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minio/pkg/ioutil/ioutil.go

263 lines
6.6 KiB

/*
* MinIO Cloud Storage, (C) 2017-2020 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"
"os"
"github.com/minio/minio/pkg/disk"
)
// WriteOnCloser implements io.WriteCloser and always
// executes 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
}
// Write 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}
}
// SameFile returns if the files are same.
func SameFile(fi1, fi2 os.FileInfo) bool {
if !os.SameFile(fi1, fi2) {
return false
}
if !fi1.ModTime().Equal(fi2.ModTime()) {
return false
}
if fi1.Mode() != fi2.Mode() {
return false
}
if fi1.Size() != fi2.Size() {
return false
}
return true
}
// DirectIO alignment needs to be 4K. Defined here as
// directio.AlignSize is defined as 0 in MacOS causing divide by 0 error.
const directioAlignSize = 4096
// CopyAligned - copies from reader to writer using the aligned input
// buffer, it is expected that input buffer is page aligned to
// 4K page boundaries. Without passing aligned buffer may cause
// this function to return error.
//
// This code is similar in spirit to io.Copy but it is only to be
// used with DIRECT I/O based file descriptor and it is expected that
// input writer *os.File not a generic io.Writer. Make sure to have
// the file opened for writes with syscall.O_DIRECT flag.
func CopyAligned(w *os.File, r io.Reader, alignedBuf []byte, totalSize int64) (int64, error) {
// Writes remaining bytes in the buffer.
writeUnaligned := func(w *os.File, buf []byte) (remainingWritten int, err error) {
var n int
remaining := len(buf)
// The following logic writes the remainging data such that it writes whatever best is possible (aligned buffer)
// in O_DIRECT mode and remaining (unaligned buffer) in non-O_DIRECT mode.
remainingAligned := (remaining / directioAlignSize) * directioAlignSize
remainingAlignedBuf := buf[:remainingAligned]
remainingUnalignedBuf := buf[remainingAligned:]
if len(remainingAlignedBuf) > 0 {
n, err = w.Write(remainingAlignedBuf)
if err != nil {
return remainingWritten, err
}
remainingWritten += n
}
if len(remainingUnalignedBuf) > 0 {
// Write on O_DIRECT fds fail if buffer is not 4K aligned, hence disable O_DIRECT.
if err = disk.DisableDirectIO(w); err != nil {
return remainingWritten, err
}
n, err = w.Write(remainingUnalignedBuf)
if err != nil {
return remainingWritten, err
}
remainingWritten += n
}
return remainingWritten, nil
}
var written int64
for {
buf := alignedBuf
if totalSize != -1 {
remaining := totalSize - written
if remaining < int64(len(buf)) {
buf = buf[:remaining]
}
}
nr, err := io.ReadFull(r, buf)
eof := err == io.EOF || err == io.ErrUnexpectedEOF
if err != nil && !eof {
return written, err
}
buf = buf[:nr]
var nw int
if len(buf)%directioAlignSize == 0 {
// buf is aligned for directio write()
nw, err = w.Write(buf)
} else {
// buf is not aligned, hence use writeUnaligned()
nw, err = writeUnaligned(w, buf)
}
if nw > 0 {
written += int64(nw)
}
if err != nil {
return written, err
}
if nw != len(buf) {
return written, io.ErrShortWrite
}
if totalSize != -1 {
if written == totalSize {
return written, nil
}
}
if eof {
return written, nil
}
}
}