docker testing

cmd/slicewriter/slicewriter.go

@@ -0,0 +1,36 @@
+package slicewriter
+
+import "io"
+
+type SliceWriter struct {
+	off int
+	buf []byte
+}
+
+func (w *SliceWriter) Write(p []byte) (int, error) {
+	if len(p)+w.off <= len(w.buf) {
+		copy(w.buf[w.off:], p)
+		w.off += len(p)
+		return len(p), nil
+	}
+
+	space := len(w.buf) - w.off
+	copy(w.buf[:w.off], p[:space])
+	w.off += space
+	return space, io.ErrShortWrite
+}
+
+func (w *SliceWriter) Reset() {
+	w.off = 0
+}
+
+func (w *SliceWriter) Bytes() []byte {
+	return w.buf[:w.off]
+}
+
+func NewSliceWriter(b []byte) *SliceWriter {
+	return &SliceWriter{
+		off: 0,
+		buf: b,
+	}
+}