OP#792 initial commit after fork

internal/ioutil/append-file_nix.go

@@ -0,0 +1,47 @@
+//go:build !windows
+// +build !windows
+
+// Copyright (c) 2015-2021 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package ioutil
+
+import (
+	"io"
+	"os"
+)
+
+// AppendFile - appends the file "src" to the file "dst"
+func AppendFile(dst string, src string, osync bool) error {
+	flags := os.O_WRONLY | os.O_APPEND | os.O_CREATE
+	if osync {
+		flags |= os.O_SYNC
+	}
+	appendFile, err := os.OpenFile(dst, flags, 0o666)
+	if err != nil {
+		return err
+	}
+	defer appendFile.Close()
+
+	srcFile, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer srcFile.Close()
+	_, err = io.Copy(appendFile, srcFile)
+	return err
+}

internal/ioutil/append-file_windows.go

@@ -0,0 +1,42 @@
+// Copyright (c) 2015-2021 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package ioutil
+
+import (
+	"io"
+	"os"
+
+	"github.com/minio/minio/internal/lock"
+)
+
+// AppendFile - appends the file "src" to the file "dst"
+func AppendFile(dst string, src string, osync bool) error {
+	appendFile, err := lock.Open(dst, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0o666)
+	if err != nil {
+		return err
+	}
+	defer appendFile.Close()
+
+	srcFile, err := lock.Open(src, os.O_RDONLY, 0o666)
+	if err != nil {
+		return err
+	}
+	defer srcFile.Close()
+	_, err = io.Copy(appendFile, srcFile)
+	return err
+}

internal/ioutil/discard.go

@@ -0,0 +1,40 @@
+// Copyright (c) 2015-2023 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package ioutil
+
+import (
+	"io"
+)
+
+// Discard is just like io.Discard without the io.ReaderFrom compatible
+// implementation which is buggy on NUMA systems, we have to use a simpler
+// io.Writer implementation alone avoids also unnecessary buffer copies,
+// and as such incurred latencies.
+var Discard io.Writer = discard{}
+
+// discard is /dev/null for Golang.
+type discard struct{}
+
+func (discard) Write(p []byte) (int, error) {
+	return len(p), nil
+}
+
+// DiscardReader discarded reader
+func DiscardReader(r io.Reader) {
+	Copy(Discard, r)
+}

internal/ioutil/hardlimitreader.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2015-2023 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+// Package ioutil implements some I/O utility functions which are not covered
+// by the standard library.
+package ioutil
+
+import (
+	"errors"
+	"io"
+)
+
+// ErrOverread is returned to the reader when the hard limit of HardLimitReader is exceeded.
+var ErrOverread = errors.New("input provided more bytes than specified")
+
+// HardLimitReader returns a Reader that reads from r
+// but returns an error if the source provides more data than allowed.
+// This means the source *will* be overread unless EOF is returned prior.
+// The underlying implementation is a *HardLimitedReader.
+// This will ensure that at most n bytes are returned and EOF is reached.
+func HardLimitReader(r io.Reader, n int64) io.Reader { return &HardLimitedReader{r, n} }
+
+// A HardLimitedReader reads from R but limits the amount of
+// data returned to just N bytes. Each call to Read
+// updates N to reflect the new amount remaining.
+// Read returns EOF when N <= 0 or when the underlying R returns EOF.
+type HardLimitedReader struct {
+	R io.Reader // underlying reader
+	N int64     // max bytes remaining
+}
+
+func (l *HardLimitedReader) Read(p []byte) (n int, err error) {
+	if l.N < 0 {
+		return 0, ErrOverread
+	}
+	n, err = l.R.Read(p)
+	l.N -= int64(n)
+	if l.N < 0 {
+		return 0, ErrOverread
+	}
+	return n, err
+}

internal/ioutil/ioutil.go

@@ -0,0 +1,440 @@
+// Copyright (c) 2015-2021 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+// Package ioutil implements some I/O utility functions which are not covered
+// by the standard library.
+package ioutil
+
+import (
+	"context"
+	"errors"
+	"io"
+	"os"
+	"runtime/debug"
+	"time"
+
+	"github.com/dustin/go-humanize"
+	"github.com/minio/minio/internal/bpool"
+	"github.com/minio/minio/internal/disk"
+)
+
+// Block sizes constant.
+const (
+	SmallBlock  = 32 * humanize.KiByte  // Default r/w block size for smaller objects.
+	MediumBlock = 128 * humanize.KiByte // Default r/w block size for medium sized objects.
+	LargeBlock  = 1 * humanize.MiByte   // Default r/w block size for normal objects.
+)
+
+// AlignedBytePool is a pool of fixed size aligned blocks
+type AlignedBytePool struct {
+	size int
+	p    bpool.Pool[*[]byte]
+}
+
+// NewAlignedBytePool creates a new pool with the specified size.
+func NewAlignedBytePool(sz int) *AlignedBytePool {
+	return &AlignedBytePool{size: sz, p: bpool.Pool[*[]byte]{New: func() *[]byte {
+		b := disk.AlignedBlock(sz)
+		return &b
+	}}}
+}
+
+// aligned sync.Pool's
+var (
+	ODirectPoolLarge  = NewAlignedBytePool(LargeBlock)
+	ODirectPoolMedium = NewAlignedBytePool(MediumBlock)
+	ODirectPoolSmall  = NewAlignedBytePool(SmallBlock)
+)
+
+// Get a block.
+func (p *AlignedBytePool) Get() *[]byte {
+	return p.p.Get()
+}
+
+// Put a block.
+func (p *AlignedBytePool) Put(pb *[]byte) {
+	if pb != nil && len(*pb) == p.size {
+		p.p.Put(pb)
+	}
+}
+
+// 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}
+}
+
+type ioret[V any] struct {
+	val V
+	err error
+}
+
+// WithDeadline will execute a function with a deadline and return a value of a given type.
+// If the deadline/context passes before the function finishes executing,
+// the zero value and the context error is returned.
+func WithDeadline[V any](ctx context.Context, timeout time.Duration, work func(ctx context.Context) (result V, err error)) (result V, err error) {
+	ctx, cancel := context.WithTimeout(ctx, timeout)
+	defer cancel()
+
+	c := make(chan ioret[V], 1)
+	go func() {
+		v, err := work(ctx)
+		c <- ioret[V]{val: v, err: err}
+	}()
+
+	select {
+	case v := <-c:
+		return v.val, v.err
+	case <-ctx.Done():
+		var zero V
+		return zero, ctx.Err()
+	}
+}
+
+// DeadlineWorker implements the deadline/timeout resiliency pattern.
+type DeadlineWorker struct {
+	timeout time.Duration
+}
+
+// NewDeadlineWorker constructs a new DeadlineWorker with the given timeout.
+// To return values, use the WithDeadline helper instead.
+func NewDeadlineWorker(timeout time.Duration) *DeadlineWorker {
+	dw := &DeadlineWorker{
+		timeout: timeout,
+	}
+	return dw
+}
+
+// Run runs the given function, passing it a stopper channel. If the deadline passes before
+// the function finishes executing, Run returns context.DeadlineExceeded to the caller.
+// channel so that the work function can attempt to exit gracefully.
+// Multiple calls to Run will run independently of each other.
+func (d *DeadlineWorker) Run(work func() error) error {
+	_, err := WithDeadline[struct{}](context.Background(), d.timeout, func(ctx context.Context) (struct{}, error) {
+		return struct{}{}, work()
+	})
+	return err
+}
+
+// DeadlineWriter deadline writer with timeout
+type DeadlineWriter struct {
+	io.WriteCloser
+	timeout time.Duration
+	err     error
+}
+
+// NewDeadlineWriter wraps a writer to make it respect given deadline
+// value per Write(). If there is a blocking write, the returned Writer
+// will return whenever the timer hits (the return values are n=0
+// and err=context.DeadlineExceeded.)
+func NewDeadlineWriter(w io.WriteCloser, timeout time.Duration) io.WriteCloser {
+	return &DeadlineWriter{WriteCloser: w, timeout: timeout}
+}
+
+func (w *DeadlineWriter) Write(buf []byte) (int, error) {
+	if w.err != nil {
+		return 0, w.err
+	}
+
+	n, err := WithDeadline[int](context.Background(), w.timeout, func(ctx context.Context) (int, error) {
+		return w.WriteCloser.Write(buf)
+	})
+	w.err = err
+	return n, err
+}
+
+// Close closer interface to close the underlying closer
+func (w *DeadlineWriter) Close() error {
+	err := w.WriteCloser.Close()
+	w.err = err
+	if err == nil {
+		w.err = errors.New("we are closed") // Avoids any reuse on the Write() side.
+	}
+	return err
+}
+
+// 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 -= 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 -= int64(n1)
+		return n, err
+	}
+	n1, err = w.Writer.Write(p)
+	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
+	}
+	if s.skipCount > 0 {
+		tmp := p
+		if s.skipCount > l && l < SmallBlock {
+			// We may get a very small buffer, so we grab a temporary buffer.
+			bufp := ODirectPoolSmall.Get()
+			tmp = *bufp
+			defer ODirectPoolSmall.Put(bufp)
+			l = int64(len(tmp))
+		}
+		for s.skipCount > 0 {
+			if l > s.skipCount {
+				l = s.skipCount
+			}
+			n, err := s.Reader.Read(tmp[: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}
+}
+
+// writerOnly hides an io.Writer value's optional ReadFrom method
+// from io.Copy.
+type writerOnly struct {
+	io.Writer
+}
+
+// Copy is exactly like io.Copy but with reusable buffers.
+func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
+	bufp := ODirectPoolMedium.Get()
+	defer ODirectPoolMedium.Put(bufp)
+	buf := *bufp
+
+	return io.CopyBuffer(writerOnly{dst}, src, buf)
+}
+
+// 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
+	}
+	return fi1.Size() == fi2.Size()
+}
+
+// DirectioAlignSize - 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 io.Writer, r io.Reader, alignedBuf []byte, totalSize int64, file *os.File) (int64, error) {
+	if totalSize == 0 {
+		return 0, nil
+	}
+
+	var written int64
+	for {
+		buf := alignedBuf
+		if totalSize > 0 {
+			remaining := totalSize - written
+			if remaining < int64(len(buf)) {
+				buf = buf[:remaining]
+			}
+		}
+
+		nr, err := io.ReadFull(r, buf)
+		eof := errors.Is(err, io.EOF) || errors.Is(err, io.ErrUnexpectedEOF)
+		if err != nil && !eof {
+			return written, err
+		}
+
+		buf = buf[:nr]
+		var (
+			n  int
+			un int
+			nw int64
+		)
+
+		remain := len(buf) % DirectioAlignSize
+		if remain == 0 {
+			// buf is aligned for directio write()
+			n, err = w.Write(buf)
+			nw = int64(n)
+		} else {
+			if remain < len(buf) {
+				n, err = w.Write(buf[:len(buf)-remain])
+				if err != nil {
+					return written, err
+				}
+				nw = int64(n)
+			}
+
+			// Disable O_DIRECT on fd's on unaligned buffer
+			// perform an amortized Fdatasync(fd) on the fd at
+			// the end, this is performed by the caller before
+			// closing 'w'.
+			if err = disk.DisableDirectIO(file); err != nil {
+				return written, err
+			}
+
+			// buf is not aligned, hence use writeUnaligned()
+			// for the remainder
+			un, err = w.Write(buf[len(buf)-remain:])
+			nw += int64(un)
+		}
+
+		if nw > 0 {
+			written += nw
+		}
+
+		if err != nil {
+			return written, err
+		}
+
+		if nw != int64(len(buf)) {
+			return written, io.ErrShortWrite
+		}
+
+		if totalSize > 0 && written == totalSize {
+			// we have written the entire stream, return right here.
+			return written, nil
+		}
+
+		if eof {
+			// We reached EOF prematurely but we did not write everything
+			// that we promised that we would write.
+			if totalSize > 0 && written != totalSize {
+				return written, io.ErrUnexpectedEOF
+			}
+			return written, nil
+		}
+	}
+}
+
+// SafeClose safely closes any channel of any type
+func SafeClose[T any](c chan<- T) {
+	if c != nil {
+		close(c)
+		return
+	}
+	// Print stack to check who is sending `c` as `nil`
+	// without crashing the server.
+	debug.PrintStack()
+}

internal/ioutil/ioutil_test.go

@@ -0,0 +1,226 @@
+// Copyright (c) 2015-2023 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package ioutil
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"io"
+	"os"
+	"strings"
+	"testing"
+	"time"
+)
+
+type sleepWriter struct {
+	timeout time.Duration
+}
+
+func (w *sleepWriter) Write(p []byte) (n int, err error) {
+	time.Sleep(w.timeout)
+	return len(p), nil
+}
+
+func (w *sleepWriter) Close() error {
+	return nil
+}
+
+func TestDeadlineWorker(t *testing.T) {
+	work := NewDeadlineWorker(500 * time.Millisecond)
+
+	err := work.Run(func() error {
+		time.Sleep(600 * time.Millisecond)
+		return nil
+	})
+	if err != context.DeadlineExceeded {
+		t.Error("DeadlineWorker shouldn't be successful - should return context.DeadlineExceeded")
+	}
+
+	err = work.Run(func() error {
+		time.Sleep(450 * time.Millisecond)
+		return nil
+	})
+	if err != nil {
+		t.Error("DeadlineWorker should succeed")
+	}
+}
+
+func TestDeadlineWriter(t *testing.T) {
+	w := NewDeadlineWriter(&sleepWriter{timeout: 500 * time.Millisecond}, 450*time.Millisecond)
+	_, err := w.Write([]byte("1"))
+	if err != context.DeadlineExceeded {
+		t.Error("DeadlineWriter shouldn't be successful - should return context.DeadlineExceeded")
+	}
+	_, err = w.Write([]byte("1"))
+	if err != context.DeadlineExceeded {
+		t.Error("DeadlineWriter shouldn't be successful - should return context.DeadlineExceeded")
+	}
+	w.Close()
+	w = NewDeadlineWriter(&sleepWriter{timeout: 100 * time.Millisecond}, 600*time.Millisecond)
+	n, err := w.Write([]byte("abcd"))
+	w.Close()
+	if err != nil {
+		t.Errorf("DeadlineWriter should succeed but failed with %s", err)
+	}
+	if n != 4 {
+		t.Errorf("DeadlineWriter should succeed but should have only written 4 bytes, but returned %d instead", n)
+	}
+}
+
+func TestCloseOnWriter(t *testing.T) {
+	writer := WriteOnClose(io.Discard)
+	if writer.HasWritten() {
+		t.Error("WriteOnCloser must not be marked as HasWritten")
+	}
+	writer.Write(nil)
+	if !writer.HasWritten() {
+		t.Error("WriteOnCloser must be marked as HasWritten")
+	}
+
+	writer = WriteOnClose(io.Discard)
+	writer.Close()
+	if !writer.HasWritten() {
+		t.Error("WriteOnCloser must be marked as HasWritten")
+	}
+}
+
+// Test for AppendFile.
+func TestAppendFile(t *testing.T) {
+	f, err := os.CreateTemp(t.TempDir(), "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	name1 := f.Name()
+	defer os.Remove(name1)
+	f.WriteString("aaaaaaaaaa")
+	f.Close()
+
+	f, err = os.CreateTemp(t.TempDir(), "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	name2 := f.Name()
+	defer os.Remove(name2)
+	f.WriteString("bbbbbbbbbb")
+	f.Close()
+
+	if err = AppendFile(name1, name2, false); err != nil {
+		t.Error(err)
+	}
+
+	b, err := os.ReadFile(name1)
+	if err != nil {
+		t.Error(err)
+	}
+
+	expected := "aaaaaaaaaabbbbbbbbbb"
+	if string(b) != expected {
+		t.Errorf("AppendFile() failed, expected: %s, got %s", expected, string(b))
+	}
+}
+
+func TestSkipReader(t *testing.T) {
+	testCases := []struct {
+		src      io.Reader
+		skipLen  int64
+		expected string
+	}{
+		{bytes.NewBuffer([]byte("")), 0, ""},
+		{bytes.NewBuffer([]byte("")), 1, ""},
+		{bytes.NewBuffer([]byte("abc")), 0, "abc"},
+		{bytes.NewBuffer([]byte("abc")), 1, "bc"},
+		{bytes.NewBuffer([]byte("abc")), 2, "c"},
+		{bytes.NewBuffer([]byte("abc")), 3, ""},
+		{bytes.NewBuffer([]byte("abc")), 4, ""},
+	}
+	for i, testCase := range testCases {
+		r := NewSkipReader(testCase.src, testCase.skipLen)
+		b, err := io.ReadAll(r)
+		if err != nil {
+			t.Errorf("Case %d: Unexpected err %v", i, err)
+		}
+		if string(b) != testCase.expected {
+			t.Errorf("Case %d: Got wrong result: %v", i, string(b))
+		}
+	}
+}
+
+func TestSameFile(t *testing.T) {
+	f, err := os.CreateTemp(t.TempDir(), "")
+	if err != nil {
+		t.Errorf("Error creating tmp file: %v", err)
+	}
+	tmpFile := f.Name()
+	f.Close()
+	defer os.Remove(f.Name())
+	fi1, err := os.Stat(tmpFile)
+	if err != nil {
+		t.Fatalf("Error Stat(): %v", err)
+	}
+	fi2, err := os.Stat(tmpFile)
+	if err != nil {
+		t.Fatalf("Error Stat(): %v", err)
+	}
+	if !SameFile(fi1, fi2) {
+		t.Fatal("Expected the files to be same")
+	}
+	if err = os.WriteFile(tmpFile, []byte("aaa"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	fi2, err = os.Stat(tmpFile)
+	if err != nil {
+		t.Fatalf("Error Stat(): %v", err)
+	}
+	if SameFile(fi1, fi2) {
+		t.Fatal("Expected the files not to be same")
+	}
+}
+
+func TestCopyAligned(t *testing.T) {
+	f, err := os.CreateTemp(t.TempDir(), "")
+	if err != nil {
+		t.Errorf("Error creating tmp file: %v", err)
+	}
+	defer f.Close()
+	defer os.Remove(f.Name())
+
+	r := strings.NewReader("hello world")
+
+	bufp := ODirectPoolSmall.Get()
+	defer ODirectPoolSmall.Put(bufp)
+
+	written, err := CopyAligned(f, io.LimitReader(r, 5), *bufp, r.Size(), f)
+	if !errors.Is(err, io.ErrUnexpectedEOF) {
+		t.Errorf("Expected io.ErrUnexpectedEOF, but got %v", err)
+	}
+	if written != 5 {
+		t.Errorf("Expected written to be '5', but got %v", written)
+	}
+
+	f.Seek(0, io.SeekStart)
+	r.Seek(0, io.SeekStart)
+
+	written, err = CopyAligned(f, r, *bufp, r.Size(), f)
+	if !errors.Is(err, nil) {
+		t.Errorf("Expected nil, but got %v", err)
+	}
+	if written != r.Size() {
+		t.Errorf("Expected written to be '%v', but got %v", r.Size(), written)
+	}
+}

internal/ioutil/read_file.go

@@ -0,0 +1,79 @@
+// Copyright (c) 2015-2021 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package ioutil
+
+import (
+	"io"
+	"io/fs"
+	"os"
+
+	"github.com/minio/minio/internal/disk"
+)
+
+var (
+	// OpenFileDirectIO allows overriding default function.
+	OpenFileDirectIO = disk.OpenFileDirectIO
+	// OsOpen allows overriding default function.
+	OsOpen = os.Open
+	// OsOpenFile allows overriding default function.
+	OsOpenFile = os.OpenFile
+)
+
+// ReadFileWithFileInfo reads the named file and returns the contents.
+// A successful call returns err == nil, not err == EOF.
+// Because ReadFile reads the whole file, it does not treat an EOF from Read
+// as an error to be reported.
+func ReadFileWithFileInfo(name string) ([]byte, fs.FileInfo, error) {
+	f, err := OsOpenFile(name, readMode, 0o666)
+	if err != nil {
+		return nil, nil, err
+	}
+	defer f.Close()
+
+	st, err := f.Stat()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	dst := make([]byte, st.Size())
+	_, err = io.ReadFull(f, dst)
+	return dst, st, err
+}
+
+// ReadFile reads the named file and returns the contents.
+// A successful call returns err == nil, not err == EOF.
+// Because ReadFile reads the whole file, it does not treat an EOF from Read
+// as an error to be reported.
+//
+// passes NOATIME flag for reads on Unix systems to avoid atime updates.
+func ReadFile(name string) ([]byte, error) {
+	// Don't wrap with un-needed buffer.
+	// Don't use os.ReadFile, since it doesn't pass NO_ATIME when present.
+	f, err := OsOpenFile(name, readMode, 0o666)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	st, err := f.Stat()
+	if err != nil {
+		return io.ReadAll(f)
+	}
+	dst := make([]byte, st.Size())
+	_, err = io.ReadFull(f, dst)
+	return dst, err
+}

internal/ioutil/read_file_noatime_notsupported.go

@@ -0,0 +1,25 @@
+//go:build windows || darwin || freebsd
+// +build windows darwin freebsd
+
+// Copyright (c) 2015-2021 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package ioutil
+
+import "os"
+
+var readMode = os.O_RDONLY

internal/ioutil/read_file_noatime_supported.go

@@ -0,0 +1,27 @@
+//go:build !windows && !darwin && !freebsd
+// +build !windows,!darwin,!freebsd
+
+// Copyright (c) 2015-2021 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package ioutil
+
+import (
+	"os"
+)
+
+var readMode = os.O_RDONLY | 0x40000 // read with O_NOATIME

internal/ioutil/wait_pipe.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2015-2021 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package ioutil
+
+import (
+	"io"
+	"sync"
+)
+
+// PipeWriter is similar to io.PipeWriter with wait group
+type PipeWriter struct {
+	*io.PipeWriter
+	once sync.Once
+	done func()
+}
+
+// CloseWithError close with supplied error the writer end.
+func (w *PipeWriter) CloseWithError(err error) error {
+	err = w.PipeWriter.CloseWithError(err)
+	w.once.Do(func() {
+		w.done()
+	})
+	return err
+}
+
+// PipeReader is similar to io.PipeReader with wait group
+type PipeReader struct {
+	*io.PipeReader
+	wait func()
+}
+
+// CloseWithError close with supplied error the reader end
+func (r *PipeReader) CloseWithError(err error) error {
+	err = r.PipeReader.CloseWithError(err)
+	r.wait()
+	return err
+}
+
+// WaitPipe implements wait-group backend io.Pipe to provide
+// synchronization between read() end with write() end.
+func WaitPipe() (*PipeReader, *PipeWriter) {
+	r, w := io.Pipe()
+	var wg sync.WaitGroup
+	wg.Add(1)
+	return &PipeReader{
+			PipeReader: r,
+			wait:       wg.Wait,
+		}, &PipeWriter{
+			PipeWriter: w,
+			done:       wg.Done,
+		}
+}