feat: stream write to zip directly

file.go

@@ -87,17 +87,55 @@ func (f *File) Write(w io.Writer) error {
 
 // WriteTo implements io.WriterTo to write the file.
 func (f *File) WriteTo(w io.Writer) (int64, error) {
-	buf, err := f.WriteToBuffer()
-	if err != nil {
+	if f.options != nil && f.options.Password != "" {
+		buf, err := f.WriteToBuffer()
+		if err != nil {
+			return 0, err
+		}
+		return buf.WriteTo(w)
+	}
+	if err := f.writeDirectToWriter(w); err != nil {
 		return 0, err
 	}
-	return buf.WriteTo(w)
+	return 0, nil
 }
 
-// WriteToBuffer provides a function to get bytes.Buffer from the saved file.
+// WriteToBuffer provides a function to get bytes.Buffer from the saved file. And it allocate space in memory. Be careful when the file size is large.
 func (f *File) WriteToBuffer() (*bytes.Buffer, error) {
 	buf := new(bytes.Buffer)
 	zw := zip.NewWriter(buf)
+
+	if err := f.writeToZip(zw); err != nil {
+		return buf, zw.Close()
+	}
+
+	if f.options != nil && f.options.Password != "" {
+		if err := zw.Close(); err != nil {
+			return buf, err
+		}
+		b, err := Encrypt(buf.Bytes(), f.options)
+		if err != nil {
+			return buf, err
+		}
+		buf.Reset()
+		buf.Write(b)
+		return buf, nil
+	}
+	return buf, zw.Close()
+}
+
+// writeDirectToWriter provides a function to write to io.Writer.
+func (f *File) writeDirectToWriter(w io.Writer) error {
+	zw := zip.NewWriter(w)
+	if err := f.writeToZip(zw); err != nil {
+		zw.Close()
+		return err
+	}
+	return zw.Close()
+}
+
+// writeToZip provides a function to write to zip.Writer
+func (f *File) writeToZip(zw *zip.Writer) error {
 	f.calcChainWriter()
 	f.commentsWriter()
 	f.contentTypesWriter()
@@ -112,19 +150,17 @@ func (f *File) WriteToBuffer() (*bytes.Buffer, error) {
 	for path, stream := range f.streams {
 		fi, err := zw.Create(path)
 		if err != nil {
-			zw.Close()
-			return buf, err
+			return err
 		}
 		var from io.Reader
 		from, err = stream.rawData.Reader()
 		if err != nil {
 			stream.rawData.Close()
-			return buf, err
+			return err
 		}
 		_, err = io.Copy(fi, from)
 		if err != nil {
-			zw.Close()
-			return buf, err
+			return err
 		}
 		stream.rawData.Close()
 	}
@@ -135,27 +171,13 @@ func (f *File) WriteToBuffer() (*bytes.Buffer, error) {
 		}
 		fi, err := zw.Create(path)
 		if err != nil {
-			zw.Close()
-			return buf, err
+			return err
 		}
 		_, err = fi.Write(content)
 		if err != nil {
-			zw.Close()
-			return buf, err
+			return err
 		}
 	}
 
-	if f.options != nil && f.options.Password != "" {
-		if err := zw.Close(); err != nil {
-			return buf, err
-		}
-		b, err := Encrypt(buf.Bytes(), f.options)
-		if err != nil {
-			return buf, err
-		}
-		buf.Reset()
-		buf.Write(b)
-		return buf, nil
-	}
-	return buf, zw.Close()
+	return nil
 }

file_test.go

@@ -3,6 +3,7 @@ package excelize
 import (
 	"bufio"
 	"bytes"
+	"os"
 	"strings"
 	"testing"
 
@@ -33,16 +34,36 @@ func BenchmarkWrite(b *testing.B) {
 }
 
 func TestWriteTo(t *testing.T) {
-	f := File{}
-	buf := bytes.Buffer{}
-	f.XLSX = make(map[string][]byte)
-	f.XLSX["/d/"] = []byte("s")
-	_, err := f.WriteTo(bufio.NewWriter(&buf))
-	assert.EqualError(t, err, "zip: write to directory")
-	delete(f.XLSX, "/d/")
+	// Test WriteToBuffer err
+	{
+		f := File{}
+		buf := bytes.Buffer{}
+		f.XLSX = make(map[string][]byte)
+		f.XLSX["/d/"] = []byte("s")
+		_, err := f.WriteTo(bufio.NewWriter(&buf))
+		assert.EqualError(t, err, "zip: write to directory")
+		delete(f.XLSX, "/d/")
+	}
 	// Test file path overflow
-	const maxUint16 = 1<<16 - 1
-	f.XLSX[strings.Repeat("s", maxUint16+1)] = nil
-	_, err = f.WriteTo(bufio.NewWriter(&buf))
-	assert.EqualError(t, err, "zip: FileHeader.Name too long")
+	{
+		f := File{}
+		buf := bytes.Buffer{}
+		f.XLSX = make(map[string][]byte)
+		const maxUint16 = 1<<16 - 1
+		f.XLSX[strings.Repeat("s", maxUint16+1)] = nil
+		_, err := f.WriteTo(bufio.NewWriter(&buf))
+		assert.EqualError(t, err, "zip: FileHeader.Name too long")
+	}
+	// Test StreamsWriter err
+	{
+		f := File{}
+		buf := bytes.Buffer{}
+		f.XLSX = make(map[string][]byte)
+		f.XLSX["s"] = nil
+		f.streams = make(map[string]*StreamWriter)
+		file, _ := os.Open("123")
+		f.streams["s"] = &StreamWriter{rawData: bufferedWriter{tmp: file}}
+		_, err := f.WriteTo(bufio.NewWriter(&buf))
+		assert.Nil(t, err)
+	}
 }