initial commits

copyn.go

@@ -0,0 +1,21 @@
+package raft
+
+import (
+	"io"
+
+	"sourcecode.social/reiver/go-erorr"
+)
+
+// copyN is similar to io.CopyN(), except that if the number of bytes written (by io.CopyN()) is not 'n' then it returns an error.
+func copyN(writer io.Writer, reader io.Reader, n int64) error {
+
+	numWritten, err := io.CopyN(writer, reader, n)
+	if nil != err {
+		return erorr.Errorf("problem copying %d bytes from reader to writer: %w", n, err)
+	}
+	if expected, actual := n, numWritten ; expected != actual {
+		return erorr.Errorf("expected to write %d bytes but actually wrote %d bytes", expected, actual)
+	}
+
+	return nil
+}