From d39556e2d59be2537f4905d1ec6ce2b6286aedb6 Mon Sep 17 00:00:00 2001
From: Ali El Gariani <alinkmaze@gmail.com>
Date: Mon, 30 Nov 2009 21:49:53 +0000
Subject: [PATCH] Add a 'temporary unit mover'.

---
 src/unit.cpp | 14 ++++++++++++++
 src/unit.hpp | 17 +++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/src/unit.cpp b/src/unit.cpp
index ac828fb820e..623684de238 100644
--- a/src/unit.cpp
+++ b/src/unit.cpp
@@ -2830,6 +2830,20 @@ temporary_unit_placer::~temporary_unit_placer()
 	}
 }
 
+temporary_unit_mover::temporary_unit_mover(unit_map& m, const map_location& src,  const map_location& dst)
+	: m_(m), src_(src), dst_(dst), temp_(m.extract(dst))
+{
+	m.move(src_, dst_);
+}
+
+temporary_unit_mover::~temporary_unit_mover()
+{
+	m_.move(dst_, src_);
+	if(temp_) {
+		m_.insert(temp_);
+	}
+}
+
 std::string unit::image_mods() const{
 	std::stringstream modifier;
 	if(flag_rgb_.size()){
diff --git a/src/unit.hpp b/src/unit.hpp
index 4b0573b74fd..0493cad63ad 100644
--- a/src/unit.hpp
+++ b/src/unit.hpp
@@ -522,6 +522,23 @@ private:
 	std::pair<map_location,unit> *temp_;
 };
 
+/**
+ * This object is used to temporary move a unit in the unit map, swapping out
+ * any unit that is already there.  On destruction, it restores the unit map to
+ * its original.
+ */
+struct temporary_unit_mover
+{
+	temporary_unit_mover(unit_map& m, const map_location& src,  const map_location& dst);
+	~temporary_unit_mover();
+
+private:
+	unit_map& m_;
+	const map_location& src_;
+	const map_location& dst_;
+	std::pair<map_location,unit> *temp_;
+};
+
 /**
  * Gets a checksum for a unit.
  *