2017-11-08 00:18:59 +01:00
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/*
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2019-04-09 20:39:42 +02:00
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* MinIO Cloud Storage, (C) 2017, 2018 MinIO, Inc.
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2017-11-08 00:18:59 +01:00
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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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2019-05-22 22:47:15 +02:00
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"os"
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2018-01-31 22:17:24 +01:00
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humanize "github.com/dustin/go-humanize"
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2019-05-22 22:47:15 +02:00
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"github.com/minio/minio/pkg/disk"
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2017-11-08 00:18:59 +01:00
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)
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2018-01-31 22:17:24 +01:00
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// defaultAppendBufferSize - Default buffer size for the AppendFile
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const defaultAppendBufferSize = humanize.MiByte
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2017-11-08 00:18:59 +01:00
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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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2018-02-24 00:07:21 +01:00
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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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2018-03-03 02:24:02 +01:00
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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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2018-09-21 04:22:09 +02:00
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// SkipReader skips a given number of bytes and then returns all
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// remaining data.
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type SkipReader struct {
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io.Reader
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skipCount int64
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}
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func (s *SkipReader) Read(p []byte) (int, error) {
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l := int64(len(p))
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if l == 0 {
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return 0, nil
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}
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for s.skipCount > 0 {
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if l > s.skipCount {
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l = s.skipCount
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}
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n, err := s.Reader.Read(p[:l])
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if err != nil {
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return 0, err
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}
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s.skipCount -= int64(n)
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}
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return s.Reader.Read(p)
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}
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// NewSkipReader - creates a SkipReader
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func NewSkipReader(r io.Reader, n int64) io.Reader {
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return &SkipReader{r, n}
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}
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2019-05-22 22:47:15 +02:00
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// DirectIO alignment needs to be 4K. Defined here as
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// directio.AlignSize is defined as 0 in MacOS causing divide by 0 error.
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const directioAlignSize = 4096
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// CopyAligned - copies from reader to writer using the aligned input
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// buffer, it is expected that input buffer is page aligned to
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// 4K page boundaries. Without passing aligned buffer may cause
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// this function to return error.
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//
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// This code is similar in spirit to io.CopyBuffer but it is only to be
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// used with DIRECT I/O based file descriptor and it is expected that
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// input writer *os.File not a generic io.Writer. Make sure to have
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// the file opened for writes with syscall.O_DIRECT flag.
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func CopyAligned(w *os.File, r io.Reader, alignedBuf []byte) (int64, error) {
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// Writes remaining bytes in the buffer.
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writeUnaligned := func(w *os.File, buf []byte) (remainingWritten int, err error) {
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var n int
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remaining := len(buf)
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// The following logic writes the remainging data such that it writes whatever best is possible (aligned buffer)
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// in O_DIRECT mode and remaining (unaligned buffer) in non-O_DIRECT mode.
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remainingAligned := (remaining / directioAlignSize) * directioAlignSize
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remainingAlignedBuf := buf[:remainingAligned]
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remainingUnalignedBuf := buf[remainingAligned:]
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if len(remainingAlignedBuf) > 0 {
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n, err = w.Write(remainingAlignedBuf)
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if err != nil {
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return remainingWritten, err
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}
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remainingWritten += n
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}
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if len(remainingUnalignedBuf) > 0 {
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// Write on O_DIRECT fds fail if buffer is not 4K aligned, hence disable O_DIRECT.
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if err = disk.DisableDirectIO(w); err != nil {
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return remainingWritten, err
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}
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n, err = w.Write(remainingUnalignedBuf)
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if err != nil {
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return remainingWritten, err
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}
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remainingWritten += n
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}
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return remainingWritten, nil
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}
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var written int64
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var err error
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for {
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nr, er := r.Read(alignedBuf)
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if nr == len(alignedBuf) {
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// Buffer read is aligned with input buffer, proceed to write.
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nw, ew := w.Write(alignedBuf)
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if nw > 0 {
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written += int64(nw)
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}
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if ew != nil {
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err = ew
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break
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}
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if nr != nw {
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err = io.ErrShortWrite
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break
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}
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} else if nr > 0 {
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// Buffer read is not aligned with input buffer, proceed to write
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// whatever possible as aligned and turn off direct I/O.
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nw, ew := writeUnaligned(w, alignedBuf[:nr])
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if nw > 0 {
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written += int64(nw)
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}
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if ew != nil {
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err = ew
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break
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}
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if nr != nw {
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err = io.ErrShortWrite
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break
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}
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}
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// For any read errors break out and return error.
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if er != nil {
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if er != io.EOF {
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err = er
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}
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break
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}
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}
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return written, err
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}
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