Added PaddedWriter

1 files changed, 32 insertions, 0 deletions

diff --git a/PaddedWriter.go b/PaddedWriter.go
new file mode 100644
index 0000000..f3430b5
--- /dev/null
+++ b/PaddedWriter.go
@@ -0,0 +1,32 @@
+package kagus
+
+import (
+	"io"
+)
+
+// PaddedWriter is a writer for data that needs to be padded / aligned.
+type PaddedWriter struct {
+	cw      *CountWriter
+	padding int
+}
+
+func NewPaddedWriter(w io.Writer, padding int) *PaddedWriter {
+	return &PaddedWriter{NewCountWriter(w), padding}
+}
+
+func (pw *PaddedWriter) Write(p []byte) (int, error) {
+	return pw.cw.Write(p)
+}
+
+// Pad needs to be called if the padding should be inserted. Data is padded with zero-bytes.
+func (pw *PaddedWriter) Pad() error {
+	mod := int(pw.cw.N % int64(pw.padding))
+	if mod == 0 {
+		return nil
+	}
+
+	paddingLen := pw.padding - mod
+	padding := make([]byte, paddingLen)
+	_, err := pw.cw.Write(padding)
+	return err
+}