClose(w io.Writer) *WriteOnCloser {
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return &WriteOnCloser{w, false}
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}
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// LimitWriter implements io.WriteCloser.
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//
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// This is implemented such that we want to restrict
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// an enscapsulated writer upto a certain length
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// and skip a certain number of bytes.
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type LimitWriter struct {
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io.Writer
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skipBytes int64
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wLimit int64
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}
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// Implements the io.Writer interface limiting upto
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// configured length, also skips the first N bytes.
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func (w *LimitWriter) Write(p []byte) (n int, err error) {
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n = len(p)
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var n1 int
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if w.skipBytes > 0 {
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if w.skipBytes >= int64(len(p)) {
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w.skipBytes = w.skipBytes - int64(len(p))
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return n, nil
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}
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p = p[w.skipBytes:]
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w.skipBytes = 0
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}
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if w.wLimit == 0 {
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return n, nil
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}
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if w.wLimit < int64(len(p)) {
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n1, err = w.Writer.Write(p[:w.wLimit])
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w.wLimit = w.wLimit - int64(n1)
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return n, err
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}
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n1, err = w.Writer.Write(p)
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w.wLimit = w.wLimit - int64(n1)
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return n, err
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}
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// Close closes the LimitWriter. It behaves like io.Closer.
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func (w *LimitWriter) Close() error {
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if closer, ok := w.Writer.(io.Closer); ok {
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return closer.Close()
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}
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return nil
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}
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// LimitedWriter takes an io.Writer and returns an ioutil.LimitWriter.
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func LimitedWriter(w io.Writer, skipBytes int64, limit int64) *LimitWriter {
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return &LimitWriter{w, skipBytes, limit}
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}
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type nopCloser struct {
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io.Writer
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}
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func (nopCloser) Close() error { return nil }
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// NopCloser returns a WriteCloser with a no-op Close method wrapping
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// the provided Writer w.
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func NopCloser(w io.Writer) io.WriteCloser {
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return nopCloser{w}
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}
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