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tools.go
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tools.go
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package toolkit
import (
"crypto/rand"
"encoding/base32"
"errors"
"fmt"
"io"
"log"
"net/http"
"os"
"path/filepath"
"strings"
)
const randomStringSource = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_+"
// Tools is the type that allows access to its various utility methods.
type Tools struct {
MaxFileSize int
AllowedFileTypes []string
}
// RandomString generates a base32 random string of n size.
func RandomString(n int) string {
bb := make([]byte, n)
_, err := rand.Read(bb)
if err != nil {
log.Println(err)
return ""
}
return base32.StdEncoding.WithPadding(base32.NoPadding).EncodeToString(bb)[:n]
}
// RandomString generates a random string from randomStringSource of n size.
func (t *Tools) RandomString(n int) string {
dst, src := make([]rune, n), []rune(randomStringSource)
for i := range dst {
p, _ := rand.Prime(rand.Reader, len(src))
x, y := p.Uint64(), uint64(len(src))
//fmt.Println("x, y, x%y:", x, y, x%y)
dst[i] = src[x%y]
}
return string(dst)
}
// UploadedFile save information about the file to send back to user.
type UploadedFile struct {
NewFileName string
OriginalFileName string
FileSize int64
}
func (t *Tools) UploadFiles(r *http.Request, uploadDir string, rename ...bool) ([]UploadedFile, error) {
renameFile := true
if len(rename) > 0 {
renameFile = rename[0]
}
var uploadedFiles []UploadedFile
// use default MaxFileSize
if t.MaxFileSize == 0 {
t.MaxFileSize = 1024 * 1024 * 1024
}
if err := r.ParseMultipartForm(int64(t.MaxFileSize)); err != nil {
return nil, err
}
for _, fileHeaders := range r.MultipartForm.File {
for _, fileHeader := range fileHeaders {
var err error
uploadedFiles, err = func(uploadedFiles []UploadedFile) ([]UploadedFile, error) {
var uploadedFile UploadedFile
srcFile, err := fileHeader.Open()
if err != nil {
return nil, err
}
defer srcFile.Close()
// Figure out the file type
bb := make([]byte, 512)
if _, err := srcFile.Read(bb); err != nil {
return nil, err
}
filetype := http.DetectContentType(bb)
// Is file type permitted?
allowed := false
if len(t.AllowedFileTypes) > 0 {
for _, allowedType := range t.AllowedFileTypes {
if strings.EqualFold(filetype, allowedType) {
allowed = true
break
}
}
} else {
allowed = true
}
if !allowed {
return nil, errors.New("uploaded file type is not permitted")
}
// Copy file
if _, err := srcFile.Seek(0, 0); err != nil {
return nil, err
}
uploadedFile.NewFileName = fileHeader.Filename
if renameFile {
uploadedFile.NewFileName =
fmt.Sprintf("%s%s", RandomString(8), filepath.Ext(fileHeader.Filename))
}
dstFile, err := os.Create(filepath.Join(uploadDir, uploadedFile.NewFileName))
if err != nil {
return nil, err
}
defer dstFile.Close()
n, err := io.Copy(dstFile, srcFile)
if err != nil {
return nil, err
}
uploadedFile.FileSize = n
uploadedFile.OriginalFileName = fileHeader.Filename
uploadedFiles = append(uploadedFiles, uploadedFile)
return uploadedFiles, nil
}(uploadedFiles)
if err != nil {
return uploadedFiles, err
}
}
}
return uploadedFiles, nil
}