Merge pull request #1 from leon-richardt/ref/check-file-existence

ref: check file existence instead of keeping in-memory set

jaf.go

@@ -3,7 +3,6 @@ package main
 import (
 	"flag"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"math/rand"
 	"net/http"
@@ -13,8 +12,7 @@ import (
 const allowedChars = "0123456789ABCDEFGHIJKLMNOPQRTSUVWXYZabcdefghijklmnopqrstuvwxyz"
 
 var (
-	savedFileNames = NewSet()
-	config         Config
+	config Config
 )
 
 type parameters struct {
@@ -42,16 +40,6 @@ func main() {
 		log.Fatalf("could not read config file: %s\n", err.Error())
 	}
 
-	files, err := ioutil.ReadDir(config.FileDir)
-	if err != nil {
-		log.Fatalf("could not read file root %s: %s\n", config.FileDir, err.Error())
-	}
-
-	// Cache taken file names on start-up
-	for _, fileInfo := range files {
-		savedFileNames.Insert(fileInfo.Name())
-	}
-
 	// Start server
 	uploadServer := &http.Server{
 		ReadTimeout:  30 * time.Second,

set.go

@@ -1,34 +0,0 @@
-package main
-
-type Set struct {
-	_map map[interface{}]struct{}
-}
-
-func NewSet() *Set {
-	set := &Set{}
-	set._map = make(map[interface{}]struct{})
-	return set
-}
-
-func (set *Set) Contains(value interface{}) bool {
-	_, ok := set._map[value]
-	return ok
-}
-
-func (set *Set) Insert(value interface{}) bool {
-	if set.Contains(value) {
-		return false
-	}
-
-	set._map[value] = struct{}{}
-	return true
-}
-
-func (set *Set) Remove(value interface{}) bool {
-	if !set.Contains(value) {
-		return false
-	}
-
-	delete(set._map, value)
-	return true
-}

set_test.go

@@ -1,75 +0,0 @@
-package main
-
-import (
-	"math/rand"
-	"testing"
-	"time"
-)
-
-func TestContains(t *testing.T) {
-	set := NewSet()
-
-	// Oracle testing
-	dummy := 0
-	in := set.Contains(dummy)
-	if in {
-		t.Errorf("oracle > set.Contains(%d) = true before insertion", dummy)
-	}
-
-	set.Insert(dummy)
-	in = set.Contains(dummy)
-	if !in {
-		t.Errorf("oracle > set.Contains(%d) = false after insertion", dummy)
-	}
-
-	// Property testing
-	rand.Seed(time.Now().UnixNano())
-	const reps = 1000
-	for i := 0; i < reps; i++ {
-		lastInsert := rand.Int()
-		set.Insert(lastInsert)
-
-		in = set.Contains(lastInsert)
-
-		if !in {
-			t.Errorf("property > set.Contains(%d) = false after insertion", dummy)
-		}
-	}
-}
-
-func TestInsert(t *testing.T) {
-	set := NewSet()
-
-	// Oracle testing
-	dummy := 0
-	innovative := set.Insert(dummy)
-
-	if !innovative {
-		t.Errorf("oracle > set.Insert(%d) = false but was innovative", dummy)
-	}
-
-	in := set.Contains(dummy)
-	if !in {
-		t.Errorf("oracle > set.Contains(%d) = false after insertion", dummy)
-	}
-
-	// Duplicate insertion should return false
-	innovative = set.Insert(dummy)
-	if innovative {
-		t.Errorf("oracle > set.Insert(%d) = true but was not innovative", dummy)
-	}
-
-	// Property testing
-	rand.Seed(time.Now().UnixNano())
-	const reps = 1000
-	for i := 0; i < reps; i++ {
-		val := rand.Int()
-
-		inBefore := set.Contains(val)
-		innovative = set.Insert(val)
-
-		if inBefore && innovative {
-			t.Errorf("property > included value reported as innovative")
-		}
-	}
-}

uploadhandler.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"io"
 	"log"
 	"math/rand"
@@ -26,29 +27,45 @@ func (h *uploadHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	defer uploadFile.Close()
 
 	_, fileExtension := splitFileName(header.Filename)
-
-	// Find an unused file name
-	fileID := createRandomFileName(h.config.LinkLength)
-	for ; savedFileNames.Contains(fileID); fileID = createRandomFileName(h.config.LinkLength) {
-	}
-
-	fullFileName := fileID + fileExtension
-	savePath := h.config.FileDir + fullFileName
-	link := h.config.LinkPrefix + fullFileName
-
-	err = saveFile(uploadFile, savePath)
+	link, err := generateLink(h, &uploadFile, fileExtension)
 	if err != nil {
 		http.Error(w, "could not save file: "+err.Error(), http.StatusInternalServerError)
 		log.Println("    could not save file: " + err.Error())
 		return
 	}
-	savedFileNames.Insert(fullFileName)
 
 	// Implicitly means code 200
 	w.Write([]byte(link))
 }
 
-func saveFile(data multipart.File, name string) error {
+// Generates a valid link to uploadFile with the specified file extension.
+// Returns the link or an error in case of failure.
+// Does not close the passed file pointer.
+func generateLink(handler *uploadHandler, uploadFile *multipart.File, fileExtension string) (string, error) {
+	// Find an unused file name
+	var fullFileName string
+	var savePath string
+	for {
+		fileStem := createRandomFileName(handler.config.LinkLength)
+		fullFileName = fileStem + fileExtension
+		savePath = handler.config.FileDir + fullFileName
+
+		if !fileExists(savePath) {
+			break
+		}
+	}
+
+	link := handler.config.LinkPrefix + fullFileName
+
+	err := saveFile(uploadFile, savePath)
+	if err != nil {
+		return "", err
+	}
+
+	return link, nil
+}
+
+func saveFile(data *multipart.File, name string) error {
 	file, err := os.Create(name)
 	if err != nil {
 		return err
@@ -56,7 +73,7 @@ func saveFile(data multipart.File, name string) error {
 
 	defer file.Close()
 
-	_, err = io.Copy(file, data)
+	_, err = io.Copy(file, *data)
 	if err != nil {
 		return err
 	}
@@ -64,6 +81,12 @@ func saveFile(data multipart.File, name string) error {
 	return nil
 }
 
+func fileExists(filename string) bool {
+	_, err := os.Stat(filename)
+
+	return !errors.Is(err, os.ErrNotExist)
+}
+
 func createRandomFileName(length int) string {
 	chars := make([]byte, length)