Merge pull request #16 from qmuntal/newwriter-reader

Add NewWriterFromReader

Author: qmuntal

example_test.go

@@ -59,3 +59,34 @@ func ExampleReader() {
 		fmt.Println()
 	}
 }
+
+func ExampleNewWriterFromReader() {
+	r, err := opc.OpenReader("testdata/component.3mf")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer r.Close()
+
+	buf := new(bytes.Buffer)
+	w, err := opc.NewWriterFromReader(buf, r.Reader)
+	if err != nil {
+		log.Fatal(err)
+	}
+	name := opc.NormalizePartName("docs\\readme.txt")
+	part, err := w.Create(name, "text/plain")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Write content to the part.
+	_, err = part.Write([]byte("This archive contains some text files."))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Make sure to check the error on Close.
+	if err := w.Close(); err != nil {
+		log.Fatal(err)
+	}
+}
+

writer.go

@@ -35,7 +35,7 @@ type Writer struct {
 	last          *Part
 }
 
-// NewWriter returns a new Writer writing an OPC file to w.
+// NewWriter returns a new Writer writing an OPC package to w.
 func NewWriter(w io.Writer) *Writer {
 	return &Writer{p: &pkg{
 		parts: make(map[string]*Part, 0),
@@ -49,6 +49,35 @@ func NewWriter(w io.Writer) *Writer {
 	}, w: zip.NewWriter(w)}
 }
 
+// NewWriterFromReader returns a new Writer writing an OPC package to w
+// and with its content initialized with r.
+// Parts comming from r cannot be modified but new parts can be appended
+// and package core properties and relationships can be updated.
+func NewWriterFromReader(w io.Writer, r *Reader) (*Writer, error) {
+	ow := NewWriter(w)
+	for _, p := range r.Files {
+		pw, err := ow.CreatePart(p.Part, CompressionNormal)
+		if err != nil {
+			return nil, err
+		}
+		rc, err := p.Open()
+		if err != nil {
+			return nil, err
+		}
+		_, err = io.Copy(pw, rc)
+		rc.Close()
+		if err != nil {
+			return nil, err
+		}
+	}
+	ow.Properties = r.Properties
+	ow.Relationships = make([]*Relationship, len(r.Relationships))
+	for i, rel := range r.Relationships {
+		ow.Relationships[i] = &(*rel)
+	}
+	return ow, nil
+}
+
 // Flush flushes any buffered data to the underlying writer.
 // Part metadata, relationships, content types and other OPC related files won't be flushed.
 // Calling Flush is not normally necessary; calling Close is sufficient.

writer_test.go

@@ -194,3 +194,24 @@ func TestWriter_createLastPartRelationships(t *testing.T) {
 		})
 	}
 }
+
+func TestNewWriterFromReader(t *testing.T) {
+	r, err := OpenReader("testdata/office.docx")
+	if err != nil {
+		t.Fatalf("failed to open test file: %v", err)
+	}
+	var buf bytes.Buffer
+	w, err := NewWriterFromReader(&buf, r.Reader)
+	if err != nil {
+		t.Fatalf("NewWriterFromReader() error: %v", err)
+	}
+	if w.Properties != r.Properties {
+		t.Error("NewWriterFromReader() haven't copied core properties")
+	}
+	if len(w.Relationships) != len(r.Relationships) {
+		t.Error("NewWriterFromReader() haven't copied package relationships")
+	}
+	if err = w.Close(); err != nil {
+		t.Errorf("NewWriterFromReader() created package that cannot be closed: %v", err)
+	}
+}