refactor buffer

common/buf/io.go

@@ -0,0 +1,15 @@
+package buf
+
+import "io"
+
+func ReadFrom(reader io.Reader) Supplier {
+	return func(b []byte) (int, error) {
+		return reader.Read(b)
+	}
+}
+
+func ReadFullFrom(reader io.Reader, size int) Supplier {
+	return func(b []byte) (int, error) {
+		return io.ReadFull(reader, b[:size])
+	}
+}