added test for file tree creation with large files

filesystem/fat32/fat32_test.go

@@ -10,10 +10,14 @@ import (
 	"crypto/rand"
 	"fmt"
 	"io"
+	mRand "math/rand"
 	"os"
+	"strconv"
 	"strings"
 	"testing"
 
+	"github.com/diskfs/go-diskfs"
+	"github.com/diskfs/go-diskfs/disk"
 	"github.com/diskfs/go-diskfs/filesystem"
 	"github.com/diskfs/go-diskfs/filesystem/fat32"
 	"github.com/diskfs/go-diskfs/testhelper"
@@ -1058,3 +1062,103 @@ func TestOpenFileCaseInsensitive(t *testing.T) {
 		}
 	}
 }
+
+// small helper function to make a large fat32 filesystem
+func mkfs(name string) filesystem.FileSystem {
+	size := int64(6 * 1024 * 1024 * 1024)
+	d, err := diskfs.Create(name, size, diskfs.Raw, diskfs.SectorSizeDefault)
+	if err != nil {
+		fmt.Printf("error creating disk: %v", err)
+		os.Exit(1)
+	}
+
+	spec := disk.FilesystemSpec{
+		Partition: 0,
+		FSType:    filesystem.TypeFat32,
+	}
+
+	fs, err := d.CreateFilesystem(spec)
+	if err != nil {
+		panic(err)
+	}
+	return fs
+}
+
+func mkdir(fs filesystem.FileSystem, name string) {
+	err := fs.Mkdir(name)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func mkMicroFile(fs filesystem.FileSystem, name string) {
+	rw, err := fs.OpenFile(name, os.O_CREATE|os.O_RDWR)
+	if err != nil {
+		panic(err)
+	}
+
+	_, err = rw.Write([]byte("hello World"))
+	if err != nil {
+		panic(err)
+	}
+}
+func mkSmallFile(fs filesystem.FileSystem, name string) {
+	rw, err := fs.OpenFile(name, os.O_CREATE|os.O_RDWR)
+	if err != nil {
+		panic(err)
+	}
+
+	size := 5 * 1024 * 1024
+	smallFile := make([]byte, size, size)
+	_, err = rw.Write(smallFile)
+	if err != nil {
+		panic(err)
+	}
+}
+func mkRandFile(fs filesystem.FileSystem, name string, rSize int) {
+	rw, err := fs.OpenFile(name, os.O_CREATE|os.O_RDWR)
+	if err != nil {
+		panic(err)
+	}
+
+	size := rSize * 1024 * 1024
+	randFile := make([]byte, size, size)
+	_, err = rw.Write(randFile)
+	if err != nil {
+		panic(err)
+	}
+}
+func mkGigFile(fs filesystem.FileSystem, name string) {
+	rw, err := fs.OpenFile(name, os.O_CREATE|os.O_RDWR)
+	if err != nil {
+		panic(err)
+	}
+
+	size := 1024 * 1024 * 1024
+	smallFile := make([]byte, size, size)
+	_, err = rw.Write(smallFile)
+	if err != nil {
+		panic(err)
+	}
+}
+func TestCreateFileTree(t *testing.T) {
+	fileName := "file-tree.img"
+	os.Remove(fileName)
+	f := mkfs(fileName)
+	mkdir(f, "/A")
+	mkdir(f, "/b")
+	mkMicroFile(f, "/rootfile")
+	r := mRand.New(mRand.NewSource(37))
+	for i := 0; i < 100; i++ {
+		inc := strconv.Itoa(i)
+		mkdir(f, "/b/sub"+inc)
+		mkdir(f, "/b/sub"+inc+"/blob/")
+		mkMicroFile(f, "/b/sub"+inc+"/blob/microfile")
+		mkRandFile(f, "/b/sub"+inc+"/blob/randfile", r.Intn(73))
+		mkSmallFile(f, "/b/sub"+inc+"/blob/smallfile")
+
+	}
+	mkGigFile(f, "/b/sub49/blob/gigfile1")
+	mkGigFile(f, "/b/sub50/blob/gigfile1")
+	mkGigFile(f, "/b/sub55/blob/gigfile1")
+}