From 01c02a1ef8ab3e1fd920d889b0555059f72edfe4 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max.kellermann@gmail.com>
Date: Sat, 29 Apr 2023 20:22:31 +0200
Subject: [PATCH] util/StaticFifoBuffer: add method MoveFrom()

---
 src/util/StaticFifoBuffer.hxx | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/util/StaticFifoBuffer.hxx b/src/util/StaticFifoBuffer.hxx
index b274861bd..5e38598b3 100644
--- a/src/util/StaticFifoBuffer.hxx
+++ b/src/util/StaticFifoBuffer.hxx
@@ -80,6 +80,31 @@ public:
 		tail += n;
 	}
 
+	/**
+	 * Move as much data as possible from the specified buffer.
+	 *
+	 * @return the number of items moved
+	 */
+	template<typename U>
+	constexpr size_type MoveFrom(std::span<U> src) noexcept {
+		auto w = Write();
+
+		if (src.size() > w.size() && head > 0) {
+			/* if the source contains more data than we
+			   can append at the tail, try to make more
+			   room by shifting the head to 0 */
+			Shift();
+			w = Write();
+		}
+
+		if (src.size() > w.size())
+			src = src.first(w.size());
+
+		std::move(src.begin(), src.end(), w.begin());
+		Append(src.size());
+		return src.size();
+	}
+
 	constexpr size_type GetAvailable() const noexcept {
 		return tail - head;
 	}