From a23524d34a67486615df96ea6309877a0f7a05c7 Mon Sep 17 00:00:00 2001
From: Felicitas Pojtinger <felicitas@pojtinger.com>
Date: Thu, 20 Jan 2022 21:34:36 +0100
Subject: [PATCH] feat: Add sequential read  tests, allow reading directory if
 length of buffer is 0

---
 pkg/fs/file.go      |   8 +--
 pkg/fs/file_test.go | 161 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 165 insertions(+), 4 deletions(-)

diff --git a/pkg/fs/file.go b/pkg/fs/file.go
index ea3f33f..699c3fd 100644
--- a/pkg/fs/file.go
+++ b/pkg/fs/file.go
@@ -451,10 +451,6 @@ func (f *File) Read(p []byte) (n int, err error) {
 		"p":    len(p),
 	})
 
-	if f.info.IsDir() {
-		return -1, config.ErrIsDirectory
-	}
-
 	if !f.flags.Read {
 		return -1, os.ErrPermission
 	}
@@ -463,6 +459,10 @@ func (f *File) Read(p []byte) (n int, err error) {
 		return 0, nil
 	}
 
+	if f.info.IsDir() {
+		return -1, config.ErrIsDirectory
+	}
+
 	f.ioLock.Lock()
 	defer f.ioLock.Unlock()
 
diff --git a/pkg/fs/file_test.go b/pkg/fs/file_test.go
index 4ad16ac..9ff1cf9 100644
--- a/pkg/fs/file_test.go
+++ b/pkg/fs/file_test.go
@@ -1,6 +1,7 @@
 package fs
 
 import (
+	"bytes"
 	"crypto/sha512"
 	"encoding/base64"
 	"errors"
@@ -1140,6 +1141,112 @@ var readTests = []struct {
 	withOsFs  bool
 	large     bool
 }{
+	{
+		"Can read / into empty buffer",
+		"/",
+		false,
+		func(f afero.Fs) error { return nil },
+		func(f afero.File) error {
+			wantContent := []byte{}
+			gotContent := make([]byte, len(wantContent))
+
+			wantLength := len(wantContent)
+			gotLength, err := f.Read(gotContent)
+			if err != io.EOF {
+				return err
+			}
+
+			if wantLength != gotLength {
+				return fmt.Errorf("invalid read length, got %v, want %v", gotLength, wantLength)
+			}
+
+			if string(wantContent) != string(gotContent) {
+				return fmt.Errorf("invalid read content, got %v, want %v", gotContent, wantContent)
+			}
+
+			return nil
+		},
+		true,
+		true,
+		false,
+	},
+	{
+		"Can read /mydir into empty buffer",
+		"/mydir",
+		false,
+		func(f afero.Fs) error {
+			if err := f.Mkdir("/mydir", os.ModePerm); err != nil {
+				return err
+			}
+
+			return nil
+		},
+		func(f afero.File) error {
+			wantContent := []byte{}
+			gotContent := make([]byte, len(wantContent))
+
+			wantLength := len(wantContent)
+			gotLength, err := f.Read(gotContent)
+			if err != io.EOF {
+				return err
+			}
+
+			if wantLength != gotLength {
+				return fmt.Errorf("invalid read length, got %v, want %v", gotLength, wantLength)
+			}
+
+			if string(wantContent) != string(gotContent) {
+				return fmt.Errorf("invalid read content, got %v, want %v", gotContent, wantContent)
+			}
+
+			return nil
+		},
+		true,
+		true,
+		false,
+	},
+	{
+		"Can not read / into non-empty buffer",
+		"/",
+		true,
+		func(f afero.Fs) error { return nil },
+		func(f afero.File) error {
+			gotContent := make([]byte, 10)
+
+			if _, err := f.Read(gotContent); err != io.EOF {
+				return err
+			}
+
+			return nil
+		},
+		true,
+		true,
+		false,
+	},
+	{
+		"Can not read /mydir into non-empty buffer",
+		"/mydir",
+		true,
+		func(f afero.Fs) error {
+			if err := f.Mkdir("/mydir", os.ModePerm); err != nil {
+				return err
+			}
+
+			return nil
+		},
+		func(f afero.File) error {
+			gotContent := make([]byte, 10)
+
+			if _, err := f.Read(gotContent); err != io.EOF {
+				return err
+			}
+
+			return nil
+		},
+		true,
+		true,
+		false,
+	},
 	{
 		"Can read /test.txt if it exists and is empty",
 		"/test.txt",
@@ -1301,6 +1408,60 @@ var readTests = []struct {
 		true,
 		true,
 	},
+	{
+		"Can read /test.txt sequentially if it exists and contains 30 MB amount of data",
+		"/test.txt",
+		false,
+		func(f afero.Fs) error {
+			file, err := f.Create("/test.txt")
+			if err != nil {
+				return err
+			}
+
+			r := newDeterministicReader(1000)
+
+			if _, err := io.Copy(file, r); err != nil {
+				return err
+			}
+
+			return file.Close()
+		},
+		func(f afero.File) error {
+			firstChunk := make([]byte, 32800768/2)
+			secondChunk := make([]byte, 32800768/2)
+
+			if _, err := f.Read(firstChunk); err != nil {
+				return err
+			}
+
+			if _, err := f.Read(secondChunk); err != nil {
+				return err
+			}
+
+			wantHash := "HTUi7GuNreHASha4hhl1xwuYk03pyTJ0IJbFLv04UdccT9m_NA2oBFTrnMxJhEu3VMGxDYk_04Th9C0zOj5MyA=="
+			wantLength := int64(32800768)
+
+			hasher := sha512.New()
+			gotLength, err := io.Copy(hasher, bytes.NewBuffer(append(firstChunk, secondChunk...)))
+			if err != nil {
+				return err
+			}
+			gotHash := base64.URLEncoding.EncodeToString(hasher.Sum(nil))
+
+			if gotLength != wantLength {
+				return fmt.Errorf("invalid read length, got %v, want %v", gotLength, wantLength)
+			}
+
+			if gotHash != wantHash {
+				return fmt.Errorf("invalid read hash, got %v, want %v", gotHash, wantHash)
+			}
+
+			return nil
+		},
+		true,
+		true,
+		false,
+	},
 }
 
 func TestFile_Read(t *testing.T) {