From b04679b42994049a5d52ba9879c8ee34c0b85318 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Wed, 5 Jul 2017 17:10:59 +0200
Subject: [PATCH] util/WritableBuffer: add method MoveFront()

---
 src/util/WritableBuffer.hxx | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/util/WritableBuffer.hxx b/src/util/WritableBuffer.hxx
index fc3b872ab..e36f24e56 100644
--- a/src/util/WritableBuffer.hxx
+++ b/src/util/WritableBuffer.hxx
@@ -235,6 +235,20 @@ struct WritableBuffer {
 		data += n;
 		size -= n;
 	}
+
+	/**
+	 * Move the front pointer to the given address, and adjust the
+	 * size attribute to retain the old end address.
+	 */
+	void MoveFront(pointer_type new_data) {
+#ifndef NDEBUG
+		assert(IsNull() == (new_data == nullptr));
+		assert(new_data <= end());
+#endif
+
+		size = end() - new_data;
+		data = new_data;
+	}
 };
 
 #endif